Alumina Ceramic Plates are flat parts used as wear plates, insulating barriers, substrate blanks, heat spreaders and precision reference surfaces.
Alumina plates are the general-purpose choice for wear liners, insulating barriers and hot platens. They give the lowest cost per square centimetre of any technical ceramic and are produced in the widest range of sizes and thicknesses.
Alumina is the default engineering ceramic. It combines high hardness (1500-1700 HV) with good electrical insulation and chemical inertness at a lower cost than most technical ceramics, and in 99.8% purity it holds strength to 1700°C while resisting most acids, alkalis and solvents.
It is not the toughest option. At 3-4 MPa·m½ fracture toughness, sharp impact or point loading will chip an edge, so chamfers and radii belong in the drawing from the start.
Specifications
| Maximum size | up to 400×400 mm |
| Thickness | 0.3-30 mm |
| Flatness | 0.005 mm per 100 mm |
| Parallelism | 0.01 mm |
| Surface finish | Ra 0.4 µm ground, Ra 0.2 µm lapped |
| Holes and slots | ground, drilled or laser cut |
| Edges | square, chamfered or radiused |
Alumina Properties
| Composition | Aluminium oxide, 96% / 99.5% / 99.8% |
| Density | 3.70-3.95 g/cm³ |
| Vickers hardness | 1500-1700 HV |
| Flexural strength | 300-400 MPa |
| Fracture toughness | 3-4 MPa·m½ |
| Max. service temperature | 1500°C (99.8%: 1700°C) |
| Thermal conductivity | 25-35 W/m·K |
| Thermal expansion (20-1000°C) | 8.0 ×10⁻⁶/K |
Machining and Tolerances
Plates are pressed or tape cast, fired, then surface ground and lapped. Thin large plates are the most likely to warp, so material is removed in equal amounts from both faces to keep the stress balanced, and grinding is followed by a relaxation step before the final passes.
Where It Is Used
- Wear plates and chute liners in bulk handling
- Electrical insulation barriers in switchgear and heaters
- Hot platens and press tooling in electronics manufacturing
- Vacuum chuck and metering surfaces in semiconductor equipment
- Precision reference and gauge blocks in metrology
Frequently Asked Questions
How flat can a large ceramic plate be held?
0.005 mm per 100 mm is the working standard for lapped plates. Larger areas are harder, and above 300×300 mm we generally specify flatness over a defined area rather than across the whole plate.
Will it warp when I bolt it down?
It can. A plate that is flat when unclamped will follow a distorted mounting face, so we recommend a relieved or lapped mounting surface, evenly torqued fixings and a compliant interlayer.