Heat capacity and thermodynamic functions of zirconia and yttria-stabilized zirconia

Heat capacities of pure zirconia ZrO2 and 7.76.10(-2) mole fraction yttria- stabilized zirconia (ZrO2)(0.9224)(Y2O3)(7.76.10-2) were measured by adiaba tic calorimetry at temperatures between 13 K and 300 K. The results were co mpared and analysed from the standpoint of the effects of yttria doping. Th e yttria-stabilized zirconia showed excess heat capacity at low temperature s which should be attributed to so-called low-energy modes caused by the de fects in the crystal. The smoothed values of molar heat capacities at round ed temperatures were calculated from the experimental data. The thermodynam ic functions enthalpy, entropy, and Gibbs free energy were also calculated and tabulated. The standard enthalpy and entropy of pure zirconia and 7.76. 10(-2) mole fraction yttria-stabilized zirconia at T = 298.15 K are 8.711 k J.mol(-1) and 49.79 J.K-1.mol(-1), and 9.595 kJ.mol(-1) and 56.47 J.K-1.mol (-1), respectively. (C) 1999 Academic Press.