Alumina 99.5 vs Synthetic Sapphire
Ceramic · grade comparison
Alumina 99.5 and Synthetic Sapphire are both ceramic grades. Synthetic Sapphire is the stronger of the two: tensile strength 400 MPa (58 ksi) against 260 MPa (37.7 ksi) for Alumina 99.5, about 54% more. Synthetic Sapphire is harder — 2,000 HV against 1,650 HV for Alumina 99.5 — which matters for wear surfaces and threads. Synthetic Sapphire is stiffer (400 GPa vs 372 GPa).
Synthetic SapphireChoose it when strength drives the design, or when surface hardness matters.
Alumina 99.5 vs Synthetic Sapphire: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all ceramic grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
How to read these bars
- One bar per material. A full bar is the highest value among all ceramic grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
Alumina 99.5Synthetic Sapphire
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Shear Modulus
Bulk Modulus
Poisson's Ratio
Tensile Strength (Ultimate)
Compressive Strength
Flexural Strength
Shear Strength
Fracture Toughness (K_IC)
Hardness, Vickers
Hardness, Knoop
Same in both: Hardness, Mohs 9
Physical
Density and transition temperatures.
Density
Melting Point (Solidus)
Refractive Index
Porosity
Light Transmission
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Specific Heat Capacity
Thermal Expansion (CTE, 20–100 °C)
Max Service Temperature (continuous)
Same in both: Min Service Temperature -269°C-452 °F
Electrical
Conductivity and insulation.
Electrical Resistivity
Dielectric Strength
Dielectric Constant (1 MHz)
Dissipation Factor (1 MHz)
Volume Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Polishability
Sintering / Firing Temperature
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Carbon (primary production)
Embodied Water
Typical Recycled Content
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
Thermal Diffusivity
Thermal Shock Resistance Index
Strength versus weight
Yield strength against density for every ceramic grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
Manufacturing and finishing
| Capability | Alumina 99.5 | Synthetic Sapphire |
|---|---|---|
| Default condition | — | — |
| Relative cost | $$$$ High | $$$$ High |
| Min. machined wall | — | — |
| Best machined surface | — | — |
Alumina 99.5 vs Synthetic Sapphire — frequently asked
Is Synthetic Sapphire stronger than Alumina 99.5?
Yes. Synthetic Sapphire has a typical tensile strength of 400 MPa (58 ksi) against 260 MPa (37.7 ksi) for Alumina 99.5 — about 54% more.
Which is cheaper, Alumina 99.5 or Synthetic Sapphire?
Both sit in the same relative cost tier ($$$$, high); the part price will be decided by machining time, tolerance and quantity rather than by the material.
When should I choose Alumina 99.5 over Synthetic Sapphire?
Pick Synthetic Sapphire when strength drives the design, or when surface hardness matters.
Ready to make it?
Upload a CAD file and FabDigit prices the part in Alumina 99.5 and Synthetic Sapphire side by side — material, machining time, tolerance and finish in one quote. Certified material data ships with the order on request.
Typical handbook values for the conditions named above, normalised for comparison. Hardness on non-Brinell scales is converted approximately for charting only. Request certified data with your order for design-critical properties.