Changes in the heat capacity of Al2O3-Cr2O3 solid solutions near the point of antiferromagnetic phase transition in Cr2O3

Al2O3-Cr2O3 solid solutions with 0, 4, 7, 10 and 20 mol% of corundum were synthesized using a high-pressure/high-temperature apparatus and characterized by X-ray powder diffraction. Calorimetric measurements were carried out using DSC-111 (Setaram). Heat capacity was measured by the enthalpy method in a temperature range of 260-340 K, near magnetic phase transition in pure Cr2O3 (305 K). Magnetic contribution into the heat capacity was derived and found to change irregularly with the composition. Heat capacity of solid solutions remains constant in a relatively wide range of composition, while the C-p values of the end members differ significantly. This phenomenon is very important for the modeling of the thermodynamic functions of intermediate solid solutions.