Heat capacities and derived thermodynamic functions of neodymium–gadolinium zirconates from 298.15 to 1050 K

Abstract

X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize Nd x Gd 2 − x Zr 2O 7 ( x = 0, 0.6, 1.0, 1.4, and 2.0) solid solutions pressureless-sintered by using ceramic powders acquired by chemical-coprecipitation and calcination method. Heat capacity measurements were performed with a heat flux-type differential scanning calorimetry in the temperature range of 298.15–1050 K. The heat capacity of Nd x Gd 2 − x Zr 2O 7 solid solutions increases with increasing the concentration x of neodymium cations from x = 0 to x = 2.0 at identical temperature levels. At 298.15 K, the heat capacities of Nd 0.6Gd 1.4Zr 2O 7, NdGdZr 2O 7 and Nd 1.4Gd 0.6Zr 2O 7 are 217, 220 and 224 J K −1 mol −1, respectively. Thermodynamic functions such as enthalpy increment, entropy and Gibbs energy functions were calculated from the measured heat capacity data.