Piezoelectric Actuator Responsive to Environmental Humidity

Abstract

Bending behavior responsive to environmental humidity was investigated on a PZT actuator consisting of porous and dense PZT plates (Pb0.995Nb0.01(Zr0.53Ti0.47)0.99O3). A dense PZT plate with a high electrical resistivity was bonded to a porous PZT plate by hot-pressing, which showed a large resistivity change from 1014 to 107Ω⋅cm for a change of relative humidity from 5 to 85%. In such a structure, DC voltage applied to the bonded plate gives an electric field on both parts at a low humidity, but only on the dense part at a high humidity. A bending displacement responsive to a change of humidity was observed in the bonded PZT plates under DC bias. The bending mode was similar to that of a unimorph. The hot-pressing temperature affected the microstructure and humidity sensitivity of the porous PZT plate, and then the bending behavior of the PZT actuator.