Phase transitions in undoped BaCeO3

The linear thermal expansion (370–1500 K) and electrical conductivity (950–1220 K) have been measured for undoped BaCeO3 in dry air, pH2O=40 Pa. Samples were made both by conventional sintering and by solidification from inductive melting. Raman spectra were measured from 298 to 773 K. The obtained temperature dependencies, ΔL(T) and σ(T) upon heating and cooling, were treated mathematically by the method of differences (difference between experimental points and approximating the dependence by a first degree polynomial). This permitted to determine the position and the order of the structural phase transitions in BaCeO3. Five second-order transitions at 480±10, 530±10, 900±10, 1030±20 and 1170±20 K, and also one first-order transition at 665±10 K, were found. The transitions at 900 and 1030 K have not been reported before.