Structural and dielectric studies of excessive Bi3+ containing perovskite PZT and pyrochlore biphasic ceramics

The influence of high concentration of Bi3+ substitution on the phase formation, microstructure, dielectric and conductivity properties of lead zirconate titanate (Pb1−xBi2x/3(Zr0.5Ti0.5O3) with x = 0.1, 0.2, 0.3 and 0.4)) (PBZT) ceramics synthesized by a high energy ball milling method, has been studied. X-ray diffraction analysis showed that the samples have crystallized to rhombohedral or tetragonal perovskite phases depending on the concentration of Bi3+ substitution. As x is increased to more than 0.1 mol% the presence of a pyrochlore phase, identified as Bi2Ti2O7, has also been observed. The crystalline and prismatic nature of the grains improved as Bi3+ concentration is increased. Dielectric studies revealed that all the samples are characterized by high values of ε′ and as Bi3+ concentration is increased Tc values are found to decrease from 450 °C to 395 °C. The DC electrical conductivity studies showed the existence of both positive and negative temperature coefficient of resistance (PTCR and NTCR) in the present systems indicating their potential applications in switching devices.