【摘要】 用传统的陶瓷工艺、通过B位氧化物预合成法制备了高质量、钙钛矿结构的0.20Pb(Fe1/2Nb1/2)O3-0.32PbZrO3-0.48PbTiO3(PFN20-PZ32-PT48)铁电陶瓷,该条件下制备的铁电陶瓷呈现相当均匀的微结构和良好的电学性能。PFN20-PZ32-PT48具有较大的室温介电常数(~410)、高的居里温度(TC,~350℃),在295K<T<525K温度区间,具有较小的介电常数温度梯度/εT=2.8/℃,并且介电常数与频率无关,特别适合高温电容器工业的应用。虽然PFN20-PZ32-PT48呈现较为典型的一级铁电相变,其介电性能在顺电相区呈现明显的频率色散现象,并伴随着介电常数和损耗的反常增加。该反常现象的产生可能与陶瓷烧结过程中Fe3+被部分还原成Fe2+离子所诱导产生的热激发的空穴导电机制有关。PFN20-PZ32-PT48的剩余极化(Pr)与频率的关系可以很好地用随机场模型模拟,表明其弛豫行为的产生与短程化学有序所诱导产生的极性簇和/或纳米尺寸的非均匀性有关。更多还原

【Abstract】 High-T_C（～350℃） ferroelectrics 0.20Pb(Fe_1/2Nb_1/2)O₃-0.32PbZrO₃-0.48PbTiO₃（PFN20-PZ32-PT48） with pure perovskite phase were synthesized using conventional ceramic processing via a B-site oxide mixing route for applications in high-temperature high-power-density electrotransducers and high-temperature capacitors.The ceramics exhibit a large room-temperature dielectric constant of ～410 and the dielectric constant is nearly independent of frequency with a temperature gradient of ε/T=2.8/℃ in the temperature region 295K<T<525K.An abnormal increase of dielectric constant,which exhibits strong frequency dependence accompanied by a large increase of dielectric loss,is observed at temperatures above T_C,which can be attributed to the partial reduction of Fe³⁺ to Fe²⁺ ions during sintering,leading to the increased thermally activated hole conduction. The frequency-dependent remanent polarization（P_r） scales well with the existing models of random field states,which indicates that the relaxor behavior correlates with the creation of chemical heterogeneity caused by the localized cationic ordering.The high T_C provides the opportunity of exploiting the near temperature-independent dielectric and electromechanical properties of this material for a wide range of applications.更多还原