Properties of RBaCuFeO5+δ (R = Y, La, Pr, Nd, Sm-Lu)

Abstract

The structural properties, thermal stability, thermal expansion, and electrical properties of the RBaCuFeO 5+δ (R = Y, La, Pr, Nd, Sm-Lu) layered ferrocuprates have been studied systematically. The linear thermal expansion coefficients of the RBaCuFeO 5+δ phases are ≃ 13 × 10 −6 and ≃ 13 × 10 −6 K −1 for R = La-Eu and R = Gd-Lu, respectively. Their electrical conductivity varies widely, from σ = 2.0 × 10 1 S/cm for LaBaCuFeO 5.47 to σ = 8.4 × 10 −8 S/cm for TmBaCuFeO 5.06 at 300 K. The lattice parameters, thermal expansion, and conductivity of RBaCuFeO 5+δ vary nonmonotonically with the ionic radius of R 3+ (atomic number of the rare earth), which is due to the fact that the 4 f electrons of the rare-earth ions play a significant role in determining the structural and transport properties of these phases.