Thermodynamics of formation for zirconolite (CaZrTi2O7) from T=298.15K to T=1500K

Zirconolite (CaZrTi2O7) has been proposed as a ceramic host for the long-te rm disposal of excess weapons-grade plutonium. Using high-temperature oxide -melt solution calorimetry, the standard molar enthalpy of formation at T = 298.15 K for zirconolite, Delta(f)H(m)(o) = -(3713.7 +/- 4.5) kJ.mol(-1) h as been obtained. In combination with the third-law entropy Delta(0)(298.15 ) S-K(m)o obtained by using adiabatic calorimetry on the same sample, the s tandard molar Gibbs free energy of formation at T = 298.15 K, Delta(f)G(m)( o) = -(3514.5 +/- 4.5) kJ.mol(-1), has also been obtained. The formation en thalpies, free energies, and third-law entropies Delta(0)(T) S-m are report ed from T = 298.15 K to T = 1500 K. Also reported for ZrTiO4, a compound of interest with respect to the (CaO, TiO2, ZrO2) phase diagram containing zi rconolite, are the first estimates of the standard molar enthalpy and Gibbs free energy of formation, Delta(f)H(m)(o)(ZrTiO4) = -(2048.7 +/- 5.0) kJ.m ol(-1), and Delta(f)G(m)(o)(ZrTiO4) = -(1935.7 +/- 5.0) kJ.mol(-1). (C) 199 9 Academic Press.