Crystal structure and thermodynamic properties of germanate CuEu$_2$Ge$_2$O$_8$

Copper-europium germanate CuEu$_2$Ge$_2$O$_8$ was obtained from the initial CuO, Eu$_2$O$_3$ and GeO$_2$ oxides using solid-phase synthesis by annealing in air in the temperature range of 1223–1273 K. Its crystal structure was determined (space group Cm). The influence of temperature on high-temperature heat capacity of the synthesized germanate was studied by the differential scanning calorimetry method. It was found that the dependence of heat capacity on temperature has an extreme value related to a phase transition. The thermodynamic properties were calculated based on the experimental data about heat capacity.