Messi Biology Co., Ltd. in Hebei states that magnesium oxide (MgO) plays a crucial role in optical glass, and its purity directly affects the optical, mechanical, and chemical properties of the glass. The following explores the impact of magnesium oxide purity on optical glass from multiple perspectives:
1. Definition of Magnesium Oxide Purity
The purity of magnesium oxide typically refers to the content of its main component, MgO, generally expressed as a mass percentage (%). The purity requirement of magnesium oxide for optical glass is usually above 99.9%, with high-end applications even requiring 99.99% (4N grade) or higher (5N grade).
Impurity components include:
- Metallic impurities (such as Fe, Al, Ca, Si, Na, etc.) – affect the transmittance, refractive index, and dispersion of the glass.
- Non-metallic impurities (such as C, S, Cl, etc.) – affect the chemical stability and optical homogeneity of the glass.
2. Impact of Purity on Optical Properties
(1) Transmittance and Impurity Absorption
High-purity MgO helps reduce impurity absorption in the glass, resulting in higher transmittance.
Metallic impurities such as Fe²⁺ and Fe³⁺ can cause absorption of visible and ultraviolet light, resulting in color deviation in the glass.
Excessive SiO₂ and Al₂O₃ may affect the optical homogeneity of the glass.
(2) Stability of Refractive Index
Low-purity magnesium oxide may introduce other metal oxides, affecting the refractive index uniformity of the optical glass.
High-purity MgO ensures that the refractive index meets design requirements, improving the accuracy of optical systems.
(3) Color and Optical Homogeneity
Low-purity magnesium oxide may cause the glass to yellow or produce uneven color spots, affecting the imaging quality of high-precision optical instruments.
The higher the purity, the closer the color of the glass is to transparent and colorless, making it suitable for high-end optical equipment such as telescopes, microscopes, and laser lenses.
3. Impact of Purity on Mechanical and Thermal Properties
(1) Heat Resistance of Glass
High-purity MgO can improve the heat resistance of optical glass, allowing it to maintain stable optical properties in high-temperature environments.
Impurities (such as alkaline metal oxides like Na, K, etc.) may lower the softening point of the glass, affecting its service life under high-temperature conditions.
(2) Mechanical Strength of Glass
High-purity MgO can improve the hardness and impact resistance of the glass, making it more suitable for high-precision optical systems.
Low-purity MgO may lead to uneven distribution of internal stress in the glass, reducing durability.
4. Impact of Purity on Chemical Stability
High-purity MgO can improve the acid and alkali resistance and moisture resistance of the glass, allowing it to maintain stable performance even in harsh environments.
Impurities (such as carbonates, sulfates, etc.) may reduce the corrosion resistance of the glass, leading to surface degradation of optical components.