Barium titanate glass-ceramic

McCauley D., Newnham R.E., and Randall, "Intrinsic Size Effects in a Barium Titanate Glass-Ceramic,"/. Am. Ceram. Soc., 81, 979-87 (1998). 

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... 

McCauley D, Newnham RE, Randall CA (1998) Intrinsic size effects in a Barium Titanate glass-ceramic. J Am Ceram Soc 81(4) 979-987... 

Titanium is an element of considerable interest in materials science because of its role in technical electroceramics such as barium titanate and lead zirconium titanate, and in engineering ceramics (TiN, TiC) and glasses. Titanium compounds also play a role in establishing catalytic activity in microporous materials. Despite the practical interest in Ti compounds, there have been relatively few NMR studies of this nucleus because of experimental difficulties, some of which are associated with the properties of its two NMR-active nuclei, which both have moderately large quadrupole moments Q in the... 

Crystalline dispersions of several niobate crystals or barium titanate (up to 70 vol %) in a silicate glass phase form transparent ferroelectric glass ceramics. The small size of the crystals ( 500 A) accounts for transparency. 

Kokubo et al. (1969) studied the crystallization mechanism of the above glass-ceramic in detail. They found that a metastable benitoite-type crystal, BaTiSi Og, was formed at 800°C, according to a mechanism of surface crystallization. Beginning at 950 C, the crystal was progressively transformed into the stable barium titanate and hexacelsian. The hexacelsian crystal grew anisotropically and parallel to the surface of the glass-ceramic. The preferred orientation of hexacelsian was attributed to the metastable benitoite-type crystals. Moreover, volume crystallization took place at the same time as surface crystallization. In volume crystaUization, however, barium titanate and hexacelsian were formed as primary crystals. 

Slow crack is also observed for systems free of alkali. Results similar to those found for silicate glasses at room temperature are also found for a variety of other ceramic materials, such as porcelains, glassy carbon, Portland cement, high-alumina ceramics, silicon nitride, lead zirconite, and barium titanate [12]. 

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