Study On The Low-Zirconium Opacified Glaze And Its Microstructure

Zirconium silicate is a kind of opacifying agent commonly used in ceramic glaze.But it exists some shortcomings,such as limited sources, high price and will cause glaze defects and make the product radiation if it was added too much. At the present time, it become a tendency to development and use low zirconium and zirconium free opacified glaze in domestic and international ceramics community.This article aims to use less or no zirconium silicate, by adjusting the addition amount of apatite, prepared P-Zr, P-Zn and P-Li-Zn three series of composite glaze. The modern testing techniques such as XRD and SEM were used to analyze the performance of the sample and its microstructures.As well as the opaque mechanism and the body-glaze combination mechanism.Body use East Lake silt, fly ash and wollastonite as raw materials.It was rose brown after firing at 1100℃, and its water absorption was 7.24%, porosity was 15.82%, bulk density was 2.19g.cm-3. thermal expansion coefficient of 4.67×10-6/℃, acidity coefficient was 0.75. The main crystal phase of the body is needle kyanite crystals (Al2SiO5), granular quartz (SiO2) and massive calcium feldspar crystals Ca(Al2Si2O8).When the zirconium silicate is added 1%,P-Zr glaze's whiteness is 47.9, microhardness is 672.9MPa. It showed that it is totally feasible to prepare low zirconium or zirconium-free glaze.The best formula of P-Zn composite glaze was D-4, thermal expansion coefficient of 4.53×10-6/℃, acidity coefficient was 0.78. the glaze microhardness is 696.5MPa, the whiteness was 63.6, the main crystal phase of glaze are granular microcrystalline quartz (SiO2),column calcium phosphate ore Ca4(PO4)3 and lath oblique zircon crystals (ZrO2) which make the best opacifying effect. And a large amount of bubbles with the size from 30μm to 80μm, and worm-like sub-phase morphology exsit in the glaze layer. P-Zn composite opaque glaze's opaque mechanism is the appropriate size of microcrystallite, sub-phase and uniform small bubbles's interaction resulted in glaze opacified, so as to cover the dark green body and glaze combination is good.In addition,two kinds of pigments praseodymium yellow pigment and vanadium blue were added to that glazes to prepare color glaze, which has good flat surface and the best chromophore effect.Because of the nice hiding power to the body, so it has good aesthetic value.The best formula of P-Zn composite glaze was B-6, thermal expansion coefficient of 4.95×10-6/℃, acidity coefficient was 0.98. the glaze microhardness is 828MPa, the whiteness was 65, the main crystal phase of glaze are calcium phosphate Ca4(PO4)3, granular microcrystalline quartz (SiO2) and diopside crystals CaMg(SiO3)2. And a large amount of bubbles with the size from 30μm to 80μm, 0.1um phase droplets and worm-like sub-phase morphology exsit in the glaze layer.The results show that it is feasible to use P-Li-Zn compound glaze replace the zirconium glaze, and then P-Li-Zn formula glaze composition was optimized by the orthogonal experiment. The results showed that apatite 15wt%, spodumene 5wt%, zirconium silicate 1wt% can made the best glaze. Glaze microhardness is 842.7MPa, whiteness is 64, the main crystal phase of the glaze are granular microcrystalline quartz (SiO2) and lath anorthite Ca (Al2Si2O8). And a large amount of bubbles with the size from 30um to 80um, 0.1um phase droplets and worm-like sub-phase morphology exsit in the glaze layer. P-Li-Zn formula opacified glaze's opaque mechanism is because the glaze layer exists bubbles, microcrystallite, phase droplets and so on. Because they and the matrix glass phase exist large refractive index difference, enhanced light scattering, which made glaze opacified.