Cadmium tungstate
Cadmium tungstate (CdWO4 or CWO), the cadmium salt of tungstic acid, 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 480 nm (with emission range between 380-660 nm), and efficiency of 13000 photons/MeV. It has a relatively high light yield, its light output is about 40% of NaI(Tl), but the time of scintillation is quite long (12−15 μs). 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 the 1940s. Very high radiopurity allows use of this scintillator as a detector of rare nuclear processes (double beta decay, other rare alpha and beta decays) in low-background applications. For example, the first indication of the natural alpha activity of tungsten (alpha decay of 180W) had been found in 2003 with CWO detectors. Due to different time of light emission for different types of ionizing particles, the alpha-beta discrimination technique has been developed for CWO scintillators.

Cadmium tungstate films can be deposited by sol-gel technology. Cadmium tungstate nanorods can be synthesized by a hydrothermal process.

Similar materials are calcium tungstate (scheelite) and zinc tungstate.

It is toxic, as are all cadmium compounds.
Q1091
cadmium
Concept
Q12370
salt
Concept
Q416538
tungstic acid
Concept
Q910990
scintillation crystal
UNK
Q11523
gamma ray
Concept
Q41803
g
Concept
Q102507
CAS number
MISC
Q216678
hygroscopic
MISC
Q11523
gamma ray
Concept
Q34777
x-ray
Concept
Q186161
ionizing radiation
Concept
Q178674
nm
Concept
Q83327
MeV
Concept
Q390305
NaI(Tl)
Concept
Q32566
computed tomography
Concept
Q417399
boron carbide
Concept
Q11523
gamma rays
Concept
Q922364
neutron radiation
Concept
Q409096
calcium tungstate
Concept
Q614984
fluoroscope
Concept
Q48350
sol-gel
UNK
Q2684948
nanorod
Concept
Q1036221
hydrothermal
UNK
Q409096
calcium tungstate
Concept
Q409096
scheelite
Concept
None
zinc tungstate
UNK
Q1969116
Cadmium tungstate
Concept
Q1969116
Cadmium tungstate
Concept
Q1969116
Cadmium tungstate
Concept
Q1969116
Cadmium tungstate
Concept
1325-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
1325
DATE
1940-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
1940
DATE
2003-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
2003
DATE
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4
NUMBER
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7.9
NUMBER
+3^^http://www.w3.org/2001/XMLSchema#decimal
3
NUMBER
-660^^http://www.w3.org/2001/XMLSchema#decimal
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NUMBER
+40^^http://www.w3.org/2001/XMLSchema#decimal
40
NUMBER
+12^^http://www.w3.org/2001/XMLSchema#decimal
12
NUMBER
+15^^http://www.w3.org/2001/XMLSchema#decimal
15
NUMBER
part of