Fatigue Property Of Lead Zirconate Titanate Ferroelectric Ceramics

In this work, a modified lead zirconate titanate ceramics（PZT） ceramic was prepared by solid state reactions. Thetemperature-dependent ferroelectric hysteresis characteristics of themodified PZT ceramics are studied from300to433K. The ceramicsamples were then fatigued by cycling with electric field; compleximpedance spectroscopy was utilized to investigate the mechanismof fatigue behavior. The dielectric properties, leakage current,polarization-electric field （P-E） loops and fatigue characteristics ofthe modified PZT ceramics with and without La0.8Sr0.2MnO3（LSM）buffer layers have been investigated with the comparative analysisof experimental data.（1） It is observed that remnant polarization, saturationpolarization and coercive field are increasing with an increase ofthe temperature in a low field region and decreasing in a high field region. Such behavior is explained by the competition betweenswitching and backswitching mechanisms. A three-stagedependence of the logarithm of the hysteresis loop area on thelogarithm of the electric field is identified. The temperaturedependence of backswitching properties has been studied. Theobtained results indicate that the temperature dependence of thepolarization backswitching can be well described by the Arrheniuslaw. The activation energy for the domain switching determinedfrom the fitting results decays to0.042eV as the electric fieldincreased.（2） Combination of impedance and conductivity plots wasutilized to understand the contributions arising from differentregions in the PZT ceramics, i.e. the grain boundary andceramic-electrode interface region. Two formulas were devoted toaccount for the presence of ceramic-electrode interface and grainboundary responses in different frequency regions. The results showedthat both the dc conductivity of the ceramic-electrode interface andthe dc conductivity of the grain boundary decrease with increasingcycle number. And the dc conductivity of the ceramic-electrodeinterface decreases larger during the fatigue process. Based on these results, we deduce that the damage zones underneath theelectrodes are the main source of fatigue in ceramics.（3） The double sided LSM buffer layers resulted in a lowerdielectric loss, a weaker frequency dependence of dielectricconstant, a lower leakage current density, and an increase in thesaturation polarization. More strikingly, it was found that up to1.4×10⁷cycle numbers, the Ag||LSM/PZT/LSM||Ag capacitor, withremanent polarization decreased by55%, was superior to theAg||PZT||Ag capacitor by85%. The results indicate that the LSMbuffer layers can improve the fatigue endurance of the PZTceramics with Ag electrodes, mainly because the accumulatedcharges were compensated at the interface junctions between theLSM buffer layers and the Ag electrodes. We fit the polarizationfatigue data using a modified model and find that the characteristicdecay time of oxygen vacancies migration in Ag||LSM/PZT/LSM||Agand Ag||PZT||Ag ceramics are calculated as4.8×10⁴s and3.4×10⁴s,respectively.