Cation disorder and the charge ordering transition temperature in La-1/3(Sr1-xCax)(2/3)FeO3-delta investigated by mechanical spectroscopy

The lattice effect on the charge ordering in La1/3Sr2/3FeO3-d is addressed by calcium ion substitution. Cation disorder effect due to size differences between A-site La3+, Sr2+, and Ca2+ has been found in La-1/3(Sr1-xCax)(2/3)FeO3-d perovskites. Below room temperature, a charge ordering transition has been detected by temperature dependent resistivity, differential scanning calorimeter, and mechanical spectroscopy. The charge ordering transition temperature T-C shows a clear dependence on the variance of the A-site cation radius distribution. This result shows an important role of local lattice distortions on the charge ordering transition. As a comparison, octahedral titling transitions above room temperature were identified by mechanical spectroscopy, and the tilting transition temperatures are sensitive to the average cation radius. Finally, the implication of the cation disorder effect is discussed by a comparison of the case in manganates.