Information

Scandium Fluoride ScF3 exhibits its unusual ability to have negative thermal expansion, which means it shrinks when heated. This phenomenon can be explained by the four oscillations of fluoride ions. 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. Furthermore, the material has cubic symmetry in this temperature range and can reach a temperature of at least 1600K at one 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)