Prepartion Of Low-temperature Fast Firing Mat Glazes

Two kinds of low-temperature fast firing mat frit glazes were developed, of which one was used in stone tile, and the other was used in fine pottery tile. The crystallization of the diopside in the CaO-MgO-SiC2 frit was studied by means of DTA, DDTA, XRA, OM, SEM and high-temperature microscope. The activation energy of the crystal growth was calculated. The relationship between sintering and crystallization in the heat treatment process was analyzed. Effects of the frit used in the above two kinds of mat glazes were investigated. The properties, compositions and micro-structures of mat glazes were studied. The forming mechanism and process conditions of mat glazes were discussed. The results show that as follow.(1) MgO, BaO, CaO, Li2O3, ZnO introduce perform a function as non-1 ight agent, the main crystal phase of two kinds of mat glazes is diopside. In addition, there are many phases such as lithium silicate, barium feldspar, anorthite, a -quartz. Crystal grain size is 3~10 u m mostly, piling equally at the glaze and scattering to visible light which make a semi- light effect.(2) Selecting proper compositions of the frit in crystallization section of diopside from CaO-MgO-SiO2 three phase diagram, we replace quite quantities of CaO by BaO and induced composition such as ZnO, LiO2. Proposition of the frit is melted at a temperature of 1560癈, the main crystal phase of the frit is diopside, crystal grain size is 3~10u m mostly. The crystal phase could analyze at a broad extension temperature, which is stable crystal phase according to thermodynamics.(3) The proportion of Al2O3:SiO2of the mat glaze is near to 1:6, while thatof non-light glaze is near to 1:3.(4) Firing schedule is a key to formation of the mat glaze besides proper proposition, extremely high firing temperature may lead to early crystallization to dissolve again, which make the glass phase increasable. The mat glaze become to the blare glaze, the main phase is the glass phase. Contrarily, low-temperature firing may lead to non-equal grown of nucleus; the grain is too thin and excessive which make semi-light effect is lost. Proper heat preservation and cooling schedule are the important composition and indispensable assure to form excellent non-light glaze.(5) The semi-light glaze and the matt glaze in a fast-firing condition at a low temperature produce in form of the fritted glaze, compared to the raw glaze, the fritted glaze have broad adaptability and stable manufacture and good surface feeling of glaze.