Magnesium Fluoride

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Magnesium Fluoride (MgF₂)

Magnesium Fluoride crystal has a wide transmission range from 110nm to 7500nm and it exhibits a slight birefringence. The crystal is relatively hard, resistance to water, but sensitive to thermal shock. It can be machined with standard diamond tools and have a good polishing using either aluminum oxide or diamond based polishing papers. It is particularly useful for excimer laser application. Generally, Magnesium Fluoride for laser use is recommended to be oriented along the optic axis to avoid birefringent effects.


	Figure 1: External transmittance curve for 7 mm Magnesium Fluoride crystal

	Crystal Structure		Tetragonal
	Lattice Constant (Å)		a=4.64, c=3.06
	Transparency Range (nm)		110~7500
	Crystal Class		Positive Uniaxial
	Constant of Dispersion (dn/dT) (/K at 0°C and 632.8nm )		dno/dT=1.24X10^-6 dne/dT=0.69X10^-6
	Melting Point (°C)		1585
	Thermal Conductivity (W/(m K) at 300 K):		11.6
	Heat Capacity: (J/gK at 276 K):		0.955
	Linear Coefficient of Thermal Expansion (20°C) ( /K)		\|\|C: 13.70X10^-6 ⊥C: 8.48X10^-6
	Refractive Indices		ne=1.38876, no=1.37698 at 632.8nm ne=1.38478, no=1.37319 at 1064nm
	Density (g/cm³)		3.1766
	Knoop Hardness		415
	Young's Modulus (GPa)		138.5
	Shear Modulus (GPa)		54.66
	Poisson Ratio		0.276
	Table 1:Magnesium Fluoride Properties