Characterization and controlling thermal expansion of materials with kosnarite- and langbeinite-type structures

Abstract

MZr2(TO4)x(PO4)3–x (M=Li, Na, K, Rb, Cs; T=As, V) solid solutions, NaFeZr(PO4)2SO4 and Pb2/3FeZr(PO4)7/3(SO4)2/3 with mineral kosnarite structure and KPbMgTi(PO4)3, K5/3MgE4/3(PO4)3 (E=Ti, Zr) with mineral langbeinite structure have been synthesized. According to the yielded results, which encompass thermal expansion data and crystallographic information about the structure of individual compounds and solid solutions, the meaningful selection of compounds with kosnarite and langbeinite structure for novel materials with controllable thermal expansion was carried out. The potassium-, rubidium-, and cesium-containing arsenates, arsenate–phosphates, vanadate–phosphates and Pb2/3FeZr(PO4)7/3(SO4)2/3 are low expansion materials (αav<2×10−6K−1); sodium–zirconium arsenate and sodium–zirconium and lithium–zirconium arsenate–phosphates, vanadate–phosphates and K5/3MgZr4/3(PO4)3 have intermediate thermal expansion (3×10−6K−1<αav<7×10−6K−1); and lithium–zirconium arsenate, KPbMgTi(PO4)3, K5/3MgTi4/3(PO4)3 are the high expansion material (αav>7×10−6K−1). The present results demonstrate that change of the size of alkali metal cation, anion substitution and varying of solid solution composition can produce kosnarite ceramics with controlled linear thermal expansion coefficients and extremely low thermal expansion anisotropy or langbeinite ceramics with isotropic expansion.