Maximising electro-mechanical response by minimising grain-scale strain heterogeneity in phase-change actuator ceramics

Abstract

Phase-change actuator ceramics directly couple electrical and mechanical energies through an electric-field-induced phase transformation. These materials are promising for the replacement of the most common electro-mechanical ceramic, lead zirconate titanate, which has environmental concerns. Here, we show that by compositional modification, we reduce the grain-scale heterogeneity of the electro-mechanical response by 40%. In the materials investigated, this leads to an increase in the achievable electric-field-induced strain of the bulk ceramic of 45%. Compositions of (100–x)Bi0.5Na0.5TiO3–(x)BaTiO3, which initially possess a pseudo-cubic symmetry, can be tuned to undergo phase transformations to combined lower symmetry phases, thus decreasing the anisotropy of the transformation strain. Further, modelling of transformation strains of individual grains shows that minimum grain-scale strain heterogeneity can be achieved by precise control of the lattice distortions and orientation distributions of the induced phases. The current results can be used to guide the design of next generation high-strain electro-mechanical ceramic actuator materials.

Defect‐Driven Structural Distortions at the Surface of Relaxor Ferroelectrics

“…[24] This mixed phase transformation has been suggested to be grain orientation dependent, allowing large strains in bulk polycrystals. [25] Thus, the skin structure observed in NBT-BT exhibits a distortion similar to the mixed phase transformation described by Oddershede et al [25] Figure 4 (a) shows laboratory XRD data fit with 3 phases. Firstly, the cubic (Pm m) structure is used to fit the bulk phase.…”

Enhanced Electromechanical Response and Thermal Stability of 0.93(Na1/2Bi1/2)TiO3‐0.07BaTiO3 Through Aerosol Deposition of Base Metal Electrodes

“…It should be noted here that the evolution of field‐induced domains in these materials can also be influenced by the grain orientation. [ 82–85 ]…”

Origin of ferroelectric P‐E loop in cubic compositions and structure of poled (1‐x)Bi(Mg1/2Zr1/2)O3‐xPbTiO3 piezoceramics

“…This has been attributed to high piezoelectric response in these materials . In addition to the maximization of piezoelectric response near MPB, the enhancement in piezoelectric response can be obtained by crystallographic texturing, microstructural engineering, formation of ceramic‐ceramic composites and core‐shell grain structures . Recently, electric field‐induced phase transitions have been reported in many MPB system .…”