Thermodynamic properties of BaCeO3 and BaZrO3 at low temperatures

Specific heat capacities (Cp) of polycrystalline samples of BaCeO3 and BaZrO3 have been measured from about 1.6 K up to room temperature by means of adiabatic calorimetry. We provide corrected experimental data for the heat capacity of BaCeO3 in the range T < 10 K and, for the first time, contribute experimental data below 53 K for BaZrO3. Applying Debyeʹs T3-law for T → 0 K, thermodynamic functions as molar entropy and enthalpy are derived by integration. We obtain Cp = 114.8 (±1.0) J mol−1 K−1, S° = 145.8 (±0.7) J mol−1 K−1 for BaCeO3 and Cp = 107.0 (±1.0) J mol−1 K−1, S° = 125.5 (±0.6) J mol−1 K−1 for BaZrO3 at 298.15 K. These results are in overall agreement with previously reported studies but slightly deviating, in both cases. Evaluations of Cp(T) yield Debye temperatures and identify deviations from the simple Debye-theory due to extra vibrational modes as well as anharmonicity. The anharmonicity turns out to be more pronounced at elevated temperatures for BaCeO3. The characteristic Debye temperatures determined at T = 0 K are Θ0 = 365 (±6) K for BaCeO3 and Θ0 = 402 (±9) K for BaZrO3.