Antimony

Antimony is a lustrous, silvery-grey metalloid with the chemical symbol Sb (from the Latin stibium) and atomic number 51. It occupies a distinctive position in the periodic table between metals and non-metals, exhibiting properties of both. Known since antiquity, antimony has been used for thousands of years in medicines, cosmetics, and metal alloys. In modern times, it has acquired immense industrial and economic importance due to its wide-ranging applications in flame retardants, alloys, semiconductors, and batteries.
Although not commonly encountered in everyday consumer form, antimony contributes indirectly to numerous products, technologies, and infrastructures that underpin daily life, including electronics, plastics, and transportation systems.

Historical Background and Discovery

The use of antimony dates back to ancient civilisations such as Egypt, Babylon, and China, where its natural sulphide mineral, stibnite (Sb₂S₃), was employed in cosmetics and medicines. The element itself was isolated and described in detail during the 15th and 16th centuries by alchemists, most notably Basil Valentine in his treatise The Triumphal Chariot of Antimony (1604).
Modern chemistry identified antimony as an element in the 18th century. The industrial exploitation of antimony began in earnest during the 19th and 20th centuries, particularly with the advent of metallurgy and flame-retardant technologies.

Occurrence and Extraction

Antimony is found in nature mainly as stibnite (Sb₂S₃), which serves as its primary ore. Other minerals containing antimony include valentinite (Sb₂O₃) and senarmontite (Sb₂O₃). The leading global producers of antimony are China, Russia, Tajikistan, and Bolivia, with China dominating both mining and refining operations.
Extraction involves roasting stibnite ore in the presence of air to form antimony oxide, followed by reduction with carbon or iron to yield metallic antimony. Depending on purity and intended use, the metal may undergo further refining processes such as electrolytic purification.

Physical and Chemical Properties

Antimony has a melting point of 630°C and a boiling point of 1635°C, with a density of 6.68 g/cm³. It is brittle, crystalline, and easily pulverised. Chemically, it exhibits multiple oxidation states—−3, +3, and +5—and forms compounds with oxygen, chlorine, and sulphur.
As a metalloid, antimony displays both metallic conductivity and non-metallic chemical reactivity. It resists corrosion and oxidation in air, making it ideal for applications requiring durability and stability.

Everyday and Industrial Applications

Antimony’s versatility gives it a wide array of applications across various industries. Though it is not encountered directly by consumers, it is integral to many common materials and devices.

• Flame Retardants: The single largest use of antimony, accounting for over 50% of global demand, lies in antimony trioxide (Sb₂O₃), which acts as a synergist in flame-retardant formulations. Combined with halogenated compounds, it enhances fire resistance in plastics, textiles, rubber, and electronics housings. Everyday products such as computers, mobile phones, and upholstery often rely on antimony-based flame retardants to meet fire safety regulations.
• Alloys: Antimony is widely used to harden soft metals. Alloys containing antimony include:
  • Lead–antimony alloys for batteries, particularly in lead-acid batteries used in cars and industrial equipment.
  • Pewter and solder, where antimony improves strength and lustre.
  • Type metal for printing presses, now largely obsolete but historically significant.The addition of antimony enhances hardness, mechanical strength, and corrosion resistance, making it vital in metal casting and engineering applications.
• Semiconductors and Electronics: In the electronics industry, antimony compounds are used as dopants in semiconductors such as indium antimonide (InSb), gallium antimonide (GaSb), and aluminium antimonide (AlSb). These materials possess unique electronic and thermoelectric properties useful in infrared detectors, Hall-effect devices, and diodes.
• Glass and Ceramics: Antimony oxide acts as a fining agent in glass production, removing bubbles and improving clarity. It is also used to decolourise glass by neutralising iron impurities. In ceramics and enamels, it functions as a colouring agent, imparting yellow and white hues.
• Pigments and Plastics: Antimony compounds are used in the manufacture of pigments, particularly antimony yellow (Pb₂Sb₂O₇), and in polyethylene terephthalate (PET) plastics as a catalyst. PET is the material used for plastic bottles, food packaging, and synthetic fibres, thus placing antimony at the heart of many everyday products.
• Batteries and Energy Storage: Beyond traditional lead-acid batteries, antimony is being explored in sodium–antimony batteries and liquid metal batteries, which promise long-term grid energy storage solutions. These emerging technologies could play a key role in renewable energy systems, improving the stability and sustainability of electricity grids.

Economic Importance

Antimony holds significant strategic and economic value, particularly as a critical mineral in modern technology and defence sectors. Due to its diverse industrial uses, global demand for antimony correlates with the growth of manufacturing, electronics, and infrastructure industries.

• Global Supply: China accounts for more than 80% of global antimony production, controlling both mining and refining capacities. This concentration of supply creates potential economic vulnerabilities and geopolitical dependencies for other nations.
• Market Value: The price of antimony fluctuates according to industrial demand and supply constraints, often influenced by environmental policies and geopolitical factors.
• Strategic Uses: Governments classify antimony as a strategic material, vital for defence technologies including ammunition, solder, bearings, and infrared systems. Its use in lead alloys for bullets and shrapnel has historical importance in military manufacturing.

Efforts to diversify supply sources and recycle antimony from spent batteries and industrial waste are increasing, aiming to reduce dependency on single-country production.

Environmental and Health Considerations

Although antimony compounds are valuable industrially, their toxicity requires careful management. Exposure to high levels of antimony dust or vapour can cause respiratory, skin, and gastrointestinal irritation. Certain antimony compounds, particularly antimony trioxide, are classified as potential carcinogens.
In the environment, antimony may enter soil and water systems through mining, smelting, and industrial discharge. Its mobility and persistence raise concerns for ecosystems, prompting stricter environmental monitoring and emission controls. Modern regulations enforce air filtration systems, closed-circuit processing, and waste containment measures in facilities handling antimony.
Recycling initiatives, particularly from lead-acid batteries, help reduce environmental impact and ensure more sustainable antimony use.

Research and Emerging Applications

Current research focuses on expanding antimony’s role in advanced technologies:

• Energy storage: Development of antimony-based batteries for renewable energy grids.
• Thermoelectric materials: Exploration of antimony chalcogenides (such as Sb₂Te₃) for converting heat into electricity.
• Nanotechnology: Antimony nanoparticles show potential in photovoltaic cells and medical imaging.
• Flame-retardant innovation: Development of non-toxic alternatives and improved recycling of antimony trioxide from plastics.

These innovations may significantly enhance the element’s role in sustainable and high-performance materials industries.

Everyday Relevance

Although consumers seldom encounter pure antimony, it is omnipresent in modern life through products such as:

• Smartphones, laptops, and electrical devices (flame-retardant casings).
• Plastic bottles and packaging (PET catalysts).
• Automobiles (lead-acid batteries and brake linings).
• Household textiles and carpets (fire-resistant coatings).

Hence, antimony’s influence extends from homes and offices to vehicles, public buildings, and power systems.