Study of PZT multilayer piezoelectric transformers

Abstract

Two types of lead zirconate titanate (PZT) multilayer structures have been investigated in this work. The first one, which consisted of thick PZT films fabricated by roll-casting and platinum (Pt) interleaving electrodes, was sintered at high temperature (1280oC). Thickness mode and length mode multilayer transformers have been fabricated from this type of multilayer structure and tested. The second type of multilayer PZT structure was fabricated by a sol-gel technique. A conductive oxide, lanthanum nickel oxide (LNO), was used as the electrode and the PZT/LNO multilayers were co-fired at below 650oC to make the process compatible with the integrated circuit (IC) technology. Original contributions reported in this thesis included: (1) Besides fabricating and evaluating PZT multilayer transformers based on the usual thickness mode, a new length mode multilayer transformer has been fabricated and its performance characterized. (2) A PZT/LNO multilayer structure was studied. A buffer layer consisting of a mixture of PZT and LNO was introduced at the interface to enhance the adhesion between the PZT and LNO. (3) To fabricate LNO films thick enough to be used as electrode, a modified sol-gel process has been used. LNO powder was introduced into the LNO sol-gel solution to induce a seeding effect in the film formation process and the annealing temperature has been reduced.