Barium titanate sintering

Barium titanate-sintered ceramics are developed with the objective of producing materials with special electrical properties, particularly a high dielectric constant. Barium titanate-based sintered ceramics are produced with... 

Barium carbonate also reacts with titania to form barium titanate [12047-27-7] BaTiO, a ferroelectric material with a very high dielectric constant (see Ferroelectrics). Barium titanate is best manufactured as a single-phase composition by a soHd-state sintering technique. The asymmetrical perovskite stmcture of the titanate develops a potential difference when compressed in specific crystallographic directions, and vice versa. This material is most widely used for its strong piezoelectric characteristics in transducers for ultrasonic technical appHcations such as the emulsification of Hquids, mixing of powders and paints, and homogenization of milk, or in sonar devices (see Piezoelectrics Ultrasonics). 

Barium titanate is made by sintering a finely powdered mixture of barium carbonate and titanium dioxide in a furnace at 1,350°C. The calcined mass is finely ground and mixed with a binder (plastic). The mixture is subjected to extrusion, pressing or film casting to obtain ceramic bodies of desired shapes. Plastic is burnt off by heating and the shaped body is sintered by firing and then pobshed. 

Very pure barium titanate is obtained by coprecipitation of barium and titanium compounds (e.g. as oxalates or citrates) followed by calcination. In the manufacture of electroceramics, this is followed by the usual ceramic processes grinding, molding and a sintering at 1300°C. 

Choi, S.-Y. and Kang, S.-J. L., Sintering kinetics by structural transition at grain boundaries in barium titanate, Acta Mater., 52, 2937 3, 2004. 

Vasyl kiv, O.O., Ragulya, A.V., Klymenko, V.P., Skorokhod, V.V. Synthesis and sintering of nanocrystalline barium titanate powder under non-isothermal conditions III. Chromatographic analysis of barium titanyl-oxalate gaseous decomposition products. Powder Metall. Metal Ceram. 36(11-12), 575-578 (1997)... 

Ragulya, A.V. Rate-controlled synthesis tmd sintering of nanocrystaUme barium titanate powder. Nanostruct. Mater. 10,349-355 (1998)... 

T. Tani, K. Takatori and N. Watanabe, Characteristics and sintering behavior of barium titanate... 

Processing, Microstructure and Properties of Nanograin Barium Titanate Ceramics by Spark Piasma Sintering... 

In addition to the multilayered ceramic capacitors just described, many of the barium titanate-based compounds that exhibit high dielectric constants are used in single-layer tape-cast capacitor devices. Relaxor materials such as lead magnesium niobate (PMN), which are characterized by high dielectric constants, broad dielectric maxima, and low sintering temperatures, have been manufactured in thin sheets by tape casting. 

Yao K, Zhang LY, Yao X, Zhu WG (1997) Preparation and properties of barium titanate glass-ceramics sintered from sol-gel-derived powders. J Mater Sci 32(14) 3659-3665... 

One of the compounds that have drawn attraction of the investigators in the area of sol-gel powderless ceramics is barium titanate, BaTiOs. An initial report came from Frey and Payne (1995) who prepared and used barium and titanium methoxyethoxides under controlled atmosphere for synthesis. The modified alkoxides were hydrolyzed by addition of a solution of water in 2-methoxyethanol. The sol was cast, sealed and aged. Drying at above 50°C yielded monolithic gels sintering of the gels at 800-1300°C produced... 

Shimooka et al. (1998, 2000), Shimooka and Kuwabara (1995) and others (Kuwabara et al., 1995 Kobayashi et al., 1999) carried out intensive work on crystallization and sintering of bulk barium titanate gels into ceramic bodies. The process of synthesis of the gels involved the following steps ... 

Kundu P., Pal D., Sen S. Preparation and thermal evolution of sol-gel derived transparent Zr02 and MgO-Zr02 gel monolith. J. Mater. Sci. 1988 23 1539-1546 Kuwabara M., Miki K., Takahashi S., Shimooka H. Preparation of monolithic barium titanate xerogels by sol-gel processing and the dielectric properties of their sintered bodies. Appl. Phys. Lett. 1995 66 1704-1706... 

Capacitor Dielectrics. Capacitor dielectrics contain barium titanate and its solid solutions, which possess high dielectric constants. The melting point of these materials is over 1600°C. Sintering additives are often used to lower the sintering temperature to 850 to 1000°C. The liquid phase formed by reaction between sintering aids and refractory... 

Ho I.-C. Semieondueting barium titanate ceramics prepared by Boron-containing liquid-phase sintering,/. Am. Ceram. Soc., (1994), 77, 829-832. 

Electroceramics. Titanates like barium, strontium, calcium and lead titanate prepared from finely divided, high-purity TiOz hydrolysates are used in capacitors, PTC-resistors and piezoelectric materials. The specifications of the Ti02 starting materials with respect to purity, reactivity, and sintering properties are expected to become more stringent. The market is estimated to be several thousand of tonnes a year as TiOz. A strong annual growth is expected. 

Wu YJ, Wang N, Wu SY, Chen XM (2011) Transparent barium strontium titanate ceramics prepared by spark plasma sintering. J Am Ceram Soc 94 1343-1345... 

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