Antimony and Antimony Alloys
Authors: Li T. , Archer G. F. , Carapella S. C. 
Published: August 2004

Abstract

Antimony, Sb, belongs to Group 15 (VA) of the Periodic Table which also includes the elements arsenic and bismuth. It is in the second long period of the table between tin and tellurium. Antimony, which may exhibit a valence of

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, is classified as a nonmetal or metalloid, although it has metallic characteristics in the trivalent state. There are two stable antimony isotopes that are both abundant and have masses of 121 (57.25%) and 123 (42.75%). Native antimony is seldom found in nature because of its high affinity for sulfur and metallic elements such as copper, lead, and silver. Over a hundred naturally occurring minerals of antimony have been identified. In areas where stibnite has been exposed to oxidation, it is converted to oxides of antimony. The important oxide minerals are stibiconite, Sb
2
O
4
·H
2
O, cervantite, Sb
2
O
4
or Sb
2
O
3
·Sb
2
O
5
, valentinite, orthorhombic Sb
2
O
3
, and senarmontite, cubic Sb
2
O
3
; kermesite, 2Sb
2
S
3
·Sb
2
O
3
, an oxysulfide ore, is also of commercial importance. World reserves of antimony are estimated to be from 4–5 million metric tons. Approximately 80% of the world's reserves are located in China, Bolivia, Russia, Thailand, the Republic of South Africa, and Mexico; China has the world's largest reserves. The United States possesses only 2% of the world's reserves. Antimony, a silvery white, brittle, crystalline solid, is a poor conductor of electricity and heat. At room temperature, antimony is ordinarily quite stable and not readily attacked by air or moisture. At higher temperatures, antimony reacts with oxygen to form the oxides Sb
2
O
3
, Sb
2
O
4
, and Sb
2
O
5
. The antimony content of commercial ores ranges from 5 to 60%, and determines the method of treatment, either pyrometallurgical or hydrometallurgical. In general, sulfide ores are volatilized as oxides; 25–40% antimony ores are smelted in a blast furnace; and 45–60% antimony ores are liquated or treated by iron precipitation. The blast furnace is generally used for mixed sulfide and oxide ores. Antimony is often found associated with lead ores. The smelting and refining of these ores yield antimony‐bearing materials that may be treated to recover elemental antimony. Recycling of antimony provides a large proportion of the domestic supply of antimony. Secondary antimony is obtained from the treatment of antimony‐bearing lead and tin scrap such as battery plates. The metal produced by a simple pyrometallurgical reduction is normally not pure enough for a commercial product and must be refined. Impurities present are usually lead, arsenic, sulfur, iron, and copper. Impure metal may be refined by electrolysis, although this procedure is not as economical as the pyrometallurgical treatment. The United States is heavily dependent on imports of both the ore and the metal. Total smelter output in the United States has been growing steadily since 1982 because of the growth in antimony oxide production. Since 1986, over 50% of the antimony imported by the United States has originated in China. Also, the demand for primary antimony in antimonial lead has increased, probably because of an increase in demand for starting–lighting–ignition (SLI) batteries. Antimony in the unalloyed state is extremely brittle and not easily fabricated; hence, the use of the pure metal is restricted to ornamental applications. Approximately one‐half of the total antimony demand is for metal used in antimony alloys. Most commercial lead‐antimony alloys have antimony contents less than 11%. The largest application for antimonial lead is its use as a grid metal alloy in the lead acid storage battery. In this use, antimony imparts fluidity, increased creep resistance, and fatigue strength, as well as electrochemical stability to the lead. In soldering, a method of joining two metallic surfaces by flowing between them a low melting point alloy, many different alloys are used; however, tin–lead alloys are the most widely used. Antimony is added to increase the hardness of tin–lead alloys. High purity (up to 99.9999%) antimony has a limited but important application in the manufacture of semiconductor devices and is utilized in such applications as infrared devices, diodes, and Hall‐effect components, and more recently, in high efficiency solar cells. The greatest use of antimony compounds is in flame retardants for plastics, paints, textiles, and rubber. Others are as decolorizing and fining agents, opacifiers in porcelain enamels, white pigments in paints, and in camouflage paints. It is recommended that direct skin contact with antimony and its alloys be avoided. Properly designed exhaust ventilation systems and/or approved respirators are required for operations that create dusts or fumes. As with other heavy metals, orderly housekeeping practice is necessary to prevent ingestion of (or exposure to) antimony. Antimony is not known to cause cancer, birth defects, or affect reproduction in humans. However, antimony has been shown to cause lung cancer in laboratory animals that inhaled antimony‐containing dusts, and prolonged exposure to antimony can cause irritation of the eyes, skin, lungs, and stomach, in the form of vomiting and diarrhea. Antimony generally enters the body through the lungs where it is transported to the blood and then to other organs. Stibine (SbH
3
), a highly toxic gas. Antimony enters the environment through mining and processing of antimony‐containing ores and in the production and working of antimony metals, alloys, and compounds. Despite the fact that antimony is in the solder used in water pipes, it does not appear to dissolve in the drinking water. Antimony and its compounds have been designated as priority pollutants by the EPA, and users, transporters, generators, and processors of antimony‐containing material must comply with regulations of the Federal Resource Conservative and Recovery Act (RCRA).