X-ray diffraction analysis and specific heat capacity of (Bi_1-xLa_x)FeO₃ perovskites

Phase relations of BiFeO₃-LaFeO₃ system at room temperature were investigated by X-ray powder diffraction. A rhombohedral (R3c) phase exists in the composition range of 0 ≤ x ≤ 0.1 and an orthorhombic (Pbnm) phase in the range of 0.6 < x ≤ 1.0. Thermal expansion of single-phase samples with x = 0, 0.1, 0.7, 0.9 and 1.0 was studied by temperature-dependent X-ray diffraction. The temperature dependences of expansion coefficients of the samples were obtained. Specific heat capacity of the samples with x = 0, 0.1, 0.8 and 1.0 was measured in the temperature range of 200-760 K by a modulated-temperature differential scanning calorimeter. The phase boundaries of the antiferromagnetic-paramagnetic transition were determined.