BaF2 Crystal

18 Dec 2020

Barium fluoride (BaF₂) is a general-purpose optical window material that offers a wide range of transparency, from the ultraviolet to the long-wave infrared, with low reflectance loss and low dispersion. BaF₂ single crystal is an intensively studied scintillator for the detection of gamma radiation due to its relatively high stopping power, radiation hardness and extremely fast response. BaF₂ possesses the fast cross-luminescence component at 195 and 220 nm with a lifetime of several hundred picoseconds. However, this component coexists with slow one at 310 nm related to the self-trapped exciton (STE). BaF₂ is a broad band gap crystal with Eg=10:9 eV. It is currently regarded as the fastest inorganic scintillator which has cross-luminescence bands peaked at 195 and 220 nm and a broad band peaking at about 300 nm due to self-trapped excitons. Much attention has been focused on the luminescent properties of rare earth ions activated BaF₂.

Parameter

Material and Specifications

Orientation	[100] or [111] < ±0.5°
Angle Tolerance	< 0.5°
Parallelism	<20〞
Perpendicularity	5ˊ
Surface Quality	10-5 (MIL-O-13830A)
Wavefront Distortion	<λ/4@633 nm
Surface Flatness	<λ/8 @633 nm
Clear Aperture	>90%
Thickness/Diameter Tolerance	±0.05 mm

Physical and Chemical Properties

Crystal System	Isometric
Habit	Cubic
Space Group	Fm3m(Oh5
Lattice Constants	6.2001 Å
Specific mass	4.886 g/cm3
Melting Point	1354°C
Flexure Strength (MPa)	27
Tenacity	Brittle
Thermal Conductivity /(W·cm-1·K-1@25°C)	0.07
Specific Heat/ (J·g-1·K-1)	1.003
Thermal Expansion /（10-6·K-1@25°C ）	13.7
Hardness (kg/mm2@Knoop)	78
Young`s Modulus /GPa	138.5
Fracture	{111} and {100}

Optical characteristics

Transmission Range	0.15 … 12 µm
Reflective Loss	6 … 16%@0.2 … 10 µm
Thermo-optic coefficient（10-6·K-1@30…90°C ）	-18.8
Poisson Ratio	0.31
Dielectric Constant	7.33@f=2MHz

Index of Refraction

λ(μm)	n	λ(μm)	n	λ(μm)	n
0.2	1.5573	4	1.4558	9	1.4144
0.5	1.4779	5	1.4511	10	1.4011
1	1.4686	6	1.4441	11	1.3865
2	14647	7	1.4357	12	1.3696
3	1.4612	8	1.4258	12.5	1.3585
				15	1.305

Spectrum

Feature

Excellent transmission from 150nm to 12um
Chemically stable
Low reflectance loss and low dispersion
High stopping power, radiation hardness and extremely fast response
Broad band gap
Susceptible to thermal shock
Possesses the fast cross-luminescence component at 195 and 220 nm with a lifetime of several hundred picoseconds

Application