EPR spectra and electrical conductivity of perovskite-like BaBi(1-x)Ln(x)O(3-delta) (Ln = La, Pr)

Perovskite-type solid solutions of BaBi1-xPrxO3-delta (x = 0-1.0) and BaBi1 -xLaxO3-delta ( x = 0-0.4) were prepared by the standard ceramic synthesis technique. Substituting bismuth with the rare-earth cations was found to re sult in transition of monoclinic crystal lattice to orthorhombic at x great er than or equal to 0.2 and in increasing perovskite unit cell volume. At m oderate dopant concentrations, the electronic conduction in BaBi(1-x)Ln(x)O (3-delta) occurs via transport of electron holes between Bi5+ and Bi3+ cati ons, decreasing with x and oxygen partial pressure. Electrical conductivity of the BaBi1-xPxO3-delta solid solutions at x = 0.4-0.8 was ascertained to be essentially independent of composition due to increasing contribution o f praseodymium cations to the electronic transport. Relationships between e lectrical conductivity, electron paramagnetic resonance (EPR) and infrared absorption (IR) spectra of BaBi(1-x)Ln(x)O(3-delta) were discussed. Thermal expansion coefficients of the BaBi(1-x)Ln(x)O(3-delta) ceramics calculated from dilatometric data vary in the range of (11.0-13.0) x 10(-6) K-1 at 30 0-1050 K. (C) 2000 Elsevier Science S.A. All rights reserved.