The effect of wollastonite on sintering of anorthite ceramic body based on illite-smectite clay and kaolin

The effect of different character of plastic raw materials based on different clay minerals (kaolin vs. I/S clay based on interstratified illite/smectite clay minerals) and different source of wollastonite (bludovite rock vs. natural wollastonite) on the sintering process of anorthite porcelain body is studied. The sintering temperature according to vacuum water absorption is defined for samples containing 40 % of wollastonite raw material in the range of firing temperatures from 850 °C to 1200 °C. The mineralogical composition of fired samples was observed from the firing temperature of 850 °C up to the sintering temperature. The sintering temperature of all studied samples is lower than 1200 °C. The lowest value is obtained by the combination of illite/smectite clay and natural wollastonite (1115 °C). The type of used plastic raw material also significantly affected the mechanism of anorthite formation during firing. The highest content of anorthite (over 90 %) in the crystalline phase of the sintered body is observed in kaolin-based samples. Primary mullite is identified in small amounts and transiently only in kaolin-based samples after a firing at 950 °C and 1050 °C, and then participates in the formation of anorthite. Diopside was detected in sintered samples based on bludovite rock as a rest from wollastonite raw material.