Synthesis, structure, and relaxation processes in Bi2Mg1-x Cu x Nb2O9 ion-conducting ceramics

Synthesis of bismuth niobates doped by copper and magnesium is performed and their structure, temperature and frequency dependences of capacitance and conductivity are studied. X-ray diffraction analysis showed that all samples are single-phase and have a cubic pyrochlore structure with a slight tetragonal distortion. Temperature memory is observed for the samples; it is manifested in hystereses in the temperature dependences of capacitance C(T) obtained in the heating-cooling mode. A mathematical model explaining the Gauss form of the experimental C(T) curve is suggested. The possibility of extracting separate components is shown for complex polarization processes in the case of materials with complex conductivity on the basis of the temperature dependences of capacitance measured at a constant frequency. In some of the studied solid solutions, three relaxation processes were found with intensity growing fast at an increase in the concentration of copper.