Thermoelectric Properties of Layered Ferrocuprates LnBaCuFeO5 + d (Ln = La, Pr, Nd, Sm, Gd–Lu)

Abstract

The electrical resistivity ρ and the thermopower S of ceramic materials LnBaCuFeO5 + δ (Ln = La, Pr, Nd, Sm, Gd–Lu) are measured in air at temperatures in the range from 300 to 1100 K. All the studied ferrocuprates are p-type semiconductors. The electrical resistivity ρ and the thermopower S of these compounds increase with a decrease in the radius of the Ln3+ cation (with an increase in the number of 4f electrons n in Ln3+). The nonmonotonic behavior of the dependences ρ = f(n) and S = f(n) indicates that the electrical properties of the layered ferrocuprates LnBaCuFeO5 + δ depend on the electronic configuration of the Ln3+ cation. The power factors P calculated for the LnBaCuFeO5 + δ ceramic materials from the experimental values of ρ and S increase with increasing temperature and, at T = 1000 K, reach the maximum values P = 102.0 and 54.1 µW m–1 K–2 for Ln = Pr (4f 2 ) and Sm (4f 5 ), respectively, and become close to each other and equal to 30– 35 µW m–1 K–2 for Ln = Gd (4f 7 ), Dy (4f 9 ), and Ho (4f 10).