Properties of RBaCuFeO_(5+δ) (R = Y, La, Pr, Nd, Sm-Lu)

摘要

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 approx＝ 15 x 10~(-6) and approx＝ 13 x 10~(-6) K~(-1) for R = La-Eu and R = Gd-Lu, respectively. Their electrical conductivity varies widely, from σ = 2.0 x 10~1 S/cm for LaBaCuFeO_(5.47) to σ = 8.4 x 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 4f electrons of the rare-earth ions play a significant role in determining the structural and transport properties of these phases.