Strong Electromechanical Response in Lead Zirconate Titanate Metamaterials
As a class of technically important functional materials, Pb(Zr,Ti)O3 (PZT)‐based materials have been widely used in different types of piezoelectric devices. These materials are also ferroelectrics, and the materials lose their piezoelectric properties above the Curie temperature, a drawback limiting applications of the materials at high temperatures. Designing piezoelectric metamaterials by exploiting the flexoelectricity of the PZT‐based materials is a possible solution to this issue. In this work, PZT‐based piezoelectric metamaterials can be designed by applying an asymmetric chemical reduction to PZT ceramics to produce a curvature. The reduced PZT ceramic wafers exhibit a high apparent piezoelectric response (>2900 pC/N), which can be sustained after a heat treatment at 550°C for 5 h, which is more than 250°C above their Curie temperature. A substantial piezoelectric response can also be directly measured well above the Curie temperature. The mechanism underlying this very high apparent piezoelectric response with high‐temperature stability is investigated. The experimental results suggest that the electromechanical response mainly originates from the flexoelectric effect when the reduction‐induced curvature is bent under stress. The formation of the curvature also causes strain gradient‐induced poling of the reduced materials, resulting in a weak piezoelectric response from partly oriented polarization, which partly contributes to the observed response.
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