Machinable spodumene–fluorophlogopite glass ceramic

Simultaneous crystallization of fluorophlogopite and beta-spodumene solid solutions is adjusted to achieve machinable porcelain with low expansion coefficient for dental application. The crystallization is guided by the thermal behavior to achieve the desired properties. The beta-spodumene phase tends to harden the body and thereby impair the machinability character when its proportion approaches more than 50%. An expansion coefficient <40×10−7 °C−1 with good machinability is achieved by adjusting the content of beta-spodumene. The rate of heating slightly above the transformation range ought not to be so rapid to achieve sufficient grain growth. Heating rates of 10 °C/min or higher is successfully employed to achieve the desired porcelain.