Cadmium tungstate

Cadmium tungstate  Names

IUPAC name

Cadmium(II) tungstate

Identifiers

CAS Number

* 7790-85-4 Y

3D model (JSmol)

* Interactive image

ChemSpider |

* 10636623

EC Number |

* 232-226-2

PubChem CID

* 3080645

UNII |

* ZNL5ZHP0Q7

InChI

* InChI=1S/Cd.4O.W/q+2;;;2*-1;

Key: OUMLAYUZCYYIOD-UHFFFAOYSA-N

SMILES

* [O-][W](=O)(=O)[O-].[Cd+2]

Properties

Chemical formula

| CdWO4
Molar mass | 360.25 g·mol−1
Appearance  | colorless crystals with a yellow tint
Density | 7.9 g/cm3, solid
Melting point |  1,325 °C (2,417 °F; 1,598 K)

Solubility in water

| 0.04642 g/100 mL (20 °C)
Hazards
GHS pictograms |
GHS Signal word | Warning

GHS hazard statements

| H302, H312, H332, H410

GHS precautionary statements

| P261, P264, P270, P271, P273, P280, P301+312, P302+352, P304+312, P304+340, P312, P322, P330, P363, P391, P501
NIOSH (US health exposure limits):

PEL (Permissible)

| [1910.1027] TWA 0.005 mg/m3 (as Cd)[1]

REL (Recommended)

| Ca[1]

IDLH (Immediate danger)

| Ca [9 mg/m3 (as Cd)][1]

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Y verify (what is YN ?)
Infobox references

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 7790-85-4.[2] 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 and 660 nm),[3] 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).[3] 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.[4][5] 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.[6] For example, the first indication of the natural alpha activity of tungsten (alpha decay of 180W) was found in 2003 with CWO detectors.[7] Due to different time of light emission for different types of ionizing particles, the alpha-beta discrimination technique has been developed for CWO scintillators.[8]

Cadmium tungstate films can be deposited by sol-gel technology. Cadmium tungstate nanorods can be synthesized by a hydrothermal process.[9]

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

It is toxic, as are all cadmium compounds.

## References

1. ↑ 1.0 1.1 1.2 NIOSH Pocket Guide to Chemical Hazards. "#0087". National Institute for Occupational Safety and Health (NIOSH). https://www.cdc.gov/niosh/npg/npgd0087.html.
2. ↑ "Cadmium tungsten oxide (CdWO4)". CAS Common Chemistry. https://commonchemistry.cas.org/detail?cas_rn=7790-85-4.
3. ↑ 3.0 3.1 Burachas S. F. (1996). "Large volume CdWO4 crystal scintillators". Nucl. Instrum. Methods Phys. Res. A 369 (1): 164–168. doi:10.1016/0168-9002(95)00675-3. Bibcode: 1996NIMPA.369..164B.
4. ↑ "Patterson Hand-Held Fluoroscope (ca. 1940s)". Oak Ridge Associated Universities. 2021. https://orau.org/health-physics-museum/collection/radiology/fluoroscopy/patterson-hand-held-fluoroscope-1940.html. Retrieved 2021-10-12.
5. ↑ Kroeger, F. A. (1948). Some Aspects of the Luminescence of Solids. Elsevier.
6. ↑ Bardelli L. (2006). "Further study of CdWO4 crystal scintillators as detectors for high sensitivity 2β experiments: Scintillation properties and pulse-shape discrimination". Nucl. Instrum. Methods Phys. Res. A 569 (3): 743–753. doi:10.1016/j.nima.2006.09.094. Bibcode: 2006NIMPA.569..743B.
7. ↑ Danevich F. A. (2003). "α activity of natural tungsten isotopes". Phys. Rev. C 67 (1). doi:10.1103/PhysRevC.67.014310. Bibcode: 2003PhRvC..67a4310D.
8. ↑ Fazzini T. (1998). "Pulse-shape discrimination with CdWO4 crystal scintillators". Nucl. Instrum. Methods Phys. Res. A 410 (2): 213–219. doi:10.1016/S0168-9002(98)00179-X. Bibcode: 1998NIMPA.410..213F.
9. ↑ "Hydrothermal synthesis and characterization of CdWO4 nanorods". Journal of the American Ceramic Society 89 (9): 2980–2982. September 2006. doi:10.1111/j.1551-2916.2006.01171.x.

## External links

* Scintillator materials

* v
* t
* e

Cadmium compounds

Cadmium(I)|

* Cd2(AlCl4)2

Cadmium(II)|

* Cd(BF4)2
* CdF2
* CdCl2
* CdBr2
* CdI2
* Cd(CN)2
* CdH2
* CdO
* CdS
* CdSe
* CdTe
* Cd(OH)2
* Cd(NO3)2
* CdSO4
* CdWO4
* Cd3As2
* CsCdCl3
* CsCdBr3

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*[CID]: Compound ID
*[H302]: Harmful if swallowed
*[H312]: Harmful in contact with skin
*[H332]: Harmful if inhaled
*[H410]: Very toxic to aquatic life with long lasting effects
*[P261]: Avoid breathing dust/fume/gas/mist/vapours/spray
*[P264]: Wash … thoroughly after handling
*[P270]: Do not eat, drink or smoke when using this product
*[P271]: Use only outdoors or in a well-ventilated area
*[P273]: Avoid release to the environment
*[P280]: Wear protective gloves/protective clothing/eye protection/face protection
*[P301+312]: IF SWALLOWED: Call a POISON CENTER or doctor/physician if you feel unwell
*[P302+352]: IF ON SKIN: Wash with soap and water
*[P304+312]: IF INHALED: Call a POISON CENTER or doctor/physician if you feel unwell
*[P304+340]: IF INHALED: Remove victim to fresh air and keep at rest in a position comfortable for breathing
*[P312]: Call a POISON CENTER or doctor/physician if you feel unwell
*[P322]: Specific measures (see … on this label)
*[P330]: Rinse mouth
*[P363]: Wash contaminated clothing before reuse
*[P391]: Collect spillage
*[P501]: Dispose of contents/container to …
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