Glass ceramics were studied, formulated in the Na2O CaO. P2O5, Na2O. BaOP2O5, Na2O. Al2O3.P2O5, and Li2O. BaO. P2O5 systems to establish their suitability for sealing to high thermal expansion metals, e.g. aluminum, copper, and 300 series stainless steels. Glass ceramics in Na2O. CaO. P2O5 and Na2O. BaO. P2O5 systems have coefficients of thermal expansion in the range 140 x 10−1 per °C less than or equal to .cap alpha. less than or equal to 225 x 10−7 per °C and fracture toughness values generally greater than those of phosphate glasses; they are suitable for fabricating seals to high thermal expansion metals. Crystal phases include NaPo3, (NaPO3)3, NaBa(PO3)3, and NaCa(PO3)3. Glass ceramics formed in the Na2O. Al2O3.P2O5 systems have coefficients of thermal expansion greater than 240 x 10−7 per °C, but they have extensive microcracking. Due to their low thermal expansion values (.cap alpha. less than or equal to 120 x 10−7 per °C), glass ceramics in the Li2O. BaO. P2O5 system are unsuitable for sealing to high thermal expansion metals.

This completely revised edition features new sections on glass-ceramic applications and their performance, CDC-grinding, and laser gyroscopes containing Zerodur®., providing an overview of Schott's activities for scientists, engineers, and managers.

The formation of a crack-free between 300 series stainless steel and a glass-ceramic is difficult owing to the high coefficients of thermal expansion of the stainless steels. Lithia-alumina-silica (LAS) glass-ceramics were successfully developed and sealed to 304L stainless steel. These crack-free seals were fabricated by two techniques: by adjusting the parent glass composition (reducing the Al2O3 content), or by adjusting the sealing/crystallization cycle. All seals were hermetic, with leak rates

This book is one of a series reporting on international research and development activities conducted by the Schott group of companies. With the series, Schott aims to provide an overview of its activities for scientists, engineers, and managers from all branches of industry worldwide where glasses and glass ceramics are of interest. Each volume begins with a chapter providing a general idea of the current problems, results, and trends relating to the subjects treated. This volume describes the fundamental principles, the manufacturing process, and applications of low thermal expansion glass ceramics. The composition, structure, and stability of polycrystalline materials having a low thermal expansion are described, and it is shown how low thermal expansion glass ceramics can be manufactured from appropriately chosen glass compositions. Examples illustrate the formation of this type of glass ceramic by utilizing normal production processes together with controlled crystallization. Thus glass ceramics with thermal coefficients of expansion of less than 0.3 x 10( -6)K( -1) can be obtained. Even for the mass production of high-quality cooktop panels (Ceran (R)), oven windows, and other household appliances a high reproducibility of the properties is achieved. Special glass ceramics (Zerodur (R)) for technological and scientific applications such as high-precision optics or large astronomical mirrors are equally discussed.

Glass-ceramics can be versatile joining materials with tailorable thermal and mechanical properties; they are not affected by oxidation and can be used as pressureless joining materials above their glass softening point. The glassy phase can be minimized by a suitable thermal treatment in order to improve the glass-ceramic creep behaviour. The use of glasses and glass-ceramics as sealants in solid oxide fuel cells and as joining materials for SiC-based materials will be discussed.