|Home | About | Journals | Submit | Contact Us | Français|
Rubidium dicalcium triniobate(V), RbCa2Nb3O10, has been synthesized by solid-state reaction and its crystal structure refined from X-ray powder diffraction data using Rietveld analysis. The compound is a three-layer perovskite Dion–Jacobson phase with the perovskite-like slabs derived by termination of the three-dimensional CaNbO3 perovskite structure along the ab plane. The rubidium ions (4/mmm symmetry) are located in the interstitial space.
For the synthesis of RbCa2Nb3O10, see: Dion et al. (1981 ). For related three-layer Dion–Jacobson analogues, see: CsCa2Nb3O10 (Dion et al., 1984 ); RbSr2Nb3O10 (Thangadurai et al., 2001 ); KCa2Nb3O10 (Fukuoka et al., 2000 ). For the application of Dion–Jacobson phases, see: Thangadurai et al. (2001 ); Li et al. (2007 ); Ida et al. (2008 ); Compton & Osterloh (2009 ). For properties of RbCa2Nb3O10, see: Thangadurai & Weppner (2001 , 2004 ); Byeon et al. (2003 ).
Data collection: X’pert Data Collector (PANalytical, 2003 ); cell refinement: GSAS (Larson & Von Dreele, 2000 ) and EXPGUI (Toby, 2001 ); data reduction: X’pert Data Collector; method used to solve structure: coordinates taken from an isotypic compound (Thangadurai et al., 2001 ); program(s) used to refine structure: GSAS and EXPGUI; molecular graphics: VESTA (Momma & Izumi, 2008 ); software used to prepare material for publication: publCIF (Westrip, 2009 ).
Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809018157/br2107sup1.cif
Rietveld powder data: contains datablocks I. DOI: 10.1107/S1600536809018157/br2107Isup2.rtv
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).
RbCa2Nb3O10 powders were prepared by a conventional solid state reaction described previously (Byeon et al., 2003). All starting materials were of analytical grade and were used without further purification. Stoichiometric amounts of CaCO3 and Nb2O5 with a 50% molar excess of Rb2CO3 were mixed together and heated in air at 1423 K for 24 h (heating rate 5 K /min). The calcination procedure was repeated one time after grinding to ensure a complete reaction. A 50% molar excess of Rb2CO3 was used in the reaction to offset the volatilization of the alkali oxides at the synthesis temperature. The products were washed thoroughly with distilled water to remove excess alkali oxides, and were then dried at 393 K overnight.
All peaks of the XRD pattern could be indexed on a tetragonal cell and the systematic absences show simple tetragonal symmetry. The P4/mmm crystal structure of RbSr2Nb3O10 (Thangadurai et al., 2001) was used as a starting model for the Rietveld refinement of the structure of RbCa2Nb3O10. The corresponding isotropic atomic displacement parameters of all oxygen atoms are constrained to be equal. The March-Dollase option in the EXPGUI program was applied to correct 00 l preferential orientation which were often observed in the Rietveld refinement of the layered perovskites.
|RbCa2Nb3O10||Dx = 4.520 Mg m−3|
|Mr = 604.34||Cu Kα radiation, λ = 1.54178 Å|
|Tetragonal, P4/mmm||T = 298 K|
|Hall symbol: -P 4 2||Particle morphology: plate-like|
|a = 3.85865 (6) Å||white|
|c = 14.9108 (3) Å||flat sheet, 10 × 15 mm|
|V = 222.01 (1) Å3||Specimen preparation: Prepared at 1423 K|
|Z = 1|
|PANalytical X'pert PRO diffractometer||Data collection mode: reflection|
|Radiation source: sealed tube||Scan method: continuous|
|graphite||2θmin = 10.01°, 2θmax = 109.99°, 2θstep = 0.02°|
|Specimen mounting: packed powder pellet|
|Refinement on F2||? data points|
|Least-squares matrix: full||Profile function: pseudo-Voigt|
|Rp = 0.035||26 parameters|
|Rwp = 0.053||0 restraints|
|Rexp = 0.008||w = 1/[σ2(Fo2) + (0.0677P)2] where P = (Fo2 + 2Fc2)/3|
|R(F2) = 0.08530||(Δ/σ)max = 0.020|
|χ2 = 6.452||Preferred orientation correction: March–Dollase (Dollase, 1986) AXIS 1 Ratio= 0.95964, h = k = 0, l = 1. Prefered orientation correction range: min = 0.94007, Max = 1.13156|
|Ca1||0.5||0.5||0.14706 (19)||0.0281 (8)*|
|Nb2||0.0||0.0||0.28537 (8)||0.0134 (5)*|
|O2||0.0||0.0||0.1258 (5)||0.0716 (14)*|
|O3||0.0||0.5||0.2599 (4)||0.0716 (14)*|
|O4||0.0||0.0||0.3960 (6)||0.0716 (14)*|
|Rb1—O4||3.138 (4)||Ca1—O3||2.560 (4)|
|Rb1—O4i||3.138 (4)||Ca1—O3ii||2.560 (4)|
|Rb1—O4ii||3.138 (4)||Ca1—O3viii||2.560 (4)|
|Rb1—O4iii||3.138 (4)||Ca1—O3ix||2.560 (4)|
|Rb1—O4iv||3.138 (4)||Nb1—O1x||1.929320 (30)|
|Rb1—O4v||3.138 (4)||Nb1—O1||1.929320 (30)|
|Rb1—O4vi||3.138 (4)||Nb1—O1xi||1.929320 (30)|
|Rb1—O4vii||3.138 (4)||Nb1—O1viii||1.929320 (30)|
|Ca1—O1||2.9207 (22)||Nb1—O2||1.877 (7)|
|Ca1—O1ii||2.9207 (22)||Nb1—O2xii||1.877 (7)|
|Ca1—O1viii||2.9207 (22)||Nb2—O2||2.379 (7)|
|Ca1—O1ix||2.9207 (22)||Nb2—O3x||1.9663 (11)|
|Ca1—O2||2.7468 (9)||Nb2—O3||1.9663 (11)|
|Ca1—O2i||2.7468 (9)||Nb2—O3xi||1.9663 (11)|
|Ca1—O2ii||2.7468 (9)||Nb2—O3viii||1.9663 (11)|
|Ca1—O2iii||2.7468 (9)||Nb2—O4||1.650 (8)|
Symmetry codes: (i) x, y+1, z; (ii) x+1, y, z; (iii) x+1, y+1, z; (iv) ; (v) ; (vi) ; (vii) ; (viii) −y+1, x, z; (ix) −y+1, x+1, z; (x) x, y−1, z; (xi) −y, x, z; (xii) .
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BR2107).