Microstructure and piezoelectric properties of barium zirconium titanate-barium calcium titanate lead-free material system
Abstract
The recently discovered piezoelectric system based on barium zirconium titanate – barium calcium titanate (BZT-BCT) is a surprising addition to the potential for lead-free materials. The composition lying near the morphotropic phase boundary offers comparable piezoelectric properties to other high performance lead-based systems. In this research, the piezoelectric properties, crystal structure and domain motion were studied on this system to understand its ultra-high piezoelectricity. Based on an in-situ temperature dependent x-ray diffraction study, detailed crystallographic information for tetragonal BZT-BCTs was obtained, and the phase transition temperature was determined. The measured piezoelectric and ferroelectric properties show peak values at the optimum composition of BZT-50BCT. However, by changing the poling condition, a further improvement of piezoelectric properties can be achieved, which is proposed to be due to the development of an internal bias field. In addition, high temperature performance of this system was investigated by studying the thermal depoling behavior of ferroelastic texture. Ferroelastic texture induced by electrical poling is found to be thermally unstable but mechanical grinding was effective in inducing large scale of ferroeleastic domain textures that persist well above Curie temperature. Furthermore, the microstructure origin of high electromechanical behavior of this system was studied by in-situ electrical x-ray diffraction measurement. The contribution from extrinsic domain motion and intrinsic lattice strain to the macroscopic converse piezoelectric effect was resolved and discussed.
Degree
M.S.M.S.E.
Advisors
Blendell, Purdue University.
Subject Area
Materials science
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