Solution coated hydrothermal BaTiO3 for low-temperature firing

US6169049A · kind A · utility

Inventors

• John P. Witham · Willow View Lane, US
• Clive A. Randall · State College, US
• Umesh Kumar · Forest Park, US
• Ulagaraj Selvaraj · Apex, US
• Sea-Fue Wang · Taipei, TW
• Joseph P. Dougherty · New York, US

Key dates

• Filing date: Apr 28, 1997
• Grant date: Jan 2, 2001
• Expiry date: Apr 28, 2017

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C04B35/468
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

Hydrothermal BaTiO.sub.3 crystallites were coated with Bismuth solutions prepared from Bismuth metal-organics and anhydrous solvents. The Bismuth metal-organics were Bi 2-ethylhexanoate and Bi-neodecanoate. Bismuth oxide was also used as a comparison to the Bismuth solutions. BaTiO.sub.3 ceramics with either 3.0 wt % equivalent Bismuth oxide or 5.0 wt % equivalent Bismuth oxide were made by sintering the compacts between 700.degree. C. and 1000.degree. C. BaTiO.sub.3 ceramics that were coated by Bi-neodecanoate densified >90% theoretical as low as 800.degree. C. for 3.0 wt % equivalent Bi.sub.2 O.sub.3. Average grain sizes of 0.2-0.4 .mu.m were observed for Bi-coated BaTiO.sub.3 ceramics, for sintering temperatures below 950.degree. C. Dielectric K versus temperature measurements of Bismuth-coated BaTiO.sub.3 ceramics, sintered in the lower temperature ranges, showed consistently superior dielectric characteristics.