Magnesium Fluoride (MgF2) tetragonal crystal

Magnesium Fluoride (MgF2) is a tetragonal crystal with a rutile structure, known for its exceptional optical properties and wide transparency range from 0.12 to 8 μm, making it highly desirable for various applications in optics and photonics . It is a positive uniaxial material with its highest birefringence in the ultraviolet region, offering unique advantages for polarization and interference filter applications . MgF2 is recognized for its good mechanical properties, low optical index of refraction, and resistance to thermal and mechanical shock, which contribute to its robustness in optical components such as windows, lenses, and polarizers .

The material's transparency and low refractive index make it suitable for use in coatings and as a host material for solid-state lasers, where dopants like vanadium, nickel, and cobalt are used to produce tunable lasers in the infrared region . MgF2's ultraviolet and infrared transparency have led to its use in space applications, such as window material for UV detectors, and in enhancing reflectivity in vacuum UV by coating aluminum mirrors .

In addition to its optical applications, MgF2 is also valued for its thermal and mechanical properties. It has a theoretical density of 3.177 g/cm³ and a melting point of approximately 1528 K, providing it with the necessary thermal stability for high-temperature applications . The material exhibits good thermal conductivity and low thermal expansion coefficients, which are crucial for maintaining optical stability under varying temperature conditions .

MgF2 is also noted for its resistance to water, similar to calcium fluoride, and its solubility in water is extremely low at 0.0002g/100g water, which is advantageous for applications where chemical stability is required . The material's hardness, with a Mohs hardness of approximately 5, further supports its durability in practical applications .

In summary, Magnesium Fluoride is a versatile optical material with a broad spectrum of applications, from optical components to space technology,thanks to its excellent optical properties, mechanical properties and thermal stability.