Transition temperature

Transition temperature is the temperature at which a material changes from one crystal state (allotrope) to another. More formally, it is the temperature at which two crystalline forms of a substance can co-exist in equilibrium. For example, when rhombic sulfur is heated above 95.6 °C it changes form into monoclinic sulfur. When cooled below 95.6 °C it reverts to rhombic sulfur. At 95.6 °C the two forms can co-exist. Transition temperature is the temperature at which a material changes from one crystal state (allotrope) to another. More formally, it is the temperature at which two crystalline forms of a substance can co-exist in equilibrium. For example, when rhombic sulfur is heated above 95.6 °C it changes form into monoclinic sulfur. When cooled below 95.6 °C it reverts to rhombic sulfur. At 95.6 °C the two forms can co-exist. Another example is tin, which transitions from a cubic shape below 13.2 °C to a tetragonal shape above that temperature. In the case of ferroelectric or ferromagnetic crystals a transition temperature may be known as the Curie temperature.