Standard Thermodynamic Functions of Crystalline Arsenate Mg0.5Zr2(AsO4)3 in the Range from T → 0 to 670 K

The temperature dependence of heat capacity C ° p = f ( T ) of crystalline arsenate Mg 0.5 Zr 2 (AsO 4 ) 3 was studied by precision adiabatic vacuum and differential scanning calorimetry in the temperature range 8−670 K. The standard thermodynamic functions C ° p ( T ), H °( T )– H °(0), S °( T ), and G °( T )– H °(0) of the arsenate for the range from Т → 0 to 670 K and the standard formation entropy at Т = 298.15 K were calculated from the obtained experimental data. Based on the low-temperature capacity data (30–50 K) the fractal dimension D of the arsenate was determined, and the topology of its structure was characterized. The results were compared with the thermodynamic data for the structurally related crystalline phosphates M 0.5 Zr 2 (PO 4 ) 3 (M = Mg, Ca, Sr, Ba, Ni) and arsenate NaZr 2 (AsO 4 ) 3 .