Thermodynamic properties of trizirconium tetraphosphate

Abstract The heat capacity measurements of the crystalline trizirconium tetraphosphate were carried out in a low-temperature adiabatic vacuum calorimeter between T  = (7 and 350) K and in dynamic calorimeter between T  = (330 and 640) K. The experimental data were used to calculate the standard ( p ∘  = 0.1 MPa) thermodynamic functions C p , m ∘ / R , Δ 0 T H m ∘ / RT , Δ 0 T S m ∘ / R , and Φ m ∘ = Δ 0 T S m ∘ - Δ 0 T H m ∘ / T (where R is the universal gas constant) in the range T  → (0 to 640) K. The fractal dimension D fr for the crystalline phosphate Zr 3 (PO 4 ) 4 between T  = (20 and 40) K was evaluated. From hydrofluoric acid solution microcalorimetry, the enthalpy of solution of Zr 3 (PO 4 ) 4 at T  = 298.15 K was determined and the standard molar enthalpy of formation was derived. By combining the data obtained by the two techniques, the standard molar Gibbs function of formation of Zr 3 (PO 4 ) 4 at T  = 298.15 K was calculated.