what is aln

1.Aln Basic Properties

Crystal Structure: Hexagonal wurtzite structure (similar to boron nitride and silicon carbide), characterized by high hardness, high melting point, and excellent thermal stability.

Color: Typically grayish-white or light gray powder; pure single crystals can appear colorless and transparent.

Density: 3.26 g/cm³.

Melting Point: Approximately 2200°C (can reach up to 2500°C without decomposition under high-pressure nitrogen).

2.Characteristics and Advantages

High Thermal Conductivity: Theoretical value up to 320 W/(m·K), comparable to beryllium oxide (BeO) and copper, but non-toxic, making it an ideal thermal management material.

Wide Bandgap: 6.2 eV (electron volts), suitable for high-temperature, high-power, and ultraviolet optoelectronic devices.

Electrical Insulation: High resistivity (>10¹⁴ Ω·cm) and low dielectric constant (~8.8), ideal for high-frequency electronic devices.

Chemical Stability: Resistant to acid and alkali corrosion (especially in dry environments), but slowly hydrolyzes in high-temperature humid air.

Thermal Expansion Coefficient: 4.5×10⁻⁶/K (close to silicon), making it compatible with silicon-based chips.

3.Preparation Methods

Chemical Vapor Deposition (CVD): Used to produce high-purity thin films or single crystals.

Direct Nitridation: Aluminum powder reacts with nitrogen or ammonia at high temperatures (800–1200°C).

Carbothermal Reduction: Aluminum oxide mixed with carbon reacts in nitrogen at high temperatures (1600–1800°C).

Sol-Gel Method: Suitable for synthesizing nano-sized powders.

4.Applications

Semiconductor Devices: High-temperature and high-frequency components (e.g., RF modules for 5G communication), substrates for UV LEDs.

Electronic Packaging: High thermal conductivity substrates (e.g., heat sinks for LEDs and power modules).

Surface Acoustic Wave (SAW) Devices: Due to high acoustic velocity (~6000 m/s) and low signal loss.

Structural Ceramics: High-temperature crucibles, cutting tool coatings.

Composite Materials: Mixed with polymers to enhance thermal conductivity (e.g., thermally conductive plastics).

5.Precautions

Toxicity: Powder may irritate the respiratory tract; protective measures are required.

Processing Difficulty: High hardness increases cutting and polishing costs, often requiring hot pressing or spark plasma sintering (SPS) techniques.

6.Comparison with Other Materials

VS Aluminum Oxide (Al₂O₃): Thermal conductivity is over 10 times higher, but cost is also higher.

VS Silicon Nitride (Si₃N₄): Aluminum nitride offers better thermal conductivity but slightly lower mechanical strength.

Aluminum nitride (AlN) holds an irreplaceable position in advanced electronics and high-temperature technologies due to its unique combination of properties. With the growth of 5G and electric vehicles, its demand continues to rise.