Effects of Silver on Barium Titanate as a Function of Stoichiometry

• Published in: Journal of the American Ceramic Society Vol. 87; no. 5; pp. 875 - 880
• Main Authors: Byrne, Tiffany A., Cann, David P.
• Format: Journal Article
• Language: English
• Published: Westerville, Ohio American Ceramics Society 01.05.2004; Blackwell; Wiley Subscription Services, Inc
• Subjects: Applied sciences; barium titanate; Building materials. Ceramics. Glasses; Ceramic industries; Ceramic microtubes; Ceramic sintering; Chemical industry and chemicals; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Dielectric properties of solids and liquids; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Electrotechnical and electronic ceramics; Exact sciences and technology; Permittivity (dielectric function); Physics; Polymer processing; silver/silver compounds; Technical ceramics; Scanning electron microscopy; Stoichiometry; Electrical properties; Property composition relationship; Dielectric properties; Polycrystal; Barium titanates; Silver addition; Experimental study; Lattice parameters; Non stoichiometric composition; X ray diffraction; Oxide ceramics; Dielectric response; Additive; Capacitance; Manufacturing; Microstructure; Electroceramics
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/j.1551-2916.2004.00875.x

This work examines the effects of Ag on stoichiometric and nonstoichiometric BaTiO3 in terms of the unit cell dimensions, the polycrystalline microstructure, and the dielectric properties. Stoichiometric BaTiO3 and compositions with 0.5 mol% TiO2 excess and 0.5 mol% BaO excess were prepared via solid‐state synthesis with varying amounts of Ag up to 0.3 mol%. Experimental results indicate that stoichiometry plays a significant role in the solubility of Ag and its effects on the physical properties. Overall, the solubility of Ag was negligible in stoichiometric BaTiO3. However, compositions with excess TiO2 stabilized the solubility of Ag as evidenced from changes in the unit cell dimensions and dielectric properties. Based on these data, it is proposed that Ag occupies the A‐site in the perovskite structure with an upper limit of Ag solubility of 0.06 mol% Ag in BaTiO3 with 0.5 mol% excess TiO2. Dielectric measurements showed that Ag concentrations approaching 0.3 mol% gave rise to an increase in the space charge effect, especially at temperatures above TC. In both nonstoichiometric compositions, the presence of a liquid Ag phase during thermal processing was found to affect microstructural development and sintering.