Phase formation, microstructure development, and copper co-firing of barium titanate - bismuth zinc titanate and related dielectrics

Abstract

Technological advancements in power electronics devices require the development of capacitors that are capable of operating at elevated temperature and under large applied electric fields. The BaTiO3 – Bi(M)O3 family of dielectrics (where M represents a net-trivalent cation or cation pair) has proven to be a promising alternative to currently available X7R- and C0G-type capacitors. However, much is yet to be known about this class of materials in order to enable design optimization and proper integration into industrial applications. This work studies the effects of atomic structure, phase formation, processing conditions, and microstructure development of (1-x)BaTiO3 – xBi(M)O3 on its measured dielectric properties, with a focus on (1-x)BaTiO3-xBi(Zn1/2Ti1/2)O3. Studies included in this work are in situ hot-stage x-ray diffraction, which elucidated the reaction pathways of precursors as they reacted to form 0.8BaTiO3-0.2Bi(Zn1/2Ti1/2)O3; Rietveld refinements of high resolution x-ray diffraction scans of 0.8BaTiO3-0.2Bi(Zn1/2Ti1/2)O3, which provided valuable information about the structure(s) at room temperature; studies about overcoming the thermodynamic challenge of cofiring copper electrodes with bismuth oxide-based dielectrics, accomplished through x-ray diffraction and thermal analysis; and a general review of the current understanding of structure-processing-property relationships in BaTiO3-Bi(M)O3 dielectrics, accompanied by a case study of the microstructure development and dielectric properties of a subset of BaTiO3-Bi(M)O3 compositions.