Double doping effect on the structural and dielectric properties of PZT ceramics

Polycrystalline samples of the modified Pb(Zr1-x, Ti-x)O-3 (PZT) composition, with representative formula Pb-0.92(LazBi1-z)(0.08)(Zr0.65Ti0.35)(0.98)O-3 (PLBZT), a family of relaxor ferroelectrics, were prepared via the chemical route with z = 0.3, 0.6 and 0.9. Crystalline phases of powders calcined at different temperatures and the microstructure of the sintered pellets were investigated by x-ray diffraction (XRD) analysis and scanning electron microscopy, respectively. XRD confirms the result obtained by differential scanning calorimetry. The XRD profile shows that the samples having z = 0.9 and 0.6 do not exhibit a pyrochlore phase, whereas the samples with z = 0.3, have 3% of the pyrochlore phase. Microstructural analysis suggests that the shape of grains and intergranular residual pores are modified upon La doping. The dielectric constant and dielectric losses were measured as a function of frequency at room temperature for different frequencies starting from 0.1 kHz to 1 MHz. The dielectric constant was found to be strongly influenced by frequency whereas the Curie temperature remained almost the same. Finally, we conclude that the dielectric constant, loss and activation energy of PLBZT strongly suggest that these compounds are suitable for the preparation of high value capacitors and may be good candidates for device applications.