What is Cadmium sulfide?

Cadmium sulfide is the inorganic compound with the formula CdS. Cadmium sulfide is a yellow solid. It occurs in nature with two different crystal structures as the rare minerals greenockite and hawleyite, but is more prevalent as an impurity substituent in the similarly structured zinc ores sphalerite and wurtzite, which are the major economic sources of cadmium. As a compound that is easy to isolate and purify, it is the principal source of cadmium for all commercial applications.
Properties
Cadmium sulfide has, like zinc sulfide, two crystal forms; the more stable hexagonal wurtzite structure (found in the mineral Greenockite) and the cubic zinc blende structure (found in the mineral Hawleyite). In both of these forms the cadmium and sulfur atoms are four coordinate. There is also a high pressure form with the NaCl rock salt structure.
Cadmium sulfide is a direct band gap semiconductor. The magnitude of its band gap means that it appears coloured.
Applications
CdS is mainly used as a pigment.
Cadmium sulfide and cadmium selenide are used in manufacturing of photoresistors (light dependent resistors) sensitive to visible and near infrared light.
In thin-film form, CdS can be combined with other layers for use in certain types of solar cells. CdS was also one of the first semiconductor materials to be used for thin-film transistors (TFTs). However interest in compound semiconductors for TFTs largely waned after the emergence of amorphous silicon technology in the late 1970s.
Pigment
CdS is known as cadmium yellow. By adding varying amounts of selenium as selenide, it is possible to obtain a range of colors, for example CI pigment orange 20 and CI pigment red 108.
Synthetic cadmium pigments based on cadmium sulfide are valued for their good thermal stability, light and weather fastness, chemical resistance and high opacity. The general commercial availability of cadmium sulfide from the 1840s led to its adoption by artists, notably Van Gogh, Monet and Matisse. The presence of cadmium in paints has been used to detect forgeries in paintings alleged to have been produced prior to the 19th century. CdS is used as pigment in plastics
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