Barium fluoride

Material
BaF2

 

Barium fluoride is commonly used for optical components in expanded spectrum band from ultraviolet to infrared regions, since it is transparent over an extremely wide range of wavelengths (from 0.15µm-0.20µm to 11µm-11.5µm). Its transmittance at 200 nm is relatively low (~60%), but at 500nm, BaF2 goes up to 96%-97% and stays at that level until 9µm, then it starts falling off (85% for 10µm and 42% for 12µm).

 

Barium fluoride is hard but very sensitive to thermal shock. In dry environment, it can be used up to 800 °C, but its resistance to water is less than that of Calcium Fluoride. That's why it is corroded by water when it is heated to 500 °C. Nevertheless, BaF2 is the most resistant of all optical fluorides to high-energy radiation.2 bis zu einer Temperatur von 800°C verwendet werden, allerdings ist die Wasserresistenz noch geringer als die von Calciumfluorid. Daher korrodiert BaF2 auch bei einer Temperatur von 500°C in Wasser. Dennoch ist Bariumflourid das resistenteste optische Fluorid in Bezug auf hochenergetische Strahlung.

 

BaF2 is used for optical windows, lenses, prisms and other optical items in the range from the ultraviolet to the infrared. For an equivalent thickness the transmission extends approximately 1 micron further into the IR than Calcium Fluoride. In addition, BaF2 has application as the fastest known scintillator material and is used for production of fast-acting and radiation resistant scintillation detectors for positron-emission tomography, nuclear calorimetry, gamma-spectroscopy and for identification of charged particles, neutrons and Cherenkov counters.2 bekannt als eines der schnellsten Szintillatormaterialien, sodass es vor allem im Bereich der schnellwirkenden und strahlungsresistenten Detektoren für Positronemissionstomographie, nuklearer Kalorimetrie, Gamma-Spektroskopie, zur Identifikation von geladenen Partikeln und Neutronen  sowie für Cherenkov-Zähler verwendet wird.

 

We use for our Barium Fluoride optics high quality crystals grown by Czochralsky and Bridgman Methods and supply high transparent and low-loss BaF2 optical windows, prisms, lenses, achromatic lenses and other optical components. BaF2 is available in two qualities (monodomain and polydomain) as well as in the three classes (IR, UV, scintillator).

Properties
Optical properties
Transmission range in µm (minimum 10%)
0,14‐15
Transmission range in µm (minimum 50%)
0,14‐14
Refractive index @633nm
1,47326

(1,45 @5µm)

Reflection losses in % at 1 surface
3,4 @4µm
Reflection losses in % at 2 surfaces
6,5 @5µm
dN/dT in 1/K
-15,2 · 10-6
Physical properties
Density in g/cm3
4,89
Melting point in °C
1368
Spezific heat capacity in J/(kg · K)
410
Thermal conductivity in W/(m · K)
10,9
Thermal expension in 1/K
18,4 · 10-6
Dielectric constants
7,33
Solubility in water in g/100g
0,16 @25°C
Mohs hardness
3
Knoop hardness in kg/mm²
82
Material type
single crystalline, synthetic
Crystal type
kubisch, CaF2 structure
Crystal structure
cF12
Lattice constant in Å
a = 6,2
Elastic coefficient in GPa
C11 = 91

C12 = 41,2

C44 = 25,3

Young's Modulus (E) in Gpa
53,07
Shear Modulus (G) in GPa
25,4
Bulk Modulus (K) in GPa
57,8
Rupture Modulus in MPa
26,9
Apparent elastic limit in MPa
26,9
Poisson ratio
0,31
Spectral properties
Optical properties
Transmission range @10% min. 0,14 - 15
Transmission range @50% min. 0,14 - 14
Brechungsindex @ 633nm 1,47326
(1,45@5µm)
Reflection losses in % at 1 surface 3,4 @ 4µm
Reflection losses in % at 2 surfaces 6,5 @ 5µm
dn/dT in 1/K -15,2 · 10-6
Physical properties
Density in g/cm³ 4,89
Melting point in °C 1368
Spezific heat capacity in J/(kg · K) 410
Thermal conductivity in W/(m · K) 10,9
Thermal expension in 1/K 18,4 · 10-6
Dielectric constants 7,33
Solubility in water in g/100g 0,16 @ 25°C
Mohs hardness 3
Knoop hardness in kg/mm² 82
Material type single crystalline, synthetic
Crystal type kubisch, CaF2 structure
Crystal structure cF12
Lattice constant in Å a = 6,2
Elastic coefficient in GPa C11 = 91
C12 = 41,2
C44 = 25,3
Young's Modulus (E) in Gpa 53,07
Shear Modulus (G) in GPa 25,4
Bulk Modulus (K) in GPa 57,8
Rupture Modulus in MPa 26,9
Apparent elastic limit in MPa 26,9
Poisson ratio 0,31
Spectral properties