MgF₂

Core Features

1. Ultra-High Purity and Low Impurity Contamination

   Purified by chemical synthesis-recrystallization-vacuum sintering process, the purity of MgF₂ is ≥99.99% (4N), and some high-end products can reach 99.999% (5N). The total content of metallic impurities (Fe, Cu, Ni, Cr, etc.) is ≤10 ppm, moisture content ≤50 ppm, and no volatile impurities. No harmful gases are released during the coating process, which will not contaminate optical substrates or coating equipment, ensuring the optical uniformity of the film layer.
2. Excellent Optical Performance
   • Low and Stable Refractive Index: The refractive index is 1.38 in the visible light band (550 nm), 1.45 in the ultraviolet band (200 nm), and 1.35 in the infrared band (10 μm), making it one of the optical coating materials with the lowest refractive index among commonly used ones.
   • Broad-Spectrum Transmission Range: It can transmit light from 120 nm (deep ultraviolet) to 7.5 μm (mid-infrared), with a transmittance ≥92% in the visible light region and ≥85% in the ultraviolet region (250 nm).
   • Low Light Absorption and Scattering: The light absorption coefficient is ≤1×10⁻⁴ cm⁻¹ in the working band, and the film scattering loss is low, which can ensure the imaging quality of optical components and laser transmission efficiency.
3. Good Mechanical and Environmental Stability

   The deposited MgF₂ film has a hardness ≥500 HV and a bonding strength ≥20 MPa with optical substrates such as glass, silicon and germanium, which is not easy to scratch or fall off. It has excellent anti-hygroscopicity and corrosion resistance, can be used stably for a long time in an environment with relative humidity ≤85%, and the film layer has no cracking or discoloration after high and low temperature cycles (-50℃~+80℃).
4. Diversified Morphologies and Process Compatibility

   According to the requirements of coating processes, it can be prepared into granular (particle size 1-3 mm, 3-5 mm), flaky (thickness 0.5-2 mm), target (planar target, rotating target) and other morphologies. Granular form is suitable for vacuum evaporation process, and target form is suitable for magnetron sputtering process, meeting the needs of different coating equipment and mass production.

Technical Parameters (Typical Values)

Application Fields

1. Anti-Reflection Films for Optical Components

   As the core material of single-layer anti-reflection films, it is used on the surface of lenses of optical instruments such as camera lenses, telescopes and microscopes. It can reduce the reflectivity of the glass surface from about 4% to less than 1%, greatly improving the light transmittance and imaging clarity of the optical system. It can also be used as the low-refractive-index layer of multi-layer anti-reflection films, suitable for optical components with wide-band and high-transmittance requirements.
2. UV and IR Optical Devices

   Used for coating of deep-UV lithography machine lenses, UV detector windows, infrared thermal imager lenses and other devices. Utilizing its broad-spectrum transmission characteristics, it ensures the light transmission efficiency in the UV and IR bands, and improves the environmental adaptability of the devices.
3. Optical Components for Laser Systems

   Applied to the coating of laser resonator lenses, laser output windows, fiber coupling lenses and other components. The low absorption and low scattering characteristics can reduce laser energy loss and avoid film damage caused by laser thermal effects, suitable for high-power laser systems.
4. Special Optical Film Systems

   As a low-refractive-index layer, it participates in the design and preparation of multi-layer film systems such as beam-splitting films, polarizing films and high-reflection films. By matching with high-refractive-index materials (such as TiO₂, ZrO₂, Nb₂O₅), specific optical functions are realized to meet the needs of optical communication, optical sensing and other fields.

Preparation Process

1. Raw Material Purification: Using industrial-grade magnesium fluoride as raw material, metal impurities and soluble salts are removed through hydrofluoric acid dissolution-ammonia precipitation-recrystallization process to obtain high-purity MgF₂ crystals.
2. Drying and Pre-Sintering: The recrystallized MgF₂ crystals are vacuum-dried at 120℃ for 12 hours to remove moisture; then pre-sintered in a vacuum environment at 600℃ for 2 hours to further remove volatile impurities.
3. Forming and Sintering:
   • Granular: The pre-sintered MgF₂ is crushed and sieved to obtain particles of different sizes;
   • Flaky/Target: The MgF₂ powder is formed by cold isostatic pressing and sintered at 800-900℃ in vacuum at high temperature to obtain high-density, high-compactness flaky or target blanks.
4. Precision Machining and Quality Inspection: The blanks are ground and polished (targets need backing target bonding), then the purity, optical performance and other indicators are detected by XRF, ICP-MS, spectrophotometer and other equipment, and vacuum-packaged after passing the inspection.

Usage and Storage Recommendations

1. Usage Notes:
   • Vacuum Evaporation Process: It is recommended to carry out in an environment with a vacuum degree ≥5×10⁻⁴ Pa, the evaporation temperature is about 1300℃, and an electron beam evaporation source can be used to improve evaporation efficiency and film quality;
   • Sputtering Process: Adopt RF sputtering mode, vacuum degree ≥1×10⁻³ Pa, power density 2-5 W/cm², and the cooling system must be turned on to control the target temperature.
   • Avoid contact with strong acids and alkalis to prevent material decomposition.
2. Storage Conditions:

   Vacuum-sealed and stored in a dry and clean environment, with storage temperature 5-30℃ and relative humidity ≤40%, avoiding moisture, dust contamination and severe collision. The shelf life of 4N grade products is 12 months, and that of 5N grade products is 6 months.