In Situ Neutron and X-Ray Powder Diffraction Study of Cation Ordering and Domain Growth in the Dielectric Ceramic Ba3ZnTa2O9–Sr2GaTaO6
Abstract:In situ methods are ideally suited to study the development of property-critical structural features during material processing. As an example of their potential in the area of complex oxide electroceramics, here, we apply X-ray synchrotron and neutron powder diffraction to investigate the ordering processes responsible for optimizing the microwave dielectric properties of the commercial electroceramic barium zinc tantalate (BZT) doped with strontium gallate. The collection of synchrotron diffraction data with high resolution and high intensity during processing has allowed the development of cation site order and growth of ordered domains to be followed during the multi-stage thermal treatment processing used by industry. Complementary neutron diffraction data reveal changes in the cation–oxygen bonding associated with development of the cation-ordered trigonal perovskite structure. The effects of material loss with processing at temperatures of up to 1525°C are discussed following experiments using open and closed systems. The complex nature of the ordering is confirmed by the coexistence of two BZT phases and the formation of a further zinc-deficient phase. The implications of these observations and relation to the industrial processing procedures are discussed.
Document Type: Research Article
Affiliations: 1: ISIS Facility—CCLRC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, U.K. 2: Department of Chemistry, University of Liverpool, Liverpool L69 7ZD, U.K. 3: European Synchrotron Radiation Facility, BP-220, F-38043 Grenoble Cedex 9, France 4: Filtronic Comtek, Ceramics Division, Enterprise Drive, Four Ashes, Wolverhampton WV10 7DB, U.K.
Publication date: June 1, 2006