Synthesis, structural refinement and physical properties of novel perovskite ceramics Ba1-xBixTi1-xMnxO3 (x=0.3 and 0.4)

International audienceThe crystal structure, morphological, optical, electrical and dielectric properties of polycrystalline perovskites of Ba1-xBixTi1-xMnxO3 (x = 0.3 and 0.4), prepared by the standard solid-state reaction process, were investigated systematically. From the X-ray diffraction results at ambient temperature, both samples showed the pure perovskite phase. Rietveld refinements revealed that the studied compounds adopt the cubic structure symmetry with Pm (3) over barm as a space group. Scanning electron microscopy demonstrated that the samples show irregularly spherical grains with an average size of 2 mu m. From UV-vis-NIR absorption spectra, the synthesized compounds exhibit a maximum absorbance in the whole visible range. Furthermore, the direct band gap energy was found to be 1.07 and 0.85 eV for x = 0.3 and 0.4, respectively. The electrical transport in these materials was studied by using the impedance spectroscopy from the room temperature to 110 degrees C. The modelling of complex impedance data was performed to separate the grain and grain-boundary contributions in the conduction process. The addition of Bi and Mn ions increased the dc electrical conductivity. The thermal variation of the dc electrical conductivity proved the semiconductor behavior of both studied compounds. The obtained activation energies from the dc conductivity for grain and grain-boundary contributions were found to be 0.39-0.36 eV for x = 0.3 and 0.20-0.32 eV for x = 0.4. The conduction mechanism was explained by hopping process along ionized oxygen vacancies. The dielectric permittivity and dielectric loss of both compositions showed an increase with increasing temperature