Structure and properties of substituted BaPbO3 and Ba2PbO4 compounds

Structure–property relations have been studied in the following systems: (a) perovskite type BaPb1−xCuxO3 and Ba1−xLaxPbO3 and (b) K2NiF4 type Ba2Pb1−xMxO4 (M = Bi, Sb) and Ba2Pb1−xBixO4−yFy. In the case of BaPb1−xCuxO3, an orthorhombic to pseudo-cubic structural transition is observed at x = 0.3 and the samples remained metallic. A similar behaviour is observed also in Ba1−xLaxPbO3. In both systems, the metallic character of BaPbO3 was found to decrease with substitution. No evidence for superconductivity is observed in any of the compositions. However, a non-reproducible superconducting like transition has been noticed in a nominal. multiphasic Ba2(Pb0.75Bi0.25)O3F composition at around 40 K.