Crystal structure and thermodynamic properties of potassium antimony tungsten oxide

In the present work potassium antimony tungsten oxide with pyrochlore structure is refined by the Rietveld method (space group Fd3m, Z = 8). The temperature dependences of heat capacity have been measured for the first time in the range from 7 to 370 K for this compound. The experimental data were used to calculate standard thermodynamic functions, namely the heat capacity Cp°(T), enthalpy H°(T) − H°(0), entropy S°(T) − S°(0) and Gibbs function G°(T) − H°(0), for the range from T → 0 to 370 K. The differential scanning calorimetry was applied to measure the incongruent melting temperature of compound under study. The high-temperature X-ray diffraction was used for the determining thermal expansion coefficients.