Sapphire R-Plane

Q: What is Sapphire R-Plane used for?

Sapphire R-Plane 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.

Q: What is the tensile strength of Sapphire R-Plane?

Sapphire R-Plane has a typical tensile strength of 360 MPa (52.2 ksi) — stronger than 92% of glass grades. Strength varies by condition: see the 4 listed tempers.

Q: Is Sapphire R-Plane easy to machine?

Not especially — machinability is rated not recommended (6/100, worse than 87% 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.

Q: What is the maximum service temperature of Sapphire R-Plane?

Sapphire R-Plane 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.

Grade

also Sapphire Window, C-Plane Sapphire

Used for silicon-on-sapphire and a-plane GaN growth; intermediate anisotropy between C- and A-plane.

Standard cost $$

Request a quote in Sapphire R-Plane Sapphire overview

Values for the R-Plane condition

Other Sapphire tempers and conditions

Sapphire is listed in 4 conditions; see the grade overview at Sapphire.

Compare all 4 conditionsHide

Condition · open for datasheet	Best for	Yield MPa	Tensile MPa	Hardness	Conductivity
R-PlaneThis page r-plane oriented wafer	Used for silicon-on-sapphire and a-plane GaN growth; intermediate anisotropy between C- and A-plane.	—	360	1,900 HV	31 W/m·K
A-Plane a-axis oriented wafer	Chosen for hybrid microelectronic/SOS substrates and optics needing the c-axis in the plane of the plate.	—	370	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	2,000 HV	27 W/m·K
C-Plane basal-plane oriented wafer/window	Standard orientation for GaN/LED epitaxy and for maximum surface hardness and isotropic in-plane CTE.	—	470	2,100 HV	33 W/m·K

What is Sapphire R-Plane?

Sapphire R-Plane is Sapphire in the R-Plane grade — used for silicon-on-sapphire and a-plane GaN growth; intermediate anisotropy between C- and A-plane. Sapphire R-Plane has a tensile strength of 360 MPa (52.2 ksi), stronger than 92% of glass grades. Elongation at break is 0% and the elastic modulus is 390 GPa (56.6 Msi). Sapphire R-Plane 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). Annealed Glass is the default condition FabDigit quotes; R-Plane is available on request or by drawing note.

Advantages

High service temperature — 1,800°C (3,272 °F), better than 100% of glass grades
Stiff — 390 GPa (56.6 Msi), better than 97% of glass grades
Tough — resists crack growth — 1.9 MPa·√m (1.73 ksi·√in), better than 95% of glass grades
Conducts heat well — 31 W/m·K (17.9 BTU/hr·ft·°F), better than 92% of glass grades
Good corrosion resistance — 95/100, better than 92% of glass grades

Limitations

Difficult to machine — 6/100, worse than 87% of glass grades
High embodied carbon — 60 kg CO₂/kg, worse than 87% of glass grades

Sapphire R-Plane properties

Typical room-temperature values for Sapphire R-Plane; 14 are specific to this condition. Other listed values are Sapphire reference data and may not represent this condition. Bars are the position among glass grades.

Physical5

Sapphire R-Plane 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).

Density3.98 g/cm³0.14 lb/in³

Melting Point (Solidus)2,053°C3,727 °F

Refractive Index1.768

Light Transmission85%

Porosity0%

Mechanical13

Sapphire R-Plane has a tensile strength of 360 MPa (52.2 ksi), stronger than 92% of glass grades. Elongation at break is 0% and the elastic modulus is 390 GPa (56.6 Msi).

Elastic (Young's) Modulus390 GPa56.6 Msi

Shear Modulus148 GPa21.5 Msi

Bulk Modulus250 GPa36.3 Msi

Poisson's Ratio0.27

Tensile Strength (Ultimate)360 MPa52.2 ksi

Elongation at Break0%

Compressive Strength2,000 MPa290 ksi

Flexural Strength700 MPa102 ksi

Shear Strength300 MPa43.5 ksi

Fracture Toughness (K_IC)1.9 MPa·√m1.7 ksi·√in

Hardness, Vickers1,900 HV

Hardness, Knoop2,000 HK

Hardness, Mohs9

Thermal5

Sapphire R-Plane is rated for continuous service to 1,800°C (3,272 °F). It conducts heat at 31 W/m·K (17.9 BTU/hr·ft·°F), better than 92% of glass grades. Thermal expansion is 6 µm/m·K (3.33 µin/in·°F).

Thermal Conductivity31 W/m·K17.9 BTU/hr·ft·°F

Specific Heat Capacity761 J/kg·K0.18 BTU/lb·°F

Thermal Expansion (CTE, 20–100 °C)6 µm/m·K3.3 µin/in·°F

Max Service Temperature (continuous)1,800°C3,272 °F

Min Service Temperature-269°C-452 °F

Electrical5

Sapphire R-Plane is an electrical insulator with a dielectric strength of 17 kV/mm (431.8 V/mil) and a resistivity of 1×10¹⁴ Ω·m.

Electrical Resistivity1×10¹⁴ Ω·m3.94×10²¹ µΩ·in

Dielectric Strength17 kV/mm432 V/mil

Dielectric Constant (1 MHz)9.8

Dissipation Factor (1 MHz)1×10⁻⁴

Volume Resistivity1×10¹⁶ Ω·cm

Chemical & Environmental2

Corrosion resistance is excellent (95/100), better than 92% of glass grades.

Corrosion ResistanceExcellent95/100

Chemical Resistance SummaryInert to water, most acids and organic solvents at RT; attacked slowly by hot concentrated H2SO4/H3PO4 and by molten alkalis, borates and HF above ~300 °C; reduced/etched by hydrogen and alkali vapours at very high temperature.

Sustainability4

Producing a kilogram of Sapphire R-Plane takes about 400 MJ of energy and emits 60 kg of CO₂ — more than 82% of glass grades. Typical recycled content is 5%.

Embodied Energy (primary production)400 MJ/kg171,969 BTU/lb

Embodied Carbon (primary production)60 kg CO₂/kg

Embodied Water250 L/kg30 gal/lb

Typical Recycled Content5%

Manufacturability2

Sapphire R-Plane's machinability is not recommended (6/100, worse than 87% of glass grades).

MachinabilityNot recommended6/100

PolishabilityExcellent98/100

Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.

Working with Sapphire R-Plane

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.

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.

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)

Sapphire R-Plane — frequently asked

What is Sapphire R-Plane used for?