Nanostructure and dielectric behavior of vanadate glasses containing BaTiO3

Abstract The ac and dc electrical conductivity of barium titanate doped bismuth-vanadate as-quenched and heat-treated materials was measured in the frequency range from 1 mHz to 1 MHz and in the temperature range from 153 K to 423 K with the impedance spectroscopy method. The microstructure was investigated by means of XRD, scanning electron microscopy (SEM), atomic force microscopy (AFM) and confocal microscopy. The obtained results showed that the structure of both as-quenched and heat-treated samples is not homogenous. Heat-treatment had significant influence on the amount, size and chemical composition of formed micro- and nanocrystallites. It also had great impact on the conduction process in investigated materials. As-quenched samples showed one relaxation process that was due to the overlapping polaron hopping. Conduction process in heat-treated samples may be caused by two different conduction mechanisms within nanostructures and in the matrix or by the interface polarization. Direct current conductivity increased and activation energies of this process decreased after heat-treatment. The experimental results were discussed based on a “core–shell” model and conductivity models collected by Elliot.