Understanding gallium's properties is essential to grasping why it's so valuable for technology and investment.
Physical Properties
Appearance and Feel
- Color: Silvery white metal
- Luster: Metallic with bright reflectivity
- Texture: Soft, can be scratched with a fingernail
- Density: 5.906 g/cm³ (lighter than iron)
Thermal Characteristics
Melting Point: 29.76°C (85.68°F)
- Just above room temperature
- Gallium is solid only in cool conditions
- Liquid gallium can be held in non-metallic containers
- This property creates unique handling challenges and opportunities
Boiling Point: 2204°C (3999°F)
- Very high vapor pressure at elevated temperatures
- Requires inert atmosphere during processing
- Industrial processing must account for volatility
Thermal Conductivity: 40.6 W/(m·K)
- Lower than aluminum but higher than stainless steel
- Important for heat dissipation in electronic devices
- Affects circuit efficiency
Mechanical Properties
- Hardness: Relatively soft (Mohs hardness ~1.5)
- Malleability: Can be shaped into sheets and wires
- Brittleness: Becomes brittle at lower temperatures
- Ductility: Limited ductility compared to traditional metals
Chemical Properties
Reactivity
With Acids:
- Soluble in concentrated sulfuric acid
- Reacts slowly with dilute acids
- Amphoteric behavior with strong acids and bases
With Bases:
- Reacts with strong alkaline solutions
- Forms gallate ions in basic conditions
With Non-metals:
- Forms important compounds with nitrogen (GaN)
- Forms important compounds with arsenic (GaAs)
- Forms important compounds with phosphorus (GaP)
- Oxidizes in air to form Ga₂O₃
Oxidation States
- Primary State: +3 (gallium trioxide, gallium compounds)
- Secondary State: +2 (less common, gallium dihalides)
- Biological State: Similar to iron in biological systems
Electronic Properties
The electronic properties of gallium are why it's revolutionary for semiconductors.
Band Gap
| Property | Gallium | Silicon |
|---|---|---|
| Band Gap | 1.42 eV | 1.12 eV |
| Significance | Higher = faster electronics | Lower = more efficient at lower frequencies |
Electron Mobility
Gallium-based semiconductors show superior electron mobility:
- GaAs: 8,500 cm²/(V·s) at 300K
- Silicon: 1,350 cm²/(V·s) at 300K
- Higher mobility = faster transistor switching speeds
Hole Mobility
- GaAs: 400 cm²/(V·s)
- Silicon: 480 cm²/(V·s)
- More comparable to silicon, but still adequate for applications
Compound Semiconductors
Gallium's true power emerges in compounds:
Gallium Arsenide (GaAs)
- Used in high-speed integrated circuits
- Superior performance for RF and microwave applications
- Essential for space-based solar cells
- Direct bandgap enables efficient light emission
Gallium Nitride (GaN)
- Wide bandgap semiconductor (3.4 eV)
- Exceptional for high-power, high-temperature applications
- Critical for power electronics and RF applications
- Enables efficient LED and laser diodes
Gallium Phosphide (GaP)
- Used in optoelectronic devices
- Lower cost than GaAs for some applications
- Good for indicators and displays
Gallium Oxide (Ga₂O₃)
- Ultra-wide bandgap (4.8 eV)
- Emerging material for power electronics
- Potential for extreme temperature applications
Optical Properties
Light Interaction
- Transparent to infrared radiation
- Opaque to visible light
- Good reflivity in certain wavelengths
- Gallium compounds efficient at light emission
Optoelectronic Applications
- LEDs (light-emitting diodes)
- Laser diodes
- Photodetectors
- Optical modulators
Magnetic Properties
- Diamagnetic: Weakly repelled by magnetic fields
- Limited magnetic applications
- Not ferromagnetic
Isotopes
- Gallium-69: 60.1% natural abundance
- Gallium-71: 39.9% natural abundance
- No radioactive isotopes in nature
Properties in Compounds
When combined with other elements, gallium creates materials with dramatically different properties:
III-V Semiconductors
Compounds of Group III (like gallium) with Group V (like nitrogen, phosphorus, arsenic) create efficient semiconductors for:
- High-speed electronics
- Optoelectronics
- Power conversion
- RF and microwave devices
Comparative Property Analysis
| Property | Gallium | Silicon | Germanium | Indium |
|---|---|---|---|---|
| Band Gap (eV) | 1.42 | 1.12 | 0.66 | 1.35 |
| Electron Mobility | 8,500 | 1,350 | 3,900 | 4,600 |
| Melting Point (°C) | 29.76 | 1414 | 938 | 157 |
| Thermal Conductivity | 40.6 | 148 | 60 | 81 |
Implications for Investment
From an investment perspective, gallium's properties mean:
- Specialization: Limited to specific high-performance applications
- Technology Lock-in: Difficult to replace in established uses
- Performance Premium: Justifies higher costs in critical applications
- Compound Dependency: Value tied to gallium compound development
- Supply Concentration: Byproduct nature limits total supply
Learn More
- Explore specific Gallium Compounds
- Understand Gallium Uses
- Review Gallium in Electronics