Thermal Expansion and Electrical Conductivity of Perovskite Oxide (Ln1-xSrx)CoO3-.DELTA. (Ln=La, Nd and Sm)

The thermal expansion and electrical resistivity for the perovskite oxide of (Ln1-xSrx)CoO3-δ(Ln=La, Nd and Sm) were measured as a function of temperature from room temperature to 1273 K in conditioned air. In the temperature range from room temperature to 1000 K, the thermal expansion coefficient was affected due to both the phase transition and change in the oxygen defect concentration. Moreover, above 1000 K, the Sr compositional dependency of the thermal expansion coefficient was quite similar to that of the electrical resistivity in all systems. In the high temperature range, all of the systems indicated the presence of metallic or semimetallic conduction, which was affected by lattice vibration. The thermal expansion also relies on lattice vibration, so that the thermal expansion coefficient at a high temperature would be linearly dependent on the electrical resistivity at the same temperature.