Cadmium tungstate
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Cadmium tungstate (CdWO4 or CWO) is a dense, chemically inert solid which is used as a scintillation crystal to detect gamma rays. It has density of 7.9 g/cm3 and melting point of 1325 °C. It is toxic if inhaled or swallowed. Its crystals are transparent, colorless, with slight yellow tint. It is odorless. Its CAS number is []. It is not hygroscopic.
The crystal is transparent and emits light when it is hit by gamma rays and x-rays, making it useful as a detector of ionizing radiation. Its peak scintillation wavelength is 520 nm (with emission range between 330-540 nm), and efficiency of 13000 photons/MeV. It has a relative high light yield, its light output is about 40% of NaI(Tl). It is often used in computed tomography. Combining the scintillator crystal with externally applied piece of boron carbide allows construction of compact detectors of gamma rays and neutron radiation.
Cadmium tungstate was used as a replacement of calcium tungstate in some fluoroscopes since 1940's.[1]
Cadmium tungstate films can be deposited by sol-gel technology. Cadmium tungstate nanorods can be synthesized by a hydrothermal process.[2]
Similar materials are calcium tungstate (scheelite) and zinc tungstate.
[edit] References
- ^ Patterson Hand-Held Fluoroscope (ca. 1940s). Oak Ridge Associated Universities (1999). Retrieved on 2008-04-26.
- ^ Wang Y, Ma J, Tao J, Zhu X, Zhou J, Zhao Z, Xie L, and Tian H (Sep 2006). "Hydrothermal synthesis and characterization of CdWO4 nanorods". Journal of the American Ceramic Society 89 (9): 2980-2982. doi:.
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