Structural and thermodynamic properties of anionically substituted solid solution ceramics Y(VO4)1-x(PO4)x with zircon structure

Abstract

Solid solution samples of yttrium orthophosphate–yttrium orthovanadate of general formula Y(VO4)1-x(PO4)x (x = 0.25; 0.50; 0.75) were obtained using solid state synthesis. The samples crystallize in zircon structure (I41/amd sp. gr.) as the pure end-members of the system do. Unit cell parameters calculated using XRD data were found to be in good agreement with those calculated from the Vegard law. SEM-EDS spectra of samples are given. Heat capacities of the samples (x = 0.50; 0.75) were measured by means of adiabatic calorimetry at low temperatures (6–344 K). Thermodynamic functions in the studied temperature range were calculated and compared to those of pure yttrium orthophosphate and orthovanadate. According to the data obtained solid solution Y(VO4)1-x(PO4)x can be considered as ideal, thus making it possible to calculate thermodynamic functions for any other substitution x by summation of obtained values for closest compounds with corresponding coefficients or pure substances.