Alumina (Al₂O₃)
Moderate to high purity |
Uniaxial pressing, cold isostatic pressing, injection molding, or slip casting followed by sintering |
Dense, hard, and electrically insulating; dimensional shrinkage during sintering commonly requires machining allowance |
Diamond grinding for dimensions; lapping or polishing for sealing and wear surfaces |
As-fired: 0.8–3.2 µm
Ground: 0.2–0.8 µm
Polished: 0.02–0.10 µm |
As-fired: typically ±0.5–1.0%
Precision ground: about ±0.01–0.05 mm, depending on size |
Cost-effective, electrically insulating, and wear resistant. Grinding is needed for tight fits because the material is difficult to machine after sintering. |
Zirconia (ZrO₂)
Partially stabilized grades |
Dry pressing, injection molding, or near-net-shape pressing followed by sintering |
High density and fracture toughness; green machining is often used before final sintering |
Diamond grinding, lapping, and polishing; avoid aggressive thermal loading during grinding |
As-fired: 0.8–2.5 µm
Ground: 0.15–0.6 µm
Polished: 0.02–0.08 µm |
As-fired: typically ±0.5–1.0%
Precision ground: about ±0.01–0.03 mm, depending on geometry |
Suitable for impact-prone parts and tight sliding interfaces. Surface damage and grinding-induced cracks must be controlled. |
| Silicon Nitride (Si₃N₄) |
Reaction bonding, gas-pressure sintering, hot pressing, or hot isostatic pressing |
High strength, low density, and strong thermal-shock resistance; complex shapes may require advanced forming |
Diamond grinding and lapping; polishing is used for bearings, seals, and precision contact surfaces |
As-fired: 0.8–3.0 µm
Ground: 0.2–0.8 µm
Polished: 0.03–0.10 µm |
As-fired: typically ±0.5–1.0%
Precision ground: about ±0.01–0.05 mm |
A strong choice for high-speed, high-temperature, and thermal-cycling applications. Higher material and grinding costs are common. |
| Silicon Carbide (SiC) |
Reaction bonding, pressureless sintering, hot pressing, or chemical vapor deposition |
Very high hardness, thermal conductivity, and temperature capability; porous reaction-bonded grades may require sealing |
Diamond grinding, lapping, polishing, or chemical-mechanical polishing for ultra-smooth surfaces |
As-fired: 1.0–4.0 µm
Ground: 0.2–0.8 µm
Polished: 0.02–0.10 µm |
As-fired: typically ±0.5–1.0%
Precision ground: about ±0.01–0.05 mm |
Excellent for abrasive wear, corrosive environments, and high temperatures. Its extreme hardness increases tool wear and finishing time. |
| Machinable Glass-Ceramic |
Glass forming followed by controlled crystallization and conventional machining |
Can be machined with carbide or diamond tools before final surface finishing; no conventional sintering shrinkage after crystallization |
Conventional milling and turning, followed by fine grinding or polishing where required |
Machined: 0.4–1.6 µm
Fine ground: 0.1–0.5 µm
Polished: 0.02–0.10 µm |
Machined features: about ±0.02–0.10 mm
Fine ground: about ±0.01–0.03 mm |
Preferred when prototypes, small batches, or complex machined features are more important than maximum wear resistance. |
| Steatite (MgSiO₃) |
Pressing or extrusion followed by sintering; high-volume parts may use automated forming |
Good electrical insulation and relatively easy ceramic processing; moderate mechanical and thermal performance |
Usually used as-fired; diamond grinding or light lapping for critical dimensions |
As-fired: 1.0–4.0 µm
Ground: 0.3–1.0 µm |
As-fired: typically ±0.5–1.0%
Ground: about ±0.02–0.08 mm |
A practical option for low-cost electrical insulators and terminal components where extreme strength or wear resistance is not required. |
