Effects of Divalent Cation Substitution on Sinterability and Electrical Properties of LaCrO3 Ceramics

A series of LaCr1-xMxO3 (M = Mg, Cu, Zn, Ni) ceramics was fabricated by a conventional sintering process in air and Ar gas. Relative density, electrical conductivity, and magnetic susceptibility were measured to investigate the electrical conduction mechanism of the doped LaCrO3 ceramic. The apparent density was improved up to 95% of theoretical density, especially in the cases of M = Cu2+ and Zn2+. The electrical conductivity (σ) increased with increasing quantities of doped divalent cation (x), and log(σT) showed a linear relationship to (1/T). Magnetic data and chemical analysis indicated that the presence of Cr4+, rather than oxygen deficiencies, is preferential for the charge compensation. As a result, the electrical conduction was substantially governed by the hopping of small polarons between Cr3+ and Cr4+ ions. The substitution of Ni ions resulted in lower than expected unit cell volumes, somewhat different conductivities, and a different antiferromagnetic response, all of which pointed to the role of Ni3+ as of the source of an additional band conduction mechanism.