Zirconia Polishing Media — Optical Lenses, Sapphire Wafers & Metal Finishing
Zirconia polishing powders and slurries occupy a critical tier between colloidal silica and alumina abrasives. For applications requiring high removal rates with controlled surface finish, ZrO₂ delivers an optimal balance of hardness, morphology, and chemical compatibility — without the rare earth cost premium of ceria.
Polishing Abrasive Comparison
| Property | ZrO₂ (Zirconia) | CeO₂ (Ceria) | Al₂O₃ (Alumina) |
|---|---|---|---|
| Mohs hardness | ~8.5 | ~6 | 9 |
| Mechanism | Mechanical + mild chemical | Chemical-mechanical (Ce³⁺/Ce⁴⁺ redox) | Primarily mechanical |
| Removal rate on glass | Medium-high | High (chemical assist) | High (aggressive) |
| Surface finish achievable | Ra 0.5–5 nm | Ra 0.3–2 nm | Ra 2–20 nm |
| Scratch risk | Low-moderate | Low | Moderate-high |
| Substrate compatibility | Glass, sapphire, metals, ceramics | Glass, SiO₂ (not metals) | Metals, hard ceramics |
| Cost (relative) | Medium | High (RE supply risk) | Low |
| Supply risk | Low | High (rare earth) | None |
Application Segments
Optical Glass Polishing
Zirconia powder (d50 0.5–2.0 μm) for intermediate and final polishing of camera lenses, telescope mirrors, and laser optics. Slurry at 10–20 wt%, pH 8–10 delivers 3–8 μm/min removal on BK7 glass with Ra <2 nm.
Sapphire Wafer Polishing
Semi-final polishing between diamond lapping and colloidal silica CMP. ZrO₂ hardness (8.5 Mohs) removes sapphire efficiently at d50 0.3–1.0 μm with controlled subsurface damage. Typical rate: 1–3 μm/min on C-plane sapphire.
Stainless Steel and Metal Finishing
Mirror polishing (Ra <50 nm) with no embedded contamination. ZrO₂ is chemically inert to stainless steel, with equiaxed morphology producing uniform scratch patterns. Paste at 5–15 wt% with felt wheels at 1500–3000 RPM.
Hard Ceramic Polishing
Matched or slightly lower hardness ensures removal without deep subsurface cracks on alumina, silicon nitride, and zirconia components.
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Zirconia Polishing Powder Specifications
| Property | Unit | Optical Grade | Metal Finishing Grade |
|---|---|---|---|
| ZrO₂ purity | Wt% | ≥99.5 | ≥99.0 |
| Crystal phase | — | Monoclinic | Monoclinic |
| Median particle size d50 | μm | 0.5–2.0 | 1.0–5.0 |
| BET surface area | m²/g | 5–20 | 3–10 |
| Fe content | ppm | <20 | <50 |
| Particle shape | — | Equiaxed / rounded | Equiaxed / rounded |
| Sedimentation stability (20 Wt% slurry) | hr | >4 | >2 |
Why SEMITECH
SEMITECH offers China-direct ZrO₂ polishing powders at 20–30% below European and Japanese suppliers, with d50 customization (0.3–10 μm), crystal phase control, and full lot documentation. Technical samples of 500 g–5 kg available for trials.
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