As part of an ongoing study of titanate-based ceramic materials for the disposal of surplus weapons-grade plutonium, we report thermodynamic properties of a sample of zirconium titanate (ZrTiO4) quenched from a high-temperature synthesis. The standard enthalpy of formation ΔfHmo was obtained by using high-temperature oxide-melt solution calorimetry. The molar heat capacity Cp, m was measured from T = 13 K to T = 400 K in an adiabatic calorimeter and extrapolated to T = 1800 K by using an equation fitted to the low-D temperature results. The results at T = 298.15 K are ΔfHmo = -(2024.1 ± 4.5) kJ·mol−1, ΔOTSmo = (116.71 ± 0.31) J·K−1·mol−1, and ΔfGmo = -(1915.8 ± 4.5) kJ·mol−1; the molar entropy includes a contribution of 2Rln 2 to account for the random mixing of Zr4+ and Ti4+ on a four-fold crystallographic site. Values for the standard molar Gibbs energies and enthalpies of formation of ZrTiO4; ΔfGmo and ΔfHmo, and for the free energies and enthalpies for the reaction to form ZrTiO4(cr) from ZrO2(cr) and TiO2(cr), are tabulated over the temperature interval, 0 ≤ (T /K) ≤ 1800. From these results, we conclude that ZrTiO4 is not stable with respect to (ZrO2 + TiO2) at T = 298.15 K, but becomes so at T = (1250 ± 150) K.
- Enthalpy of formation
- Heat capacity
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics
- Materials Science(all)
- Physical and Theoretical Chemistry