Sapphire is a single-crystal form of aluminum oxide (Al₂O₃) with extraordinary mechanical, thermal and optical properties. Its extreme hardness and broad transmission make it the material of choice for demanding environments where durability matters.
Extreme-environment windows
Medical and dental optics
Aerospace and defense systems
High-pressure and vacuum systems
Wear-resistant optical surfaces
| Property | Value |
|---|---|
| Coefficient of Thermal Expansion (CTE) | 5.0 × 10⁻⁶ /K (⊥), 5.3 × 10⁻⁶ /K (∥) |
| Thermal Conductivity | 35 W/m·K |
| dn/dT (Thermo-optic Coefficient) | 13.8 × 10⁻⁶ /K |
| Maximum Operating Temperature | ~1800°C (melting point 2050°C) |
Sapphire exhibits excellent thermal shock resistance due to high thermal conductivity and moderate CTE. Suitable for extreme temperature environments.
Standard coating types available for this material. Custom coating designs available on request.
Very hard (9 Mohs), requires diamond tooling throughout. Slow machining rate increases fabrication time.
Excellent polish achievable but time-consuming process. Requires specialized polishing methods for hard materials.
Excellent chemical and scratch resistance. Virtually inert in most environments. Ideal for harsh conditions.
High cost, especially for large apertures. Crystal growth limitations affect maximum available size.
No single optical material is perfect for every application. Here are situations where Sapphire may not be the best fit, and what to consider instead.
→ Consider: Fused Silica or BK7
Sapphire is birefringent (ordinary and extraordinary rays differ). In polarization-sensitive systems, this can cause problems. Isotropic materials like fused silica or BK7 avoid this issue.
→ Consider: UV Fused Silica or CaF₂
Sapphire transmits down to about 150nm, but fused silica reaches deeper UV (~180nm) more cost-effectively. For vacuum UV, CaF₂ extends further.
→ Consider: BK7 or Borosilicate
Sapphire is expensive due to its crystal growth process and machining difficulty. For applications that don't require extreme hardness, BK7 is a budget-friendly alternative.
→ Consider: BK7 or Fused Silica
Sapphire's extreme hardness (Mohs 9) makes grinding and polishing difficult and costly. For complex geometries, BK7 or fused silica are easier to fabricate.
Browse our catalog of precision optical components available in Sapphire
Consider fused silica or BK7 if extreme hardness is not required — sapphire is more expensive and difficult to polish. Sapphire is the right choice when scratch resistance, chemical inertness or high-temperature stability are critical.
Send us your specifications. Our engineering team will review and respond with material and coating recommendations within 24 hours.
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