锆锡钛酸铅反铁电陶瓷场致相变储能特性及失效机制研究

High-power pulse technology is the important developing fields of high-technology industry nowadays. The study on pulse discharge capacitor with high energy storage density becomes a hot spot in this field currently. Owing to the high energy storage density, antiferroelectric ceramics become a prime candidate for high-energy pulse discharge capacitor. However, the application of high-energy pulse discharge capacitor made with antiferroelectric ceramics is seriously limited due to strain-induced cracking in the capacitors during repeatedly antiferroelectric-ferroelectric phase transformations, which occur in charge-discharge cycling, as a result, the capacitors only undergo very small number of charge-discharge cycles. In order to improve the charge-discharge cycles and keep the high energy storage density of antiferroelectic ceramics, a new working thought that the forward switching field is chosen as the working field is proposed,and the compositions of lead zirconte stannate titanate (PZST) antiferroelectric ceramics are devised in the tetragonal phase area near the tetragonal-orthogonal phase boundary but far away from the rich zirconte content. The study focuses on the effects of compositions, types of dopants and microstructure on the phase transformation, energy storage and strain development in the ceramics. In order to understand the mechanism of energy storage of the field-induced phase transformation, dielectric properties and domain switching varied with applied field are also studied. The study also includes investigations of the effect of the strain on the stress and the microcrack growth in the ceramics in order to illuminate the failure mechanism of the antiferroelectric ceramics during charge-discharge cycles, and to pursue the way for improving service life of high-energy pulse discharge capacitor made with antiferroelectric ceramics. It is believed that this study will help the development of new pulse discharge capacitor in our country.

脉冲功率技术是当今高新技术的重要发展方向，目前的研究重点是高性能脉冲电容器。反铁电陶瓷因储能密度高而成为高性能脉冲电容器的重要候选材料。但在充放电过程中，反铁电陶瓷由于短时间内反复发生完全反铁电-铁电结构相变，容易产生较大内应力而导致材料开裂失效，严重制约其广泛应用。为了延长反铁电陶瓷充放电寿命并兼顾高储能密度，本项目首次提出将正向转折电场作为其工作电场的新思路，并将锆锡钛酸铅(PZST)反铁电陶瓷的组成设计在四方-正交相界附近且远离富锆的四方相区。研究组成、掺杂、微结构对材料的相变行为、储能特性、应变性能的影响；研究电场作用下材料的介电性能、电畴反转的演变规律，揭示反铁电陶瓷场致相变储能的物理机理；研究场致应变对内应力和微裂纹扩展的影响，阐明反铁电陶瓷的失效机制；结合储能特性和应变性能随电场的变化规律，探求提高反铁电陶瓷循环充放电寿命的有效途径，为发展我国新型脉冲电容器奠定材料基础。

脉冲功率技术在国防、高新技术、民用等领域均有着广泛的应用，研制高储能密度、高储能效率的脉冲陶瓷电容器是当前脉冲功率技术领域的重点研究任务。反铁电陶瓷因为具有储能密度高、放电速度快等优点成为脉冲陶瓷电容器的重要候选材料。Pb(Zr,Sn,Ti)O3(PZST)基陶瓷是一种重要的反铁电材料。本项目选取La3+和Nb5+掺杂的PZST基陶瓷开展反铁电陶瓷的储能特性及相变行为研究。研究了组成对陶瓷电性能以及储能特性的影响，并确定出适合脉冲电容器应用的组成；研究了温度对PZST基反铁电陶瓷储能特性的影响以及电场对其温度稳定性的影响，通过改变工作电场成功的获得了随温度基本不变的储能陶瓷电容器组成；结合电性能测试和脉冲放电实验分析，揭示了反铁电陶瓷电容器的储能及放电特性，确定了其优选工作电场，同时实现了较大的放电电流、较快的放电速度和数千次的循环充放电寿命。.首先，制备了不同组成的PZST基反铁电陶瓷，系统研究了组成对四方反铁电陶瓷电性能的影响。随着Ti含量降低，相变电场变大，储能密度Wre变大，并且与Ti含量呈线性关系。随着Zr含量增多，正、反向相变电场变小，电滞变大，储能效率变小，其中PLZST58/34/8反铁电陶瓷的Wre为1.87J/cm3。 .其次，研究了Pb0.97La0.02 (Zr0.58Sn0.335Ti0.085)O3反铁电陶瓷储能特性的温度稳定性。当电场为8.6kV/mm，频率为1Hz时，陶瓷在20-100℃的温度区间内Wre都大于1.2 J/cm3，变化率小于15%，而且储能效率都高于78%。改变电场可以调控陶瓷可用储能密度随温度的依赖关系，存在一个合适的工作电场（8 kV/mm），使得其可用储能密度具有非常好的温度稳定性，平均每10℃变化率在0.5%以内。.最后，研究了反铁电陶瓷电容器的放电性能，揭示了放电特性，并确定出优选工作电场。在电场诱导反铁电-铁电相变时，反铁电陶瓷电容器的极化强度、理论储能密度、脉冲放电首峰电流随电场增大发生了突增。基于极化强度、理论储能密度、脉冲放电首峰电流和径向应变随电场变化的不同步性，指出反铁电陶瓷电容器的优选工作电场略高于其正向转折电场。在优选工作电场下，(Pb0.925La0.05)(Zr0.42Sn0.40Ti0.18)O3陶瓷电容器的脉冲放电首峰电流超过900A，周期约200ns，循环充放电2000次性能无衰减。