..::Argus International::..CaF2 & MgF2

Argus International - CaF2 & MgF2

CaF2 | MgF2

CaF2

MATERIAL: Calcium Fluoride (CaF2)
APPLICATIONS: Widespread IR application as spectroscopic accessories, prisms and lenses. Useful application in the UV as Eximer laser windows. Available doped with europium as a gamma ray scintillator.

PROPERTY	VALUE

-OPTICAL-
Transmission Range	0.13 to 10 microns
Refractive Index	1.39908 at 5 microns
Reflection Loss	5.4% at 5 microns (2 surfaces)
Restrahlen Peak	35 microns
dN/dT	-10.6 x 10-6/°C

-PHYSICAL-
Density	3.18 gm/cc
Melting Point	1360 °C
Thermal Conductivity	9.71 Wm-1 °K-1
Thermal Expansion	18.85 x 10-6/°C
Hardness	Knoop 158.3 (100)
Specific Heat Capacity	854JKgm-1 °K-1
Dielectric Constant	6.76 at 1MHz
Young's Modulus (E)	75.8 GPa
Shear Modulus (G)	33.77 GPa
Bulk Modulus (K)	82.71 GPa
Elastic Coefficients	C11=164 C12=53 C44=33.7
Apparent Elastic Limit	36.54 MPa
Poisson Ratio	0.26

-CHEMICAL-
Solubility	0.001 7gm/100gm water at 20 °C
Molecular Weight	78.08
Class/Structure	Cubic (111) cleavage

NOTES
Calcium fluoride is grown by vacuum Stockbarger technique in diameters up to 35cm. Material for IR use is grown using naturally mined fluorite, in large quantities at relatively lowcost. Optipur® CaF2 is recommended for UV applications and is manufactured from chemically pure powder.

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MgF2

MATERIAL: Magnesium Fluoride (MgF2) APPLICATIONS: UV and Vacuum UV windows, lenses, polarisers,
PROPERTY	VALUE

-OPTICAL-
Transmission Range	0.11 to 7.5 microns
Refractive Index	N0=1.3836 Ne=1.3957 at 0.405 microns
Reflection Loss	11.2% at 0.12 microns (2 surfaces)
Restrahlen Peak	20 microns
dN/dT and dN./dT	+2.3 and +1.7 x 10-6/ °C at 0.4 microns

-PHYSICAL-
Density	3.177 gm/cc
Melting Point	1255 °C
Thermal Conductivity	0.3 Wm-1 °K-1 at 27 °C
Thermal Expansion	13.7and 8.48 x 10-6/ °C
Hardness	Knoop 415
Specific Heat Capacity
Dielectric Constant	4.87 parallel and 5.45 perpendicular
Young's Modulus (E)	138.5 GPa
Shear Modulus (G)	54.66 GPa
Bulk Modulus (K)	101.32 GPa
Elastic Coefficients	C11=140.2 C12=89.5 C44=56.8
	C33=204.7 C13=62.9 C66=95.7
Apparent Elastic Limit	49.64 MPa
Poisson Ratio	0.276

-CHEMICAL-
Solubility	<0.0002 gm/100gm water at 0 °C
MolecularWeight	62.32
Class/Structure	Tetragonal, can cleave on C-axis
NOTES Magnesium fluoride is a positive birefringent crystal grown normally to 135mm diameter by vacuum Stockbarger technique, seeding along the C-axis. The main application is in the Vacuum UV region and so particular care is taken with the raw material and each ingot is sampled and tested to achieve a minimum transmission of 40% at Lyman-alpria (0.1216 micron) through a 2mm window, and all ingots are tested with a deuterium lamp for the weak fluorescence which can occur. Magnesium fluoride is a proven window material for Eximer lasers and resistance to laser damage is good, nevertheless permanent colour centre formation does occur. Magnesium fluoride is a rugged, hard material which is resistant to thermal and mechanical shock. Considerable mechanical shock is needed to cause cleavage which is near perfect when it occurs. The natural form of MgF2 is known as Sellaite. A hot pressed polycrystalline form of MgF2 was developed by the Eastman Kodak company and known as lrtran-1. Magnesium fluoride doped with cobalt is under investigation for laser systems.

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