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Empirical Formula (Hill Notation) PbS
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Molecular Weight 239.27
Lead(II) sulfide (also spelled sulphide) is an inorganic compound with the formula PbS. PbS, also
known as galena, is the
principal ore, and most important compound of lead. It is a semiconducting material with niche
uses.
Detailed description
Applications
PbS was once used as a black pigment, but current
applications exploit its semiconductor properties, which have long been
recognized.[13]
Infrared sensor (Photoconductor)
PbS is one of the oldest and most common detection
element materials in various infrared detectors. As an infrared
detector, PbS functions as a photon detector, responding directly to the
photons of radiation, as opposed to thermal detectors, which respond to a
change in detector element temperature caused by the radiation. A PbS element
can be used to measure radiation in either of two ways: by measuring the tiny photocurrent the photons cause
when they hit the PbS material, or by measuring the change in the material's electrical resistance that the photons
cause. Measuring the resistance change is the more commonly used method. At room temperature, PbS is sensitive
to radiation at wavelengths between
approximately 1 and 2.5 μm. This range corresponds to the shorter wavelengths
in the infra-red portion of the spectrum, the so-called short-wavelength infrared (SWIR). Only very hot
objects emit radiation in these wavelengths.
Cooling the PbS elements, for example using liquid
nitrogen or a Peltier element system, shifts its
sensitivity range to between approximately 2 and 4 μm. Objects that emit radiation in these wavelengths still have to
be quite hot—several hundred degrees Celsius—but not as hot as
those detectable by uncooled sensors. (Other compounds used for this purpose
include indium antimonide (InSb) and mercury-cadmium telluride (HgCdTe), which have
somewhat better properties for detecting the longer IR wavelengths.) The high dielectric constant of PbS leads to
relatively slow detectors (compared to silicon, germanium, InSb, or HgCdTe).
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