Phase transitions and ionic conductivity of BaBi x O1.5x+1 (x≥5) oxides

Crystals of the BaBi _x O_1.5x+1 family are studied using X-ray diffraction, calorimetric, and impedance methods. It is shown that the compounds with x>5 are thermally stable in the temperature range as wide as 300–870 K, in spite of the first-order phase transition with a large heat effect. The conductivity is found to be anisotropic both in low- and high-temperature phases.