Synthetic Sapphire
Synthetic Sapphire is single-crystal alumina (Al₂O₃) grown by Verneuil, Czochralski, Kyropoulos or EFG routes, supplied as boule-sliced blanks, EFG sheet, tube and rod, and orientation-specific wafers such as A-plane.
Reference datasheet — Synthetic 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 KY-OPT condition
Synthetic Sapphire tempers and conditions
Synthetic Sapphire is supplied in 5 conditions, soft to hard. KY-OPT is the default FabDigit quotes; the values on this page are for it.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Edge-defined film-fed grown sheet/tube | Choose for long strips, tubes or profiled near-net shapes such as furnace tubes, wear strips and lamp envelopes; edge-defined film-fed growth cuts machining stock but leaves higher residual stress and striae. | 350 | 0 | 1,950 HV | 34 W/m·K | |
Verneuil (flame-fusion) boule, jewel/bearing grade | Pick the lowest-cost flame-fusion boule route for watch jewel bearings, wire guide wheels, wear nozzles and decorative stones; internal stress and striae are higher, so avoid high-end imaging optics. | 350 | 0 | 1,950 HV | 34 W/m·K | |
KY-OPTDefault Kyropoulos-grown optical grade, random/C-plane | Default optical and window quality: Kyropoulos-grown large boules with low dislocation density and no bubbles, for phone cover plates, watch crystals, windows and wear parts. | 400 | 2,000 HV | 35 W/m·K | ||
Czochralski/HEM epi-ready substrate grade | Choose Czochralski/HEM epi-ready substrates for LED/GaN epitaxy and silicon-on-sapphire RF wafers: low dislocation density, CMP atomic-level surface and tightly controlled miscut angle. | 420 | 0 | 2,050 HV | 35 W/m·K | |
A-plane / R-plane oriented sapphire | Specify crystal-oriented cuts when you need higher flexural strength and defined anisotropy: infrared domes, R-plane substrates for silicon-on-sapphire, and high-pressure sight glasses. | 480 | 0 | 2,100 HV | 32 W/m·K |
What is Synthetic Sapphire?
Synthetic Sapphire is single-crystal alumina (Al₂O₃) grown by Verneuil, Czochralski, Kyropoulos or EFG routes, supplied as boule-sliced blanks, EFG sheet, tube and rod, and orientation-specific wafers such as A-plane. Engineers choose it over polycrystalline alumina for optical clarity, scratch resistance and thermal stability, with about 400 MPa tensile strength, 400 GPa modulus, 35 W/m·K thermal conductivity, service to 1600 °C and a corrosion resistance rating of 96. The limits are cost and processing: machinability rates 4, so all shaping is by diamond or laser, and the crystal chips along cleavage planes. Dense polycrystalline alumina is the lower-cost alternative where transparency is not required. Synthetic Sapphire has a density of 3.98 g/cm³ (0.144 lb/in³), lighter than 58% of ceramic grades. It melts at 2,053°C (3,727 °F). Synthetic Sapphire has a tensile strength of 400 MPa (58 ksi), stronger than 74% of ceramic grades. The elastic modulus is 400 GPa (58 Msi).
What is Synthetic Sapphire used for?
- optical windows
- watch crystals
- scratch-resistant camera lens covers
- semiconductor wafer substrates
- high-pressure viewports
Advantages
- Polishes to a fine finish — 98/100, better than 100% of ceramic grades
- Good corrosion resistance — 96/100, better than 99% of ceramic grades
- High service temperature — 1,600°C (2,912 °F), better than 86% of ceramic grades
Limitations
- High embodied carbon — 60 kg CO₂/kg, worse than 98% of ceramic grades
Synthetic Sapphire properties
Typical room-temperature values for Synthetic Sapphire-KY-OPT; bars are the position among ceramic grades.
Physical5
Synthetic Sapphire has a density of 3.98 g/cm³ (0.144 lb/in³), lighter than 58% of ceramic grades. It melts at 2,053°C (3,727 °F).
Mechanical12
Synthetic Sapphire has a tensile strength of 400 MPa (58 ksi), stronger than 74% of ceramic grades. The elastic modulus is 400 GPa (58 Msi).
Thermal5
Synthetic Sapphire is rated for continuous service to 1,600°C (2,912 °F). It conducts heat at 35 W/m·K (20.2 BTU/hr·ft·°F), better than 65% of ceramic grades. Thermal expansion is 5.6 µm/m·K (3.11 µin/in·°F).
Electrical5
Synthetic Sapphire is an electrical insulator with a dielectric strength of 48 kV/mm (1,219.2 V/mil) and a resistivity of 1×10¹⁴ Ω·m.
Chemical & Environmental2
Corrosion resistance is excellent (96/100), better than 99% of ceramic grades.
Sustainability4
Producing a kilogram of Synthetic Sapphire takes about 950 MJ of energy and emits 60 kg of CO₂ — more than 97% of ceramic grades. Typical recycled content is 5%.
Manufacturability3
Synthetic Sapphire's machinability is not recommended (4/100, worse than 85% of ceramic 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 ceramic family
Yield strength against density for every ceramic grade FabDigit runs. Synthetic Sapphire is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Synthetic Sapphire
Is Synthetic Sapphire easy to machine?
Diamond tooling only: ID or multi-wire sawing, diamond grinding, ultrasonic drilling and picosecond laser cutting. Feeds must be very light to prevent cleavage chipping, and R-plane and C-plane material splits readily along cleavage planes.
Can Synthetic Sapphire be welded?
Not weldable; metal joints are made by active-metal brazing (Mo-Mn plus Ni metallisation, or Ti-Ag-Cu active filler), diffusion bonding, or elastic seals such as O-rings and gaskets, with CTE matched to avoid thermal-stress cracking.
Can Synthetic Sapphire be formed, bent or molded?
No plastic forming exists; shape is set by the melt-growth route — KY/CZ boules that are sliced, or EFG direct growth of sheet, tube and rod — and complex geometry is produced by grinding.
Synthetic 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 %) |
|---|---|
| Natypical impurity limit | ≤ 5×10⁻⁴ |
| Sitypical impurity limit | ≤ 0 |
| Fetypical impurity limit | ≤ 5×10⁻⁴ |
| Catypical impurity limit | ≤ 5×10⁻⁴ |
| Ticolorant; blue sapphire is Ti+Fe doped, ruby is Cr doped | ≤ 5×10⁻⁴ |
| Al2O3α-Al2O3 single crystal from 4N–5N alumina or Kyropoulos crackle | ≥ 99.99 (balance) |
What surface finishes work on Synthetic Sapphire?
Rough grinding, then diamond-slurry lapping, then CMP with colloidal silica reaches Ra below 0.2 nm. Optical faces are commonly coated with AR or DLC layers, and edges are chamfered to remove microcracks and raise strength.
How much does Synthetic Sapphire cost?
Synthetic Sapphire is a high-cost ceramic ($$$$), pricier than about 78% 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.
Synthetic Sapphire — frequently asked
What is Synthetic Sapphire used for?
Synthetic Sapphire is typically used for optical windows, watch crystals, scratch-resistant camera lens covers, semiconductor wafer substrates and high-pressure viewports. In short: transparent, hardest oxide window; single-crystal alumina; diamond machining only.
What is the tensile strength of Synthetic Sapphire?
Synthetic Sapphire has a typical tensile strength of 400 MPa (58 ksi) — stronger than 74% of ceramic grades. Strength varies by condition: see the 5 listed tempers.
Is Synthetic Sapphire easy to machine?
Not especially — machinability is rated not recommended (4/100, worse than 85% of ceramic grades). Diamond tooling only: ID or multi-wire sawing, diamond grinding, ultrasonic drilling and picosecond laser cutting. Feeds must be very light to prevent cleavage chipping, and R-plane and C-plane material splits readily along cleavage planes.
Can Synthetic Sapphire be welded?
Not weldable; metal joints are made by active-metal brazing (Mo-Mn plus Ni metallisation, or Ti-Ag-Cu active filler), diffusion bonding, or elastic seals such as O-rings and gaskets, with CTE matched to avoid thermal-stress cracking.
What surface finishes work on Synthetic Sapphire?
Rough grinding, then diamond-slurry lapping, then CMP with colloidal silica reaches Ra below 0.2 nm. Optical faces are commonly coated with AR or DLC layers, and edges are chamfered to remove microcracks and raise strength.
Can Synthetic Sapphire be formed, bent or molded?
No plastic forming exists; shape is set by the melt-growth route — KY/CZ boules that are sliced, or EFG direct growth of sheet, tube and rod — and complex geometry is produced by grinding.
What is the maximum service temperature of Synthetic Sapphire?
Synthetic Sapphire is rated for continuous use to about 1,600°C (2,912 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does Synthetic Sapphire cost?
Synthetic Sapphire is a high-cost ceramic ($$$$), pricier than about 78% 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
- ASM Engineered Materials Handbook Vol.4: Ceramics and Glasses — ASM International (1991)
- Sapphire (Al2O3) Optical Material Data — Crystran Ltd. (2023)
- Monocrystalline Sapphire Properties — Saint-Gobain Crystals (2022)
- Single Crystal Sapphire Components — Kyocera Corporation (2023)
- Optical constants and thermophysical data of α-Al2O3 — NIST / Handbook of Optical Constants of Solids (1998)
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.