Sapphire
also Sapphire Window, C-Plane Sapphire
Sapphire is single-crystal alumina grown by Kyropoulos, HEM, Czochralski or EFG and supplied in C-plane, A-plane and R-plane orientations.
Reference datasheet — Sapphire is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the Annealed Glass condition
Sapphire tempers and conditions
Sapphire is supplied in 4 conditions, soft to hard. Annealed Glass is the default FabDigit quotes; the values on this page are for it.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
r-plane oriented wafer | Used for silicon-on-sapphire and a-plane GaN growth; intermediate anisotropy between C- and A-plane. | 360 | 0 | 1,900 HV | 31 W/m·K | |
a-axis oriented wafer | Chosen for hybrid microelectronic/SOS substrates and optics needing the c-axis in the plane of the plate. | 370 | 0 | 1,950 HV | 30 W/m·K | |
Annealed GlassDefault as-grown / annealed optical sapphire (random or C-plane blank) | Default choice for windows, lenses and wear parts: stress-relief annealed sapphire blank with typical polycrystal-free optical quality. | 400 | 0 | 2,000 HV | 27 W/m·K | |
basal-plane oriented wafer/window | Standard orientation for GaN/LED epitaxy and for maximum surface hardness and isotropic in-plane CTE. | 470 | 0 | 2,100 HV | 33 W/m·K |
Supply forms, finishes and certifications
Ways Sapphire is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
EFG | Edge-defined film-fed growth ribbon/tube | Supply option |
HEM-KY | HEM / Kyropoulos boule | Supply option |
What is Sapphire?
Sapphire is single-crystal alumina grown by Kyropoulos, HEM, Czochralski or EFG and supplied in C-plane, A-plane and R-plane orientations. It transmits from 0.15 to 5.5 µm and combines extreme hardness and chemical inertness with 27 W/m·K thermal conductivity, roughly 400 MPa tensile strength and service to 1800 °C, so it is used for windows and optics in abrasive, corrosive or hot environments. Cost and lead time are high because the shape is fixed at growth and all finishing is diamond work. Chemically strengthened cover glass is the alternative where scratch resistance can be traded for price. Sapphire has a density of 3.98 g/cm³ (0.144 lb/in³), heavier than 71% of glass grades. It melts at 2,053°C (3,727 °F). Sapphire has a tensile strength of 400 MPa (58 ksi), stronger than 93% of glass grades. Elongation at break is 0% and the elastic modulus is 400 GPa (58 Msi).
What is Sapphire used for?
- Watch crystals
- Smartphone camera lens covers
- Barcode scanner and sensor windows
- High-pressure and high-temperature sight glasses
- IR domes and harsh-environment optics
- Semiconductor process chamber windows
- LED epitaxy substrates
- Wear plates and bearing surfaces
Advantages
- High service temperature — 1,800°C (3,272 °F), better than 100% of glass grades
- Stiff — 400 GPa (58 Msi), better than 97% of glass grades
- Tough — resists crack growth — 2.2 MPa·√m (2 ksi·√in), better than 96% of glass grades
- Good corrosion resistance — 95/100, better than 92% of glass grades
- Conducts heat well — 27 W/m·K (15.6 BTU/hr·ft·°F), better than 88% of glass grades
Limitations
- Difficult to machine — 5/100, worse than 92% of glass grades
- High embodied carbon — 60 kg CO₂/kg, worse than 87% of glass grades
Sapphire properties
Typical room-temperature values for Sapphire-Annealed Glass; bars are the position among glass grades.
Physical5
Sapphire has a density of 3.98 g/cm³ (0.144 lb/in³), heavier than 71% of glass grades. It melts at 2,053°C (3,727 °F).
Mechanical13
Sapphire has a tensile strength of 400 MPa (58 ksi), stronger than 93% of glass grades. Elongation at break is 0% and the elastic modulus is 400 GPa (58 Msi).
Thermal5
Sapphire is rated for continuous service to 1,800°C (3,272 °F). It conducts heat at 27 W/m·K (15.6 BTU/hr·ft·°F), better than 88% of glass grades. Thermal expansion is 5.8 µm/m·K (3.22 µin/in·°F).
Electrical5
Sapphire is an electrical insulator with a dielectric strength of 17 kV/mm (431.8 V/mil) and a resistivity of 1×10¹⁴ Ω·m.
Chemical & Environmental2
Corrosion resistance is excellent (95/100), better than 92% of glass grades.
Sustainability4
Producing a kilogram of Sapphire takes about 400 MJ of energy and emits 60 kg of CO₂ — more than 82% of glass grades. Typical recycled content is 5%.
Manufacturability2
Sapphire's machinability is not recommended (5/100, worse than 92% of glass grades).
Common Calculations4
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the glass family
Yield strength against density for every glass grade FabDigit runs. Sapphire is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Sapphire
Is Sapphire easy to machine?
No conventional cutting: use diamond wire/ID saw, diamond core drilling, creep-feed diamond grinding, laser or waterjet for rough shapes, then lap and CMP.
Can Sapphire be welded?
Not weldable; join by active-metal (Ti/Nb) brazing, diffusion bonding to Nb/Mo, or glass-frit/epoxy sealing with CTE-matched metals such as Kovar avoided in favour of Nb.
Can Sapphire be formed, bent or molded?
Shape is fixed at crystal growth (Kyropoulos, HEM, Czochralski, EFG for tubes/ribbon); no plastic forming below ~1000 °C, so near-net EFG growth is used for tubes and rods.
Sapphire chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance.
| Element | Spec limit (wt %) |
|---|---|
| Alstoichiometric metal fraction | ≈ 52.9 |
| Ostoichiometric oxygen fraction | ≈ 47.1 |
| Al2O3single crystal α-Al2O3; typical impurities Si, Fe, Ti, Cr, Na each < 20 ppm | ≥ 99.99 (balance) |
What surface finishes work on Sapphire?
Sub-nanometre Ra achievable by colloidal-silica CMP; AR/DLC coatings, ion-beam figuring for optics; avoid edge chipping with chamfers and keep tensile surface flaws minimal to realise full strength.
Equivalent designations
Standards and trade names that resolve to Sapphire in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Trade names
- Sapphire WindowC-Plane Sapphire
- Also called
- Synthetic SapphireAl2O3 Single Crystal
- Other
- Al2O3
How much does Sapphire cost?
Sapphire is a standard-cost glass ($$), cheaper than about 60% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sapphire — frequently asked
What is Sapphire used for?
Sapphire is typically used for watch crystals, smartphone camera lens covers, barcode scanner and sensor windows, high-pressure and high-temperature sight glasses, IR domes and harsh-environment optics and semiconductor process chamber windows. In short: single-crystal optical sapphire.
What is the tensile strength of Sapphire?
Sapphire has a typical tensile strength of 400 MPa (58 ksi) — stronger than 93% of glass grades. Strength varies by condition: see the 4 listed tempers.
Is Sapphire easy to machine?
Not especially — machinability is rated not recommended (5/100, worse than 92% of glass grades). No conventional cutting: use diamond wire/ID saw, diamond core drilling, creep-feed diamond grinding, laser or waterjet for rough shapes, then lap and CMP.
Can Sapphire be welded?
Not weldable; join by active-metal (Ti/Nb) brazing, diffusion bonding to Nb/Mo, or glass-frit/epoxy sealing with CTE-matched metals such as Kovar avoided in favour of Nb.
What surface finishes work on Sapphire?
Sub-nanometre Ra achievable by colloidal-silica CMP; AR/DLC coatings, ion-beam figuring for optics; avoid edge chipping with chamfers and keep tensile surface flaws minimal to realise full strength.
Can Sapphire be formed, bent or molded?
Shape is fixed at crystal growth (Kyropoulos, HEM, Czochralski, EFG for tubes/ribbon); no plastic forming below ~1000 °C, so near-net EFG growth is used for tubes and rods.
What is the maximum service temperature of Sapphire?
Sapphire is rated for continuous use to about 1,800°C (3,272 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does Sapphire cost?
Sapphire is a standard-cost glass ($$), cheaper than about 60% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- Sapphire (Al2O3) optical material data — Crystran Ltd (2023)
- Single Crystal Sapphire product properties — Saint-Gobain Crystals (2022)
- Sapphire single crystal technical data — Kyocera Corporation (2022)
- Engineered Materials Handbook Vol.4: Ceramics and Glasses — ASM International (1991)
- Sapphire crystal properties and orientation data — Rubicon Technology / Monocrystal (2021)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.