Crystal structure of calcium tin phosphate(V), CaSn4(PO4)6

Abstract

Ca0.50O12P3Sn2, trigonal, R3 (no. 148), a = 8.360(1) A, c = 22.722(7) A, V = 1375.3 A, Z = 6, Rgt(F) = 0.016, wRref(F ) = 0.040, T = 293 K. Source of material Single crystal of Ca0.5Sn2P3O12was initially obtained by the high temperature solid state reaction of CaCO3, SnO2 and NH4H2PO4, with themolar ratio of 5 : 1 : 10 (Ca : Sn : P). The reactionmixture was thoroughly ground in an agate mortar and pressed into a pellet to ensure the best homogeneity and reactivity. The pellet was put into a platinum crucible. The crucible was transferred into an furnace and heated at 1473 K in the air for 2 days, and then it was allowed to coolwith a rate of 5Kmin –1 to 773Kbefore switching off the furnace. After boiling in water, block-shaped colorless crystals were obtained in very low yield. Discussion Recently, a family of AM2(PO4)3 (A = alkali metals; M = Ti, Zr, Ge, Sn) crystals with the NASICON (Na3Zr2Si2PO12) or NZP (NaZr2P3O12) of crystal structure have been extensively investigated for their intriguing properities. E.g. the ionic conductivity may due to the complex and subtle interactions between NASICON framework and mobile ions [1-5]. Furthermore, the chemical and thermal stability ensures the feasibility of the industrial applications. The substitution of alkali by alkali-earth metals(II) can retain the NASICON framework. Such compounds have been reported in literature [6]. Until now, this family of materials has not been fully explored. We investigate the CaO–SnO2–P2O5 ternary system, and discover the Ca0.5Sn2P3O12 single crystals. The title compound is isostructural to Ca0.5Ti2P3O12 and Sr0.5Ti2P3O12 showing the NASICON framework in which half of the A(I) sites is occupied by the Ca cations. The Sn atoms are coordinated by six oxygen atoms, forming nearly ideal SnO6 octahedra. The Sn—O bonds have two groups of different lengths, 1.980(2) and 2.060(2)A. The P atoms have a tetrahedral coordination with the P—O bond lengths ranging from 1.511(2) to 1.549(2) A. Calcium atoms are six-coordinated by O atoms with equal Ca—O bond length of 2.477(2) A. Z. Kristallogr. NCS 225 (2010) 627-628 / DOI 10.1524/ncrs.2010.0274 627 © by Oldenbourg Wissenschaftsverlag, Munchen Crystal: colorless block, size 0.15 × 0.16 × 0.18 mm Wavelength: Mo K+ radiation (0.71073 A) .: 63.19 cm−1 Diffractometer, scan mode: Rigaku Mercury70 CCD, % 2,max: 54.92° N(hkl)measured, N(hkl)unique: 3372, 702 Criterion for Iobs, N(hkl)gt: Iobs > 2 )(Iobs), 676 N(param)refined: 55 Programs: SHELXS-97, SHELXL-97 [7], PLATON [8] Table 1. Data collection and handling.