Transition temperature

In crystallography, the transition temperature is the temperature at which a material changes from one crystal state (allotrope) to another.[1] 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 crystal below 13.2 °C to a tetragonal crystal above that temperature.

In the case of ferroelectric or ferromagnetic crystals, a transition temperature may be known as the Curie temperature.


  1. ^ Daintith, John (2008). "allotropy". A Dictionary of Chemistry (6th ed.). Oxford University Press. ISBN 9780199204632.

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