关键词: 结晶釉, 硅锌矿, 晶体, 分相

Abstract: In view of the traditional problems of crystalline glaze, such as high sintering temperature, long holding time and difficult continuous production, crystalline glaze of K₂O-Na₂O-CaO-ZnO-SiO₂-Al₂O₃ system was successfully prepared at 1 220 ℃. Ceramic raw materials such as potassium feldspar, calcite, zinc oxide and glass powder were used in the experiment. The effects of kiln cooling system and coloring agent on glaze surface were mainly studied. The results indicate that during the cooling process of 3 h “heat preservation” at fixed1 100 ℃, the combination of 2% (mass fraction) NiO and 2% (mass fraction) CuO makes the surface of glaze produce coarse grains. These grains are about 4.5 cm in diameter with white flower lace and green inner clusters. While during the cooling system of “slowly cooling” rate of 125 ℃/h, beautiful and natural plum blossom shaped crystals are also generated, which present in a micro size of 8 mm and display internal green radial clusters and clear boundaries. By the combining use of field emission scanning electron microscope(FESEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis, the microstructure and chemical composition were investigated. It is found that there are internal hexagonal columnar and acicular isomorphic zinc silicate crystals in the plum blossom crystal. Hexagonal columnar crystals are mainly concentrated in the center of plum blossom. Due to the space limitation in the vertical direction of glaze layer, they grew slowly and generally exist in a size of 2 μm. The acicular crystals are mainly parallel to the glaze layer and grew radically toward the petal. There are a large number of nanoscale microsphere structures in the amorphous glass phase of bottom glaze, which present the effect of green opacification. The pairwise combinations of Fe₂O₃, CuO, MnO and NiO make the ceramic glaze present a multi-color and variable crystallization effect, the combination of Fe₂O₃ and MnO, NiO and CuO are best.

Key words: crystalline glaze, willemite, crystal, phase-separation