Some Properties of Magnesium Fluoride crystallized from the Melt

Magnesium fluoride crystals can be grown in vacuo using the Stockbarger technique. The melting point is 1255 ± 3°C. The crystal structure is of the tetragonal SnO2 type, with lattice constant a = 4.621 ± 0.001 A and axial ratio 1: 0.6601 ± 0.0001 giving c = 3.050 A at 18°C. The density is 3.1766 ± 0.0002 g cm-3 at 18°C. MgF2 is a uniaxial positive crystal, and the refractive indices are given for the ordinary and extraordinary rays at various wavelengths in the visible spectrum. The transparent region extends from 1100 A to 1360 cm-1. Infra-red reflectivity begins to rise at about 620 cm-1, and peaks around 500 cm-1. The mean dielectric constant is m = 5.26.