High‑purity Aluminum Fluoride-CAS 7784‑18‑1
Product Overview
High-purity Aluminum Fluoride (AlF₃), CAS No. 7784-18-1, is an inorganic crystalline compound widely recognized for its exceptional thermal stability, low refractive index, and broad optical transparency. As a critical functional material, it serves as an indispensable additive in primary aluminum smelting, a high-performance coating material in precision optics, and an emerging electrolyte component in advanced lithium-ion battery systems. Our high-purity grade is manufactured under strictly controlled conditions to deliver consistent purity levels of 99.9% and above, meeting the most demanding specifications across metallurgical, optical, and electronic industries.
Chemical Identity and Key Properties
| Parameter | Specification |
|---|---|
| Chemical Name | Aluminum Fluoride |
| CAS Number | 7784-18-1 |
| Molecular Formula | AlF₃ |
| Molecular Weight | 83.98 g/mol |
| Appearance | White crystalline powder / solid |
| Density | 3.10 g/cm³ |
| Melting / Sublimation Point | ~1290 °C |
| Refractive Index | ~1.35 (at 500–632 nm) |
| Optical Band Gap | >10 eV |
| Solubility | Insoluble in water, acids, alkalis, and most organic solvents |
| Purity (High-Purity Grade) | ≥99.9% (99.99% available upon request) |
Aluminum fluoride exists as a colorless-to-white crystalline solid with a trigonal crystal structure. It is chemically inert under normal conditions, exhibiting remarkable resistance to hydrolysis and oxidation. The compound sublimes at approximately 1290 °C without significant decomposition, making it suitable for high-temperature processing environments. Its exceptionally wide optical transmission range — from the deep ultraviolet (200 nm) through the mid-infrared (20,000 nm) — positions it as one of the few materials capable of serving across the entire optical spectrum.
High-Purity Grade: Why It Matters
The distinction between industrial-grade and high-purity aluminum fluoride lies in trace element control. Standard industrial AlF₃ may contain residual impurities such as silica (SiO₂), iron oxide (Fe₂O₃), sodium (Na), calcium (Ca), and sulfate (SO₄²⁻) at parts-per-hundred levels. In high-purity grades, these impurities are rigorously reduced to ppm or sub-ppm levels through advanced purification techniques including recrystallization, sublimation refining, and controlled atmosphere calcination.
This purity control is critical for several reasons:
- Optical coatings: Even trace metallic impurities can cause absorption bands, scattering losses, and reduced laser damage thresholds in thin-film coatings.
- Electrolyte systems: Impurity ions can alter electrochemical stability and introduce side reactions in battery electrolytes.
- Semiconductor-adjacent processes: Low impurity levels ensure compatibility with cleanroom manufacturing and prevent contamination of sensitive substrates.
Manufacturing Process
Our high-purity aluminum fluoride is produced through a multi-stage process designed to maximize purity while maintaining consistent particle morphology:
- Raw Material Preparation: High-purity aluminum hydroxide or alumina is selected as the starting material, with pre-screening to ensure low initial impurity profiles.
- Hydrofluorination: The aluminum source is reacted with anhydrous hydrogen fluoride (HF) under controlled temperature and pressure. This direct fluorination route minimizes the introduction of foreign ions compared to wet chemical methods.
- Crystallization and Filtration: The resulting aluminum fluoride is crystallized under controlled conditions to achieve uniform particle size distribution, followed by thorough washing to remove residual acid and soluble impurities.
- Calcination and Dehydration: The material is calcined at elevated temperatures (typically 500–700 °C) under inert or fluorinating atmosphere to remove residual moisture and crystal water, converting any hydrated phases to the anhydrous form.
- Sublimation Refinement (Optional): For ultra-high-purity grades (99.99%), an additional vacuum sublimation step is employed, exploiting AlF₃'s high vapor pressure at elevated temperatures to separate it from less volatile impurities.
- Quality Control and Packaging: Each batch undergoes comprehensive analysis including ICP-MS for trace metal impurities, XRD for phase confirmation, and laser diffraction for particle size distribution before being packaged in moisture-barrier containers.
Primary Applications
1. Primary Aluminum Smelting (Hall-Héroult Process)
The largest industrial application of aluminum fluoride is as an electrolyte additive in the Hall-Héroult process for primary aluminum production. When combined with molten cryolite (Na₃AlF₆), AlF₃:
- Lowers the melting point of the electrolyte bath below 1000 °C, significantly reducing energy consumption
- Increases the electrical conductivity of the molten electrolyte
- Improves current efficiency by reducing sodium deposition at the cathode
- Helps control the bath ratio (NaF/AlF₃) for optimal operating conditions
High-purity AlF₃ ensures stable bath chemistry and minimizes impurity carryover into the final aluminum metal.
2. Optical Thin-Film Coatings
AlF₃ is one of the most important low-refractive-index materials for optical coatings, particularly in the ultraviolet region. Its key optical advantages include:
- Deep UV transparency: Transmissive down to ~200 nm, far beyond most oxide-based coating materials
- Low refractive index (~1.35): Ideal for antireflective (AR) coating stacks when paired with high-index materials
- High laser damage threshold: Suitable for high-power UV laser optics
- Wide spectral coverage: Functional from UV through mid-IR
Applications include UV antireflective coatings for lithography optics, excimer laser components, astronomical instruments, and spectroscopic windows. It is deposited via electron-beam evaporation, thermal evaporation, or atomic layer deposition (ALD) techniques.
3. Lithium-Ion Battery Electrolytes
High-purity aluminum fluoride is gaining traction as an electrolyte additive and coating material in advanced lithium-ion battery systems:
- As an electrolyte additive, it can modify the solid-electrolyte interphase (SEI) layer, improving cycle stability
- Used in the synthesis of lithium aluminum fluoride (LiAlF₄) and other complex fluoride electrolytes for solid-state batteries
- Serves as a coating material for cathode particles to suppress transition metal dissolution and electrolyte decomposition
4. Glass and Ceramics
In the glass and ceramic industries, aluminum fluoride functions as:
- A fluxing agent that lowers melting temperatures and improves melt homogeneity
- An opacifier and crystallizing agent in specialty glass formulations
- A component in low-expansion glass-ceramics and fluorophosphate glasses
- An additive in ceramic glazes to modify surface properties and firing behavior
5. Refractory and Welding Applications
AlF₃ is used in specialty refractory products and as a flux component in non-ferrous metal welding and brazing, where it helps remove oxide layers and improves wetting characteristics.
Packaging, Storage, and Handling
Our high-purity aluminum fluoride is available in various packaging configurations to suit different application requirements:
- Standard packaging: 25 kg moisture-proof bags or fiber drums with polyethylene liners
- Bulk packaging: 500 kg or 1000 kg jumbo bags for industrial-scale consumption
- Custom packaging: Vacuum-sealed bags or argon-purged containers for ultra-high-purity grades
Storage: Store in a cool, dry, well-ventilated area away from moisture and incompatible materials (particularly strong acids and alkalis). Keep containers tightly sealed to prevent moisture absorption and contamination.
Handling: Use appropriate personal protective equipment including gloves, safety goggles, and dust masks. Avoid generating dust. Aluminum fluoride dust may cause irritation to the respiratory tract, skin, and eyes. In case of contact, rinse thoroughly with water and seek medical attention if irritation persists.
Quality Assurance
Every batch of our high-purity aluminum fluoride is accompanied by a Certificate of Analysis (CoA) detailing:
- Purity assay (AlF₃ content)
- Trace metal impurity profile (Fe, Si, Na, Ca, Mg, K, etc.) via ICP-MS
- Loss on drying / moisture content
- Particle size distribution (D10, D50, D90)
- XRD phase confirmation
- Bulk density
We can accommodate custom specifications, particle size distributions, and purity grades tailored to specific application requirements.
Conclusion
High-purity Aluminum Fluoride (CAS 7784-18-1) is a versatile, high-performance inorganic material whose unique combination of thermal stability, optical transparency, and chemical inertness makes it indispensable across multiple high-technology sectors. From reducing energy consumption in primary aluminum production to enabling deep-UV optical coatings and advancing next-generation battery technologies, its role continues to expand. Our commitment to rigorous purity control, consistent quality, and customizable specifications ensures that our high-purity AlF₃ meets the exacting requirements of the most demanding industrial and research applications.