Excess heat capacity in yttria stabilized zirconia

The heat capacity of 9.70 and 11.35 mol% yttria stabilized zirconia ((ZrO2) (1-x)(Y2O3)(x); x=0.0970, 0.1135) was measured by adiabatic calorimetry bet ween 13 and 300 K, and some thermodynamic functions were calculated and giv en in a table. A large excess heat capacity extending from the lowest tempe rature to room temperature with a broad maximum at about 75 K was found in comparison with the heat capacity calculated from those of pure zirconia an d yttria on the basis of simple additivity rule. The shape of the excess he at capacity is very similar to the Schottky anomaly, which may be attribute d to a softening of lattice vibration. The amount of the excess heat capaci ty decreased with increasing yttria doping, while the maximum temperature d id not vary. The relationships among the excess heat capacity, defect struc ture and interatomic force constants, and also the role of oxygen vacancy w ere discussed.