铌酸钾钠基无铅压电陶瓷掺杂改性的研究进展

Research Progress of Doping Modification of Potassium Sodium Niobate-based Lead-free Piezoelectric Ceramics

压电陶瓷材料因具有优异的机电转换特性而被广泛应用,主要分为铅基压电陶瓷和无铅基压电陶瓷。然而,铅基压电陶瓷因含有高浓度的重金属铅而对环境损害极大,目前世界各国均已立法限制其应用。因此,环境友好型的无铅压电陶瓷成为学者的研究重点。其中,铌酸钾钠(KNN)基陶瓷因含有较大的压电系数、较高的居里温度,且通过适当的成分设计和晶体相位调整,在多晶型相界处可获得最佳电学性能,有的甚至可与锆钛酸铅(PZT)相媲美,从而备受人们的青睐。但对于在多晶型相界处可获得最佳电学性能的物理机理并未明确,同时多晶型相界不易调控以及KNN基陶瓷自身K、Na元素易挥发,对其电学性能产生了严重影响。本文以离子取代、添加新组元和添加烧结助剂为切入点,论述KNN基陶瓷的掺杂机理和烧结特性,讨论A位掺杂、B位掺杂以及A、B位共掺对KNN陶瓷晶体结构的影响,重点论述三方相-正交相(R-O)、正交相-四方相(O-T)或三方相-四方相(R-T)共存与高压电性的物理机制,总结KNN基无铅压电陶瓷的发展。其中,在离子取代基础上添加新组元化合物,更加有利于构建多相共存的微观相结构;同时,开发的烧结助剂可有效地解决KNN基陶瓷烧结性能较差的问题。综上可知,KNN基无铅压电陶瓷在取代PZT基压电陶瓷材料方面具有极大潜力。

Piezoelectric ceramic materials are widely used due to their excellent electromechanical conversion characteristics.They are mainly divided into lead-based and lead-free piezoelectric ceramics.However,high lead concentration is extremely harmful to the environment,and international legislation has prohibited the application of lead-based piezoelectric ceramics.Therefore,environmentally friendly lead-free piezoelectric ceramics have become the research focus.Potassium sodium niobate(KNN)-based lead-free ceramics are favored because of their large piezoelectric coefficient and high Curie temperature.KNN-based ceramics with appropriate composition and crystal phase adjustment can achieve the best electrical properties at the polycrystalline phase boundary,and some are even comparable to PZT.However,difficulty in controlling the polycrystalline phase boundary and the volatile nature of K and Na in KNN-based ceramics have seriously affected their electrical properties.In addition,the fundamental reasons behind the optimum electrical properties at the polycrystalline phase boundary remain undiscovered.Taking ion substitution,adding new components and adding sintering additives as the starting point,this article discusses the doping mechanism and sintering characteristics of KNN-based ceramics in detail.It also discusses the effects of A-site doping,B-site doping,and A and B-site co-doping on the crystal structure of KNN-based ceramics with a focus on the physical mechanism of the coexistence of R-O,O-T,or R-T phases and high piezoelectric properties,and summarizes prospects and developments in KNN-based piezoelectric ceramics.The results show that adding a new component based on ion substitution is more conducive to constructing a multiphase coexistence microstructure.And the deve-loped sintering aid can effectively improve the poor sintering performance of KNN-based ceramics.Based on the results,it is established that KNNbased piezoelectric ceramics have great potential in replacing lead-based piezoelectric ceramics.