Grain-size dependent electric-field induced structural changes and its role in determining the piezoelectric response of 0–3 piezoceramic-polymer composite

Abstract

Polymer-piezoceramic 0–3 composites combine the flexibility of polymers and the excellent piezoelectric properties of ferroelectric based ceramics. While the grain size of ceramic powder is one of the important considerations in the fabrication of such composites, a correlation relating poling field induced structural changes and its possible influence on the overall piezoelectric response of the composite is still lacking. In this paper, we examine this issue on a 0–3 piezo-composite comprising ceramic powders of a low-lead piezoelectric alloy (x)Bi(Ni_1/2Zr_1/2O₃-(1-x)PbTiO₃ in the proximity of its morphotropic phase boundary and polyvinylidene fluoride as the polymer component. Composites were fabricated by fixing the volume fraction of the ceramic while varying the grain size. We found a non-monotonic variation in the piezo-response as a function of grain size. Structural analysis before and after poling of the piezo-composites revealed evidence of poling induced cubic-like to tetragonal irreversible transformation, the extent of which is dependent on the grain size. Our findings suggest that the non-monotonic grain size dependence of the composite's piezoelectric response is associated with inducing a coexistence of long ranged and short ranged ferroelectric domains in the ferroelectric grains of the composite by the poling field. Our observations contradict a conjecture reported in the past, which attributed a similar non-monotonic grain size dependent piezoelectric behavior to the larger grains becoming off-stoichiometric