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Thallium Halogenide Crystals (KRS-5, KRS-6)
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Lithium Tetraborate
Thallium Halogenide crystals (KRS-5, KRS-6) are designed for transmission, refraction and focusing of visible and infrared radiation. Wide transparence range, radiation, thermal and vibrational stability, low water solubility make these crystals valuable for applications in optical devices working in atmosphere conditions and outer space without special protection. Low absorbtion in MID-IR and large refractive index make these crystals suitable for internal reflection elements.
   KRS-5 is used for attenuated total reflection prisms, IR windows and lenses where transmission in the 0.6 µm - 40 µm range is desired. It has a tendency to cold-flow and change its shape with time. KRS-5 is only slightly soluble in water but can be dissolved in alcohol, nitric acid, and aqua regia. KRS-5 (TlBr-TlI) is a gorgeous red crystal commonly used for attenuated total reflection prisms for IR spectroscopy. It is also used as an infrared transmission window in gas and liquid sample cells used with FTIR spectrophotometers in place of Potassium Bromide (KBr) or Cesium Iodide (CsI) for analysis of aqueous samples that would attack KBr or CsI optics. It has a wide transmission range and is virtually insoluble in water. It is a useful alternative to AgCl since it is not photo-sensitive and for ATR applications it will transmit well beyond the 18 micron useful range of ZnSe. KRS-5 is considered toxic, however in our opinion it is safe for IR spectroscopic applications when properly handled.
Main properties:

KRS-5 KRS-6
Chemical composition TlBr - 40%, Tll - 60% TlBr - 30%, TlCl - 70%
Spectral transparency range, µm 0.56 - 50 0.4 - 40
Density, g/cm3 7.37 7.19
Water solubility at 20°C, g/100 g 0.05 0.32
Optical transmission, %
at 0.633 µm > 60 > 65
at 2 - 25 µm > 68 > 72
Absorbtion at 10.6 µm, cm-1 < 1 x 10-3 < 1 x 10-3
Refractive index, at 0.633 - 10.6 µm 2.57 - 2.37 2.33 - 2.17
Max. sizes, mm dia.= 100, length=100 dia.= 150, length = 100

The deliveries from ground blanks to finished as well as processed optical elements are possible.

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