research communications
2Ni0.5Hf1.5(PO4)3
of the langbeinite-type phosphate KaCollege of Physics, Jilin University 2699 Qianjin St., 130012 Changchun, People's Republic of China, bShimUkraine LLC, 18, Chigorina Str., office 429, 01042 Kyiv, Ukraine, and cV. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, 41 Pr. Nauki, 03028 Kyiv, Ukraine
*Correspondence e-mail: zvigo@yandex.ru
Polycrystalline potassium nickel(II) hafnium(IV) tris(orthophosphate), a langbeinite-type phosphate, was synthesized by a solid-state method. The three-dimensional framework of the title compound is built up from two types of [MO6] octahedra [the M sites are occupied by Hf:Ni in ratios of 0.754 (8):0.246 (8) and 0.746 (8):0.254 (8), respectively] and [PO4] tetrahedra are connected via O vertices. The K+ cations are located in two positions within large cavities of the framework, having coordination numbers of 9 and 12. The Hf, Ni and K sites lie on threefold rotation axes, while the P and O atoms are situated in general positions.
CCDC reference: 2026681
1. Chemical context
Langbeinite-related complex oxides have a variety of interesting properties, for example, ferroelectricity or ferroelasticity (Norberg, 2002). In particular, complex phosphates of this type have attracted attention for their high thermal and chemical stability, and many different combinations for structural substitutions are possible (Wulff et al., 1992; Slobodyanik et al., 2012). These characteristics made it possible to propose the family of langbeinite-type phosphates as successful hosts for the immobilization of (Orlova et al., 2011). Moreover, in the last decade rare-earth (RE)-containing langbeinite-type phosphates have been studied intensively owing to their outstanding luminescent properties and applications in LEDs (Liang & Wang, 2011; Liu et al., 2016; Sadhasivam et al., 2017; Terebilenko et al., 2020). Accordingly, further studies of iso- and heterovalent substitution within the cationic sites of the langbeinite structure are important. Structural data for langbeinite-type Hf-containing phosphates are scarce and include only K1.93Mn0.53Hf1.47(PO4)3 (Ogorodnyk et al., 2007a) and K2YHf(PO4)3 (Ogorodnyk et al., 2009).
In this report, we describe the powder X-ray 2Ni0.5Hf1.5(PO4)3 (I), structurally isotypic with the mineral langbeinite, K2Mg2(SO4)3 (Zemann & Zemann, 1957).
using the for the multimetal phosphate K2. Structural commentary
As shown in Fig. 1, in the structure of (I) the K, Ni and Hf sites are localized on threefold rotation axes (Wyckoff position 4 a), while the P and all O atoms occupy general sites (12 b). Two metallic sites (Hf,Ni)1 and (Hf,Ni)2 show mixed occupancy with a Hf:Ni ratio of about 0.75:0.25 (nickel proportion 0.246 (8) for the M1 site and 0.254 (8) for the M2 site). A similar MII:MIV ratio was also observed for isostructural phosphates of general composition MIMII0.5MIV1.5(PO4)3, viz. K2Ni0.5Ti1.5(PO4)3 (Ogorodnyk et al., 2007b), Rb2Ni0.5Ti1.5(PO4)3 (Strutynska et al., 2015), K2Co0.5Ti1.5(PO4)3 and K2Mn0.5Ti1.5(PO4)3 (Ogorodnyk et al., 2006), K2Ni0.5Zr1.5(PO4)3 (Zatovsky, 2014), K1.96Mn0.57Zr1.43(PO4)3 and K1.93Mn0.53Hf1.47(PO4)3 (Ogorodnyk et al., 2007a).
The (Hf,Ni)—O distances in (I) are 1.989 (15) and 2.121 (14) Å for the [(Hf,Ni)1O6] octahedron, and 2.131 (17) and 2.172 (16) Å for the [(Hf,Ni)2O6] octahedron. The two independent [(Hf,Ni)O6] octahedra are linked by three [PO4] tetrahedra to form an [M2P3O18] building unit (Fig. 2). These building units are arranged along three directions (threefold rotation axes) and linked together via oxygen vertices, forming a three-dimensional framework structure. Pairs of K+ cations (two independent sites) are localized in large cavities of the resulting framework. The potassium cations are found in 9- and 12-coordination by O atoms with K—O distances ranging from 2.854 (17) Å to 3.372 (18) Å (Table 1, Fig. 3), leading to distorted polyhedra. The [PO4] tetrahedron shows considerable distortion (Table 1).
For (I), the calculation of BVS (bond-valence sums) was performed using the parameters for Hf from Brese & O'Keeffe (1991), for Ni from Brown (private communication, 2001) and for K, P from Brown & Altermatt (1985). The corresponding occupation of the M sites by Hf and Ni atoms was taken into account. The sum of BVS of the cations is +23.67 valence units (v.u.), which is close to the −24 v.u. required for the O atoms.
3. Synthesis and crystallization
Compound (I) was synthesized using a solid-state reaction method. A well-ground starting mixture of 3.157 g HfO2, 0.374 g NiO, 2.361 g KPO3 and 1.150 g NH4H2PO4 (molar ratio K:Ni:Hf:P = 4:1:3:6) was transferred to a ceramic crucible and pre-heated at 553 K for 2 h. The powder was re-ground, heated at 823 K for 3 h and then milled for 0.5 h in an agate mortar. The resulting fine powder was pressed into a pill and finally calcined at 1273 K for 100 h. The sample was ground before performing powder XRD data collection. (SEM, Magellan 400, recorded at 10 kV) showed that the obtained sample is an aggregate of small crystallites with a size less than 1 µm (Fig. 4).
4. Refinement
The experimental, calculated and difference pattern are shown in Fig. 5. Crystal data, data collection and structure details are summarized in Table 2. Structure was performed using K2YHf(PO4)3 (Ogorodnyk et al., 2009) as a starting model. A modified pseudo-Voigt function (Thompson et al., 1987) was used for the profile The similar shape of the transition-metal octahedra indicated that both M positions are occupied by Ni and Hf simultaneously. For the of their occupancies their coordinates and Uiso values were constrained together, and the sum of occupancies constrained to unity for both sites.
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Supporting information
CCDC reference: 2026681
https://doi.org/10.1107/S2056989020012062/wm5581sup1.cif
contains datablocks global, I. DOI:Rietveld powder data: contains datablock I. DOI: https://doi.org/10.1107/S2056989020012062/wm5581Isup2.rtv
Data collection: Software supplied by instrument manufacturer (https://www.haoyuanyiqi.com/en/xsxysy/s_23_30.html); cell
FULLPROF (Rodriguez-Carvajal, 2020); data reduction: Software supplied by instrument manufacturer (https://www.haoyuanyiqi.com/en/xsxysy/s_23_30.html); program(s) used to solve structure: isomorphic replacement; program(s) used to refine structure: FULLPROF (Rodriguez-Carvajal, 2020); molecular graphics: DIAMOND (Brandenburg, 2006); software used to prepare material for publication: PLATON (Spek, 2020), WinGX (Farrugia, 2012) and enCIFer (Allen et al., 2004).K2Ni0.5Hf1.5(PO4)3 | Dx = 4.228 Mg m−3 |
Mr = 660.19 | Cu Kα radiation, λ = 1.540598 Å |
Cubic, P213 | T = 293 K |
Hall symbol: P 2ac 2ab 3 | Particle morphology: tetrahedra |
a = 10.12201 (5) Å | yellow |
V = 1037.05 (1) Å3 | flat_sheet, 15 × 15 mm |
Z = 4 | Specimen preparation: Prepared at 293 K and 101.3 kPa |
Haoyuan Instrument Co. Ltd DX-2700B diffractometer | Data collection mode: reflection |
Radiation source: X-ray tube, X-ray | Scan method: step |
Graphite monochromator | 2θmin = 10.008°, 2θmax = 105.008°, 2θstep = 0.020° |
Specimen mounting: glass container |
Rp = 6.111 | 107 parameters |
Rwp = 7.831 | 3 restraints |
Rexp = 4.020 | 3 constraints |
RBragg = 4.709 | Standard least squares refinement |
R(F) = 3.21 | (Δ/σ)max = 0.001 |
4751 data points | Background function: Linear Interpolation between a set background points with refinable heights |
Profile function: Thompson-Cox-Hastings pseudo-Voigt * Axial divergence asymmetry | Preferred orientation correction: Modified March's Function |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
K1 | 0.7042 (5) | 0.7042 (5) | 0.7042 (5) | 0.028 (4)* | |
K2 | 0.9319 (8) | 0.9319 (8) | 0.9319 (8) | 0.044 (4)* | |
Ni1 | 0.14423 (16) | 0.14423 (16) | 0.14423 (16) | 0.0022 (12)* | 0.246 (8) |
Ni2 | 0.4147 (2) | 0.4147 (2) | 0.4147 (2) | 0.0019 (12)* | 0.254 (8) |
Hf1 | 0.14423 (16) | 0.14423 (16) | 0.14423 (16) | 0.0022 (12)* | 0.754 (8) |
Hf2 | 0.4147 (2) | 0.4147 (2) | 0.4147 (2) | 0.0019 (12)* | 0.746 (8) |
P1 | 0.4624 (6) | 0.2349 (10) | 0.1229 (9) | 0.004 (2)* | |
O1 | 0.3218 (13) | 0.2314 (17) | 0.0752 (16) | 0.011 (6)* | |
O2 | 0.5508 (14) | 0.3023 (16) | 0.0201 (15) | 0.008 (4)* | |
O3 | 0.5028 (13) | 0.0973 (17) | 0.1500 (18) | 0.008 (6)* | |
O4 | 0.4953 (16) | 0.2985 (17) | 0.2533 (14) | 0.009 (6)* |
K1—O1i | 2.854 (17) | Hf1—O1 | 2.121 (14) |
K1—O4ii | 3.082 (17) | Hf1—O2x | 1.989 (15) |
K1—O2ii | 3.103 (15) | Hf1—O1xi | 2.121 (14) |
K1—O1iii | 2.854 (17) | Hf1—O2xii | 1.989 (15) |
K1—O4iv | 3.082 (17) | Hf2—O4 | 2.172 (16) |
K1—O2iv | 3.103 (15) | Hf2—O3i | 2.131 (17) |
K1—O1v | 2.854 (17) | Hf2—O4xi | 2.172 (16) |
K1—O4vi | 3.082 (17) | Hf2—O3iii | 2.131 (17) |
K1—O2vi | 3.103 (15) | Ni1—O1 | 2.121 (14) |
K2—O3ii | 2.944 (16) | Ni1—O2x | 1.989 (15) |
K2—O2vii | 2.987 (18) | Ni1—O1xi | 2.121 (14) |
K2—O4ii | 3.041 (18) | Ni1—O2xii | 1.989 (15) |
K2—O4vii | 3.372 (18) | Ni2—O4 | 2.172 (16) |
K2—O3iv | 2.944 (16) | Ni2—O3i | 2.131 (17) |
K2—O2viii | 2.987 (18) | Ni2—O4xi | 2.172 (16) |
K2—O4iv | 3.041 (18) | Ni2—O3iii | 2.131 (17) |
K2—O4viii | 3.372 (18) | P1—O1 | 1.503 (15) |
K2—O3vi | 2.944 (16) | P1—O2 | 1.533 (17) |
K2—O2ix | 2.987 (18) | P1—O3 | 1.48 (2) |
K2—O4vi | 3.041 (18) | P1—O4 | 1.506 (18) |
K2—O4ix | 3.372 (18) | ||
O1—Hf1—O2x | 90.8 (6) | O1xi—Ni1—O2x | 87.8 (6) |
O1—Hf1—O1xi | 93.7 (6) | O2x—Ni1—O2xii | 87.7 (6) |
O1—Hf1—O2xii | 175.2 (6) | O1xi—Ni1—O2xii | 90.8 (6) |
O1xi—Hf1—O2x | 87.8 (6) | O3i—Ni2—O4 | 95.2 (6) |
O2x—Hf1—O2xii | 87.7 (6) | O4—Ni2—O4xi | 94.5 (6) |
O1xi—Hf1—O2xii | 90.8 (6) | O3iii—Ni2—O4 | 168.5 (6) |
O3i—Hf2—O4 | 95.2 (6) | O3i—Ni2—O4xi | 78.6 (6) |
O4—Hf2—O4xi | 94.5 (6) | O3i—Ni2—O3iii | 92.7 (6) |
O3iii—Hf2—O4 | 168.5 (6) | O3iii—Ni2—O4xi | 95.2 (6) |
O3i—Hf2—O4xi | 78.6 (6) | O1—P1—O2 | 110.2 (10) |
O3i—Hf2—O3iii | 92.7 (6) | O1—P1—O3 | 107.4 (10) |
O3iii—Hf2—O4xi | 95.2 (6) | O1—P1—O4 | 120.1 (10) |
O1—Ni1—O2x | 90.8 (6) | O2—P1—O3 | 112.6 (10) |
O1—Ni1—O1xi | 93.7 (6) | O2—P1—O4 | 106.0 (10) |
O1—Ni1—O2xii | 175.2 (6) | O3—P1—O4 | 100.3 (11) |
Symmetry codes: (i) −x+1, y+1/2, −z+1/2; (ii) −x+3/2, −y+1, z+1/2; (iii) −z+1/2, −x+1, y+1/2; (iv) −y+1, z+1/2, −x+3/2; (v) y+1/2, −z+1/2, −x+1; (vi) z+1/2, −x+3/2, −y+1; (vii) −z+1, x+1/2, −y+3/2; (viii) −y+3/2, −z+1, x+1/2; (ix) x+1/2, −y+3/2, −z+1; (x) x−1/2, −y+1/2, −z; (xi) z, x, y; (xii) −z, x−1/2, −y+1/2. |
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