Analysis of high temperature reduction processing of RAINBOW actuator

Abstract

Reduced and internally biased oxide wafer (RAINBOW) actuator, a new type of monolithic bending device, is composed of a chemically reduced non-piezoelectric layer and a piezoelectric ceramic layer. The formation of the reduced layer is achieved through high temperature chemical reduction of one side of piezoelectric ceramic disc or plate by contact with a reduction agent (i.e., solid graphite). Samples with different reduction thickness are prepared under different conditions and the fabrication processing is discussed from thermodynamic and kinetic considerations. It is proposed that the reduction reaction of PZT ceramic is proceeded by the formation and diffusion of oxygen vacancies. This process simply follows parabolic law. The diffusion rate constant and activation energy of this reduction process are also determined in this study, which can be used to predict the reduction layer thickness at a given temperature.