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 370K for this compound. The experimental data were Used to calculate standard thermodynamic functions, namely the heat capacity C-p(degrees)(T). enthalpy H degrees(T) - H degrees(O), entropy S degrees(T) - S degrees(0) and Gibbs function G degrees(T) - H degrees(O), 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. (C) 2009 Elsevier B.V. All rights reserved.