GNP Method Synthesis And Properties Of Perovskite-type Complex Oxides Of La_1-xCa_xCrO₃

Perovskite-type complex oxides of La1-xCaxCrO3 compositions are attracting growing attention because of their superior electronic conductivity and excellent chemical stability in both oxidizing and reducing atmospheres, which makes them promising candidate materials for many important applications, such as interconnectors for solid oxide fuel cells (SOFC), heating elements for high temperature furnaces, and current collecting electrodes in Magneto-hydrodynamics (MHD). In this dissertation, the GNP (Glycine-Nitrate process) method has been employed to synthesize La1-xCaxCrO3 oxides. The synthesis and preparation, sinterability, electrical conducting properties and thermal expansion properties of La1-xCaxCrO3 oxides have been investigated. The effect of Ca2+ substitution and morphological characteristics of La1-.xCaxCrO3 powders on sinterability, electrical conductivity and thermal expansion properties of La1-xCaxCrO3 ceramics has been probed.La1-xCaxCrO3 fine powders have been synthesized by the GNP method. The influences of the mole ratio of glycine to total metal cation content (abbreviated as G/Mn+), pH of precursor solution, combustion condition, calcining temperature and Ca2+ substitution on the crystal structure and morphology of synthesized powders have been examined. The preferred synthesis conditions to produce La1-xCaxCrO3 fine powders with a pure perovskite-type structure were ascertained.The relative density, crystalline structure and microstructure of La1-xCaxCrO3 ceramics were characterized by Archimedes method, XRD and SEM. The sinterability of La1-xCaxCrO3 oxides was examined. It was found that the introduction of Ca2+ enhanced the sinterability of the material. The relative density of sintered specimens increase with the content of Ca2+ in the composition range of 03 ceramics were investigated using a DC four-terminal method and a push-rod type thermal dilatometer method, respectively. It was found that electrical conducting properties and thermal expansion properties of ceramic specimens closely depend on sintering temperature, Ca2+ substitution and morphological characteristics of La1-xCaxCrO3 powders. With the increase of sintering temperature, the relative density, electrical conductivity and linear thermal expansion coefficient of La1-xCaxCrO3 ceramics increase, while the activation energy for small polaron hopping decreases. For La1-xCaxCrO3 ceramics with similar relative densities, the electricalconductivity and linear thermal expansion coefficient increase with the content of Ca2+ in the composition range of 0