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Three functions + Zr content differences + selection criteria
🧪 Zirconium Silicate in Ceramics:
Functions & Differences by Zr Content
Zirconium Silicate (chemical formula ZrSiO₄) is a functional powder material processed from natural zircon by ultra-fine grinding, iron and titanium removal, and surface modification. It is an indispensable opacifier and whitening agent in the modern ceramic industry, offering excellent corrosion resistance, abrasion resistance, hydrolysis resistance, and whitening power.
• Extremely high melting point: 2550°C, chemically stable
• Mohs hardness: 7.5–8, good wear resistance
• Unaffected by firing atmosphere, significantly improves body-glaze bonding
• Whitening mechanism: forms zirconia (ZrO₂) during firing, scattering incident light to achieve opacifying and whitening effects
Industry standards for zirconium silicate require D50 ≤ 2.0μm, D98 ≤ 10.0μm, with (ZrHf)O₂ content not less than 63.5%. Premium customers typically require (ZrHf)O₂ ≥ 64.5%, with some high-end products reaching 65% or higher.
- Imparts an opaque white appearance to ceramic glazes, covering body color
- Widely used in sanitary ware, building ceramics, and tableware glazes
- Recommended dosage: 12%–20% for white glazes, 4%–8% for colored glazes
- Forms zirconia crystals during firing, scattering incident light to produce whiteness
- The higher the Zr content, the greater the whiteness
- Ultra-fine zirconium silicate (D50 0.6–0.8μm) can achieve the same whiteness with 20% less dosage
- ZrSiO₄ particles disperse in the ceramic matrix, pinning cracks and preventing propagation
- Adding 6% zirconium silicate can increase flexural strength from 58MPa to 106MPa — an 83% improvement
- Due to thermal expansion mismatch with the matrix, creating compressive stress upon cooling
Zirconium silicate products are graded by (ZrHf)O₂ content. Common commercial grades include 40%, 50%, 60%, 64%, and 65%. The number directly represents the purity of zirconium in the product — higher content means better performance and higher price.
| Zr Content | Typical Grade | Performance Characteristics | Typical Applications |
|---|---|---|---|
| 40% | Zircon Flour Grade | Lower whiteness, moderate opacifying effect, lowest cost | Low-end ceramics, refractory fillers |
| 50% | Zircon Flour Grade | Medium whiteness, limited opacifying effect | General building ceramics, low-cost glazes |
| 60% | Standard Zirconium Silicate | Good whiteness, meets basic opacifying needs | Mid-range tiles, tableware ceramics |
| 64% | Premium Zirconium Silicate | Excellent whiteness, stable opacifying effect | Sanitary ware, high-end wall & floor tiles |
| 65% | Ultra-fine High-Purity | Highest whiteness, up to 20% dosage reduction | Premium sanitary ware, export-grade coffee cups, fine ceramics |
• Reduced opacifying power — requires higher dosage to achieve the same opacity
• Lower melting temperature of glaze — ZrSiO₄ melts at 2550°C; lower Zr content affects high-temperature performance
• Changes in glaze viscosity — strong Zr–O bonds increase viscosity; lower content alters this behavior
• Increased thermal expansion coefficient — ZrO₂ effectively lowers CTE; insufficient content reduces this effect
• Decreased mechanical strength — both compressive and tensile strength are compromised
• Reduced chemical durability — including water and acid/alkali resistance
During the production of zirconium silicate, there is a delicate balance between grinding fineness and Zr content. High-quality zircon sand typically has a (ZrHf)O₂ content of 65.5%–66.0%. However, during ultra-fine grinding, alumina from the grinding media and mill lining contaminates the product, causing Zr content to steadily decrease.
• At D50 = 1.10μm, alumina ball and mill lining consumption is approximately 0.9%–1.4%
• Further grinding can cause Zr content to drop below 64.5% or even 64.0%, failing to meet premium customer requirements
• Premium ultra-fine zirconium silicate can maintain (ZrHf)O₂ ≥ 65.5% while achieving D50 = 0.6–0.8μm submicron fineness
Therefore, when purchasing zirconium silicate, don't just look at Zr content. You must also consider particle size distribution (D50, D90) and impurity levels (Fe₂O₃, TiO₂, Al₂O₃). Quality zirconium silicate products strike a balance between high Zr content and ultra-fine particle size, while maintaining low impurities to achieve optimal opacifying and whitening performance.
- Opacifier — produces opaque white glaze finish
- Whitening Agent — scatters light to increase whiteness
- Reinforcement — dispersion strengthening improves strength by 83%
- 40–60% → Mid/low-end, moderate opacifying effect
- 64% → Premium, excellent whiteness
- 65%+ → Ultra-fine high-purity, up to 20% dosage reduction
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