Thermodynamic properties of NaZr2(PO4)(3)

The heat capacity of crystalline NaZr2(PO4)(3) was measured between 7 and 3 40 K by adiabatic calorimetry. The results were used to calculate the therm odynamic functions C-p(0), H-0(T) - H-0(0), S-0(T), and G(0)(T)- H-0(0) in the range 0-340 K. The absolute entropy was found to be S-0(NaZr2(PO4)(3), cr, 298.15 K) = 327.1 +/- 1.0 J/(mol K), and the standard entropy of format ion Delta(f)S(0)(NaZr2(PO4)(3), cr, 298.15 K) = -1101 +/- 1 J/(mol K). Solu tion calorimetry was used to determine the standard enthalpy of formation, Delta(f)H(0)(NaZr2(PO4)(3), cr, 298.15 K) = -5236 +/- 5 kJ/mol. By combinin g the data obtained by the two techniques, the standard Gibbs energy of for mation was determined to be Delta(f)G(0)(NaZr2(PO4)(3), cr, 298.15 K) = -49 08 +/- 5 kT/mol.