New Perovskite Oxides LaBaMCoO5 + d (M = Fe, Cu): Synthesis, Structure, and Properties

Abstract

Perovskite oxides LaBaMCoO5 + δ (M = Fe, Cu) are synthesized, and the parameters of their crystal structure are determined in the temperature range 300–1100 K. The thermal stability, thermal expansion, electrical resistivity ρ, and thermopower S of the synthesized compounds are investigated. The compounds have a cubic structure with the unit cell parameter a = 3.9085 Å for M = Fe (δ = 0.97) and a = 3.9228 Å for M = Cu (δ = 0.62) and, at room temperature, are semiconductors (n-type for M = Fe and p-type for M = Cu). At high temperatures, the thermopower and the coefficients ∂ρ/∂T and ∂S/∂T reverse sign due to the release of oxygen from the samples. Measurements of the magnetic susceptibility have revealed ferromagnetic ordering of the magnetic moments of the iron and cobalt cations in the LaBaFeCoO5.97 compound at a temperature of 168 K.