What Are Metalloids? Properties and Uses Explained

If a common alloy material, aluminum alloy with silicon（Si）addition, happens to be used in your engineering project, you surely understand that the additon of silicon（Si） must be enhancing certain properties of the aluminum alloy. But maybe you will be wondering—what does the silicon（Si）belongs to ? Metal or nonmetal?

 

This article will illustrate elements like silicon（Si）—the metalloids, and their properties and applications. After learning about how metalloids play an important role in industries, there might be some useful references provided for your material selection and application design.

 

 

What Are Metalloids？

 

Metalloids are a class of elements whose properties lie between those of metals and nonmetals , which have a metallic luster but are relatively brittle. 

 

Metalloids exhibit a dual nature physically and chemically, combining metallic and nonmetallic characteristics. Physically, they typically possess a balance of semiconductor properties, moderate strength, and good adaptability. Chemically, they can gain or lose electrons and react with both acids and bases.

 

This dual nature makes metalloids irreplaceable in fields such as alloy manufacturing, semiconductors, and chemistry etc.

 

 

 

Which Elements Are Metalloids?

 

Common metalloids include boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te), polonium (Po), and astatine (At).

 

 

 

Table 1: Physical and Chemical Properties of Common Metalloids

 

 

 

 

It’s worth noting that there’re currently some controversies about Polonium (Po) and astatine (At) . 

 

Polonium (Po) is sometimes considered a metal because it shows some characteristics of a metal. Like, it tends to form cations in aqueous solutions, and its electrical conductivity decreases with increasing temperature.

 

Astatine (At) is sometimes considered a nonmetal. Astatine (At) is located in Group 17 of the halogens, while the other elements in that group are nonmetals.

 

 

 

 

What Are the General Properties of Metalloids?

 

 

The main properties of metalloids can be explored from both physical and chemical perspectives.

 

 

Physical Properties of Metalloids

 

Metalloids typically possess physical properties that fall between those of metals and nonmetals, which I will refer to as “moderate” .

 

 

1.Electrical Conductivity

 

Moderate. The electrical conductivity of metalloids (usually the semiconductors) increases with increasing temperature (free electron flow is increased ). This is something metals cannot do; metals impede free electron flow as temperature rises. This unique conductivity property makes them (such as semiconductor silicon (Si)) uniquely suited for electronic device and chip manufacturing.

 

 

2.Temperature Conductivity

 

Moderate. Boron (B) and silicon (Si) are examples of metalloids with relatively good thermal conductivity, suitable for high-performance electronic products.

 

 

3.Mechanical Properties

 

The hardness of metalloids is moderate. But metalloids don’t have ductility, toughness, and elasticity. So, metalloids are unsuitable for structural applications in construction, machinery, etc.

 

 

4.Boiling and Melting Points

 

Moderate. It is worth noting that the boiling and melting points of metalloids are not lower than all the metals. The boiling and melting points of metalloids depend on their atomic structure, particularly their tendency to form covalent network structures (atomic structures connected by strong covalent bonds to form a three-dimensional network). 

 

These three-dimensional network structures possess strong covalent bonds, requiring much energy to break. So, the melting and boiling points of metalloids are higher than those of some common metals (such as aluminum and copper).

 

 

5.Density

 

Moderate. The density of metalloids increases with increasing atomic number.

 

 

6.Allotropes

 

Allotropy is very common in metalloids (except for polonium (Po) and astatine (At)), exhibiting different physical properties in different forms. It reflects their mixed-type characteristics between metals and nonmetals.

 

 

 

Chemical Properties of Metalloids

 

Metalloids exhibit chemical behavior intermediate between metals and nonmetals, possessing dual characteristics, but they generally behave more like nonmetals in chemical reactions.

 

 

1.Reactivity with Nonmetals

 

Metalloids react with strong oxidizing agents, exhibiting reducing properties (losing electrons). They react with strong reducing agents, exhibiting oxidizing properties (gaining electrons). In metallurgy, corrosion, electrochemistry, and catalysis, this "electron gain/loss" controls the direction of the reaction.

 

 

2.Reacted As Additive Elements

 

Metalloids are often added as additive elements to metals or alloys, influencing the crystal structure during chemical reactions or alloy formation, thereby enhancing or transitioning the properties of the metal (e.g., hardness, stability, or conductivity).

 

 

3.Reaction with Acids and Bases

 

Metalloids can react with both acids and bases, possessing good chemical adaptability. For example, metalloid oxides are amphoteric oxides, reacting with acids and bases respectively to produce salts and water. Some metalloids can also react under strong acid or strong base conditions.

 

 

 

 

What Are the Applications of Metalloids?

 

 

Alloys

 

 

1.Aerospace Components

 

• Boron (B) is added to steel or nickel-based alloys to improve hardness, strength, and corrosion resistance, used in high-strength aerospace components.
  
• Silicon (Si) is added to aluminum alloys to strengthen them, improving machinability, corrosion resistance, and strength, used in aerospace applications.

 

 

2.Solar Panels

 

Tellerium (Te) is added to cadmium compounds to form cadmium telluride (CdTe). Its low thermal conductivity and suitable band gap (approximately 1.5 eV) reduce heat conduction losses in cells, making it suitable for high-efficiency solar panels.

 

 

3.Thermoelectric Conversion Equipment

 

Tellerium (Te) is added to bismuth compounds to form bismuth telluride (Bi₂Te₃). Its low thermal conductivity and high electrical conductivity make it an ideal material for thermoelectric conversion equipment.

 

 

4.Ammunition Manufacturing and Mechanical Components

 

Antimony (Sb) is combined with lead to form antimony-lead alloys, improving material hardness and wear resistance, used in ammunition manufacturing and mechanical components.

 

 

 

Glass

 

 

1.Ordinary Glass

 

Silicon (Si) forms silicon dioxide (SiO₂), the main raw material for glass.

 

 

2.Borosilicate Glass

 

Boron (B) forms borosilicate glass, reducing the coefficient of thermal expansion, used in laboratory instruments, heat-resistant cookware, and architectural glass.

 

 

3.Optical Glass

 

• Germanium (Ge) has infrared transmission properties and is used in optical glass.
  
• Tellulone (Te) forms tellurium dioxide (TeO₂), used in infrared-transmitting glass.

 

 

Silicone Rubber

 

Silicon (Si) is used in its compound form to prepare silicone rubber, sealants, lubricants and insulating materials. It has excellent heat resistance and chemical stability and is often used in cookware and electronic sealing components.

 

 

Flame Retardant Materials

 

Antimony (Sb) provides flame retardancy and is used in industrial machinery, construction, textiles, plastics, and wire coatings. Antimony (Sb) is also commonly added as a flame retardant to molded plastics.

 

 

Pyrotechnic Uses

 

• Boron (B) produces a bright green flame when burned and is used as a green colorant in fireworks.
  
• Bismuth (Bi) is used as a colorant to produce colored sparks.
  
• Silicon (Si) is used as an ignition or extinguishing agent in fireworks.

 

 

Semiconductors

 

• Silicon (Si) is used in semiconductor materials and is widely used in electronic products.
• Antimony (Sb) is used in semiconductor devices such as optical storage media, diodes, and infrared detectors.

 

 

Medical Uses

 

 

1.Equipment

 

• Silicon (Si) is used in electronic components and silicone materials in medical devices.
• Boron (B) is used in glassware and disinfectants.

 

 

2.Therapeutic and Pharmaceutical Uses

 

• Astatine (At) is used in the radioactive isotope astatine-211 for cancer treatment research, especially thyroid cancer.
• Boron (B) is used in the production of boric acid, which is used to treat yeast infections.
• Antimony (Sb) is used in antiparasitic drugs, but it has some toxicity.

 

 

3.Medical Chemicals

 

Antimony (Sb) has medicinal properties and can be used as a preservative or oral antifoaming agent.

 

 

Agricultural Uses

 

• Boron (B) is an essential micronutrient for plants and is used as a crop nutrient supplement.
  
• Arsenic (As) was once used as an insecticide and herbicide, but it has been gradually phased out due to its high toxicity.

 

 

 

 

FAQs on Metalloids

 

 

What is the difference between metals and metalloids? 

 

Metals are generally hard, malleable, and conduct electricity and heat faster; metalloids are brittle, not malleable, and have moderate electrical and thermal conductivity.

 

 

Are metalloids used in solar panels?

 

Besides tellurium (Te), silicon and germanium are also widely used in solar panels.

 

 

Which metalloid is most abundant? 

 

Silicon dioxide (SiO₂) and silicate minerals, formed from silicon, are widely found in nature, such as sand and gravel.

 

 

 

Summary

 

This article discussed metalloids as well as their physical and chemical properties and applications. If you want to learn more on the application of metalloids in alloys, and how to use metalloids to enhance the performance of alloy materials and benefit you, contact a VMT expert today for assistance.

 

As a CNC machining factory, VMT is committed to providing high-precision custom CNC machining alloy parts for various industries. With professional knowledge, advanced CNC equipment, a strict quality control system, and exquisite surface treatment processes, we can meet all your prototype design and production needs. Contact VMT to require a free consult or quote, we provide 24/7 service.