High-temperature macroscopic piezoelectricity in Nb-doped PbZr1-xTixO3 ceramics driven by the existence of polar regions -: art. no. 144114

The dielectric, elastic, and piezoelectric properties of a niobium-doped PbZr1-xTixO3 ceramic with a composition located near the morphotropic phase boundary have been studied from 25 to 400 degrees C. A strong softening of the elastic coefficients was observed far below the temperature corresponding to the dielectric permittivity maximum, T-epsilon max=366 degrees C. The steep decrease of the stiffness coefficient c(44) from 400 to 350 degrees C is probably a stepwise anomaly which is expected at an improper ferroelastic transition. In addition, it was found that all macroscopic piezoelectric activity had disappeared well above T-epsilon max. This is explained by the combined effects of compositional fluctuations in the Zr/Ti sublattice and the presence of polar nanoregions. The elastic properties have an anomaly at the temperature at which the lattice becomes predominantly centrosymmetric. The piezoelectric activity vanishes when the polar nanoregions reach a critical size below which they can no longer interact coherently through the nonpolar matrix to induce a macroscopic piezoelectric response.