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驰豫型铁电体是很重要的功能材料,其介电性能和极化机制一直是研究的热点。作者通过对掺钛铌镁酸铅系列铁电陶瓷介电、铁电、热电等宏观性能和微观结构详细、系统的实验研究,提出铁电微畴为三方相畸变结构散布于立方钙钛矿母相中,通过类马氏体预相变的位移型形核过程,实现顺电—驰豫型铁电态的弥散相变,进一步通过类马氏体相变,完成驰豫型铁电态无序态分布的微畴向正常铁电态长程序铁电宏畴转变;提出T_1可调整A(B′B″)O_3型复合钙钛矿铁电体B′和B″离子价态和离子半径等不同所产生的内电场和弹性场,使立方母相所承受切应力发生变化,诱发极性微区、铁电微畴随组成变化表现不同活性。对弛豫型铁电体介电谱分析与计算表明,其在介电常数峰值温度Tm附近的介电弛豫过程连续变化,不对应结构突变的相变过程,较接近偶极介质。通过铌锌酸铅基系列铁电陶瓷在准同型相界附近异常特性的研究,进一步揭示弛豫型铁电体中结构特征决定宏观行为的必要性,反映出铁电材料由微观到介观、再到宏观的有趣规律性。在此基础上,对复合钙钛矿弛豫型铁电体偏压介电行为、电致伸缩特性、介电老化行为等进行了系统研究,合理解释了一系列新的实验现象和结果;并对钨青铜结构铌酸锶钡弛豫型铁电陶瓷复介电响应进行了详细的对比分析和讨?
Relaxation-type ferroelectrics are very important functional materials, and their dielectric properties and polarization mechanisms have been the research hotspots. Based on the detailed and systematic experimental study on the macro-performance and microstructure of lead-doped niobium-magnesium titanate series ferroelectric ceramics such as dielectric, ferroelectric, thermoelectric and so on, the author proposed that the ferroelectric micro-domains were distributed in cubic perovskite Phase, through martensite-like phase transition nucleation process, to achieve paraelectric - relaxation of the ferroelectric dispersion phase transition, and further through martensitic transformation to complete the relaxation of the ferroelectric disorder State micro-domains to the ferroelectric macro-domains of the normal ferroelectric long-range ferroelectric materials. The valence and ionic radius of B ’and B “ions of T 1 adjustable A (B’B”) O 3 -type perovskite ferroelectrics The different internal electric field and elastic field produced change the shear stress of the cubic mother phase, induce the polar micro-domains, and the ferroelectric micro-domains exhibit different activities with the composition changes. The analysis and calculation of the dielectric spectrum of the relaxed ferroelectric show that the dielectric relaxation process continuously changes near the dielectric constant peak temperature Tm, which does not correspond to the sudden change of the structure, and is closer to the dipole medium. Based on the study of the anomalous properties of lead niobate-based ferroelectric ceramics near the quasi-homophase boundary, it is necessary to further reveal the structural behavior of the relaxed ferroelectrics to determine the macroscopic behavior of the ferroelectric ceramics, Then to the macroscopic interesting regularity. On this basis, the dielectric behavior, electrostrictive properties and dielectric aging behavior of the composite perovskite ferroelectric are studied systematically, and a series of new experimental phenomena and results are reasonably explained. In the tungsten bronze structure barium strontium barium ferroelectric relaxation ferroelectric ceramics complex dielectric response in detail comparative analysis and discussion?