Glass-to-metal seal formation of lithium tungstate. Due to its low thermal expansion coefficient, matched to glass, tungsten is frequently used for glass-metal bonds. Tungsten forms satisfying bonds with glasses with similar thermal expansion coefficient such as high-borosilicate glass. The surface of both the metal and glass should be smooth, without scratches. Tungsten has the lowest expansion coefficient of metals and the highest melting point. 304 Stainless steel forms bonds with glass via an intermediate layer of chromium(III) oxide and iron(III) oxide. Further reactions of chromium, forming chromium silicide dendrites, are possible. The thermal expansion coefficient of steel is however fairly different from
Liquid metal Liquid metal Liquid metal consists of alloys with very low melting points which form a eutectic that is liquid at room temperature. The standard metal used to be mercury, but gallium-based alloys, which are lower both in their vapor pressure at room temperature and toxicity, are being used as a replacement in various applications. A few elemental metals are liquid at or near room temperature. The most well known is mercury(Hg), which is molten above −38.8 °C (234.3 K, −37.9 °F). Others include caesium(Cs), which has a melting point of 28.5 °C (83.3 °F), rubidium (Rb)(39 °C [102 °F]), francium