Structural transformation of Sb-based high-speed phase-change material

Matsunaga, T.; Kojima, R.; Yamada, N.; Kubota, Y.; Kifune, K.

doi:10.1107/S0108768112039961

research papers

STRUCTURAL SCIENCE
CRYSTAL ENGINEERING
MATERIALS

ISSN: 2052-5206

Volume 68| Part 6| December 2012| Pages 559-570

doi:10.1107/S0108768112039961

Structural transformation of Sb-based high-speed phase-change material

Toshiyuki Matsunaga,^a ^* Rie Kojima,^b Noboru Yamada,^c Yoshiki Kubota ^d and Kouichi Kifune ^e

^aDevice Solutions Center, R&D Division, Panasonic Corporation, 3-1-1 Yagumo-Nakamachi, Moriguchi, Osaka 570-8501, Japan, ^bAVC Networks Company, Panasonic Corporation, 1-15 Matsuo-cho, Kadoma, Osaka 571-8504, Japan, ^cDepartment of Materials Science & Engineering, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501, Japan, ^dGraduate School of Science, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka 599-8531, Japan, and ^eFaculty of Liberal Arts and Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka 599-8531, Japan
^*Correspondence e-mail: matsunaga.toshiyuki@jp.panasonic.com

(Received 28 March 2012; accepted 20 September 2012; online 23 October 2012)

The crystal structure of a phase-change recording material (the compound Ag_3.4In_3.7Sb_76.4Te_16.5) enclosed in a vacuum capillary tube was investigated at various temperatures in a heating process using a large Debye–Scherrer camera installed in BL02B2 at SPring-8. The amorphous phase of this material turns into a crystalline phase at around 416 K; this crystalline phase has an A7-type structure with atoms of Ag, In, Sb or Te randomly occupying the 6c site in the space group. This structure was maintained up to around 545 K as a single phase, although thermal expansion of the crystal lattice was observed. However, above this temperature, phase separation into AgInTe₂ and Sb–Te transpired. The first fragment, AgInTe₂, reliably maintained its crystal structure up to the melting temperature. On the other hand, the atomic configuration of the Sb–Te gradually varied with increasing temperature. This gradual structural transformation can be described as a continuous growth of the modulation period γ.

Keywords: chalcogenide compounds; homologous structure; modulated layer structure; phase change; AIST.

B-IncStrDB reference: 6732EXfQbW

1. Introduction

Phase change recording is now extensively used for high-density non-volatile memories (Wuttig & Yamada, 2007 ). Since the 1970s, various materials have been proposed for this purpose, and today we have obtained two superior materials: GeTe–Sb₂Te₃ (GST) (Yamada et al., 1991 ) and Sb–Te-based alloys such as Ag_3.4In_3.7Sb_76.4Te_16.5 (AIST or silver indium antimony tellurium; Iwasaki et al., 1992 ); these materials are now practically used as the memory layers in phase-change optical disk media, as well as in the memory cells of solid-state electrical memories. Recording can be achieved using laser irradiation or ohmic heating to cause reversible phase changes between the amorphous and crystalline phases. We analyzed the crystal structure of AIST about 10 years ago (Matsunaga et al., 2001 ), revealing that AIST has an A7-type structure, the same as that of pure Sb, in which four elements randomly occupy the 6c site in the space group. It has been presumed that this simple and spatially isotropic p–p connected six-coordination structure enables instantaneous transformation from the amorphous phase to the crystalline phase by minimal atomic rearrangement (Matsunaga et al., 2006 ; Matsunaga, Yamada et al., 2011 ). Our analysis also revealed that this A7-type quaternary crystal held its rhombohedral structure, showing a continuous atomic shift along the axis from z = 0.233 to 1/4, when the temperature was raised close to the melting point. We examined the crystal structures of Sb–Te binary compounds, which are the mother alloys of the AIST materials, as well as those of Bi–Te compounds. These compounds are known, in thermal equilibrium, to have a series of commensurately or incommensurately modulated long-period layer structures, depending on their binary compositions, between Sb and Sb₂Te₃ or between Bi and Bi₂Te₃. Our present investigation of an as-deposited Ag_3.4In_3.7Sb_76.4Te_16.5 amorphous film in a sealed quartz tube revealed that when the temperature was raised, this quaternary alloy maintained an A7-type structure, hardly showing any atomic shift. However, decomposition into two phases, AgInTe₂ and Sb–Te, occurred at around 545 K. After this decomposition, the atomic configuration of the Sb–Te fragment with the A7-type disordered structure gradually moved into an ordered arrangement to finally obtain a stable homologous structure ruled by its composition. This can be considered as follows: the dopants, Ag and In, played roles in simplifying the structure of the quaternary alloy. However, once these dopants were lost, the structural feature of the Sb–Te binary compound revealed itself.

2. Experimental

A thin film of Ag_3.4In_3.7Sb_76.4Te_16.5 with a thickness of approximately 300 nm was formed by sputtering on a glass disk 120 mm in diameter. The film was scraped off with a spatula to create a powder, which was then packed into a quartz capillary tube with an internal diameter of 0.3 mm. To prevent it from reacting with components of air, we sealed the opening of the capillary tube using an oxyacetylene flame. The diffraction experiments were carried out using the large-diameter Debye–Scherrer camera with an imaging plate on the BL02B2 beamline at the Japan Synchrotron Radiation Research Institute (Nishibori et al., 2001 ). The energy of the incident beam was approximately 29.4 keV. An imaging plate with a pixel area of 100 µm² was used as the detector; this pixel area corresponded to an angular resolution of 0.02° (287 mm camera diameter). However, for more precise structure analyses, intensity data in increments of 0.01° were obtained by reading the imaging plate for a pixel area of 50 µm². Experiments at low and high temperatures were carried out while blowing nitrogen gas onto the capillary tube at the specified temperatures. The crystal structures were examined and refined using the Rietveld method (Rietveld, 1969 ); the programs JANA2000 (Petříček & Dušek, 2000 ) and JANA2006 (Petříček et al., 2006 ) were used for this purpose. The energy of the synchrotron radiation was confirmed by recording the diffraction intensity of CeO₂ (a = 5.4111 Å) powder as a reference specimen at room temperature under the same conditions, which showed that the wavelength used for the structural analyses was 0.4187 (3) Å. Neutral atomic scattering factors were employed for them.

3. Results and discussion

3.1. Crystals observed in this experiment

The diffraction patterns obtained for the sputtered Ag_3.4In_3.7Sb_76.4Te_16.5 amorphous film are shown in Fig. 1. The amorphous phase transformed into an A7-type crystalline single phase, as seen in this graph, at around 416 K. The results of a search match and Rietveld analyses revealed the diffraction patterns taken from 435 to 545 K to be almost identical to that of an As, Sb or Bi crystal with an A7-type structure (Clark, 1955 ), as has been previously elucidated (Matsunaga et al., 2001). The (conventional three-dimensional) Rietveld analysis results at 545 K are shown in Table 1(a). This crystal belongs to the space group $[R\bar 3m]$ ; the four constituent elements, Ag, In, Sb and Te, randomly occupy the 6c site (Matsunaga, Akola et al., 2011 ). The changes in the diffraction lines with increasing temperature show that the single-phase A7-type structure is maintained up to around 545 K. However, the peaks for CuFeS₂-type AgInTe₂ (Wyckoff, 1986 ) appear at around 590 K, along with those of the A7-type structure. This decomposition can be written as

$[{\rm Ag}_{3.4}{\rm In}_{3.7}{\rm Sb}_{76.4}{\rm Te}_{16.5} \rightarrow {\rm Ag}_{3.4}{\rm In}_{3.4}{\rm Te}_{6.8} + {\rm In}_{0.3}{\rm Sb}_{76.4}{\rm Te}_{9.7}. \eqno(1)]$

These two phases formed by heating coexisted up to the high temperatures at which their Bragg peaks almost disappeared as a result of dissolving. As seen in this equation, the second decomposition product can virtually be regarded as an Sb–Te binary compound. Even at high temperatures close to the melting temperature, AgInTe₂ tightly held the CuFeS₂-type structure irrespective of temperature. However, our present analysis revealed that the structure of the second fragment, the Sb–Te compound, gradually changed with increasing temperature until obtaining its final stable atomic configuration. These structures can be closely approximated by the A7-type structure but are not real A7-type ones.

Table 1
Final structural parameters for Ag_3.4In_3.7Sb_76.4Te_16.5 at 545 K refined by Rietveld analysis

The standard deviations are shown in parentheses. The diffraction data used for the analysis: 5.50 ≤ 2θ ≤ 31.50°. (a) Conventional three-dimensional Rietveld analysis results. The space group $[R\bar 3m]$ was applied. (b) Results of a four-dimensional superspace analysis refined as a commensurately modulated structure, using the `commensurate case' in the refinement program JANA; the modulation period γ was maintained at 3/2 during the refinements (the analysis assuming an incommensurate case also concluded that this crystal has a commensurate structure with γ = 3/2). The superspace group was assumed to be $[R\overline{3}m\left(00\gamma \right)00]$ (de Wolff, 1974 ; de Wolff et al., 1981 ). B^s₁ represents the positional modulation amplitude. The determined z-slope (the form factor of the sawtooth function) value corresponds to z = 0.2359 in the three-dimensional description; this z value shows good agreement with z = 0.2365, which was derived from the three-dimensional analysis. U^ij represent the atomic displacement parameters. It was assumed that the four atoms randomly occupy the atomic sites in both analyses.

(a) R_p = 0.0215, R_wp = 0.0313, RF_obs = 0.0157, RF_wobs = 0.0238, a = 4.3037 (5) and c = 11.290 (1) Å. M: Ag_0.034In_0.037Sb_0.764Te_0.165.

Atom	Site	g	x	y	z	U¹¹ (Å²)	U³³ (Å²)
M	6c	1.0	0	0	0.2365 (1)	0.0235 (5)	0.042 (2)

(b) Commensurate case ( $[{t}_{0} = {{1}\over{4}}, {{3}\over{4 }}]$ ).

R factors of profile and all reflections
	R_p	0.0202
	R_wp	0.0292
	RF_obs	0.0133
	RF_wobs	0.0198

R factors of main and satellite reflections
Main	RF_obs	0.0111
	RF_wobs	0.0141

R factors of satellites
First-order	RF_obs	0.0184
	RF_wobs	0.0273

γ = 3/2; a = 4.3037 (5), c = 5.6452 (6) Å

Atom	g	x	y	z	z-slope	U¹¹ (Å²)	U³³ (Å²)
M	1.0	0	0	0	−0.0563 (8)	0.0229 (5)	0.043 (1)

Figure 1
Temperature dependence of X-ray powder diffraction profiles for sputtered Ag_3.4In_3.7Sb_76.4Te_16.5 amorphous film in the heating process. The amorphous halo patterns are observed at low temperatures from 295 to 416 K. However, at around 416 K the Bragg peaks of the A7-type structure appear in the halo pattern. As the temperature is raised further, the A7-type single phase separates into two phases, AgInTe₂ and an Sb–Te binary compound, at around 545 K. At 2θ angles lower than 5°, Bragg peaks were hardly observed at any measurement temperatures.

3.2. Homologous structures

We examined many types of chalcogenide materials to clarify the high-speed phase-change mechanism and develop new materials for future ultra-high-density phase-change recording devices. This revealed that, after sufficient heat treatments, almost all these materials finally fell into their stable crystals with so-called homologous structures. It has been found that in thermal equilibrium, the typical phase-change materials, the GeTe–Sb₂Te₃ pseudobinary system, the Sb–Te or Bi–Te binary system, form various intermetallic compounds represented by the chemical formulae (GeTe)_n(Sb₂Te₃)_m, (Sb₂)_n(Sb₂Te₃)_m or (Bi₂)_n(Bi₂Te₃)_m (n, m: integer). All these compounds have trigonal structures with 2n + 5m cubic close-packed periodicity (almost) without exception. [More specifically, the residual of (2n + 5m)/3 = 0 and ≠ 0 leads to the formation of crystals having structures with primitive (P) and rhombohedral (R) unit cells; they form structures with N = (2n + 5m) and N = 3*(2n + 5m) layers, respectively.] Table 2 shows the case of the GeTe–Sb₂Te₃ compounds; all of the existing intermetallic compounds in these systems follow this rule (Matsunaga & Yamada, 2004a ; Matsunaga, Yamada & Kubota, 2004 ; Matsunaga et al., 2007a ,b , 2010 ; Matsunaga, Kojima et al., 2008 ). This could also be confirmed from the relevant tables in other papers (Karpinsky et al., 1998 ; Kuznetsova et al., 2000 ; Shelimova et al., 2000 , 2004 ; Shelimova, Karpinskii et al., 2001 ; Shelimova, Konstantinov et al., 2001 ; Poudeu & Kanatzidis, 2005 ). These structures are similar to each other and systematically characterized by the stacking of the (GeTe)_n and (Sb₂Te₃)_m, (Sb₂)_n and (Sb₂Te₃)_m, or (Bi₂)_n and (Bi₂Te₃)_m blocks along the $[{{\bf c}}_{H}]$ axes, with very long cell dimensions in the conventional three-dimensional structure description (Karpinsky et al., 1998; Shelimova et al., 2000; Shelimova, Karpinskii et al., 2001; Poudeu & Kanatzidis, 2005; Matsunaga & Yamada, 2004a, Matsunaga, Yamada & Kubota, 2004; Matsunaga et al., 2007a,b, 2010; Matsunaga, Kojima et al., 2008; Matsunaga, Morita et al., 2008 ). More generally and more precisely it has been assumed that these structures should be described as commensurately or incommensurately modulated four-dimensional structures characterized by modulation vectors $[{\bf q} = \gamma\cdot{\bf c}^*]$ (Lind & Lidin, 2003 ), where γ values are real numbers equal to or around 3(n + 3m)/(2n + 5m) [see equation (3); $[{\bf c}^*]$ is the fundamental reciprocal vector formed by three-layer cubic stacking]. For instance, it has been clarified that, in the thermal equilibrium, Sb₈Te₃ (n = 3 and m = 1) has a homologous structure characterized by a modulation vector $[{\bf q} = 18/11 \cdot {\bf c}^*]$ (Kifune et al., 2005 , 2011 ). Thus, we applied this more universal four-dimensional superspace method for analysis of the Sb–Te compound formed by thermal decomposition [see equation (1)].

Table 2
Space groups for (GeTe)_n(Sb₂Te₃)_m pseudobinary compounds

N shows the number of atomic layers in the unit cell.

Compound	n	m	N	Space group
Ge₃Sb₂Te₆	3	1	33	$[R\bar 3 m]$
Ge₂Sb₂Te₅	2	1	9	$[P\bar 3m1]$
Ge₁Sb₂Te₄	1	1	21	$[R\bar 3 m]$
Ge₁Sb₄Te₇	1	2	12	$[P\bar 3m1]$
Ge₁Sb₆Te₁₀	1	3	51	$[R\bar 3 m]$

3.3. Structures of Ag_3.4In_3.7Sb_76.4Te_16.5 and Sb₈₉Te₁₁ compounds

As the initial structure models for the four-dimensional Rietveld refinements we adopted the layer stacking structures defined by the respective γ values. In other words, in the Sb–Te compounds examined in this study, the modulation functions for Sb and Te atoms were respectively distributed around t = 0 and t = 1/2 (t: internal parameter along the x₄ axis, the fourth crystal axis in four-dimensional space; Lind & Lidin, 2003). This corresponds to a structure in which Sb and Te are placed at 0, 0, 0 and their atomic species are distinguished using crenel functions (for Sb₈₉Te₁₁, width: 0.89 + center: 0 for Sb and width: 0.11 + center: 0.5 for Te). As there is a difference of only one between the atomic numbers of Sb⁵¹ and Te⁵², it is very difficult for us to distinguish the kinds of atoms in their unit cells. We use the assumption that all of the Sb–Te crystals examined in this study have perfectly ordered atomic arrangements like those of other (binary) systems. The intensities of the satellites for Sb–Te compounds are rather weak in general. Those of Sb₈₉Te₁₁ are no exception; almost all of the satellites observed were reproduced by adopting the maximum satellite index of 2 for the Rietveld analyses. The atomic displacements were represented using harmonic functions.

The four-dimensional Rietveld analyses performed with the diffraction patterns in Fig. 1, as mentioned above, provided the structural dependence on the temperature for Ag_3.4In_3.7Sb_76.4Te_16.5 (at low temperatures) and its thermally decomposed materials (at high temperatures). The results of the Rietveld analyses at 545 K for Ag_3.4In_3.7Sb_76.4Te_16.5, whose crystal still maintains an A7-type structure, are shown in Table 1(b) and Fig. 2 (cf. Table 1a, from the three-dimensional Rietveld analysis). In the four-dimensional analysis for this crystal, displacement for only a single atom in a three-dimensional asymmetric unit has to be described by selecting the appropriate one from among several kinds of modulation functions; in this case, the use of a sawtooth function (Dušek et al., 2010 ) was revealed to give better results than a harmonic function, as seen in Fourier maps based on F_o (Fig. 3). We can see from Fig. 4, γ maintained a constant value of 1.5 up to a temperature of around 590 K, at which AgInTe₂ came out. However, above this temperature, γ grew larger with increasing temperature and reached a value of around 1.55 at high temperatures near the melting point of Sb_76.4Te_9.7 (= Sb_88.7Te_11.3 when expressed as a percentage), which was found at around 870 K according to our present high-temperature measurement. The γ value was maintained at around 1.55 even when the powder specimen was cooled back to room temperature. The results of the Rietveld analysis at room temperature are shown in Table 3(a) and Fig. 5. The refined modulation functions of Sb and Te and the corresponding de Wolff section of the observed Fourier map are shown in Fig. 6(a), together with a Fourier map based on F_o. The difference Fourier maps obtained from the determined structure models exhibited few significant residual peaks, which showed the need for further structural modification or improvement. This was similar to those obtained at the high temperatures of 774 and 820 K. The γ values of around 1.55 found in these stagnated structures correspond well with the value of 1.5565 expected from the composition of Sb_88.7Te_11.3. Here we can simply derive γ in terms of x as

$[\gamma = 2 - x/2, \eqno(2)]$

when the chemical formula for the binary system is written as Sb_xTe_1 − x or Bi_xTe_1 − x (Lind & Lidin, 2003). It can be considered that after Sb_76.4Te_9.7 was segregated from AgInTe₂, it revealed its original crystalline nature to change the layer period (γ) from 1.5 (n = 1, m = 0; A7-type six-layer structure) to 1.55 (another long-period layer structure), and it also clarified that, surprisingly enough, even an Sb–Te compound with as much as 89% Sb can exist as a single homologous structure in its binary system. We can obtain

$[\gamma = 3(n + 3m)/(2n + 5m)\,\, {\rm and}\,\, x = 2(n + m)/(2n + 5m), \eqno(3)]$

by comparing Sb_xTe_1 − x with (Sb₂)_n(Sb₂Te₃)_m. The crystal structure (γ ≃ 1.55) at high temperatures at which the γ growth became stagnant can be approximated reasonably well by a commensurately modulated 29-layer structure with n = 12 and m = 1 (γ = 45/29; this three-dimensional structure model is shown in Fig. 7a). We also carried out a Rietveld analysis assuming that this Sb–Te crystal had a commensurately modulated structure with this rational number of γ. As shown in Table 3(d), this analysis gave almost the same good results as in the incommensurate case (however, for this material it could not be concluded that it had transformed to a commensurate three-dimensional structure, in contrast to Sb₈₇Te₁₃, which will be discussed later). The Fourier map obtained from this four-dimensional analysis performed in the commensurate case is almost identical with all those in Fig. 6, as expected. In addition to the γ dependence on temperature of this Sb–Te material, the Sb₈Te₃ sputtered amorphous film showed a small γ value just after the transformation to the crystalline phase. However, γ became larger with increasing temperature to finally obtain its original long-period layer structure. We found that, in addition to the Sb₈Te₃ film, some other Sb–Te films at various compositions show very similar behavior (we will show the results for these materials elsewhere in the near future). These results strongly suggest that not a few (at least) Sb–Te compounds, just after their crystal formations, transiently assume small γ values (it is highly probable that these γ values all start at 3/2), and when adequately treated with heat, they become larger to attain their respective, intrinsic homologous structures, depending on their binary compositions.

Table 3
Final structural parameters

(a) Final structural parameters determined by four-dimensional superspace refinements of Sb₈₉Te₁₁ and conventional three-dimensional refinements of AgInTe₂ at room temperature. The R factors for the entire pattern (Sb₈₉Te₁₁ + AgInTe₂) are R_p = 0.0205 and R_wp = 0.0297. The superspace group for Sb₈₉Te₁₁ was assumed to be $[R\overline{3}m\left(00\gamma \right)00]$ ; on the other hand, $[I\bar 42d]$ was applied for AgInTe₂. Both structures were refined simultaneously using a multiphase refinement. Diffraction data used for the analysis: 5.50 ≤ 2θ ≤ 42.10°. The standard deviations are shown in parentheses. B^s_n represents the positional modulation amplitude, whereas Us represent the atomic displacement parameters. (b) and (c) Final structural parameters obtained by four-dimensional superspace refinements of Sb₈₉Te₁₁ performed by applying sawtooth functions (Dušek et al., 2010) or harmonic functions orthogonalized to the crenel interval (Lind & Lidin, 2003) instead of conventional harmonic functions. The R factors for the entire pattern (Sb₈₉Te₁₁ + AgInTe₂) are R_p = 0.0205 and R_wp = 0.0297, and R_p = 0.0204 and R_wp = 0.0298. (d) The results obtained by the four-dimensional Rietveld analyses performed assuming that Sb₈₉Te₁₁ has a commensurately modulated structure; the modulation period γ was maintained at 45/29 during the refinements. The R factors for the entire pattern are R_p = 0.0202 and R_wp = 0.0295. The superspace group was assumed to be the same as in the above incommensurate case. The electron density map and atomic positions obtained from this analysis in the commensurate case are not shown in this paper, but were almost identical to those seen in Fig. 6. Only the first- and second-order satellites were considered for these four-dimensional analyses (f = 0, 1 and 2 were used for the analyses). This assumption gave sufficiently low R values.

(a) Sb₈₉Te₁₁:

R factors of profile and all reflections
	RF_obs	0.0162
	RF_wobs	0.0159

R factors of main and satellite reflections
Main	RF_obs	0.0144
	RF_wobs	0.0158

R factors of satellites
First order	RF_obs	0.0186
	RF_wobs	0.0196

Second order	RF_obs	0.0138
	RF_wobs	0.0132

γ = 1.5516 (4); a = 4.2969 (1), c = 5.6759 (2) Å.

Atom	g	x	y	z	B^s₁	B^s₂	U¹¹ (Å²)	U³³ (Å²)
Sb	1.0	0	0	0	−0.0394 (4)	0.003 (1)	0.0123 (2)	0.0101 (7)
Te	1.0	0	0	0	−0.27 (1)	–	0.0123	0.0101

AgInTe₂: RF_obs = 0.0253, RF_wobs = 0.0281, a = 6.4275 (3) and c = 12.6089 (9) Å.

Atom	Site	g	x	y	z	U_iso (Å²)
Ag	4b	1/4	0	0	1/2	0.029
In	4a	1/4	0	0	0	0.029
Te	8d	1/2	0.252 (11)	1/4	1/8	0.029 (1)

(b) Sb₈₉Te₁₁:

R factors of profile and all reflections
	RF_obs	0.0168
	RF_wobs	0.0176

R factors of main and satellite reflections
Main	RF_obs	0.0123
	RF_wobs	0.0136

R factors of satellites
First order	RF_obs	0.0221
	RF_wobs	0.0238

Second order	RF_obs	0.0141
	RF_wobs	0.0152

γ = 1.5511 (4); a = 4.2968 (1), c = 5.6758 (2) Å.

Atom	g	x	y	z	B^s₁	z-slope	U¹¹ (Å²)	U³³ (Å²)
Sb	1.0	0	0	0	−0.0345 (3)	−0.009 (4)	0.0122 (2)	0.0102 (9)
Te	1.0	0	0	0	−	0.095 (5)	0.0122	0.0102

AgInTe₂: RF_obs = 0.0227, RF_wobs = 0.0266, a = 6.4275 (3) and c = 12.6079 (9) Å.

Atom	Site	g	x	y	z	U_iso (Å²)
Ag	4b	1/4	0	0	1/2	0.029
In	4a	1/4	0	0	0	0.029
Te	8d	1/2	0.26 (5)	1/4	1/8	0.029 (1)

R factors of profile and all reflections
	RF_obs	0.0156
	RF_wobs	0.0164

R factors of main and satellite reflections
Main	RF_obs	0.0115
	RF_wobs	0.0128

R factors of satellites
First order	RF_obs	0.0202
	RF_wobs	0.0218

Secnd order	RF_obs	0.0141
	RF_wobs	0.0142

γ = 1.5511 (4); a = 4.2968 (1), c = 5.6759 (2) Å.

Atom	g	x	y	z	Zort1	Zort3	U¹¹ (Å²)	U³³ (Å²)
Sb	1.0	0	0	0	−0.0314 (3)	−0.001 (1)	0.0122 (2)	0.0102 (8)
Te	1.0	0	0	0	−0.049 (3)	−	0.0122	0.0102

AgInTe₂: RF_obs = 0.0227, RF_wobs = 0.0257, a = 6.4274 (3) and c = 12.6084 (9) Å.

Atom	Site	g	x	y	z	U_iso (Å²)
Ag	4b	1/4	0	0	1/2	0.028
In	4a	1/4	0	0	0	0.028
Te	8d	1/2	0.255 (6)	1/4	1/8	0.028 (1)

(d) Commensurate case ( $[{t}_{0} = {{1}\over{50}}+{{n}\over{25 }};n = 0, 1, 2,]$ …). Sb₈₉Te₁₁:

R factors of profile and all reflections
	RF_obs	0.0158
	RF_wobs	0.0159

R factors of main and satellite reflections
Main	RF_obs	0.0135
	RF_wobs	0.0150

R factors of satellites
First order	RF_obs	0.0182
	RF_wobs	0.0197

Second order	RF_obs	0.0160
	RF_wobs	0.0137

γ = 45/29; a = 4.2968 (1), c = 5.6758 (2) Å.

Atom	g	x	y	z	B^s₁	B^s₂	U¹¹ (Å²)	U³³ (Å²)
Sb	1	0	0	0	−0.0401 (4)	0.001 (1)	0.0119 (2)	0.0107 (9)
Te	1	0	0	0	−0.31 (2)	−	0.0119	0.0107

AgInTe₂: RF_obs = 0.0241, RF_wobs = 0.0273, a = 6.4276 (3) and c = 12.6082 (9) Å.

Atom	Site	g	x	y	z	U_iso (Å²)
Ag	4b	1.0	0	0	1/2	0.028
In	4a	1.0	0	0	0	0.028
Te	8d	1.0	0.254 (7)	1/4	1/8	0.028 (1)

Figure 2
Observed (+) and calculated (gray line) X-ray diffraction profiles for Ag_3.4In_3.7Sb_76.4Te_16.5 (crystallized into an A7-type single structure) at 545 K by four-dimensional Rietveld analysis in the commensurate case. A difference curve (observed − calculated) appears at the top of the figure; reflection markers are indicated by vertical spikes below the diffraction patterns: the longer ones are for the peaks of the main reflections and the shorter ones for the satellites.

Figure 3
Electron-density maps for Ag_3.4In_3.7Sb_76.4Te_16.5 at 545 K depicted with F_o; only positive contours are drawn at intervals of 200 e Å⁻³. (a) The sawtooth-type modulation function used to describe the displacement of the atom in an asymmetric unit of this three-dimensional crystal is indicated by a solid line. As seen by comparison with map (b) obtained from the Rietveld analysis with a harmonic function, analysis with the sawtooth function provided better results.

Figure 4
Temperature dependences of modulation period γ obtained from four-dimensional structural analyses. The diffraction measurements were first made in the heating process up to 820 K; then the powder specimen was cooled down for a room-temperature measurement. Error bars were omitted because they were smaller than the symbols shown.

Figure 5
Observed (+) and calculated (gray line) X-ray diffraction profiles for AgInTe₂ + Sb₈₉Te₁₁ at room temperature by Rietveld analysis. A difference curve (observed–calculated) appears at the top of the figure; reflection markers are indicated by vertical spikes below the diffraction patterns. Of the first line of spikes, the longer ones are for the peaks of the main reflections of Sb₈₉Te₁₁, and the shorter ones are for the satellites. Those at the bottom show the peak positions for AgInTe₂. As seen in the figure depicted in d spacing, a few unmatched weak peaks were observed, which were presumed to be from another contaminant phase.

Figure 6
Electron-density maps for Sb₈₉Te₁₁ at room temperature based on F_o; only positive contours are drawn at intervals of 500 e A⁻³. These maps, (a), (b) and (c), correspond to the results obtained from three kinds of the Rietveld analyses, (a), (b) and (c), shown in Table 3

. The crystal obtained a stagnant atomic arrangement after high-temperature measurements. These maps are almost identical to Fourier maps based on F_c. The modulations in the displacement of the two atoms in this binary alloy are indicated by the cross-lying curves for Sb in black and for Te in gray. These were analyzed by using different functions to describe the atomic displacement; however, we can see that they are almost the same.

Figure 7
Structural models of (a) Sb₂₆Te₃ and (b) Sb₂₀Te₃. The atomic positions of Sb and Te are shown by gray and black, respectively.

The atomic displacements (modulation functions) have already been shown in a stagnant structure of Sb₈₉Te₁₁ (see Fig. 6). However, just after the phase decomposition, the atomic displacements varied appreciably, as seen in Fig. 8. This figure shows, however, that such a varied atomic arrangement becomes more moderate with increasing temperature, and comes closer to those observed in the stagnated structures. In response to this structural change, although the interatomic distances in Sb₈₉Te₁₁ just after the phase decomposition are rather dispersed, especially for Te–Sb pairs, they converge with the structural inactivation, as seen in Fig. 9. As mentioned above, before the phase decomposition, Sb and Te atoms (and the dopants) were randomly distributed in the A7-type structure. Therefore, it is expected that just after the decomposition, the crystal still has a strongly disordered atomic arrangement. However, during the structural change with increasing temperature, it gradually attains the perfectly ordered structure shown above (Kifune et al., 2011).

Figure 8
Displacements of z as a function of t. Each profile is shifted by dz = 0.5 with respect to the previous one (horizontal lines correspond to dz = 0 for each group of profiles). The centers of modulation functions of Sb and Te atoms are located at the centers of t = 0 and 1/2, which are shown in black and gray, respectively.

Figure 9
Interatomic distances versus t for Sb₈₉Te₁₁: (a) at 820 K near the melting temperature and (b) at 637 K just after phase decomposition. The central atoms are shown in italics.

As mentioned above, we used harmonic functions to describe the atomic displacements. However, to examine them more precisely, the JANA2006 program provides several other functions in addition to the harmonic one. We performed further analyses by using some of these functions. However, these analyses gave us almost the same results as shown in Fig. 6 and Tables 3(b) and (c).

3.4. Suitability of Sb–Te-based compounds for high-speed phase-change recording devices

As has so far been shown, an Sb–Te compound containing Ag and In maintains a six-layer structure (γ = 3/2) up to a high temperature, at which phase separation occurs. On the other hand, Sb–Te films without such dopants show γ values larger than 3/2 immediately after the crystallization. This strongly suggests that the Ag and In dopants play roles in maintaining the simple structure of the Sb–Te matrix. It also inversely implies that every Sb–Te binary-compound film will experience a six-layer structure in a very short time right after the crystal formation because six layers is the simplest and shortest layer structure out of all of the possible homologous structures from Sb (γ = 3/2) to Sb₂Te₃ (γ = 9/5). Many studies (for instance, Matsunaga, Akola et al., 2011) have shown that phase-change chalcogenide amorphous materials have spatially isotropic atomic arrangements; it is highly likely that they crystallize once into simple and spatially isotropic structures, like a cubic crystal, because a six-layer (A7-type) structure can be well approximated by simple cubic lattices (Matsunaga & Yamada, 2004b ).

The atomic configuration in the amorphous phase of this material, which has already been revealed (Matsunaga, Akola et al., 2011), is highly disordered, similar to that of a liquid, and spatially has a completely isotropic symmetry. However, it has also been revealed that it has 3 + 3 coordination structures even in such a disordered atomic arrangement, as well as that of the crystalline phase: that is, both phases have very similar coordination structures, i.e. locally very similar atomic arrangements (it is well known that an A7-type crystal has a 3 + 3 coordination structure; Clark, 1955; Hoffmann, 1988 ). This is one of the major reasons that this material achieves a sufficiently high phase-change speed by locally minimal bond interchanges. As for the dopants, it has been presumed that either or both Ag and In atoms probably raise the crystallization temperature of the amorphous phase to obtain a sufficient endurance for long-term data preservation. In addition, as mentioned above, they make the atomic arrangement of the crystal simple and spatially isotropic, holding the material in a single phase. It is expected that these are indispensable features for high-speed rewritable data storage media. In the near future, however, the individual roles played by Ag and In in the phase change of this material should be clarified.

3.5. Three- or six-layer structure approximation for Sb–Te compounds

In our previous work (Matsunaga et al., 2001) Sb–Te compounds with small amounts of Ag or In were concluded to hold an A7-type structure up to the melting point. However, we must say that these compounds do not have an exact A7-type structure but a long-period modulated structure defined by the binary composition in thermal equilibrium. The A7-type (six-layer) structure is also one of the modulated structures (corresponding to the shortest period one). All the above-mentioned modulated structures can be approximated by a (cubic stacked) three-layer structure, which provides the fundamental lines in the diffraction patterns. If atoms at the 6c site are located at z = 1/4 in the A7-type structure, it corresponds to the three-layer structure. In the previous temperature measurement, one end of the capillary holding the powder specimen was open to the air, which yielded not a little Sb oxide (Fig. 10). This oxide formed a line of unnecessary Bragg peaks, which hindered us from determining the (weak) satellite peaks identifying the layer period of the structure. Further, at that time, such modulated structures were not familiarly associated with the Sb–Te binary system. All these factors made it difficult for us to discern that these Sb–Te-based alloys can take modulated structures. Thus, in previous work the A7-type structure was exclusively applied in the structural analyses, irrespective of the measurement temperature, which provided apparently sufficient results. In addition, in this work the same structural analysis was carried out to confirm the reproducibility of the previous work; we analyzed the structures by applying this simple 6R structure to them. The results are shown in Table 4. As shown in this table, the R factors were sufficiently low and the positional parameter z gradually increased with temperature (which meant that the structure model for the Rietveld analysis gradually became closer to the three-layer structure), which accurately reproduced the previous results. However, the agreement between the profiles of the observed and calculated intensities became worse as the temperature rose, especially for the (weak) satellite reflections. On the other hand, those obtained through the four-dimensional analyses showed good agreement with each other, even at high temperatures near the melting point, as seen in Fig. 10. This strongly indicates that at high temperatures beyond the phase separation (or in the thermal equilibrium), this Sb–Te compound is not an A7-type structure (γ = 3/2) itself but one of the homologous structures defined by γ > 3/2.

Table 4
Final structural parameters and R factors

(a) Final structural parameters for Ag_3.4In_3.7Sb_76.4Te_16.5 refined using conventional three-dimensional Rietveld analyses. In these analyses it was assumed that this material kept an unchanged A7-type structure while AgInTe₂ formed at around 590 K with increasing temperature. The space group $[R\bar 3m]$ was applied to all structure models, despite the fact that for z = 1/4 R3m or R32 should be used instead (Matsunaga et al., 2001). The standard deviations are shown in parentheses, and the reliability factors are indicated as percentages. (b) The R-factors (shown as percentages) obtained through the four-dimensional analyses (see Table 5a) are also tabulated for comparison.

(a)						(b)
T (K)	a (Å)	c (Å)	z	RF_obs	RF_wobs	RF_obs	RF_wobs
435	4.3010 (6)	11.202 (2)	0.2356 (1)	1.37	1.83
453	4.3013 (6)	11.212 (2)	0.2359 (1)	1.47	2.15
471	4.3015 (6)	11.223 (2)	0.2360 (1)	1.90	2.15
490	4.3019 (6)	11.242 (2)	0.2362 (1)	2.06	2.35
508	4.3033 (6)	11.267 (2)	0.2364 (1)	1.73	2.33
545	4.3037 (5)	11.290 (1)	0.2365 (1)	1.57	2.38
591	4.3084 (1)	11.330 (1)	0.2365 (1)	1.80	2.36	1.71	1.82
637	4.3094 (3)	11.357 (1)	0.2373 (1)	1.84	2.02	1.49	1.71
682	4.3110 (4)	11.399 (1)	0.2400 (1)	2.37	2.79	1.23	1.29
728	4.3127 (3)	11.438 (1)	0.2460 (4)	2.65	3.60	1.43	1.45
774	4.3159 (3)	11.439 (1)	0.25	2.25	2.14	1.60	1.74
820	4.3202 (3)	11.429 (1)	0.25	1.94	1.81	1.75	1.78

Figure 10
Observed (+) and calculated (gray line) X-ray diffraction profiles for Ag_3.4In_3.7Sb_76.4Te_16.5 (Sb₈₇Te₁₃ + Sb₂O₃) at 873 K by Rietveld analysis in the commensurate case (see Table 5

b1). This diffraction data were obtained in 1999 at SPring-8 (Matsunaga et al., 2001

). A difference curve (observed − calculated) appears at the top of the figure; reflection markers are indicated by vertical spikes below the diffraction patterns. Of the first line of spikes the longer ones are for the peaks of the main reflections of Sb₈₇Te₁₃, and the shorter ones are for the satellites. Those at the bottom show the peak positions for Sb₂O₃.

The present examination clarified that this Sb–Te compound has a long-period modulated structure like that of the aforementioned Sb₈₉Te₁₁. The modulation period γ kept a constant value of almost 1.5 up to a temperature of around 600 K, at which the oxidation of Sb started. However, above this temperature, just as in the Sb₈₉Te₁₁ case, γ grew larger with increasing temperature and reached a value of around 1.56 at high temperatures near the melting point (in contrast, in the previous experiment, Bragg peaks corresponding to AgInTe₂ were hardly observed for some reason). This γ value indicated that the composition of the compound should be ca Sb₈₇Te₁₃ [see equation (2)]. Here, we ignore the locations of Ag and In because they are minor elements. We carried out four-dimensional structural analyses for the two cases where this Sb–Te crystal took an incommensurately or commensurately modulated structure. As shown in Table 5 these analyses gave almost the same good results, when γ = 36/23 (n = 9, m = 1; Sb_87.0Te_13.0) was applied in the commensurate case (this three-dimensional structure model is shown in Fig. 7b). However, the results of the commensurate case could be considered somewhat better than those of the incommensurate case (cf. Table 5a with Table 5b1), in contrast to the examination of Sb₈₉Te₁₁. In addition, we can find a clear t₀ dependence of the R values in the results of the Rietveld analyses performed in the commensurate case (cf. Table 5b1 with Table 5b2). This strongly suggests that this Sb₈₇Te₁₃ compound eventually obtained a (probably stable) commensurate structure through rearrangement of the atoms from the A7-type atomic configuration after sufficient heat treatment for this material, as observed in the case of Sb₈Te₃ (Kifune et al., 2011). Generally, the determination between the commensurate and incommensurate case seems to be beyond the information contained in our powder data. However, we believe that it is very likely that many of these compounds ultimately obtain commensurate structures after sufficient heat treatment. We intend to conduct further experiments and analyses for these materials to reveal their structural features more precisely.

Table 5
Final R factors for Sb₈₇Te₁₃ at 773 K obtained through four-dimensional Rietveld analyses performed assuming that it has (a) an incommensurately modulated structure (R factors for the entire pattern are R_p = 0.0201 and R_wp = 0.0294) and (b) a commensurately modulated structure

The modulation period, γ, was maintained at 36/23 during the refinements. The R factors for the entire pattern are: (b1) R_wp = 0.0201 and R_p = 0.0294 for t₀ = 1/46 + n/23 and (b2) R_wp = 0.0251 and R_p = 0.0364 for t₀ = 0 + n/23. The superspace group for Sb₈₇Te₁₃ was assumed to be $[R\overline{3}m\left(00\gamma \right)00]$ for both analyses; on the other hand, $[Fd\bar 3m]$ was applied for Sb₂O₃. The diffraction data used for the analysis: 3.0 ≤ 2θ ≤ 30.5°. The standard deviations are shown in parentheses. B^s_n represents the positional modulation amplitude; Us represent the atomic displacement parameters. Only the first satellites were considered for these analyses.

(a) Incommensurate case Sb₈₇Te₁₃:

R factors of profile and all reflections (Sb₈₉Te₁₁₊)
	RF_obs	0.0300
	R_wp	0.0189

R factors of profile and all reflections
	RF_obs	0.0207
	R_wp	0.0106

R factors of satellites
First order	RF_obs	0.0414
	RF_wobs	0.0325

Second order	RF_obs	0.0492
	RF_wobs	0.0280

γ = 1.5660 (5); a = 4.3180 (2), c = 5.7268 (4) Å.

Atom	g	x	y	z	B^s₁	B^s₂	U¹¹ (Å²)	U³³ (Å²)
Sb	1	0	0	0	−0.0306 (1)	0.0097 (3)	0.0368 (1)	0.0408 (1)
Te	1	0	0	0	−0.276 (3)	−	0.0368	0.0408

Sb₂O₃: RF_obs = 0.0384, RF_wobs = 0.0343, a = 11.2470 (6) Å.

Atom	Site	g	x	y	z	U_iso (Å²)
Sb	4b	1.0	0.8870 (1)	x	x	0.026 (1)
O	8d	1.0	0.188 (2)	0	0	0.026

(b1) Commensurate case ( $[{t}_{0} = {{1}\over{46}}+{{n}\over{23 }};n = 0, 1, 2,]$ …). Sb₈₇Te₁₃:

R factors of profile and all reflections (Sb₈₉Te₁₁₊)
	RF_obs	0.0293
	R_wp	0.0176

R factors of profile and all reflections
Main	RF_obs	0.0192
	R_wp	0.0100

R factors of satellites
First order	RF_obs	0.0424
	RF_wobs	0.0320

Second order	RF_obs	0.0472
	RF_wobs	0.0246

γ = 36/23; a = 4.3181 (2), c = 5.7267 (4) Å.

Atom	g	x	y	z	B^s₁	B^s₂	U¹¹ (Å²)	U³³ (Å²)
Sb	1.0	0	0	0	−0.0306 (1)	0.0105 (3)	0.0368 (1)	0.0413 (3)
Te	1.0	0	0	0	−0.285 (3)	−	0.0368	0.0413

Sb₂O₃: RF_obs = 0.0360, RF_wobs = 0.0314, a = 11.2471 (6) Å.

Atom	Site	g	x	y	z	U_iso (Å²)
Sb	4b	1.0	0.8870 (1)	x	x	0.026 (1)
O	8d	1.0	0.188 (2)	0	0	0.026

(b2) Commensurate case ( $[{t}_{0} = 0+{{n}\over{23 }};n = 0, 1, 2,]$ …). Sb₈₇Te₁₃:

R factors of profile and all reflections (Sb₈₉Te₁₁₊)
	RF_obs	0.0455
	R_wp	0.0257

R factors of profile and all reflections
Main	RF_obs	0.0321
	R_wp	0.0155

R factors of satellites
First order	RF_obs	0.0719
	RF_wobs	0.0636

Second order	RF_obs	0.0559
	RF_wobs	0.0246

γ = 36/23; a = 4.3181 (2), c = 5.7275 (5) Å.

Atom	g	x	y	z	B^s₁	B^s₂	U¹¹ (Å²)	U³³ (Å²)
Sb	1.0	0	0	0	−0.0243 (2)	0.0065 (3)	0.0382 (2)	0.0331 (4)
Te	1.0	0	0	0	−0.326 (2)	–	0.0382	0.0331

Sb₂O₃: RF_obs = 0.0552, RF_wobs = 0.0358, a = 11.2478 (8) Å.

Atom	Site	g	x	y	z	U_iso (Å²)
Sb	4b	1.0	0.8871 (2)	x	x	0.021 (2)
O	8d	1.0	0.187 (3)	0	0	0.021

4. Conclusions

An Ag_3.4In_3.7Sb_76.4Te_16.5 quaternary amorphous film was first crystallized into an A7-type structure, in which the four types of atoms randomly occupied the atomic sites, right after the phase transformation. However, as the temperature was raised, this single crystalline phase separated into two crystalline phases, AgInTe₂ and an Sb–Te binary compound. Of these two crystals, AgInTe₂ was stable up to the melting point. In contrast, the latter crystal, Sb₈₉Te₁₁, had a modulated layer structure, and its modulation vector grew with an increasing in temperature.

Supporting information

B-IncStrDB reference: 6732EXfQbW

Crystal structure: contains datablocks global, I, II, III, IV, V. DOI: 10.1107/S0108768112039961/dk5006sup1.cif

Rietveld powder data: contains datablock I. DOI: 10.1107/S0108768112039961/dk5006Isup2.rtv

Rietveld powder data: contains datablock II. DOI: 10.1107/S0108768112039961/dk5006IIsup3.rtv

Rietveld powder data: contains datablock III. DOI: 10.1107/S0108768112039961/dk5006IIIsup4.rtv

Rietveld powder data: contains datablock IV. DOI: 10.1107/S0108768112039961/dk5006IVsup5.rtv

Rietveld powder data: contains datablock V. DOI: 10.1107/S0108768112039961/dk5006Vsup6.rtv

Computing details top

Program(s) used to refine structure: Jana2000 (Petricek, Dusek & Palatinus, 2000) for (IV), (V). Software used to prepare material for publication: Jana2000 (Petricek, Dusek & Palatinus, 2000) for (IV), (V).

Figures top

(I) top

Crystal data top

Ag_0.034In_0.037Sb_0.764Te_0.165	Z = 3
M_r = 122	F(000) = 1834
Trigonal, R3m(00γ)00†	D_x = 6.709 Mg m⁻³
q = 1.500000c*	? radiation, λ = 0.41873 Å
a = 4.3037 (5) Å	T = 545 K
c = 5.6452 (6) Å	?, ? × ? × ? mm
V = 90.55 (2) Å³

Data collection top

2θ_min = 5.5°, 2θ_max = 31.5°, 2θ_step = 0.01°

Refinement top

R_p = 0.020	56 parameters
R_wp = 0.029	0 restraints
R_exp = 0.030	12 constraints
R(F) = 0.013	Weighting scheme based on measured s.u.'s
χ² = 0.960	(Δ/σ)_max = 7.061
2601 data points	Background function: 36 Legendre polynoms
Profile function: Pseudo-Voigt	Preferred orientation correction: none

Crystal data top

Ag_0.034In_0.037Sb_0.764Te_0.165	V = 90.55 (2) Å³
M_r = 122	Z = 3
Trigonal, R3m(00γ)00†	? radiation, λ = 0.41873 Å
q = 1.500000c*	T = 545 K
a = 4.3037 (5) Å	?, ? × ? × ? mm
c = 5.6452 (6) Å

Data collection top

2θ_min = 5.5°, 2θ_max = 31.5°, 2θ_step = 0.01°

Refinement top

R_p = 0.020	2601 data points
R_wp = 0.029	56 parameters
R_exp = 0.030	0 restraints
R(F) = 0.013	(Δ/σ)_max = 7.061
χ² = 0.960

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Sb1	0	0	0	0.0296 (6)	0.764
Te1	0	0	0	0.0296 (5)	0.165
Ag1	0	0	0	0.0296 (5)	0.034
In1	0	0	0	0.0296 (5)	0.037

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Sb1	0.0229 (5)	0.0229 (5)	0.0431 (14)	0.0114 (2)	0	0
Te1	0.0229 (5)	0.022892	0.0431 (14)	0.011446	0	0
Ag1	0.0229 (5)	0.022892	0.0431 (14)	0.011446	0	0
In1	0.0229 (5)	0.022892	0.0431 (14)	0.011446	0	0

(II) top

Crystal data top

Sb_0.89Te_0.11	Z = 3
M_r = 122.4	F(000) = 800
Trigonal, R3m(00γ)00†	D_x = 6.716 Mg m⁻³
q = 1.551587c*	? radiation, λ = 0.41873 Å
a = 4.29686 (13) Å	T = 293 K
c = 5.67590 (19) Å	?, ? × ? × ? mm
V = 90.75 (1) Å³

Data collection top

2θ_min = 5.5°, 2θ_max = 42.1°, 2θ_step = 0.01°

Refinement top

R_p = 0.021	68 parameters
R_wp = 0.030	0 restraints
R_exp = 0.030	4 constraints
R(F) = 0.016	Weighting scheme based on measured s.u.'s
χ² = 1.000	(Δ/σ)_max = 5.113
3661 data points	Background function: 36 Legendre polynoms
Profile function: Pseudo-Voigt	Preferred orientation correction: March & Dollase

Crystal data top

Sb_0.89Te_0.11	V = 90.75 (1) Å³
M_r = 122.4	Z = 3
Trigonal, R3m(00γ)00†	? radiation, λ = 0.41873 Å
q = 1.551587c*	T = 293 K
a = 4.29686 (13) Å	?, ? × ? × ? mm
c = 5.67590 (19) Å

Data collection top

2θ_min = 5.5°, 2θ_max = 42.1°, 2θ_step = 0.01°

Refinement top

R_p = 0.021	3661 data points
R_wp = 0.030	68 parameters
R_exp = 0.030	0 restraints
R(F) = 0.016	(Δ/σ)_max = 5.113
χ² = 1.000

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Sb1	0	0	0	0.0116 (3)	0.887
Te1	0	0	0	0.0116 (3)	0.113

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Sb1	0.0123 (2)	0.0123 (2)	0.0101 (7)	0.00614 (12)	0	0
Te1	0.0123 (2)	0.012285	0.0101 (7)	0.006143	0	0

(III) top

Crystal data top

AgInTe₂	Z = 4
M_r = 477.9	F(000) = 800
Tetragonal, I42d	D_x = 6.092 Mg m⁻³
Hall symbol: I -4;2bw	? radiation, λ = 0.41873 Å
a = 6.4275 (3) Å	T = 293 K
c = 12.6089 (9) Å	?, ? × ? × ? mm
V = 520.91 (5) Å³

Data collection top

2θ_min = 5.5°, 2θ_max = 42.1°, 2θ_step = 0.01°

Refinement top

R_p = 0.021	68 parameters
R_wp = 0.030	0 restraints
R_exp = 0.030	4 constraints
R(F) = 0.016	Weighting scheme based on measured s.u.'s
χ² = 1.000	(Δ/σ)_max = 5.113
3661 data points	Background function: 36 Legendre polynoms
Profile function: Pseudo-Voigt	Preferred orientation correction: none

Crystal data top

AgInTe₂	V = 520.91 (5) Å³
M_r = 477.9	Z = 4
Tetragonal, I42d	? radiation, λ = 0.41873 Å
a = 6.4275 (3) Å	T = 293 K
c = 12.6089 (9) Å	?, ? × ? × ? mm

Data collection top

2θ_min = 5.5°, 2θ_max = 42.1°, 2θ_step = 0.01°

Refinement top

R_p = 0.021	3661 data points
R_wp = 0.030	68 parameters
R_exp = 0.030	0 restraints
R(F) = 0.016	(Δ/σ)_max = 5.113
χ² = 1.000

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Ag1	0	0	0.5	0.0289 (13)*
In1	0	0	0	0.0289 (13)*
Te2	0.252 (11)	0.25	0.125	0.0289 (13)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
?	?	?	?	?	?	?

(IV) top

Crystal data top

Sb_0.87Te_0.13	Z = 3
M_r = 122.5	F(000) = 1841
Trigonal, R3m(00γ)00†	D_x = 6.598 Mg m⁻³
q = 1.56522c*	X-ray radiation, λ = 0.41853 Å
a = 4.3181 Å	T = 773 K
c = 5.7267 Å	?, ? × ? × ? mm
V = 92.47 Å³

† Symmetry operations: (1) x₁, x₂, x₃, x₄; (2) −x₂, x₁−x₂, x₃, x₄; (3) −x₂, −x₁, x₃, x₄; (4) −x₁+x₂, −x₁, x₃, x₄; (5) x₁, x₁−x₂, x₃, x₄; (6) −x₁+x₂, x₂, x₃, x₄; (7) −x₁, −x₂, −x₃, −x₄; (8) x₂, −x₁+x₂, −x₃, −x₄; (9) x₂, x₁, −x₃, −x₄; (10) x₁−x₂, x₁, −x₃, −x₄; (11) −x₁, −x₁+x₂, −x₃, −x₄; (12) x₁−x₂, −x₂, −x₃, −x₄; (13) 2/3+x₁, 1/3+x₂, 1/3+x₃, x₄; (14) 2/3−x₂, 1/3+x₁−x₂, 1/3+x₃, x₄; (15) 2/3−x₂, 1/3−x₁, 1/3+x₃, x₄; (16) 2/3−x₁+x₂, 1/3−x₁, 1/3+x₃, x₄; (17) 2/3+x₁, 1/3+x₁−x₂, 1/3+x₃, x₄; (18) 2/3−x₁+x₂, 1/3+x₂, 1/3+x₃, x₄; (19) 2/3−x₁, 1/3−x₂, 1/3−x₃, −x₄; (20) 2/3+x₂, 1/3−x₁+x₂, 1/3−x₃, −x₄; (21) 2/3+x₂, 1/3+x₁, 1/3−x₃, −x₄; (22) 2/3+x₁−x₂, 1/3+x₁, 1/3−x₃, −x₄; (23) 2/3−x₁, 1/3−x₁+x₂, 1/3−x₃, −x₄; (24) 2/3+x₁−x₂, 1/3−x₂, 1/3−x₃, −x₄; (25) 1/3+x₁, 2/3+x₂, 2/3+x₃, x₄; (26) 1/3−x₂, 2/3+x₁−x₂, 2/3+x₃, x₄; (27) 1/3−x₂, 2/3−x₁, 2/3+x₃, x₄; (28) 1/3−x₁+x₂, 2/3−x₁, 2/3+x₃, x₄; (29) 1/3+x₁, 2/3+x₁−x₂, 2/3+x₃, x₄; (30) 1/3−x₁+x₂, 2/3+x₂, 2/3+x₃, x₄; (31) 1/3−x₁, 2/3−x₂, 2/3−x₃, −x₄; (32) 1/3+x₂, 2/3−x₁+x₂, 2/3−x₃, −x₄; (33) 1/3+x₂, 2/3+x₁, 2/3−x₃, −x₄; (34) 1/3+x₁−x₂, 2/3+x₁, 2/3−x₃, −x₄; (35) 1/3−x₁, 2/3−x₁+x₂, 2/3−x₃, −x₄; (36) 1/3+x₁−x₂, 2/3−x₂, 2/3−x₃, −x₄.

Data collection top

2θ_min = 3.02°, 2θ_max = 30.5°, 2θ_step = 0.02°

Refinement top

R_p = 0.020	Profile function: Pseudo-Voigt
R_wp = 0.029	59 parameters
R_exp = 0.024	Weighting scheme based on measured s.u.'s
R(F) = 0.030	(Δ/σ)_max = 0.628
χ² = NOT FOUND	Background function: 36 Legendre polynoms
1375 data points	Preferred orientation correction: none

Crystal data top

Sb_0.87Te_0.13	V = 92.47 Å³
M_r = 122.5	Z = 3
Trigonal, R3m(00γ)00†	X-ray radiation, λ = 0.41853 Å
q = 1.56522c*	T = 773 K
a = 4.3181 Å	?, ? × ? × ? mm
c = 5.7267 Å

Data collection top

2θ_min = 3.02°, 2θ_max = 30.5°, 2θ_step = 0.02°

Refinement top

R_p = 0.020	χ² = NOT FOUND
R_wp = 0.029	1375 data points
R_exp = 0.024	59 parameters
R(F) = 0.030	(Δ/σ)_max = 0.628

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Sb1	0	0	0	0.03832 (14)	0.870
Te1	0	0	0	0.03832 (12)	0.130

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Sb1	0.03681 (14)	0.03681 (14)	0.0413 (3)	0.01841 (7)	0	0
Te1	0.03681 (14)	0.03681	0.0413 (3)	0.018405	0	0

Bond lengths (Å) top

	Average	Minimum	Maximum
Sb1—Sb1ⁱ	3.1499 (14)	2.9339 (7)	3.3530 (8)
Sb1—Sb1ⁱⁱ	3.1499 (14)	2.9339 (7)	3.3530 (8)
Sb1—Sb1ⁱⁱⁱ	3.1499 (14)	2.9339 (7)	3.3530 (8)
Sb1—Sb1^iv	3.1499 (14)	2.9339 (7)	3.3530 (8)
Sb1—Sb1^v	3.1499 (14)	2.9339 (7)	3.3530 (8)
Sb1—Sb1^vi	3.1499 (14)	2.9339 (7)	3.3530 (8)
Sb1—Te1ⁱ	3.1483 (6)	2.8798 (9)	3.4307 (9)
Sb1—Te1ⁱⁱ	3.1483 (6)	2.8798 (9)	3.4307 (9)
Sb1—Te1ⁱⁱⁱ	3.1483 (6)	2.8798 (9)	3.4307 (9)
Sb1—Te1^iv	3.1491 (6)	2.8804 (9)	3.4316 (9)
Sb1—Te1^v	3.1491 (6)	2.8804 (9)	3.4316 (9)
Sb1—Te1^vi	3.1491 (6)	2.8804 (9)	3.4316 (9)

Symmetry codes: (i) x₁−1/3, x₂−2/3, x₃+1/3, x₄; (ii) x₁−1/3, x₂+1/3, x₃+1/3, x₄; (iii) x₁+2/3, x₂+1/3, x₃+1/3, x₄; (iv) x₁−2/3, x₂−1/3, x₃−1/3, x₄; (v) x₁+1/3, x₂−1/3, x₃−1/3, x₄; (vi) x₁+1/3, x₂+2/3, x₃−1/3, x₄.

(V) top

Crystal data top

Sb₂O₃	Z = 16
M_r = 291.5	F(000) = 1841
Cubic, Fd3m	D_x = 5.442 Mg m⁻³
Hall symbol: -F 4vw;2vw;3	X-ray radiation, λ = 0.41853 Å
a = 11.2471 Å	T = 773 K
V = 1422.71 Å³	?, ? × ? × ? mm

Data collection top

2θ_min = 3.02°, 2θ_max = 30.5°, 2θ_step = 0.02°

Refinement top

R_p = 0.020	Profile function: Pseudo-Voigt
R_wp = 0.029	59 parameters
R_exp = 0.024	Weighting scheme based on measured s.u.'s
R(F) = 0.030	(Δ/σ)_max = 0.628
χ² = NOT FOUND	Background function: 36 Legendre polynoms
1375 data points	Preferred orientation correction: none

Crystal data top

Sb₂O₃	Z = 16
M_r = 291.5	X-ray radiation, λ = 0.41853 Å
Cubic, Fd3m	T = 773 K
a = 11.2471 Å	?, ? × ? × ? mm
V = 1422.71 Å³

Data collection top

2θ_min = 3.02°, 2θ_max = 30.5°, 2θ_step = 0.02°

Refinement top

R_p = 0.020	χ² = NOT FOUND
R_wp = 0.029	1375 data points
R_exp = 0.024	59 parameters
R(F) = 0.030	(Δ/σ)_max = 0.628

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Sb2	0.88704 (13)	0.88704 (13)	0.88704 (13)	0.0264 (14)*
O1	0.188 (2)	0	0	0.0264 (14)*

Bond lengths (Å) top

Sb2—O1ⁱ	1.986 (10)	O1—O1^viii	2.99 (2)
Sb2—O1ⁱⁱ	2.936 (16)	O1—O1^ix	2.979 (8)
Sb2—O1ⁱⁱⁱ	2.936 (16)	O1—O1^x	2.99 (2)
Sb2—O1^iv	1.986 (10)	O1—O1^xi	2.979 (8)
Sb2—O1^v	2.936 (16)	O1—O1^xii	2.99 (2)
Sb2—O1^vi	1.986 (10)	O1—O1^xiii	2.979 (8)
O1—O1^vii	2.979 (8)	O1—O1^xiv	2.99 (2)

Symmetry codes: (i) −x+1, −y+1, z+1; (ii) −x+5/4, z+3/4, y+3/4; (iii) y+3/4, −x+5/4, z+3/4; (iv) −z+1, −x+1, y+1; (v) z+3/4, y+3/4, −x+5/4; (vi) −y+1, z+1, −x+1; (vii) −y+1/4, x−1/4, z−1/4; (viii) z, x, y; (ix) y+1/4, −x+1/4, z+1/4; (x) −z, −x, y; (xi) z+1/4, −y−1/4, x−1/4; (xii) y, z, x; (xiii) z+1/4, y+1/4, −x+1/4; (xiv) −y, z, −x.

Experimental details

	(I)	(II)	(III)	(IV)
Crystal data
Chemical formula	Ag_0.034In_0.037Sb_0.764Te_0.165	Sb_0.89Te_0.11	AgInTe₂	Sb_0.87Te_0.13
M_r	122	122.4	477.9	122.5
Crystal system, space group	Trigonal, R3m(00γ)00†	Trigonal, R3m(00γ)00‡	Tetragonal, I42d	Trigonal, R3m(00γ)00§
Temperature (K)	545	293	293	773
Wave vectors	q = 1.500000c*	q = 1.551587c*	I -4;2bw	q = 1.56522c*
a, b, c (Å)	4.3037 (5), 4.3037 (5), 5.6452 (6)	4.29686 (13), 4.29686 (13), 5.67590 (19)	90, 90, 90	4.3181, 4.3181, 5.7267
α, β, γ (°)	90, 90, 120	90, 90, 120	520.91 (5)	90, 90, 120
V (Å³)	90.55 (2)	90.75 (1)	4	92.47
Z	3	3	800	3
Radiation type	?, λ = 0.41873 Å	?, λ = 0.41873 Å	–	X-ray, λ = 0.41853 Å
µ (mm⁻¹)	–	–	?	–
Specimen shape, size (mm)	?, ? × ? × ?	?, ? × ? × ?		?, ? × ? × ?

Data collection
Diffractometer	?	?	?	?
Specimen mounting	?	?	?	?
Data collection mode	?	?	?	?
Scan method	?	?	?	?
2θ values (°)	2θ_min = 5.5 2θ_max = 31.5 2θ_step = 0.01	2θ_min = 5.5 2θ_max = 42.1 2θ_step = 0.01	2θ_min = 5.5 2θ_max = 42.1 2θ_step = 0.01	2θ_min = 3.02 2θ_max = 30.5 2θ_step = 0.02

Refinement
R factors and goodness of fit	R_p = 0.020, R_wp = 0.029, R_exp = 0.030, R(F) = 0.013, χ² = 0.960	R_p = 0.021, R_wp = 0.030, R_exp = 0.030, R(F) = 0.016, χ² = 1.000	R_p = 0.021, R_wp = 0.030, R_exp = 0.030, R(F) = 0.016, χ² = 1.000	R_p = 0.020, R_wp = 0.029, R_exp = 0.024, R(F) = 0.030, χ² = NOT FOUND
No. of data points	2601	3661	3661	1375
No. of parameters	56	68	68	59
No. of restraints	0	0	0	?
(Δ/σ)_max	7.061	5.113	5.113	0.628

	(V)
Crystal data
Chemical formula	Sb₂O₃
M_r	291.5
Crystal system, space group	Cubic, Fd3m
Temperature (K)	773
Wave vectors	-F 4vw;2vw;3
a, b, c (Å)	90, 90, 90
α, β, γ (°)	1422.71
V (Å³)	16
Z	1841
Radiation type	–
µ (mm⁻¹)	?
Specimen shape, size (mm)

Data collection
Diffractometer	?
Specimen mounting	?
Data collection mode	?
Scan method	?
2θ values (°)	2θ_min = 3.02 2θ_max = 30.5 2θ_step = 0.02

Refinement
R factors and goodness of fit	R_p = 0.020, R_wp = 0.029, R_exp = 0.024, R(F) = 0.030, χ² = NOT FOUND
No. of data points	1375
No. of parameters	59
No. of restraints	?
(Δ/σ)_max	0.628

† Symmetry operations: (1) x₁, x₂, x₃, x₄; (2) −x₂, x₁−x₂, x₃, x₄; (3) −x₁+x₂, −x₁, x₃, x₄; (4) x₂, x₁, −x₃, −x₄; (5) x₁−x₂, −x₂, −x₃, −x₄; (6) −x₁, −x₁+x₂, −x₃, −x₄; (7) −x₁, −x₂, −x₃, −x₄; (8) x₂, −x₁+x₂, −x₃, −x₄; (9) x₁−x₂, x₁, −x₃, −x₄; (10) −x₂, −x₁, x₃, x₄; (11) −x₁+x₂, x₂, x₃, x₄; (12) x₁, x₁−x₂, x₃, x₄; (13) x₁+2/3, x₂+1/3, x₃+1/3, x₄; (14) −x₂+2/3, x₁−x₂+1/3, x₃+1/3, x₄; (15) −x₁+x₂+2/3, −x₁+1/3, x₃+1/3, x₄; (16) x₂+2/3, x₁+1/3, −x₃+1/3, −x₄; (17) x₁−x₂+2/3, −x₂+1/3, −x₃+1/3, −x₄; (18) −x₁+2/3, −x₁+x₂+1/3, −x₃+1/3, −x₄; (19) −x₁+2/3, −x₂+1/3, −x₃+1/3, −x₄; (20) x₂+2/3, −x₁+x₂+1/3, −x₃+1/3, −x₄; (21) x₁−x₂+2/3, x₁+1/3, −x₃+1/3, −x₄; (22) −x₂+2/3, −x₁+1/3, x₃+1/3, x₄; (23) −x₁+x₂+2/3, x₂+1/3, x₃+1/3, x₄; (24) x₁+2/3, x₁−x₂+1/3, x₃+1/3, x₄; (25) x₁+1/3, x₂+2/3, x₃+2/3, x₄; (26) −x₂+1/3, x₁−x₂+2/3, x₃+2/3, x₄; (27) −x₁+x₂+1/3, −x₁+2/3, x₃+2/3, x₄; (28) x₂+1/3, x₁+2/3, −x₃+2/3, −x₄; (29) x₁−x₂+1/3, −x₂+2/3, −x₃+2/3, −x₄; (30) −x₁+1/3, −x₁+x₂+2/3, −x₃+2/3, −x₄; (31) −x₁+1/3, −x₂+2/3, −x₃+2/3, −x₄; (32) x₂+1/3, −x₁+x₂+2/3, −x₃+2/3, −x₄; (33) x₁−x₂+1/3, x₁+2/3, −x₃+2/3, −x₄; (34) −x₂+1/3, −x₁+2/3, x₃+2/3, x₄; (35) −x₁+x₂+1/3, x₂+2/3, x₃+2/3, x₄; (36) x₁+1/3, x₁−x₂+2/3, x₃+2/3, x₄.

‡ Symmetry operations: (1) x₁, x₂, x₃, x₄; (2) −x₂, x₁−x₂, x₃, x₄; (3) −x₁+x₂, −x₁, x₃, x₄; (4) x₂, x₁, −x₃, −x₄; (5) x₁−x₂, −x₂, −x₃, −x₄; (6) −x₁, −x₁+x₂, −x₃, −x₄; (7) −x₁, −x₂, −x₃, −x₄; (8) x₂, −x₁+x₂, −x₃, −x₄; (9) x₁−x₂, x₁, −x₃, −x₄; (10) −x₂, −x₁, x₃, x₄; (11) −x₁+x₂, x₂, x₃, x₄; (12) x₁, x₁−x₂, x₃, x₄; (13) x₁+2/3, x₂+1/3, x₃+1/3, x₄; (14) −x₂+2/3, x₁−x₂+1/3, x₃+1/3, x₄; (15) −x₁+x₂+2/3, −x₁+1/3, x₃+1/3, x₄; (16) x₂+2/3, x₁+1/3, −x₃+1/3, −x₄; (17) x₁−x₂+2/3, −x₂+1/3, −x₃+1/3, −x₄; (18) −x₁+2/3, −x₁+x₂+1/3, −x₃+1/3, −x₄; (19) −x₁+2/3, −x₂+1/3, −x₃+1/3, −x₄; (20) x₂+2/3, −x₁+x₂+1/3, −x₃+1/3, −x₄; (21) x₁−x₂+2/3, x₁+1/3, −x₃+1/3, −x₄; (22) −x₂+2/3, −x₁+1/3, x₃+1/3, x₄; (23) −x₁+x₂+2/3, x₂+1/3, x₃+1/3, x₄; (24) x₁+2/3, x₁−x₂+1/3, x₃+1/3, x₄; (25) x₁+1/3, x₂+2/3, x₃+2/3, x₄; (26) −x₂+1/3, x₁−x₂+2/3, x₃+2/3, x₄; (27) −x₁+x₂+1/3, −x₁+2/3, x₃+2/3, x₄; (28) x₂+1/3, x₁+2/3, −x₃+2/3, −x₄; (29) x₁−x₂+1/3, −x₂+2/3, −x₃+2/3, −x₄; (30) −x₁+1/3, −x₁+x₂+2/3, −x₃+2/3, −x₄; (31) −x₁+1/3, −x₂+2/3, −x₃+2/3, −x₄; (32) x₂+1/3, −x₁+x₂+2/3, −x₃+2/3, −x₄; (33) x₁−x₂+1/3, x₁+2/3, −x₃+2/3, −x₄; (34) −x₂+1/3, −x₁+2/3, x₃+2/3, x₄; (35) −x₁+x₂+1/3, x₂+2/3, x₃+2/3, x₄; (36) x₁+1/3, x₁−x₂+2/3, x₃+2/3, x₄.

§ Symmetry operations: (1) x₁, x₂, x₃, x₄; (2) −x₂, x₁−x₂, x₃, x₄; (3) −x₂, −x₁, x₃, x₄; (4) −x₁+x₂, −x₁, x₃, x₄; (5) x₁, x₁−x₂, x₃, x₄; (6) −x₁+x₂, x₂, x₃, x₄; (7) −x₁, −x₂, −x₃, −x₄; (8) x₂, −x₁+x₂, −x₃, −x₄; (9) x₂, x₁, −x₃, −x₄; (10) x₁−x₂, x₁, −x₃, −x₄; (11) −x₁, −x₁+x₂, −x₃, −x₄; (12) x₁−x₂, −x₂, −x₃, −x₄; (13) 2/3+x₁, 1/3+x₂, 1/3+x₃, x₄; (14) 2/3−x₂, 1/3+x₁−x₂, 1/3+x₃, x₄; (15) 2/3−x₂, 1/3−x₁, 1/3+x₃, x₄; (16) 2/3−x₁+x₂, 1/3−x₁, 1/3+x₃, x₄; (17) 2/3+x₁, 1/3+x₁−x₂, 1/3+x₃, x₄; (18) 2/3−x₁+x₂, 1/3+x₂, 1/3+x₃, x₄; (19) 2/3−x₁, 1/3−x₂, 1/3−x₃, −x₄; (20) 2/3+x₂, 1/3−x₁+x₂, 1/3−x₃, −x₄; (21) 2/3+x₂, 1/3+x₁, 1/3−x₃, −x₄; (22) 2/3+x₁−x₂, 1/3+x₁, 1/3−x₃, −x₄; (23) 2/3−x₁, 1/3−x₁+x₂, 1/3−x₃, −x₄; (24) 2/3+x₁−x₂, 1/3−x₂, 1/3−x₃, −x₄; (25) 1/3+x₁, 2/3+x₂, 2/3+x₃, x₄; (26) 1/3−x₂, 2/3+x₁−x₂, 2/3+x₃, x₄; (27) 1/3−x₂, 2/3−x₁, 2/3+x₃, x₄; (28) 1/3−x₁+x₂, 2/3−x₁, 2/3+x₃, x₄; (29) 1/3+x₁, 2/3+x₁−x₂, 2/3+x₃, x₄; (30) 1/3−x₁+x₂, 2/3+x₂, 2/3+x₃, x₄; (31) 1/3−x₁, 2/3−x₂, 2/3−x₃, −x₄; (32) 1/3+x₂, 2/3−x₁+x₂, 2/3−x₃, −x₄; (33) 1/3+x₂, 2/3+x₁, 2/3−x₃, −x₄; (34) 1/3+x₁−x₂, 2/3+x₁, 2/3−x₃, −x₄; (35) 1/3−x₁, 2/3−x₁+x₂, 2/3−x₃, −x₄; (36) 1/3+x₁−x₂, 2/3−x₂, 2/3−x₃, −x₄.

Computer programs: Jana2000 (Petricek, Dusek & Palatinus, 2000).

Selected bond lengths (Å) for (IV) top

	Average	Minimum	Maximum
Sb1—Sb1ⁱ	3.1499 (14)	2.9339 (7)	3.3530 (8)
Sb1—Sb1ⁱⁱ	3.1499 (14)	2.9339 (7)	3.3530 (8)
Sb1—Sb1ⁱⁱⁱ	3.1499 (14)	2.9339 (7)	3.3530 (8)
Sb1—Sb1^iv	3.1499 (14)	2.9339 (7)	3.3530 (8)
Sb1—Sb1^v	3.1499 (14)	2.9339 (7)	3.3530 (8)
Sb1—Sb1^vi	3.1499 (14)	2.9339 (7)	3.3530 (8)
Sb1—Te1ⁱ	3.1483 (6)	2.8798 (9)	3.4307 (9)
Sb1—Te1ⁱⁱ	3.1483 (6)	2.8798 (9)	3.4307 (9)
Sb1—Te1ⁱⁱⁱ	3.1483 (6)	2.8798 (9)	3.4307 (9)
Sb1—Te1^iv	3.1491 (6)	2.8804 (9)	3.4316 (9)
Sb1—Te1^v	3.1491 (6)	2.8804 (9)	3.4316 (9)
Sb1—Te1^vi	3.1491 (6)	2.8804 (9)	3.4316 (9)

Selected bond lengths (Å) for (V) top

Sb2—O1ⁱ	1.986 (10)	O1—O1^viii	2.99 (2)
Sb2—O1ⁱⁱ	2.936 (16)	O1—O1^ix	2.979 (8)
Sb2—O1ⁱⁱⁱ	2.936 (16)	O1—O1^x	2.99 (2)
Sb2—O1^iv	1.986 (10)	O1—O1^xi	2.979 (8)
Sb2—O1^v	2.936 (16)	O1—O1^xii	2.99 (2)
Sb2—O1^vi	1.986 (10)	O1—O1^xiii	2.979 (8)
O1—O1^vii	2.979 (8)	O1—O1^xiv	2.99 (2)

Acknowledgements

The synchrotron radiation experiments were performed on BL02B2 at SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (proposal Nos. 2010B0084, 2010B1827 and 2011B0030. We express our sincere gratitude to Dr J. Kim at JASRI and to graduate students K. Shakudo, Y. Sato and T. Tachizawa of the Graduate School of Science at Osaka Prefecture University for their assistance with the experiments. The structural models in Fig. 7 were displayed using the Java Structure Viewer (JSV 1.08 lite) created by Dr Steffen Weber.

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Volume 68| Part 6| December 2012| Pages 559-570

doi:10.1107/S0108768112039961

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research papers\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Structural transformation of Sb-based high-speed phase-change material

1. Introduction

2. Experimental

3. Results and discussion

3.1. Crystals observed in this experiment

3.2. Homologous structures

3.3. Structures of Ag3.4In3.7Sb76.4Te16.5 and Sb89Te11 compounds

3.4. Suitability of Sb–Te-based compounds for high-speed phase-change recording devices

3.5. Three- or six-layer structure approximation for Sb–Te compounds

4. Conclusions

Supporting information

Acknowledgements

References

research papers

3.3. Structures of Ag_3.4In_3.7Sb_76.4Te_16.5 and Sb₈₉Te₁₁ compounds