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 (Tc=300∘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 v=3) electrode with Cr (v=6) 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 400∘C and cooling to Tnorm.

Keywords

• strain gradient
• unpolarized ferroceramic
• pyroelectric effect
• bolometer