The Effect Of CaCo3 Addition on the Crystallization Behavior of ZnO Crystal Glaze Fired at Different Gloss Firing and Crystallization Temperatures

A glazed ceramic product with crystalline structure gives an artistic effect. In this study, the effects of calcium carbonate (CaCO3) addition into glaze batches on the crystallization behavior of crystal glaze were studied. Samples were fired at different gloss firing temperatures ranging from 1000-1200 degrees C with 1060 degrees C crystallization temperature. X-ray diffraction (XRD) and energy dispersive X-ray spectrometer (EDX) analysis of the phases identified these crystals as willemite (Zn2SiO4) in the form of spherulites. Scanning electron microscope (SEM) analysis indicated that willemite crystals are in the acicular needle like shape. XRD result showed that the intensities of crystal peaks decreased with the addition of CaCO3 up to 3.0 wt%. However, there was no willemite crystals formation as the amount of CaCO3 raised to 5.0 wt%. Besides that, the results also indicated that willemite growth occurs during isothermal holding at crystallization temperature instead of during cooling from gloss firing temperature.