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Heat capacity of neodymium zirconate (Nd 2 Zr 2 O 7) with pyrochlore structure was measured by adiabatic calorimetry and the hybrid adiabatic relaxation method in the temperature range (0.45 to 400) K. Its excess component was obtained by comparison with the heat capacity of the lanthanum zirconate. A thermal anomaly was observed below T ¼ 7:2 K. From the heat capacity measurements, the thermodynamic functions of Nd 2 Zr 2 O 7 were determined.

The heat capacities of the lanthanide zirconates Gd 2 Zr 2 O 7 and Eu 2 Zr 2 O 7 with pyrochlore structure were measured by adiabatic calorimetry and the hybrid adiabatic relaxation method in the temperature range (0.3 to 400) K. A thermal anomaly was observed for Gd 2 Zr 2 O 7 below T ¼ 15 K. From the measurements the thermodynamic functions of Gd 2 Zr 2 O 7 and Eu 2 Zr 2 O 7 were determined. By combining our results with the heat capacity data of La 2 Zr 2 O 7 , the lattice component of the heat capacity and the entropy were derived for the lanthanide series Ln 2 Zr 2 O 7 (Ln ¼ La to Gd). The Schottky contributions were derived for Ce 2 Zr 2 O 7 , Nd 2 Zr 2 O 7 and Eu 2 Zr 2 O 7 by subtracting the lattice component from the experimental data, and compared to the values calculated from the crystal field energy levels.

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