Possibilities of the practical use of a stationary strain gradient in the interelectrode volume of unpolarized ferroceramic plates

Abstract

It has been established that in plates made of hot-pressed ferroelectric ceramics PZT-19 ([Formula: see text]C), after metal electrodes from Ag are burned into opposite surfaces with different depths of mechanical damage, counter-directional stationary deformation gradients and, accordingly, internal electric displacement fields create a stationary flexoelectric effect. As a result, unpolarized ceramics below the Curie temperature become a pyroelectric, and above it become a pyroelectric bolometer. After polishing the less damaged surface and replacing the Ag (valency [Formula: see text]) electrode with Cr ([Formula: see text]) by thermal evaporation in vacuum from the intact surface, a new thermally stable polarization is created, directed from the damaged surface in the interelectrode volume. Such plates have an asymmetric dielectric hysteresis loop, retain the values of the pyroelectric effect and piezoelectric effect in the ferroelectric phase, as well as the bolometric effect in the paraelectric phase after repeated heating cycles to [Formula: see text]C and cooling to [Formula: see text].

Overview: State-of-the-Art in the Energy Harvesting Based on Piezoelectric Devices for Last Decade

“…As a rule, the presence of unipolarity is explained by the presence of a surface layer with a polarization state various from the main one. Many theoretical and experimental investigations have been devoted to proving and confirming the connection between the unipolar state and the spatial distribution of polarization in ferroelectrics [186][187][188][189]. Unipolarity can be caused by a stationary strain gradient near surfaces of non-polar ferroelectric ceramics.…”