Low-temperature heat-capacities of corundum-type structured (Fe2O3)1−x(Al2O3)x solid solutions with x = 0.25, 0.50 and 0.75.

We have prepared the metastable solid solutions of (Fe2O3)1−x(Al2O3)x (x = 0.25, 0.50, and 0.75) with the corundum-type structure through the mechanical alloying method and measured the low-temperature heat-capacity below 300 K using the Physical Property Measurement System (PPMS), which have not been measured so far since the solid solution is not available through the conventional synthesis procedure. The measured heat capacities exhibit similar general trends of temperature dependence with the pure α-Fe2O3 and α-Al2O3 listed in the JANAF thermodynamic table, while the measured values are a little higher than that of their weighted averages. This might be due to the defects or lattice distortion introduced at the preparation using the mechanical alloying method. Moreover, heat capacity anomaly was observed at low-temperature regions below 25 K, which grows larger and shifts toward the higher temperature with increasing aluminum substitution, which might be caused by the unexpected phase transition or point defects of cations. [ABSTRACT FROM AUTHOR]