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

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890

Rietveld refinement of KLaTiO4 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, People's Republic of China
*Correspondence e-mail: kbtang@ustc.edu.cn

(Received 27 December 2010; accepted 23 February 2011; online 12 March 2011)

Potassium lanthanum titanate(IV), KLaTiO4, has been synthesized by conventional solid-state reaction. It crystallizes isotypically with the NaLnTiO4 (Ln = La, Pr, Nd, Sm, Eu, Gd, Y and Lu) family. Five of the six atoms in the asymmetric unit (one K, one La, one Ti and two O atoms) are situated on sites with 4mm symmetry, whereas one O atom has 2mm. site symmetry. The crystal structure can be described as being composed of single layers of distorted corner-sharing TiO6 octa­hedra extending parallel to (001). The layers are alternately separated by K+ and La3+ cations along [001]. The coordination number of both K+ and La3+ cations is nine, resulting in distorted KO9 and LaO9 polyhedra.

Related literature

For the isotypic NaLnTiO4 (Ln = La, Pr, Nd, Sm, Eu, Gd, Y and Lu) family, see: Toda et al. (1996a[Toda, K., Kameo, Y., Kurita, S. & Sato, M. (1996a). J. Alloys Compd, 234, 19-25.]). Ortho­rhom­bic symmetry for other members of this family has been reported by Nishimoto et al. (2006[Nishimoto, S., Matsuda, M., Harjo, S., Hoshikawa, A., Kamiyama, T., Ishigaki, T. & Miyake, M. (2006). J. Solid State Chem. 179, 1892-1897.]). Decomposition products of NaLnTiO4 were investigated by Toda et al. (1996b[Toda, K., Watanabe, J. & Sate, M. (1996b). Mater. Res. Bull. 31, 1427-1435.]). For preparation by ion-exchange and structure analysis of KLnTiO4 (Ln = La, Nd, Sm, Eu, Gd, Dy) compounds, see: Schaak & Mallouk (2001[Schaak, R. E. & Mallouk, T. E. (2001). J. Solid State Chem. 161, 225-232.]). For hydro­thermal preparation of similar compounds, see: Dairong et al. (1999[Dairong, C., Xiuling, J. & Ruren, X. (1999). Mater. Res. Bull. 34, 685-691.]). 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
  • KLaTiO4

  • Mr = 289.90

  • Tetragonal, P 4/n m m

  • a = 3.84155 (10) Å

  • c = 13.4695 (4) Å

  • V = 198.78 (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 = 9.872°, 2θmax = 109.815°, 2θstep = 0.017°

Refinement
  • Rp = 0.046

  • Rwp = 0.068

  • Rexp = 0.046

  • R(F2) = 0.047

  • χ2 = 2.220

  • 5880 data points

  • 60 parameters

Table 1
Selected bond lengths (Å)

K1—O1 3.065 (4)
K1—O2 2.765 (9)
K1—O2i 2.7242 (7)
La1—O1 2.530 (3)
La1—O3ii 2.339 (7)
La1—O3i 2.7628 (12)
Ti1—O1 1.9635 (12)
Ti1—O2iii 1.775 (9)
Ti1—O3iii 2.558 (7)
Symmetry codes: (i) -x, -y, -z+1; (ii) x, y, z+1; (iii) -x+1, -y+1, -z+1.

Data collection: X'pert Data Collector (PANalytical, 2003[PANalytical (2003). X'pert Data Collector. 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 Data Collector; method used to solve structure: coordinates taken from an isotypic compound (Toda et al., 1996b[Toda, K., Watanabe, J. & Sate, M. (1996b). Mater. Res. Bull. 31, 1427-1435.]); 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 A'2[An-1B2O3n+1] familiy (A' = alkali, A = alkaline earth or rare earth cation; B= transition metal cation) possess a variety of interesting properties, such as superconductivity, colossal magnetoresistance, ferroelectricity, as well as catalytic activity. The structure of KLaTiO4 we report here is a n = 1 member of this familiy. Isotypic crystal structures have been reported for NaLnTiO4 (Ln = La, Pr, Nd, Sm, Eu, Gd, Y and Lu; Toda et al., 1996a) in the space group P4/nmm.

Schaak & Mallouk (2001) reported the KLnTiO4 (Ln= La, Nd, Sm, Eu, Gd, Dy) family of compounds to crystallize in space group Pbcm, as determined from Rietveld refinements of X-ray powder data. We tested both Pbcm and P4/nmm space groups with the underlying structures KLnTiO4 (P4/nmm; Schaak & Mallouk, 2001) and NaLnTiO4 (P4/nmm; Toda et al., 1996a) as starting models for Rietveld refinement of KLaTiO4. The results revealed the P4/nmm model to be significantly better than the Pbcm model. It is well-know that different rare earth elements can affect the crystal structure dramatically. In single layer Ruddlesden-Popper phase perovskites some studies reported that NaLnTiO4 compounds have tetragonal symmetry for Ln = La—Nd, while an orthorhombic symmetry is observed for Ln = Sm—Lu and Y (Nishimoto et al., 2006). We can infer that a similar situation might be present for KLnTiO4 compounds. We ascribe the difference in symmetry between KLaTiO4 obtained through solid state reactions (tetragonal) and through ion-exchange (orthorhombic) to the different temperature treatment (higher temperatures for the solid state reaction route).

Other methods used to prepare KLaTiO4 have been reported previously, like an ion exchange method by Schaak & Mallouk (2001) and a hydrothermal method by Dairong et al. (1999). To our knowledge, a solid state route to synthesize this compound and its detailed structure analysis based on Rietveld refinement from X-ray powder diffraction data has not been reported. KLaTiO4 easily decomposes at high temperature and is converted into the three-layer Ruddlesden-Popper phase K2La2Ti3O10. This phenomenon is also found in during preparation of NaLaTiO4 reported by Toda et al. (1996b). Therefore we modified the reaction conditions on the basis of the preparation of NaLaTiO4 and obtained a single phase product successfully.

Fig. 1 shows the observed difference plots (calculated, observed) of the Rietveld refinement.

Fig. 2 illustrates the structure of KLaTiO4. It consists of a single layer of corner-sharing distorted TiO6 octahedra extending parallel to (001). The layers are separated by alternating layers of K+ and La3+ cations along [001]. The TiO6 octahedra (4mm symmetry) are considerably distorted. They have four equal equatorial Ti—O distances [1.9635 (12) Å], one very short Ti—O distance [1.775 (9) Å] toward the K layer and a significantly longer Ti—O distance [2.558 (7) Å] towards the La layer. The corresponding coordination polyhedra around the K+ and La3+ cations are distorted KO9 and LaO9 polyhedra, each with 4mm symmetry.

Related literature top

For the isotypic NaLnTiO4 (Ln = La, Pr, Nd, Sm, Eu, Gd, Y and Lu) family, see: Toda et al. (1996a). Orthorhombic symmetry for other members of this family has been reported by Nishimoto et al. (2006). Decomposition products of NaLnTiO4 were investigated by Toda et al. (1996b). For preparation by ion-exchange and structure analysis of KLnTiO4 (Ln = La, Nd, Sm, Eu, Gd, Dy) compounds, see: Schaak & Mallouk (2001). For hydrothermal preparation of similar compounds, see: Dairong et al. (1999). For crystallographic background, see: Howard (1982); Thompson et al. (1987).

Experimental top

The sample was prepared by conventional solid-state reaction. The starting materials were KNO3, La2O3 and TiO2 in a molar ratio of 2:1:2. An excess of KNO3 (55 mol%) was added to compensate for the loss due to the volatilization of the potassium component. La2O3 was heated to 1173 K for 10 h prior to use to remove water and carbonate impurities. The mixture was then ground and calcined at 1223 K for 30 min.

Refinement top

The crystal structure of NaLaTiO4 (Toda et al., 1996b) in the spacegroup P4/nmm was used as a starting model for the final Rietveld refinement of the KLaTiO4 structure. Isotropic displacement parameters were used for all atoms. The March-Dollase option in the EXPGUI program (Toby, 2001) was applied to correct for preferential orientation along [00l] which is often observed for such layered perovskites.

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 Data Collector (PANalytical, 2003); program(s) used to solve structure: coordinates taken from an isotypic compound (Toda et al., 1996b); 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. Rietveld difference plot for the refinement of KLaTiO4.
[Figure 2] Fig. 2. The crystal structure of KLaTiO4 in a projection along [010].
Potassium lanthanum titanate top
Crystal data top
KLaTiO4Z = 2
Mr = 289.90Dx = 4.848 Mg m3
Tetragonal, P4/nmmCu Kα radiation, λ = 1.54060, 1.54443 Å
Hall symbol: -p 4a 2aT = 298 K
a = 3.84155 (10) Åwhite
c = 13.4695 (4) Åflat sheet, 20 × 20 mm
V = 198.78 (1) Å3Specimen preparation: Prepared at 1223 K
Data collection top
PANalytical X'pert PRO
diffractometer
Data collection mode: reflection
Radiation source: sealed tubeScan method: continuous
Graphite monochromator2θmin = 9.872°, 2θmax = 109.815°, 2θstep = 0.017°
Specimen mounting: packed powder pellet
Refinement top
Refinement on F2Excluded region(s): none
Least-squares matrix: fullProfile 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) = 0.000 #2(GV) = -2.261 #3(GW) = -9.290 #4(LX) = 4.310 #5(LY) = 17.630 #6(trns) = 0.000 #7(asym) = 3.5282 #8(shft) = 0.0000 #9(GP) = 17.284 #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
Rp = 0.04660 parameters
Rwp = 0.0680 restraints
Rexp = 0.046 w = 1/[σ2(Fo2) + (0.0677P)2]
where P = (Fo2 + 2Fc2)/3
R(F2) = 0.04713(Δ/σ)max = 0.01
χ2 = 2.220Background function: GSAS Background function number 1 with 36 terms. Shifted Chebyshev function of 1st kind 1: 353.285 2: -361.136 3: 220.846 4: -104.260 5: 61.8271 6: -33.1030 7: 19.7877 8: -5.01446 9: 3.42337 10: -3.14370 11: 0.340114 12: 2.15882 13: -0.130836 14: -1.88421 15: 5.08631 16: -1.48077 17: 4.42719 18: 2.91556 19: -3.924060E-0220: 0.679453 21: 5.77738 22: -2.47188 23: 3.81643 24: 3.21357 25: -4.71396 26: -1.63350 27: 0.665874 28: -7.16378 29: -7.040150E-0230: 3.04932 31: -2.36381 32: 0.787399 33: 4.27144 34: -2.96952 35: 4.90415 36: 1.54599
5880 data pointsPreferred orientation correction: March-Dollase AXIS 1 Ratio= 0.96438 h= 0.000 k= 0.000 l= 1.000 Prefered orientation correction range: Min= 0.94706, Max= 1.11492
Crystal data top
KLaTiO4V = 198.78 (1) Å3
Mr = 289.90Z = 2
Tetragonal, P4/nmmCu Kα radiation, λ = 1.54060, 1.54443 Å
a = 3.84155 (10) ÅT = 298 K
c = 13.4695 (4) Åflat sheet, 20 × 20 mm
Data collection top
PANalytical X'pert PRO
diffractometer
Scan method: continuous
Specimen mounting: packed powder pellet2θmin = 9.872°, 2θmax = 109.815°, 2θstep = 0.017°
Data collection mode: reflection
Refinement top
Rp = 0.046χ2 = 2.220
Rwp = 0.0685880 data points
Rexp = 0.04660 parameters
R(F2) = 0.047130 restraints
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
K10.250.250.5950 (2)0.0278 (9)*
LA10.250.250.89446 (6)0.0199 (4)*
TI10.750.750.74203 (19)0.0151 (7)*
O10.750.250.7723 (4)0.0189 (17)*
O20.250.250.3897 (6)0.039 (2)*
O30.250.250.0681 (5)0.018 (2)*
Geometric parameters (Å, º) top
K1—O1i3.065 (4)La1—O1iii2.530 (3)
K1—O13.065 (4)La1—O3viii2.339 (7)
K1—O1ii3.065 (4)La1—O3iv2.7628 (12)
K1—O1iii3.065 (4)La1—O3v2.7628 (12)
K1—O22.765 (9)La1—O3vi2.7628 (12)
K1—O2iv2.7242 (7)La1—O3vii2.7628 (12)
K1—O2v2.7242 (7)Ti1—O11.9635 (12)
K1—O2vi2.7242 (7)Ti1—O1ix1.9635 (12)
K1—O2vii2.7242 (7)Ti1—O1iii1.9635 (12)
La1—O1i2.530 (3)Ti1—O1x1.9635 (12)
La1—O12.530 (3)Ti1—O2vii1.775 (9)
La1—O1ii2.530 (3)Ti1—O3vii2.558 (7)
O1i—K1—O177.62 (13)O1i—La1—O3v65.85 (12)
O1i—K1—O1ii52.61 (8)O1i—La1—O3vi130.30 (11)
O1i—K1—O1iii52.61 (8)O1i—La1—O3vii130.30 (11)
O1i—K1—O2141.19 (6)O1—La1—O1ii64.95 (9)
O1i—K1—O2iv59.94 (15)O1—La1—O1iii64.95 (9)
O1i—K1—O2v59.94 (15)O1—La1—O3viii130.59 (9)
O1i—K1—O2vi112.52 (18)O1—La1—O3iv130.30 (11)
O1i—K1—O2vii112.52 (18)O1—La1—O3v130.30 (11)
O1—K1—O1ii52.61 (8)O1—La1—O3vi65.85 (12)
O1—K1—O1iii52.61 (8)O1—La1—O3vii65.85 (12)
O1—K1—O2141.19 (6)O1ii—La1—O1iii98.81 (17)
O1—K1—O2iv112.52 (18)O1ii—La1—O3viii130.59 (9)
O1—K1—O2v112.52 (18)O1ii—La1—O3iv65.85 (12)
O1—K1—O2vi59.94 (15)O1ii—La1—O3v130.30 (11)
O1—K1—O2vii59.94 (15)O1ii—La1—O3vi65.85 (12)
O1ii—K1—O1iii77.62 (13)O1ii—La1—O3vii130.30 (11)
O1ii—K1—O2141.19 (6)O1iii—La1—O3viii130.59 (9)
O1ii—K1—O2iv59.94 (15)O1iii—La1—O3iv130.30 (11)
O1ii—K1—O2v112.52 (18)O1iii—La1—O3v65.85 (12)
O1ii—K1—O2vi59.94 (15)O1iii—La1—O3vi130.30 (11)
O1ii—K1—O2vii112.52 (18)O1iii—La1—O3vii65.85 (12)
O1iii—K1—O2141.19 (6)O3viii—La1—O3iv79.48 (14)
O1iii—K1—O2iv112.52 (18)O3viii—La1—O3v79.48 (14)
O1iii—K1—O2v59.94 (15)O3viii—La1—O3vi79.48 (14)
O1iii—K1—O2vi112.52 (18)O3viii—La1—O3vii79.48 (14)
O1iii—K1—O2vii59.94 (15)O3iv—La1—O3v88.09 (5)
O2—K1—O2iv94.34 (18)O3iv—La1—O3vi88.09 (5)
O2—K1—O2v94.34 (18)O3iv—La1—O3vii159.0 (3)
O2—K1—O2vi94.34 (18)O3v—La1—O3vi159.0 (3)
O2—K1—O2vii94.34 (18)O3v—La1—O3vii88.09 (5)
O2iv—K1—O2v89.67 (3)O3vi—La1—O3vii88.09 (5)
O2iv—K1—O2vi89.67 (3)O1—Ti1—O1ix156.1 (3)
O2iv—K1—O2vii171.3 (4)O1—Ti1—O1iii87.53 (7)
O2v—K1—O2vi171.3 (4)O1—Ti1—O1x87.53 (7)
O2v—K1—O2vii89.67 (3)O1—Ti1—O2vii101.97 (16)
O2vi—K1—O2vii89.67 (3)O1ix—Ti1—O1iii87.53 (7)
O1i—La1—O198.81 (17)O1ix—Ti1—O1x87.53 (7)
O1i—La1—O1ii64.95 (9)O1ix—Ti1—O2vii101.97 (16)
O1i—La1—O1iii64.95 (9)O1iii—Ti1—O1x156.1 (3)
O1i—La1—O3viii130.59 (9)O1iii—Ti1—O2vii101.97 (16)
O1i—La1—O3iv65.85 (12)O1x—Ti1—O2vii101.97 (16)
Symmetry codes: (i) x1, y, z; (ii) y+1/2, x1, z; (iii) y+1/2, x, z; (iv) x, y, z+1; (v) x, y+1, z+1; (vi) x+1, y, z+1; (vii) x+1, y+1, z+1; (viii) x, y, z+1; (ix) x, y+1, z; (x) y+3/2, x, z.

Experimental details

Crystal data
Chemical formulaKLaTiO4
Mr289.90
Crystal system, space groupTetragonal, P4/nmm
Temperature (K)298
a, c (Å)3.84155 (10), 13.4695 (4)
V3)198.78 (1)
Z2
Radiation typeCu Kα, λ = 1.54060, 1.54443 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 = 9.872 2θmax = 109.815 2θstep = 0.017
Refinement
R factors and goodness of fitRp = 0.046, Rwp = 0.068, Rexp = 0.046, R(F2) = 0.04713, χ2 = 2.220
No. of data points5880
No. of parameters60

Computer programs: X'pert Data Collector (PANalytical, 2003), GSAS (Larson & Von Dreele, 2004) and EXPGUI (Toby, 2001), coordinates taken from an isotypic compound (Toda et al., 1996b), DIAMOND (Brandenburg, 1999), publCIF (Westrip, 2010).

Selected bond lengths (Å) top
K1—O13.065 (4)La1—O3i2.7628 (12)
K1—O22.765 (9)Ti1—O11.9635 (12)
K1—O2i2.7242 (7)Ti1—O2iii1.775 (9)
La1—O12.530 (3)Ti1—O3iii2.558 (7)
La1—O3ii2.339 (7)
Symmetry codes: (i) x, y, z+1; (ii) x, y, z+1; (iii) x+1, y+1, z+1.
 

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 citationBrandenburg, K. (1999). DIAMOND. Crystal Impact GbR, Bonn, Germany.  Google Scholar
First citationDairong, C., Xiuling, J. & Ruren, X. (1999). Mater. Res. Bull. 34, 685–691.  Google Scholar
First citationHoward, C. J. (1982). J. Appl. Cryst. 15, 615–620.  CrossRef CAS Web of Science IUCr Journals Google Scholar
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.  Google Scholar
First citationNishimoto, S., Matsuda, M., Harjo, S., Hoshikawa, A., Kamiyama, T., Ishigaki, T. & Miyake, M. (2006). J. Solid State Chem. 179, 1892–1897.  CrossRef CAS Google Scholar
First citationPANalytical (2003). X'pert Data Collector. PANalytical BV, Almelo, The Netherlands.  Google Scholar
First citationSchaak, R. E. & Mallouk, T. E. (2001). J. Solid State Chem. 161, 225–232.  CrossRef CAS Google Scholar
First citationThompson, P., Cox, D. E. & Hastings, J. B. (1987). J. Appl. Cryst. 20, 79–83.  CrossRef CAS Web of Science IUCr Journals Google Scholar
First citationToby, B. H. (2001). J. Appl. Cryst. 34, 210–213.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationToda, K., Kameo, Y., Kurita, S. & Sato, M. (1996a). J. Alloys Compd, 234, 19–25.  CrossRef CAS Google Scholar
First citationToda, K., Watanabe, J. & Sate, M. (1996b). Mater. Res. Bull. 31, 1427–1435.  CrossRef CAS Google Scholar
First citationWestrip, S. P. (2010). J. Appl. Cryst. 43, 920–925.  Web of Science CrossRef CAS IUCr Journals Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Follow Acta Cryst. E
Sign up for e-alerts
Follow Acta Cryst. on Twitter
Follow us on facebook
Sign up for RSS feeds