Lead, Tin and Low Melting Alloys

Lead, tin and low melting alloys are non-ferrous alloys used in the manufacture of solders, semiconductors, batteries, optical and decorative products. Examples include antimony (Sb), bismuth (Bi), cadmium (Cd), indium (In), zinc (Zn), lead (Pb), and tin (Sn). Lead, tin and low melting alloys such as indium are used in bearing alloys, transistors, rectifiers, thermistors, and photoconductors. While many metals or alloys have a white or silvery appearance, white metal is term commonly used to describe the group of low melting point metals and alloys. 

Many lead, tin and low melting alloys are important constituents or components of compound semiconductors (III-V compounds), optical, or optoelectronic materials and thin film coatings. For instance, indium tin oxide (ITO) coatings provide a transparent and conductive layer and are used on photovoltaic cells, solar panels and window heaters. Examples of compound semiconductors or optical materials using a low melting point metal constituent include gallium arsenide (GaAs) and indium antimonide (InSb), cadmium selenide (CdSe), and lead telluride (PbTe). Many lead, tin and low melting alloys have a diffusion coefficient comparable to arsenic and an order of magnitude that is lower than the diffusion coefficient of phosphorous.

Selecting lead, tin and low melting alloys such as antimony, indium, and bismuth requires an analysis of material characteristics and recommended applications. Antimony is an n-type donor in silicon that is used to dope epitaxial layers. Indium is a very soft, lustrous, silvery white metal that produces a high-pitched sound when bent. Bismuth is a white, brittle metal with a pinkish tinge. It occurs in both the native metal and ores such as bismuthinite and bismite. Lead, tin and low melting alloys such as bismuth are produced commercially as a by-product of refining lead, copper, tin, silver and gold ores. Typically, bismuth is used in products such as fire detectors, extinguishers, electric fuses, and solders.

Cadmium and zinc are common lead, tin and low melting alloys. Cadmium is a soft, bluish-white metal that is obtained from greenockite and sphalerite. Cadmium is produced as a by-product of treating zinc, copper and lead, and ores. Typically, cadmium is used in electroplating, solders, nickel-cadmium batteries, rods to control atomic fission, and color television sets. Zinc is a grayish transition metal that can be alloyed with copper and other metals for metallurgical use. Zinc lead, tin and low melting alloys are less costly than copper alloys, and have an inherent corrosion resistance that is superior to cast iron.

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