Structural refinement using high-resolution powder X-ray diffraction data of Ca_0.5Ti₂P₃O₁₂, a low-thermal-expansion material

Abstract

The structures of Ca_0.5Ti₂P₃O₁₂ and Sr_0.5Ti₂P₃O₁₂, low-thermal-expansion materials, have been refined by the Rietveld method using high-resolution powder X-ray diffraction (XRD) data. The assignment of space group R3 to NASICON-type compounds containing divalent cations is confirmed. ³¹P magic-angle spinning nuclear magnetic resonance (MASNMR) data are presented as supporting data. A comparison of changes in the polyhedral network resulting from the cation distribution, is made with NaTi₂P₃O₁₂ and Nb₂P₃O₁₂. Factors that may govern thermal expansion in this family of compounds are discussed.