Microstructure Characterization and Electrical Conductivity Measurement of La_1−xCa_xCrO₃ (x = 0.25, 0.4, 0.5) Prepared by Aspartic Acid‐Assisted Solution Combustion

Abstract

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.

Synthesis, dielectric properties, and influences oxygen vacancies have on electrical properties of Na1/2Bi1/2Cu3Ti4O12 ceramics prepared by a urea combustion method

“…Gel combustion methods have the advantages of relatively low cost, high-energy efficiency, fast heating rates, short reaction times, and high composition homogeneity [32]. Organic materials such as urea, glycine, citric acid, and EDTA have been widely used as fuels for gel combustion processes [33].…”

Improved Dielectric and Nonlinear Electrical Properties of Fine‐Grained CaCu3Ti4O12 Ceramics Prepared by a Glycine‐Nitrate Process

“…Among of these four primary methods as mentioned above, the combustion method using ammonia as a fuel and EDTA route are classified as the combustion process. Organic compounds like glycine, urea, citric acid, and EDTA have been widely used as fuels for gel combustion . The glycine‐nitrate process (GNP) is one of the most attractive methods.…”

Microwave-assisted combustion synthesis of nanocrystalline Sm-doped La 2 Mo 2 O 9 oxide-ion conductors for SOFC application

“…This sintering temperature, somewhat lower compared to those of samples prepared by solid state reaction method. This might be the formation of highly sinter-active nanopowder with low roughness during combustion synthesis [23]. The decrease in sintering temperature helped to avoid the formation of newer phases at high temperature.…”