Crystal structure, electrical conductivity and thermal expansion of Nd1–xCaxCoO3–δ (0≤x≤0·5)

Abstract

The synthesis, crystal structure, thermal expansion and electrical conductivity of the ceramic oxide materials (Nd1–xCax)CoO3 (0≤x≤0·5) were investigated. These powders with perovskites structure were synthesized using the sol–gel method. Compositions have a pure orthorhombic structure up to 0·3 Ca doping. The lattice parameters were determined at room temperature (RT) by powder X-ray diffraction. Thermal expansion measurements on the sintered samples were carried out from RT to 900°C. The average linear thermal expansion coefficient range was found to decrease with increasing Ca doping up to x=0·4 and thereafter it increased. The thermal expansion curves for all values of x displayed rapid increase in slope at high temperatures. Electrical DC conductivity measurements were taken from RT to 600°C. The conductivity of the samples increased with Ca concentration up to 0·3.