Ruby (Al₂O₃:Cr) – Optical Precision with Structural Integrity
Ruby, a chromium-doped single-crystal form of aluminum oxide, delivers outstanding performance in hermetic assemblies requiring exceptional hardness, thermal endurance, wear resistance, and optical performance. Its iconic red hue also provides traceability in transparent applications.
Material Properties
- Chemical Formula: Al₂O₃ doped with Cr³⁺
- Crystal System: Trigonal (Hexagonal scalenohedral)
- Hardness: 9 on Mohs scale
- Density: 3.97–4.05 g/cm³
- Melting Point: ~2,050°C (3,722°F)
- Thermal Conductivity: 35–40 W/m·K at 20°C
- Coefficient of Thermal Expansion: 5.8 × 10⁻⁶ /K (20–1000°C)
- Refractive Index: 1.762–1.770
- Birefringence: 0.008–0.010
- Optical Transmission Range: 150–5,500 nm
- Dielectric Constant: 7.5–11.5
- Dielectric Strength: 15–50 kV/mm
- Volume Resistivity: >10¹⁴ Ω·cm at 25°C
- Color: Pinkish-red to deep red (due to Cr³⁺ doping)
Applications in Hermetic Engineering
Optical Windows & Lenses
Used in systems where both visibility and mechanical protection are required, including laser enclosures and sight windows.
Laser Gain Media
Ruby's crystalline structure is a foundational element in Q-switched solid-state lasers, known for high-energy pulse generation.
Wear-Resistant Bearings
Employed in low-friction bearing systems, medical devices, and metrology instruments requiring long-lasting performance.
Sapphire-Ruby Hybrid Windows
In some applications, ruby is laminated with sapphire for additional contrast or wavelength filtering in multispectral systems.
High-Precision Alignment Tools
Ruby spheres and tips are used in coordinate measuring machines (CMMs) for their hardness, dimensional stability, and wear resistance.
Specialized Medical Equipment
Used in optical biopsy tools and sterilizable surgical lasers where precision, biocompatibility, and thermal resistance are crucial.
Enhance Your Hermetic Solutions with Ruby Precision
Connect with Advanced Hermetic Solutions to explore how ruby can elevate your next-generation optical, laser, or structural component. From custom machining to brazing integration, our team is ready to assist.
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