Properties of Scandium Fluoride ScF3
Scandium Fluoride ScF3 exhibits the unusual ability of negative thermal expansion, ie it contracts when heated. This phenomenon can be explained by the fourth oscillation of the fluoride ion. This energy stored in flexural stress is proportional to the fourth power of the displacement angle, unlike most other materials which are proportional to the square of the displacement angle. One fluorine atom and two scandium atoms, and as the temperature increases, the fluorine atom oscillates more perpendicular to its bond.
Scandium Fluoride ScF3 exhibits normal positive thermal expansion from 10K to above 1100K, in addition, the material has cubic symmetry in this temperature range and can reach temperatures of at least 1600K at a standard atmospheric pressure. Negative thermal expansion is very strong at low temperature (between 60K and 110K, the thermal expansion coefficient is around -14 ppm/K)