inorganic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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Li2Ca1.5Nb3O10 from X-ray powder data

aDepartment of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China, and bDepartment of Nanomaterial and Nanochemistry, Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
*Correspondence e-mail: kbtang@ustc.edu.cn

(Received 7 January 2011; accepted 23 February 2011; online 12 March 2011)

Lithium calcium niobium oxide (2/1.5/3/10), Li2Ca1.5Nb3O10, has been synthesized by conventional solid-state reaction. Its structure consists of triple-layer perovskite slabs of corner-sharing NbO6 octa­hedra inter­leaved with lithium ions; Ca cations partially occupy the perovskite A sites at 75% occupancy probability. All eight atoms in the asymmetric unit are on special positions: one Nb atom has site symmetry 4/mmm; the second Nb, both K, the Sr and two O atoms have site symmetry 4mm; the remaining two O atoms have site symmetries 2mm. and mmm., respectively.

Related literature

For background to Ruddlesden–Popper layered perovskites, see: Schaak & Mallouk (2002[Schaak, R. E. & Mallouk, T. E. (2002). Chem. Mater. 14, 1455-1471.]). Structures of related crystal A-site deficient three-layer Ruddlesden–Popper phases have been reported for K2Sr1.5Ta3O10 (Le Berre et al., 2002[Le Berre, F., Crosnier-Lopez, M. P., Laligant, Y. & Fourquet, J. L. (2002). J. Mater. Chem. 12, 258-263.]), Li4Sr3Nb6O20 (Bhuvanesh et al., 1999a[Bhuvanesh, N. S. P., Crosnier-Lopez, M. P., Bohnke, O., Emery, J. & Fourquet, J. L. (1999a). Chem. Mater. 11, 634-641.]), Li2La1.78Nb0.66Ti2.34O10 (Bhuvanesh et al., 1999b[Bhuvanesh, N. S. P., Crosnier-Lopez, M. P., Duroy, H. & Fourquet, J. L. (1999b). J. Mater. Chem. 9, 3093-3100.]) and Li2CaTa2O7 (Liang et al., 2008[Liang, Z., Tang, K., Shaoa, Q., Lia, G., Zenga, S. & Zheng, H. (2008). J. Solid State Chem. 181, 964-970.]). For crystallographic background, see: Howard (1982[Howard, C. J. (1982). J. Appl. Cryst. 15, 615-620.]); Thompson et al. (1987[Thompson, P., Cox, D. E. & Hastings, J. B. (1987). J. Appl. Cryst. 20, 79-83.]).

Experimental

Crystal data
  • Li2Ca1.5Nb3O10

  • Mr = 512.71

  • Tetragonal, I 4/m m m

  • a = 3.87880 (6) Å

  • c = 26.2669 (4) Å

  • V = 395.19 (1) Å3

  • Z = 2

  • Cu Kα radiation, λ = 1.54060, 1.54443 Å

  • T = 298 K

  • flat sheet, 20 × 20 mm

Data collection
  • PANalytical X'pert PRO diffractometer

  • Specimen mounting: packed powder pellet

  • Data collection mode: reflection

  • Scan method: continuous

  • 2θmin = 10.004°, 2θmax = 129.939°, 2θstep = 0.017°

Refinement
  • Rp = 0.050

  • Rwp = 0.076

  • Rexp = 0.009

  • R(F2) = 0.068

  • χ2 = 0.706

  • 7056 data points

  • 51 parameters

Table 1
Selected bond lengths (Å)

Nb1—O1i 1.9394 (1)
Nb1—O4 2.027 (11)
Nb2—O2 1.689 (8)
Nb2—O3i 1.9704 (11)
Nb2—O4 2.029 (11)
Ca1—O1ii 2.805 (4)
Ca1—O3ii 2.567 (4)
Ca1—O4iii 2.7427 (1)
Li1—O2 1.599 (4)
Symmetry codes: (i) x, y-1, z; (ii) [x-{\script{1\over 2}}, y-{\script{1\over 2}}, z+{\script{1\over 2}}]; (iii) [x+{\script{1\over 2}}, y+{\script{1\over 2}}, z+{\script{1\over 2}}].

Data collection: X'pert Data Collector (PANalytical, 2003[PANalytical (2003). X'pert Data Collector and X'pert Highscore. PANalytical BV, Almelo, The Netherlands.]); cell refinement: GSAS (Larson & Von Dreele, 2004[Larson, A. C. & Von Dreele, R. B. (2004). General Structure Analysis System (GSAS). Report LAUR 86-748. Los Alamos National Laboratory, New Mexico, USA.]) and EXPGUI (Toby, 2001[Toby, B. H. (2001). J. Appl. Cryst. 34, 210-213.]); data reduction: X'pert Highscore (PANalytical, 2003[PANalytical (2003). X'pert Data Collector and X'pert Highscore. PANalytical BV, Almelo, The Netherlands.]); method used to solve structure: coordinates taken from an isotypic compound (Bhuvanesh et al., 1999a; Liang et al., 2008[Liang, Z., Tang, K., Shaoa, Q., Lia, G., Zenga, S. & Zheng, H. (2008). J. Solid State Chem. 181, 964-970.]); program(s) used to refine structure: GSAS and EXPGUI; molecular graphics: DIAMOND (Brandenburg, 1999[Brandenburg, K. (1999). DIAMOND. Crystal Impact GbR, Bonn, Germany.]); software used to prepare material for publication: publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

Supporting information


Comment top

Layered perovskites that belong to the Ruddlesden-Popper family have a general formula A'2[An-1BnO3n+1] (Schaak et al., 2002), where B is a small transition metal cation, A is a larger s-, d-, or f-block cation and A' is always an alkali cation. The Ruddlesden-Popper phases which are intergrowths of the perovskite and rocksalt structures posses a wide variety of interesting properties including superconductivity, colossal magnetoresistance, ferroelectricity, and catalytic activity. Related crystal structures of A sites deficiency three-layer Ruddlesden-Popper phases have been reported for K2Sr1.5Ta3O10(Le Berre et al., 2002), Li2La1.78Nb0.66Ti2.34O10 ( Bhuvanesh et al., 1999b), and Li4Sr3Nb6O20 ( Bhuvanesh et al., 1999a).

Fig. 1 shows the observed, calculated and difference plots of the Rietveld refinement. We applied the March-Dollase formalism for a correction of the 00l preferential orientation which is frequently observed in Rietveld refinement of layered perovskites.

The structure of the compound is illustrated in Fig. 2. It is formed from two differently stacked NbO6 octahedra thick slabs cut along the c direction. Two successive layers are shifted by (a+b)/2 with Ca cations partially occupying the 12-coordinated sites. The Li cations occupy the interlayer spacing at Wyckoff site 8f and not the 4e site since the distance between two adjacent layers is short. Ca cations partially occupy the perovskite A sites at 75% occupancy probability. The Nb cations are coordinated by six oxygen atoms to form NbO6 octahedra with Nb—O distances ranging from 1.689 (8) to 2.029 (11) Å. The octahedra forming the outer layer of the slabs are characterized by off-centering of the Nb atoms, leading to four equal equatorial Nb—O distances within the perovskite layers [1.9704 (11) Å], a short Nb—O bond toward the interlayer spacing [1.689 (8) Å], and a long opposite Nb—O bond [2.029 (11) Å]. The octahedra forming the inner layer are less distorted with four equal equatorial Nb—O distances[1.9394 (1) Å] and other two equal Nb—O distances [2.027 (11) Å] parallel to the c axis. These type of distorsions are well known in triple-layer perovskites.

Related literature top

For background to Ruddlesden–Popper layered perovskites, see: Schaak & Mallouk (2002). Structures of related crystal A-site deficient three-layer Ruddlesden–Popper phases have been reported for K2Sr1.5Ta3O10 (Le Berre et al., 2002), Li4Sr3Nb6O20 (Bhuvanesh et al., 1999a), Li2La1.78Nb0.66Ti2.34O10 (Bhuvanesh et al., 1999b) and Li2CaTa2O7 (Liang et al., 2008). Profile coefficients for Simpson's rule integration of the pseudo-Voigt function were taked from Howard (1982) and Thompson et al. (1987).

Experimental top

The sample was prepared by conventional solid-state reaction. Stoichiometric amounts of Li2CO3,CaCO3 and Nb2O5 were mixed, ground, and calcined at 1423 K for 6 h with one intermediate grid. An excess amount of Li2CO3(20 mol%) was added to compensate for the loss due to the volatilization of alkali metal carbonate.

Refinement top

The crystal structures of Li4Sr3Nb6O20 (Bhuvanesh et al., 1999a) and Li2CaTa2O7 (Liang et al., 2008) were used as a starting model for the Rietveld refinement. The X-ray powder diffraction patterns of Li2Ca1.5Nb3O10 were indexed in a body-centered tetragonal space group I4/mmm. Structure refinement was carried out by the Rietveld method using the GSAS profile refinement program (Larson & Von Dreele, 2004). The site occupancy factors of Ca and Li were set at 0.75 and 0.50, respectively in view of the close ressemblance of the cell parameters with those of the related structures and they were not further refined. The corresponding isotropic atomic displacement parameters of all oxygen atoms and niobium atoms were constrained to be equal, respectively. The March-Dollase option in the EXPGUI program (Toby, 2001) was applied to correct 00l preferential orientation.

Computing details top

Data collection: X'pert Data Collector (PANalytical, 2003); cell refinement: GSAS (Larson & Von Dreele, 2004) and EXPGUI (Toby, 2001); data reduction: X'pert Highscore (PANalytical, 2003); program(s) used to solve structure: coordinates taken from an isotypic compound (Bhuvanesh et al., 1999a) and (Liang et al., 2008); program(s) used to refine structure: GSAS (Larson & Von Dreele, 2004) and EXPGUI (Toby, 2001); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top
[Figure 1] Fig. 1. Experimental and calculated X-ray diffraction pattern of Li2Ca1.5Nb3O10. The difference profile is given at the bottom. The Bragg positions are indicated by the vertical markers below the observed pattern.
[Figure 2] Fig. 2. The crystal structure of Li2Ca1.5Nb3O10 in a projection along [010].
Lithium calcium niobium oxide (2/1.5/3/10) top
Crystal data top
Li2Ca1.5Nb3O10Z = 2
Mr = 512.71Dx = 4.309 Mg m3
Tetragonal, I4/mmmCu Kα radiation, λ = 1.540600, 1.544430 Å
Hall symbol: -I 4 2T = 298 K
a = 3.87880 (6) Åwhite
c = 26.2669 (4) Åflat sheet, 20 × 20 mm
V = 395.19 (1) Å3Specimen preparation: Prepared at 1423 K
Data collection top
PANalytical X'pert PRO
diffractometer
Data collection mode: reflection
Radiation source: sealed tubeScan method: continuous
Graphite monochromator2θmin = 10.004°, 2θmax = 129.939°, 2θstep = 0.017°
Specimen mounting: packed powder pellet
Refinement top
Refinement on F2Profile function: CW Profile function number 2 with 18 terms Profile coefficients for Simpson's rule integration of pseudovoigt function C.J. Howard (1982). J. Appl. Cryst.,15,615-620. P. Thompson, D.E. Cox & J.B. Hastings (1987). J. Appl. Cryst.,20,79-83. #1(GU) = 149.621 #2(GV) = -120.364 #3(GW) = 31.573 #4(LX) = 1.000 #5(LY) = 17.840 #6(trns) = 0.000 #7(asym) = 0.0000 #8(shft) = 0.0000 #9(GP) = 0.000 #10(stec)= 0.00 #11(ptec)= 0.00 #12(sfec)= 0.00 #13(L11) = 0.000 #14(L22) = 0.000 #15(L33) = 0.000 #16(L12) = 0.000 #17(L13) = 0.000 #18(L23) = 0.000 Peak tails are ignored where the intensity is below 0.0010 times the peak Aniso. broadening axis 0.0 0.0 1.0
Least-squares matrix: full51 parameters
Rp = 0.0500 restraints
Rwp = 0.0764 constraints
Rexp = 0.009 w = 1/[σ2(Fo2) + (0.0677P)2]
where P = (Fo2 + 2Fc2)/3
R(F2) = 0.06796(Δ/σ)max = 0.01
χ2 = 0.706Background function: GSAS Background function number 1 with 36 terms. Shifted Chebyshev function of 1st kind 1: 10229.8 2: -3178.07 3: 2423.18 4: -808.112 5: 540.944 6: -198.924 7: 271.065 8: 94.4177 9: 234.644 10: 188.507 11: 146.243 12: 265.504 13: -11.6147 14: 51.8836 15: 137.742 16: 26.3316 17: -53.6065 18: 3.80136 19: 279.859 20: -56.8162 21: -60.3405 22: 50.5886 23: 41.8504 24: 9.38150 25: -48.8258 26: -20.5686 27: -49.8098 28: 74.7145 29: -37.5745 30: 90.5252 31: -21.2918 32: -56.1545 33: 0.932266 34: -17.8446 35: -27.9120 36: -2.66006
7056 data pointsPreferred orientation correction: March-Dollase AXIS 1 Ratio= 0.89341 h= 0.000 k= 0.000 l= 1.000 Prefered orientation correction range: Min= 0.84444, Max= 1.40236
Excluded region(s): none
Crystal data top
Li2Ca1.5Nb3O10V = 395.19 (1) Å3
Mr = 512.71Z = 2
Tetragonal, I4/mmmCu Kα radiation, λ = 1.540600, 1.544430 Å
a = 3.87880 (6) ÅT = 298 K
c = 26.2669 (4) Åflat sheet, 20 × 20 mm
Data collection top
PANalytical X'pert PRO
diffractometer
Scan method: continuous
Specimen mounting: packed powder pellet2θmin = 10.004°, 2θmax = 129.939°, 2θstep = 0.017°
Data collection mode: reflection
Refinement top
Rp = 0.050χ2 = 0.706
Rwp = 0.0767056 data points
Rexp = 0.00951 parameters
R(F2) = 0.067960 restraints
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
Nb10.00.00.00.0112 (3)*
Nb20.00.00.15442 (5)0.0112 (3)*
Ca10.00.00.5771 (2)0.0157 (3)*0.75
O10.00.50.00.0132 (3)*
O20.00.00.2187 (3)0.0132 (3)*
O30.00.50.1412 (2)0.0132 (3)*
O40.00.00.0772 (4)0.0132 (3)*
Li10.250.250.250.0182 (3)*0.5
Geometric parameters (Å, º) top
Nb1—O1i1.9394 (1)Ca1—O1ii2.805 (4)
Nb1—O42.027 (11)Ca1—O3ii2.567 (4)
Nb2—O21.689 (8)Ca1—O4iii2.7427 (1)
Nb2—O3i1.9704 (11)Li1—O21.599 (4)
Nb2—O42.029 (11)
O1i—Nb1—O1180.0O1ii—Ca1—O3vi118.25 (6)
O1i—Nb1—O1iv90.0O1ii—Ca1—O4ii60.7 (2)
O1i—Nb1—O490.0O1ii—Ca1—O4v119.3 (3)
O2—Nb2—O3i100.17 (18)O1v—Ca1—O3v87.19 (9)
O2—Nb2—O4180.0O3ii—Ca1—O3v98.1 (2)
O3i—Nb2—O3159.7 (4)O3ii—Ca1—O3vi64.58 (12)
O3i—Nb2—O3iv88.21 (6)O3ii—Ca1—O4vii57.70 (19)
O3i—Nb2—O479.83 (18)O3ii—Ca1—O4v122.3 (3)
O1ii—Ca1—O1v87.49 (16)O4ii—Ca1—O4vii90.0000 (2)
O1ii—Ca1—O1vi58.54 (9)O4ii—Ca1—O4iii180.0000 (3)
O1ii—Ca1—O3v174.68 (17)O2—Li1—O2viii180.0
Symmetry codes: (i) x, y1, z; (ii) x1/2, y1/2, z+1/2; (iii) x+1/2, y+1/2, z+1/2; (iv) y, x, z; (v) x+1/2, y1/2, z+1/2; (vi) y+1/2, x1/2, z+1/2; (vii) x1/2, y+1/2, z+1/2; (viii) x1/2, y1/2, z1/2.

Experimental details

Crystal data
Chemical formulaLi2Ca1.5Nb3O10
Mr512.71
Crystal system, space groupTetragonal, I4/mmm
Temperature (K)298
a, c (Å)3.87880 (6), 26.2669 (4)
V3)395.19 (1)
Z2
Radiation typeCu Kα, λ = 1.540600, 1.544430 Å
Specimen shape, size (mm)Flat sheet, 20 × 20
Data collection
DiffractometerPANalytical X'pert PRO
diffractometer
Specimen mountingPacked powder pellet
Data collection modeReflection
Scan methodContinuous
2θ values (°)2θmin = 10.004 2θmax = 129.939 2θstep = 0.017
Refinement
R factors and goodness of fitRp = 0.050, Rwp = 0.076, Rexp = 0.009, R(F2) = 0.06796, χ2 = 0.706
No. of data points7056
No. of parameters51

Computer programs: X'pert Data Collector (PANalytical, 2003), GSAS (Larson & Von Dreele, 2004) and EXPGUI (Toby, 2001), X'pert Highscore (PANalytical, 2003), coordinates taken from an isotypic compound (Bhuvanesh et al., 1999a) and (Liang et al., 2008), DIAMOND (Brandenburg, 1999), publCIF (Westrip, 2010).

Selected bond lengths (Å) top
Nb1—O1i1.9394 (1)Ca1—O1ii2.805 (4)
Nb1—O42.027 (11)Ca1—O3ii2.567 (4)
Nb2—O21.689 (8)Ca1—O4iii2.7427 (1)
Nb2—O3i1.9704 (11)Li1—O21.599 (4)
Nb2—O42.029 (11)
Symmetry codes: (i) x, y1, z; (ii) x1/2, y1/2, z+1/2; (iii) x+1/2, y+1/2, z+1/2.
 

Acknowledgements

The authors are grateful for financial support by the National Natural Science Foundation of China, the 973 Projects of China and the Program for New Century Excellent Talents in Universities (NCET).

References

First citationBhuvanesh, N. S. P., Crosnier-Lopez, M. P., Bohnke, O., Emery, J. & Fourquet, J. L. (1999a). Chem. Mater. 11, 634–641.  CrossRef CAS
First citationBhuvanesh, N. S. P., Crosnier-Lopez, M. P., Duroy, H. & Fourquet, J. L. (1999b). J. Mater. Chem. 9, 3093–3100.  CrossRef CAS
First citationBrandenburg, K. (1999). DIAMOND. Crystal Impact GbR, Bonn, Germany.
First citationHoward, C. J. (1982). J. Appl. Cryst. 15, 615–620.  CrossRef CAS Web of Science IUCr Journals
First citationLarson, A. C. & Von Dreele, R. B. (2004). General Structure Analysis System (GSAS). Report LAUR 86-748. Los Alamos National Laboratory, New Mexico, USA.
First citationLe Berre, F., Crosnier-Lopez, M. P., Laligant, Y. & Fourquet, J. L. (2002). J. Mater. Chem. 12, 258–263.  CrossRef CAS
First citationLiang, Z., Tang, K., Shaoa, Q., Lia, G., Zenga, S. & Zheng, H. (2008). J. Solid State Chem. 181, 964–970.  CrossRef CAS
First citationPANalytical (2003). X'pert Data Collector and X'pert Highscore. PANalytical BV, Almelo, The Netherlands.
First citationSchaak, R. E. & Mallouk, T. E. (2002). Chem. Mater. 14, 1455–1471.  Web of Science CrossRef CAS
First citationThompson, P., Cox, D. E. & Hastings, J. B. (1987). J. Appl. Cryst. 20, 79–83.  CrossRef CAS Web of Science IUCr Journals
First citationToby, B. H. (2001). J. Appl. Cryst. 34, 210–213.  Web of Science CrossRef CAS IUCr Journals
First citationWestrip, S. P. (2010). J. Appl. Cryst. 43, 920–925.  Web of Science CrossRef CAS IUCr Journals

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ISSN: 2056-9890
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