Effective Dielectric Function of BaTiO3-NiO Composites

Using spark plasma sintering we have processed and studied two ceramic composites of 70 vol% BaTiO3 (BTO) and 30 vol% NiO with standard and core-shell microstructure. Quantitative broadband dielectric spectroscopy up to the infrared range at 10-450 K showed substantial differences between both composites. The evaluated dielectric spectra revealing all three ferroelectric phase transitions were compared with modelled spectra using three different models based on effective medium approximation (Bruggeman, Lichtenecker and coated spheres). The results, including the soft-mode dynamics, were discussed using the concept of the BTO percolation.