Study On The Electrical Properties Of Lead Zirconate Titanate (PZT) Ferroelectric Ceramics

Lead zirconate titanate system with the Zr/Ti ratio around 95/5 has been reported to own high pyroelectric coefficient and low dielectric constant, which can be used in infrared detection and thermo-electronic converting. The system has a low temperature FRL-FRH phase transition. During the phase transition, the little crystal lattice distortion results in little change of spontaneous polarization. Meanwhile, the dielectric constant and loss vary not too much. However, near the transition point, a large pyroelectric peak can be observed and the figure of merit is also very higher. But during the practical application of PZT95/5 ceramics, we found there existed several problems such as large impedance hard to be matched, larger dielectric loss. Compared to PZT95/5 ceramics, the two systems of PMS-PZT and PFN-PZT were found to have much less resistivity but large dielectric constants and loss. Therefore, we hope to improve the global dielectric properties by doping different ions.Based on the principle of"the same valance, different ionic radius; similar ionic radius, different valances", the additives such as ZnO,Cr2O3,Ga2O3 and SnO2 were doped into PMS-PZT system and In2O3,Ga2O3,Co2O3 and Cr2O3 were doped into PFN-PZT system. The dielectric properties, piezoelectric properties, polarization properties, FRL-FRH phase transition behavior and Curie temperature were studied. The samples were characterized with IR, UV and SEM methods. The relation between the physical properties and microstructures was also discussed.The results show that acceptor additives make the resistivity, dielectric constant and loss decrease in the PMS-PZT system and with the increase of the ionic valance, the dielectric constant and loss decrease gradually. The resistivity, dielectric constant and loss were 1.7×1011? cm, 190 and 0.2%, respectively when 0.3wt% SnO2 was doped. The measured pyroelectric coefficient is 2.876 E-8Ccm-2K-1. At the same time, no thermo-hysteresis exists during the heating and cooling runs. With increase of the content of SnO2, the dielectric constant and loss has a minimum. The best doping content of SnO2 is 0.3wt%. As for the PFN-PZT system, when it was doped with 0.3wt% Cr2O3, the best dielectric performance was obtained with the dielectric constant and loss of 373, 1.6%, respectively. The corresponding resistivity is 1.7×1011? cm. Furthermore, our investigation also reveals the relationships between the IR, UV and dielectric properties, resistivity.