多孔未极化Pb(Zr0.95Ti0.05)O3铁电陶瓷单轴压缩力学响应与相变

通过添加造孔剂的方法制备了四种不同孔隙率未极化PZT95/5铁电陶瓷. 采用非接触式的数字散斑相关性分析(digital image correltation, DIC)全场应变光学测量技术, 对多孔未极化PZT95/5 铁电陶瓷开展了单轴压缩实验研究, 讨论了孔隙率对未极化PZT95/5铁电陶瓷的力学响应与畴变、相变行为的影响. 多孔未极化PZT95/5铁电陶瓷的单轴压缩应力-应变关系呈现出类似于泡沫或蜂窝材料的三阶段变形特征, 其变形机理主要归因于畴变和相变的共同作用, 与微孔洞塌缩过程无关. 多孔未极化PZT95/5铁电陶瓷的弹性模量、压缩强度都随着孔隙率的增加而明显降低, 而孔隙率对断裂应变的影响较小. 预制的微孔洞没有改善未极化PZT95/5铁电陶瓷材料的韧性, 这是因为单轴压缩下未极化PZT95/5铁电陶瓷的断裂机理是轴向劈裂破坏, 微孔洞对劈裂裂纹传播没有起到阻碍和分叉作用. 准静态单轴压缩下多孔未极化PZT95/5铁电陶瓷畴变和相变开始的临界应力都随着孔隙率的增大而呈线性衰减, 但相变开始的临界体积应变却不依赖孔隙率.

Mechanical properties and phase transformation of porous unpoled Pb(Zr0.95Ti0.05)O3 ferroelectric ceramics under uniaxial compression

Four kinds of unpoled lead zirconate titanate (PZT95/5) ferroelectric ceramics were fabricated in a range of different porosity levels by systematic additions of added pore formers. By using the non-contact digital image correlation (DIC) optical technique to measure the full-field strain, the response of unpoled PZT95/5 ferroelectric ceramics to statically applied uniaxial stresses was investigated. The influences of porosities on the mechanical behavior, domain switching, and phase transformation of the porous unpoled PZT95/5 ferroelectric ceramics were explored. All the measured stress versus strain curves for the tested porous unpoled PZT95/5 ferroelectric ceramic samples can be divided into three stages: the initial linear elastic region, the approximate plateau region, and the second linear elastic region, similar to the behavior of foam or honeycomb materials. However, the deformation mechanism of porous unpoled PZT95/5 ferroelectric ceramics should be attributed to the domain switching and phase transformation processes, but not related to the collapse of voids. With the increase of porosity, the elastic modulus, fracture strength and fracture strain of the porous unpoled PZT95/5 ferroelectric ceramics would decrease. Effect of dispersed voids does not improve plasticity of the porous unpoled PZT95/5 ferroelectric ceramics, which is mainly attributed to no effect of the pores on the obstacle and proliferation of crack propagation during the axial splitting failure processes. Critical stresses of the domain switching and phase transformation decrease linearly with increasing porosity. The macroscopic critical volumetric strain needed for phase transformation is independent of the porosity in the unpoled PZT95/5 ferroelectric ceramics.