Thermodynamic properties of NaZr2(PO4)3

The heat capacity of crystalline NaZr2(PO4)3 was measured between 7 and 340 K by adiabatic calorimetry. The results were used to calculate the thermodynamic functionsCp0,H0(T) -H0(0),S0(T), andG0(T) -H0(0) in the range 0-340 K. The absolute entropy was found to be S0NaZr2(PO4)3, cr, 298.15 K) = 327.1 ±1.0 J/(mol K), and the standard entropy of formation ΔfS0(NaZr2(PO4)3, cr, 298.15 K) = -1101±1 J/(mol K). Solution calorimetry was used to determine the standard enthalpy of formation, ΔfH0(NaZr2(PO4)3, cr, 298.15 K) = -5236 ±5 kJ/mol. By combining the data obtained by the two techniques, the standard Gibbs energy of formation was determined to be ΔfG0(NaZr2(PO4)3, cr, 298.15 K) = -4908 ±5 kJ/mol.