Synthetic Sapphire EFG
Other
EFG = 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.
Values for the EFG condition
Other Synthetic Sapphire tempers and conditions
Synthetic Sapphire is listed in 5 conditions; see the grade overview at Synthetic Sapphire.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
EFGThis page 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 EFG?
Synthetic Sapphire EFG is Synthetic Sapphire in the EFG condition — 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. Synthetic Sapphire EFG has a tensile strength of 350 MPa (50.8 ksi), stronger than 71% of ceramic grades. The elastic modulus is 400 GPa (58 Msi). Synthetic Sapphire EFG 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). KY-OPT is the default condition FabDigit quotes; EFG is available on request or by drawing note.
Advantages
- Good corrosion resistance — 95/100, better than 97% of ceramic grades
- Polishes to a fine finish — 95/100, better than 97% of ceramic grades
- High service temperature — 1,700°C (3,092 °F), better than 90% of ceramic grades
Limitations
- High embodied carbon — 60 kg CO₂/kg, worse than 98% of ceramic grades
Synthetic Sapphire EFG properties
Typical room-temperature values for Synthetic Sapphire EFG; 15 are specific to this condition. Other listed values are Synthetic Sapphire reference data and may not represent this condition. Bars are the position among ceramic grades.
Physical5
Synthetic Sapphire EFG 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 EFG has a tensile strength of 350 MPa (50.8 ksi), stronger than 71% of ceramic grades. The elastic modulus is 400 GPa (58 Msi).
Thermal5
Synthetic Sapphire EFG is rated for continuous service to 1,700°C (3,092 °F). It conducts heat at 34 W/m·K (19.6 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 EFG 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 (95/100), better than 97% of ceramic grades.
Sustainability4
Producing a kilogram of Synthetic Sapphire EFG 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 EFG's machinability is not recommended (5/100, worse than 59% of ceramic grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Synthetic Sapphire EFG
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.
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.
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) |
Synthetic Sapphire EFG — frequently asked
What is Synthetic Sapphire EFG used for?
Synthetic Sapphire EFG 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 EFG?
Synthetic Sapphire EFG has a typical tensile strength of 350 MPa (50.8 ksi) — stronger than 71% of ceramic grades. Strength varies by condition: see the 5 listed tempers.
Is Synthetic Sapphire EFG easy to machine?
Not especially — machinability is rated not recommended (5/100, worse than 59% 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 EFG 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 EFG?
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 EFG 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 EFG?
Synthetic Sapphire EFG is rated for continuous use to about 1,700°C (3,092 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.