提高铌酸钾钠基陶瓷准同型相界处温度稳定性的研究

The properties of potassium sodium niobate (KNN)-based ceramics around the morphotropic phase boundary (MPB) are comparable to those of Pb-based ceramics. However, the MPB of KNN-based ceramics can only exist within a relatively narrow temperature range. As a result，strong piezoelectric temperature dependence is usually observed，which is often very undesirable for practical applications. Therefore, in order to enhance the piezoelectric properties and temperature stability of the ceramics, KNN-based materials with extended orthorhombic-tetragonal polymorphic phase transition region are prepared using the composite method by optimizing the compensating amount of A-site K and Na elements, doping with quinquevalent cation combination at B-site, and adding new components. Meanwhile, this project deals with the effects of phase structure and domain configurations on the piezoelectric properties and temperature stability of the ceramics around the MPB. The goal of this project is to reach excellent properties of piezoelectric constant d33≥360 pC/N and temperature stability range -50-150oC, and reveal the physical mechanism of the structural conversion and property change around the orthorhombic-tetragonal phase transition. This research project is of importance for the practical application of KNN-based lead-free materials.

铌酸钾钠基陶瓷在准同型相界附近的压电性能有望取代含铅压电材料，但铌酸钾钠基陶瓷的准同型相界只能在较窄的温度区间内存在，不能满足实际应用的要求。为提高铌酸钾钠基无铅压电陶瓷的压电性能温度稳定性，本项目拟采用复合合成法，通过调节A位K、Na元素的过量范围得到具有较高压电性能的正交-四方两相共存结构陶瓷；研究添加新组元和五价复合金属离子对拓宽铌酸钾钠基陶瓷两相共存温度范围的影响；同时深入研究陶瓷在准同型相界处相结构、电畴构型等因素与压电性能和温度稳定性之间的关系，揭示正交-四方相变温度附近压电性能变化的物理机制，进而研制出压电常数d33不低于360 pC/N, 温度稳定性范围在-50-150oC的高性能KNN基压电陶瓷材料。本项目的研究对促进铌酸钾钠基无铅压电材料的实用化具有重要意义。

本项目以高性能的铌酸钾钠（KNN）基陶瓷为研究对象，采用传统的电子陶瓷固熔烧结工艺，确定了陶瓷体系中的准同型相界的相变行为和性能特征，通过相结构控制和显微形貌构筑相结合，研制出温度稳定性较高的KNN基无铅压电陶瓷。用两步合成法，通过调节A位K、Na元素的过量比例得到了具有较高压电性能的准同型相界结构陶瓷，其中制备的(Na0.52K0.45Li0.03)1-xLax(Nb0.88Sb0.09Ta0.03)O3陶瓷在x=0.003处，d33高达346 pC/N，机电耦合系数kp为40%，剩余极化强度高达Pr=37.80 μC/cm2，其优异的性能可以媲美铅基陶瓷。通过外掺碱土、稀土离子拓宽了KNN基陶瓷两相共存温度范围，其中制备的0.948(K0.5Na0.5)NbO3-0.052LiSbO3-0.01MgTiO3陶瓷，在30-120 oC温度范围内，剩余极化强度和单向电致应变表现出优异的温度稳定性，其剩余极化在此温度范围内仅仅降低了18%，并且具有优异的抗疲劳特性。同时，本项目还研究了多功能稀土掺杂KNN陶瓷的光、电性能，制备出具有优异抗疲劳特性的Pr、Eu掺杂的KNN无铅压电陶瓷，并在陶瓷中观察到了明亮的发光现象，对于拓宽压电发光材料的选择范围、寻求新的发光调制手段、研发出抗疲劳特性好的实用化新型光电多功能陶瓷元件具有重要价值。