Effect of talc on the microstructure and properties of zirconium-free microcrystalline opaque raw glazes for slabs

Abstract

Zirconium opaque glazes are the most widely used opacifier due to their stability and adaptability to sintering temperatures, and are highly used in building materials to meet both decorative and functional needs. The high cost of zirconium materials and the high-temperature melting required for frit glazes result in increased energy usage and production costs. There is an urgent need for a more affordable and efficient alternative in raw glazes. Zirconium-free microcrystalline opaque raw glazes, formulated from natural minerals, eliminate zirconium sand, reducing production costs by 15–20 % per tonne while lowering energy consumption and carbon emissions. And talc as raw materials, and investigated the influence of talc additions on both the microstructure and properties. The appropriate incorporation of talc can significantly lower the melting temperature, enhance the hardness and toughness, and promote a uniform distribution of small closed pores. The glaze yields magnesium-aluminum spinel and cordierite microcrystals, as well as a uniform distribution of small closed pores, which collectively contribute to improved opacity. The A3 sample, with a talc addition of 19.76 wt%, fired at 1240 ℃, had the best performance, exhibiting a high hardness of 7.35 GPa, a fracture toughness of 2.25 MPa·m^1/2, a roughness (Sa) of 0.3356 μm, a gloss of 67.67 GU, and chromaticity parameters of L* 87.38, a* −1.90, and b* 7.41. The Vickers microhardness of the glazes in this study was higher than that of commercial zirconium-based ceramic glazes, indicating that this type of raw glaze can replace the widely used zirconium-containing ceramic opaque glazes.