Medium Temperature High Whiteness Raw Material Phase Separation Glaze For Building And Sanitary Ceramics

Bone ash was used in this research to partly or even completely substitute for zirconium opacification agent in the preparation of P-Zr opaque glaze. On the basis of zirconium free opaque glaze, P-Li opaque glaze was produced by adding spodumene to zirconium-free opaque glaze. Then the influence of the amount of spodumene addition on the whiteness and performances of the glazes was investigated. Finally bone ash, spodumene and zirconium silicate were simultaneously added to prepare P-Li-Zr opaque glaze, and the effect of different components on whiteness and performance of the as-prepared glazes were discussed. The samples were characterized by XRD, TEM, FE-SEM, EDS, TG-DTA and whiteness colorimeter for the analysis of the variations of whiteness and performance as well as the opacifying mechanism.The results show that the optimum formula of the P-Zr series is C-3(K2O:3.61%, Na2O:1.54%, MgO:2.12%, CaO:7.95%, ZnO:5.02%, Al2O3:9.34%, Fe2O3:0.12%, SiO2:64.43%, ZrO2:4.00%, P2O5:1.87%, SiO2/Al2O3=11.7). The sintering temperature is1200℃, the whiteness value is81.71, which is higher than marketed sanitary ceramics. A large number of isolated spherical droplets were dispersed in the glaze with the size about0.2μm, or long strip droplets larger than0.3μm were formed by two or more spherical droplets connecting together, and meanwhile, some small ZrSiO4crystals are evenly dispersed which could cause strong scattering of light leading to the opacification of glaze.The optimum formula of the P-Li series is E-2(K2O:3.77%, Na2O:1.62%, Li2O:0.13%, MgO:2.21%, CaO:8.28%, ZnO:5.24%, Al2O3:10.19%, Fe2O3:0.11%, SiO2:66.5%, P2O5:1.95%, SiO2/Al2O3=11.1). The sintering temperature is1200℃, the whiteness value is72.26, higher than usual Zirconium glaze. Most of the sizes of the spherical droplets lie between0.1and0.15μm and a small amount of Ca3(PO4)2crystals are detected. The addition of spodumene reduced the high temperature viscosity, increased the volume fraction of isolated droplets, thus, it enforced the opacification effect.The optimum formula of the P-Li-Zr series is F-7(K2O:3.52%, Na2O:1.51%, Li2O:0.18%, MgO:2.07%, CaO:7.72%, ZnO:6.83%, Al2O3:9.74%, Fe2O3:0.12%, SiO2:63.92%, ZrO2:2.58%, P2O5:1.81%, SiO2/Al2O3=11.1). The sintering temperature is1200℃and the whiteness is81.98. The size of isolated droplets is between0.1and0.2μm, which were uniformly dispersed in connected glass matrix. Orthogonal experiments show that the factors affecting whiteness and quality of the opaque glaze lie in the order as follows:zirconium silicate, bone ash, spodumene and zinc oxide.