The enthalpies of the solution of MZr2(PO4)(3) (M=Na, K, Rb or Cs) compound
s have been measured by the help of a differential automatic isothermal Cal
vet calorimeter and the standard enthalpies of formation have been derived.
The temperature dependencies of the standard heat capacity of the samples
of crystalline NaZr2(PO4)(3) and CsZr2(PO4)(3) were studied between 7 and 3
40 K in an automatic adiabatic vacuum calorimeter. The main thermodynamic f
unctions H-0(T)-H-0(0), S-0(T) and G(0)(T)-H-0(0) have been determined. The
Gibbs energies of formation of the NaZr2(PO4)(3) and CsZr2(PO4)(3) at 298.
15 K were calculated on the basis of these experimental data and the enthal
py of formation data. Qualitative explanations for the results observed wer
e presented.