Structure and Physical 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 (gap 2.42 eV). The magnitude of its band gap means that it appears coloured.
As well as this obvious property others properties result:
- the conductivity increases when irradiated with light(leading to uses as a photoresistor)
- when combined with a p-type semiconductor it forms the core component of a photovoltaic (solar) cell and a CdS/Cu2S solar cell was one of the first efficient cells to be reported (1954)
- when doped with for example Cu+ ("activator") and Al3+ ("coactivator") CdS luminesces under electron beam excitation (cathodoluminescence) and is used as phosphor
- both polymorphs are piezoelectric and the hexagonal is also pyroelectric
- electroluminescence
- CdS crystal can act as a solid state laser
Read more about this topic: Cadmium Sulfide
Famous quotes containing the words structure, physical and/or properties:
“Why does philosophy use concepts and why does faith use symbols if both try to express the same ultimate? The answer, of course, is that the relation to the ultimate is not the same in each case. The philosophical relation is in principle a detached description of the basic structure in which the ultimate manifests itself. The relation of faith is in principle an involved expression of concern about the meaning of the ultimate for the faithful.”
—Paul Tillich (1886–1965)
“There could be no fairer destiny for any physical theory than that it should point the way to a more comprehensive theory in which it lives on as a limiting case.”
—Albert Einstein (1879–1955)
“The reason why men enter into society, is the preservation of their property; and the end why they choose and authorize a legislative, is, that there may be laws made, and rules set, as guards and fences to the properties of all the members of the society: to limit the power, and moderate the dominion, of every part and member of the society.”
—John Locke (1632–1704)