Structure, morphological and dielectric properties of BZT-BST ceramics

Barium zirconate titanate (BZT), a relaxor ferroelectric ceramic based on barium titanate (BT), has received substantial research. In this study, Ba(Zr0.2Ti0.8)O3 and Ba0.85Sr0.15TiO3 were separately prepared by solid state method and thereafter they were mixed in the following ratio (1-x){Ba(Zr0.2Ti0.8)O3} – x{Ba0.85Sr0.15TiO3} (x = 0, 0.1, 0.2) (BZT-BST) to make ceramic composite using high energy ball mill. The structure, morphology, and dielectric properties of these composites have been systematically studied. The crystal structure of the BZT-BST composite was determined by X-ray diffraction technique. The XRD pattern shows a well-developed tetragonal perovskite crystal structure. Without a second phase, all samples exhibit the perovskite structured BZT diffraction peaks. Permittivity measurements show that the relative permittivity (εr) of the composite increases as the amount of BST increases from ×  = 0 to ×  = 0.1, but then decreases at ×  = 0.2, indicating a broad transition in dielectric constant. The observed Curie temperatures (Tc) for all the compositions mentioned are 31 °C, 36 °C, and 43 °C, of ​​which the dielectric maximum for each composition is found to be ∼ 5000, 6100, and 3810 at the frequency of 1 kHz. It can be seen that the relative permittivity (εr) of all three BZT-BST compositions decreases gradually with increasing frequency. At low frequency, there are several different polarizations mechanisms. However, at high frequencies, only electronic displacement polarization exists. Morphological analysis of the sintered samples by Field emission scanning electron microscopy (FESEM) shows that the pure BZT ceramics have numerous pores. The compactness of BZT-BST ceramics was significantly enhanced by the addition of BST. The grain size of BZT-BST ceramics increases with increasing BST content. Pure BZT ceramics exhibit ferroelectric diffusion phase transition characteristics with weak relaxation behaviour. BZT-BST composites exhibit increasing relaxation behaviour with increasing BST content. These may be the most promising candidate materials for capacitor applications.