Alumina ceramic is a sintered aluminium oxide (Al₂O₃) body used where a part has to insulate electrically, resist wear, or hold its shape at high temperature — the most widely used technical ceramic in industry. It is specified by purity: 96% for brazed and moulded assemblies, 99% and above where density, hardness, stiffness, resistivity and plasma resistance decide the design.

Alumina density is 3.7 to 3.93 g/cm³, depending on purity: 3.7 g/cm³ at 96% (AOW37), 3.8 at 99% (AOI38), 3.9 at 99.5% (AOI39) and 3.93 at 99.7% (AOI393). Higher purity means less glass phase and a more completely sintered body, so density rises with purity. All four grades are fully dense with zero water absorption, which is what makes them vacuum-tight. For comparison, that puts alumina heavier than silicon carbide (3.1–3.3 g/cm³) and aluminium nitride (3.4) but much lighter than zirconia (5.6–6).

The thermal conductivity of alumina is 24 to 32 W/(m·K) at 20 °C: 24 at 96%, 29 at 99%, 30 at 99.5% and 32 at 99.7%. That is high enough to spread heat but far short of a heat-sink material — if the part has to carry heat away from a die, aluminium nitride at 220 W/(m·K) or silicon carbide at 60 W/(m·K) are the alternatives. Specific heat is 880 J/(kg·K) for all four grades.

Alumina hardness is 13.7 to 16.8 GPa measured as Vickers HV1, rising with purity: 13.7 at 96%, 15.2 at 99%, 16 at 99.5% and 16.8 at 99.7%. That is harder than zirconia (12.3 GPa) and aluminium nitride (10.4 GPa), but below silicon carbide at 22 GPa. Hardness is why alumina survives abrasive wear; it is also why every feature has to be cut with diamond tooling after sintering.

99.5% alumina (AOI39) is denser (3.9 vs 3.7 g/cm³), harder (16 vs 13.7 GPa), stiffer (370 vs 320 GPa) and more conductive thermally (30 vs 24 W/(m·K)) than 96% (AOW37). But 96% is not simply the worse material: its glass phase gives it equal flexural strength (350 MPa, against 330 for 99.5%), makes it markedly easier to metallize and vacuum braze, and costs less per part. Pick 96% for brazed and bonded assemblies, 99.5% for wear surfaces, plasma-facing parts and anything where rigidity or purity drives the design.

In semiconductor equipment alumina is used for wafer chuck and fixture base plates, vacuum chamber insulators and liners, electrical feedthroughs and standoffs, plasma-facing rings and shields, and process tube and furnace components. The reasons are its combination of >10¹⁴ Ω·cm insulation, 1700 °C service temperature, zero porosity for vacuum integrity and predictable machining to micron tolerances. 99% and above is the usual specification because higher purity resists plasma erosion better. Where the part touches a wafer or a bare die, anti-static ceramic is specified instead, because alumina's insulation lets charge build up.

Yes — the term changes with the region, the material does not. Engineers in Europe and the UK say technical ceramics or engineering ceramics (German: Technische Keramik), North America and Taiwan say advanced ceramics, and Japan says fine ceramics. All three describe the same family of high-performance oxide and non-oxide ceramics, alumina included. Ask for either name and you will get the same part from us.

No, and two properties prove it. Flexural strength does not rise monotonically — 96% reaches 350 MPa while 99% drops to 310 — because the glass phase in the lower-purity body blunts cracks. And fracture toughness falls as purity rises, from 3–4 MPa·m½ at 99% and 99.5% to 2.5–3.5 at 99.7%. Purity reliably buys density, hardness, stiffness and volume resistivity. It does not buy toughness, and it does not buy thermal shock resistance at all.

AOI393 at 99.7%, with 1×10¹⁵ Ω·cm at 20 °C and 18 kV/mm dielectric strength. The advantage widens with temperature, which is where it matters: at 500 °C it still holds 1×10¹¹ Ω·cm, against 10⁸ Ω·cm for the 96% and 99% grades — a thousandfold difference. If the part is a hot feedthrough, standoff or chamber insulator, that gap is the reason to pay for the top grade.

As-sintered surfaces typically hold around ±1% of dimension because of sintering shrinkage, and as-moulded parts hold ±0.3 mm at 94–96% or ±0.1 mm at 99% and above. Ground and lapped surfaces go far tighter, into the single-digit micron range for flatness and dimension. Tolerance should be specified only on the faces that need it — grinding every surface multiplies cost without adding function.

To drawing, and to sample, and it is made in Taiwan. Forming, sintering, CNC and 5-axis machining, metallizing, brazing and final inspection are all handled in our own plant in Taoyuan — outside the China supply chain, which matters to customers who have to document origin. Custom OEM / ODM geometry is our normal work rather than an exception. Send a 2D drawing or a 3D model with the critical dimensions identified.