LnGa0.5Sb1.5O6 Complex Oxides with a Rosiaite-Type Structure: Synthesis, Structure, and Thermal Properties

Abstract

A series of Ln^III\({\text{Ga}}_{{0.{\text{5}}}}^{{{\text{III}}}}\)\({\text{Sb}}_{{{\text{1}}.{\text{5}}}}^{{\text{V}}}\)O₆ (Ln = La–Tb) complex oxides were prepared by coprecipitation followed by annealing. The phases where Ln = Ce, Pr, Eu, and Tb were prepared for the first time. The 900°С isothermal section of the Ce₂O_x–Ga₂O₃–Sb₂O_y phase diagram was plotted. Structures were calculated by the Rietveld method to show that all of the LnGa_0.5Sb_1.5O₆ (Ln = La–Tb) compounds have rosiaite (PbSb₂O₆) type structures. By the way of example, for LaGa_0.5Sb_1.5O₆ the isobaric heat capacity was determined and thermodynamic functions (entropy, enthalpy increment, and reduced Gibbs energy) were calculated at temperatures in the range from 15 to 1300 K.