Effect of Oxygen Nonstoichiometry on the Thermal and Electrophysical Properties of Layered Ferrocuprates LnBaCuFeO5 + d (Ln = La, Pr; (0 ≤ d ≤ 0.5)

Abstract

The influence of the oxygen content (5 + δ) on the structure, thermal expansion, and electrical properties of the LnBaCuFeO5 + δ phases (Ln = La, Pr) is investigated. It is found that, for 0 ≤ δ ≤ 0.25, the unit cell parameters of the ferrocuprates decrease and the linear thermal expansion coefficient increases linearly with increasing δ. In the range 0.25 ≤ δ ≤ 0.50, the thermal expansion coefficient and the structural parameters of the samples depend weakly on their oxygen nonstoichiometry δ. The LnBaCuFeO5 + δ ferrocuprates (0 ≤ δ ≤ 0.48) are p-type semiconductors with the electrical resistivity ρ, thermopower coefficient S, and activation energy for electrical conduction EA decreasing with increasing δ and the dependence EA = f(δ) being close to linear.