Nippon Electric Glass Co., Ltd.

Kazuhiro Matsui

Takehiro Shibuya

Makoto Matsumoto

An infrared transparent glass ceramic article is useful for top plates of cooking stoves and has a black appearance but an infrared transmittance of about 80% or more for an infrared light of a wavelength 1,500 nm, and .beta.-quartz solid solution crystals substantially alone dispersed within glassy matrix without any other crystals. The article consists essentially, by weight, of 60-72% SiO.sub.2, 14-28% Al.sub.2 O.sub.3, 2.5-5.5% Li.sub.2 O, 0.1-0.9% MgO, 0.1-0.9% ZnO, 3-6% TiO.sub.2, 0.03-0.5% V.sub.2 O.sub.5, 0.1-1% Na.sub.2 O, 0-1% K.sub.2 O, 0-2% CaO, 0-2% BaO, 0-2% PbO, 0-2% As.sub.2 O.sub.3, 0-3% ZrO.sub.2, and 0-3% P.sub.d O.sub.5. The article is produced by forming a desired shape of glass article having the ingredients, heating the glass article at a temperature of 650.degree.-800.degree. C. to nucleate in the glass, heating the glass article at a temperature of 800.degree.-950.degree. C. to thereby precipitate .beta.-quartz solid solution crystals alone in the glass, and cooling the article to the room temperature.

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Shiga, Japan

Kazuhiro Matsui