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Glass and Glass ceramics
Glass Definition and Transition temperature
Glass is an amorphous (non-crystalline) solid material, which is often transparent and has widespread practical, technological, and decorative usage in things like windowpanes, tableware, and optoelectronics. The most familiar, and historically the oldest, types of glass are based on the chemical compound silica (silicon dioxide), the primary constituent of sand. The term glass, in popular usage, is often used to refer only to this type of material, which is familiar from use as window glass and in glass bottles. Of the many silica-based glasses that exist, ordinary glazing and container glass is formed from a specific type called soda-lime glass, composed of approximately 75% silicon dioxide (SiO2), sodium oxide (Na2O) from sodium carbonate (Na2CO3), calcium oxide, also called lime (CaO), and several minor additives. A very clear and durable quartz glass can be made from pure silica; the other compounds above are used to improve the temperature workability of the product.
The glass–liquid transition (glass transition) is the reversible transition in amorphous materials from a hard and relatively brittle state into a molten or rubber-like state. An amorphous solid that exhibits a glass transition is called a glass. Super-cooling a viscous liquid into the glass state is called vitrification.
Despite the massive change in the physical properties of a material through its glass transition, the transition is not itself a phase transition of any kind; rather it is a laboratory phenomenon extending over a range of temperature and defined by one of several conventions.
Definition of glass:
The glass is an amorphous solid completely lacking in long range, periodic atomic structure, and exhibiting a region of glass transformation (transition) behavior. Any material, inorganic, organic, or metallic, formed by any technique, which exhibits glass transformation (transition) behavior, is a glass.