The effect of CaCO3 addition on the crystallization behavior of ZnO crystal glaze fired at different gloss firing and crystallization temperatures

Abstract

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°C with 1060°C crystallization temperature. Xray 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

The thermal and microstructural behavior of a R2O–RO–(ZnO)–Al2O3–(TiO2)–SiO2 based macro-crystalline raw glaze system

“…When the amount of TiO 2 is increased, predominantly titanate and secondly zinc orthotitanate crystals are formed after heat treatment. It is reported that willemite is the main phase of zinc containing crystalline glazes [6,17]. In this study, a well-developed macro-crystal glaze surface was achieved in the ZnO based Z3 glaze with willemite crystallization.…”

“…Its unmatured surface is related to the high levels of Al 2 O 3 and SiO 2 . Depending on the type of compositions and clay bodies, the gloss firing temperatures of crystalline glazes can vary from 1250 to 1300 1C [6,7,11,12,[17][18][19][20]. In contrast with previous studies, R 2 O-RO-(ZnO)-Al 2 O 3 -(TiO 2 )-SiO 2 system raw macro-crystal glazes were successfully developed at a relatively low maximum firing temperature of 1205 1C, promising a time consuming and cost effective production.…”

“…Moreover, the white final color and suitable chemical composition of the porcelain bodies improve the crystalline formation and final appearance [6,7]. Besides the firing schedule and substrate composition, other factors such as glaze thickness and viscosity also affect the crystallization, resultant reflectance, and color of the porcelain glazes [8].…”

“…In the literature, many studies have been conducted on nucleation and crystallization of ZnO containing crystalline glazes, but generally for fritted compositions or high firing temperatures [6,7,11,12,17,19,20]. Moreover, a comparative study of the effect of TiO 2 both as a nucleating agent and a major crystallite in macrocrystalline glazes has not been evaluated in terms of thermal behavior, viscosity, and microstructure [14][15][16].…”

Characteristic of synthesis and transformations of hardystonite in willemite glass-crystalline glaze based on thermal analysis

“…However, the literature review not reported any information about hardystonite in glazes. Jamaludin [11] studied influence of CaCO 3 addition on the phase crystallization in willemite glass-crystalline glazes. Author focused on final crystalline phase composition of glaze, and probably, this was a reason of not registered a hardystonite in glaze.…”