Abstract
The influence of A site doping on the crystal structure, electrical and magnetic properties of mixed metal perovskites of the type La1-xAxRh0.5Cu0.5O3 where A= Bi3+ and Pb2+ is reported. The samples have been synthesised by solid state methods, and characterized by synchrotron X-ray powder diffraction methods, XANES measurements, magnetic property measurements and, for La0.75Pb0.25Rh0.5Cu0.5O3, neutron diffraction. The diffraction measurements show no evidence for any cation ordering or oxygen vacancies in the crystal structure. The changes in the A-site compositions results in anomalous trends of cell volumes, octahedral distortions, electrical resistivity and magnetic susceptibility. Bi doped oxides have smaller cell volumes and magnetic susceptibilities than those of the Pb doped oxides. That is possibly related to the local ordering effects and due to 6s2 lone pair electrons of the Pb2+ and Bi3+ ions. Electron delocalisation between the Rh (3.5+) and Cu (2.5+) ions are thought to be also important. Changes in the magnitude of the oxides properties are mainly attributed to the influences of the ionic size, formal charge, electronegativity and electron configuration for each A site doped cation.