反铁电体的非线性介电响应及其介电可调性研究

Nonlinear dielectric response of ferroelectricity and their tunable dielectrics is the hot point of dielectric materials. Antiferroelectricity is one of the ferroelectricity, but their structures are very different. Due to the anti-parallel of sub-lattice in antiferroelectricity, the remanent polarization is zero. Under the applied electric field, the ferroelectric phase is induced by the electric field from antiferroelectric phase, and polarization is observed. As a result, the nonlinear dielectric response of antiferroelectric phase is also very different from the ferroelectric phase. The tunable dielectrics of antiferroelectric phase show a change of bi-direction, i.e., the dielectric constant increases with the increasing of the applied electric field first, and then decreases after the applied field is more than the critical field. But, the tunable dielectrics of ferroelectric phase only show a change of uni-direction, i.e., the dielectric constant decreases with the increasing of the applied field. So, the antiferroelectric phase is more suitable for the application of the energy storage due to the increasing of dieletcir constant with the applied field. For the energy storage with dielectric materials, the higher of dielectric constant is the better. Comparing the ferroelctricity, the high energy storage density is desired to explore in antiferroelectricity. The mechanism of the dielectric constant increasing with the applied is also desired to reveal after detailed research, and the relationship between the sub-lattice and nonlinear dielectric response will be displayed.

铁电材料的非线性介电响应及其介电可调性一直为大家所关注。反铁电体是铁电材料的一种，但又与其在结构上明显不同。反铁电体由于结构上相邻子晶格自发极化方向的反向平行排列，宏观极化强度为零，但在电场作用下子晶格可以被反转诱导为铁电体，呈现出场诱相变的特点。因此同铁电体的介电可调随电场的单向变化相比，反铁电体在电场作用下的介电非线性响应，呈现出介电常数先增大后减小的双向可调变化，这意味着在某些应用方面反铁电体比铁电体更具独特优势，如在介质储能应用方面就需要在高电场下继续保持高介电常数，但铁电体介电常数却随偏置电场呈快速下降趋势。因此本项目拟通过对反铁电体的非线性介电响应及其可调双向变化机制的系统研究，探索在电场诱导下子晶格反转、取向对介电响应的贡献，以及电场的调控机理，拓展和丰富非线性介电响应和介电可调性的研究深度，并以介电常数随偏置电场增大这一物理效应为出发点，开展高储能密度反铁电介质材料的研究。

本课题围绕着反铁电体材料的组份、结构、工艺和性能之间的相互关系，对反铁电体的非线性介电响应及其介电可调性进行了重点研究，取得了以下几方面成果：搭建和完善了反铁电材料的制备和性能测试系统，为项目研究的顺利完成奠定了基础；详细研究了反铁电体材料组份变化对结构和性能的影响，特别是通过组分调节Ti/Sn、Zr/Sn比和微量离子掺杂来裁剪场诱相变性能，如相变电场、回滞、介电常数、居里温度等的大小，以及铁电相与反铁电相的结构变化，为设计反铁电材料的场诱相变性能参数、满足不同的应用要求打下了基础，并以此为基础通过工艺制备条件和组分的优化，获得了可针对不同研究需求的样品；研究了组分、温度、电场对非线性介电响应的影响和调控，对比和分析了铁电和反铁电相介电常数随偏置电场变化的异同，以及反铁电体非线性介电响应双向变换机制，通过样品温度和居里温度的相互关系，实现了对非线性介电响应在临界电场处的双向变换幅度的调控，并研究了其对放电性能的影响规律；在高储能密度反铁电材料的制备与性能研究方面，采用扎膜制备工艺并通过优化，有效地提高了反铁电体介质材料的击穿场强，由块体的25kV/mm左右增加到厚膜的41kV/mm以上，并观测到了反铁电体中存在的多次相变，电场诱导出的总极化强度可达41μC/cm2，对应储能密度可达10.4J/cm3，这一数值对陶瓷样品而言是比较高的。这些研究成果将推动反铁电体介质材料朝着高储能密度瓷料和多层陶瓷电器应用方向发展。