EPR spectra and electrical conductivity of perovskite-like BaBi1−xLnxO3−δ (Ln = La, Pr)

Perovskite-type solid solutions of BaBi1−xPrxO3−δ (x = 0–1.0) and BaBi1−xLaxO3−δ (x = 0–0.4) were prepared by the standard ceramic synthesis technique. Substituting bismuth with the rare-earth cations was found to result in transition of monoclinic crystal lattice to orthorhombic at x ≥ 0.2 and in increasing perovskite unit cell volume. At moderate dopant concentrations, the electronic conduction in BaBil−xLnxO3−δ occurs via transport of electron holes between Bi5+ and Bi3+ cations, decreasing with x and oxygen partial pressure. Electrical conductivity of the BaBi1−xPrxO3−δ solid solutions at x = 0.4–0.8 was ascertained to be essentially independent of composition due to increasing contribution of praseodymium cations to the electronic transport. Relationships between electrical conductivity, electron paramagnetic resonance (EPR) and infrared absorption (IR) spectra of BaBi1−xLnxO3−δ were discussed. Thermal expansion coefficients of the BaBi1−xLnxO3−δ ceramics calculated from dilatometric data vary in the range of (11.0–13.0) × 10−6 K−1 at 300–1050 K.