The thermodynamic properties of the α and β polymorphs of NiMoO4 were directly investigated by calorimetry. The standard entropies of formation, ΔfS°T, of α and β were determined from measuring the molar heat capacity, Cp,m, from near absolute zero (2 K) to high temperature (1380 K) by a relaxation method and differential scanning calorimetry. The standard enthalpies of formation, ΔfH°T, of α and β were determined by combining Cp,m with the standard enthalpy of formation, ΔfH°298,n at 298 K obtained from drop solution calorimetry in molten sodium molybdate at 973 K. The standard Gibbs energies of formation, ΔfG°T, of α and β were determined from their ΔfS°T and Δ fH°T values. The ΔfG° T values indicate that the polymorphic transformation from α to β occurs at 1000 K, consistent with the observed phase transformation at 1000 K.
|Original language||English (US)|
|Number of pages||6|
|Journal||Journal of the American Ceramic Society|
|State||Published - Nov 2003|
ASJC Scopus subject areas
- Ceramics and Composites
- Materials Chemistry