Microstructure Characterization and Electrical Conductivity Measurement of La1−xCaxCrO3 (x = 0.25, 0.4, 0.5) Prepared by Aspartic Acid-Assisted Solution Combustion


Author to whom correspondence should be addressed. e-mail: aktyagi@barc.gov.in


Nanocrystalline La1−xCaxCrO3 (x = 0.25, 0.40, 0.50) powders were synthesized by gel-combustion process using aspartic acid as a fuel. Phase identification of the samples was carried out by powder X-ray diffraction. Pore distribution and microstructure of sintered pellets were investigated by small angle neutron scattering (SANS) and scanning electron microscopy (SEM). SANS and relative density measurement results indicate better sinterability for products with lower Ca2+ concentration. Four-probe direct current electrical conductivity of LaCrO3 with different Ca2+ concentrations was measured in the temperature range 350°C–1000°C in air as well as in hydrogen atmosphere. Linear behavior of Arrhenius plots of electrical conductivities in both air and hydrogen atmosphere indicates charge carrier transport is due to thermally activated hopping conduction of small hole-polarons. It was observed that the electrical conductivity decreased with increasing substitution of Ca2+ concentration instead of increasing small polaron concentration as expected. This trend in electrical conductivity is attributed to the neutralization of some small polarons due to formation of oxygen vacancies with increase in Ca2+ concentration.