text: The commercially most important system is the LiO × AlO × nSiO system (LAS system). The LAS system mainly refers to a mix of lithium, silicon, and aluminum oxides with additional components, e.g., glass-phase-forming agents such as NaO, KO and CaO and refining agents. As nucleation agents most commonly zirconium(IV) oxide in combination with titanium(IV) oxide is used. This important system was studied first and intensively by Hummel, and Smoke.
  After crystallization the dominant crystal phase in this type of glass-ceramic is a high-quartz solid solution (HQ s.s.). If the glass-ceramic is subjected to a more intense heat treatment, this HQ s.s. transforms into a keatite-solid solution (K s.s., sometimes wrongly named as beta-spodumene). This transition is non-reversible and reconstructive, which means bonds in the crystal-lattice are broken and new arranged. However, these two crystal phases show a very similar structure as Li could show.
  An interesting property of these glass-ceramics is their thermomechanical durability. Glass-ceramic from the LAS system is a mechanically strong material and can sustain repeated and quick temperature changes up to 800–1000 °C. The dominant crystalline phase of the LAS glass-ceramics, HQ s.s., has a strong negative coefficient of thermal expansion (CTE), keatite-solid solution as still a negative CTE but much higher than HQ s.s. These negative CTEs of the crystalline phase contrasts with the positive CTE of the residual glass.  Adjusting the proportion of these phases offers a wide range of possible CTEs in the finished composite. Mostly for today's applications a low or even zero CTE is desired. Also a negative CTE is possible, which means, in contrast to most materials when heated up, such a glass-ceramic contracts. At a certain point, generally between 60% [m/m] and 80%  [m/m] crystallinity, the two coefficients balance such that the glass-ceramic as a whole has a thermal expansion coefficient that is very close to zero. Also, when an interface between material will be subject to thermal fatigue, glass-ceramics can be adjusted to match the coefficient of the material they will be bonded to.
  Originally developed for use in the mirrors and mirror mounts of astronomical telescopes, LAS glass-ceramics have become known and entered the domestic market through its use in glass-ceramic cooktops, as well as cookware and bakeware or as high-performance reflectors for digital projectors.