DETERMINATION OF THE FİRİNG SCHEDULE FOR A SELF GLAZİNG PORCELAİN

In this study the aim was the production of a self glazing porcelain which depended upon the formation of the anorthite phase (CaO. A12O3. 2SİO2), by single firing. A frit was prepared by mixing 24.5 % K2CO3, 31.7 % SİO2 and 43.8 % H3PO4at 1050 °C in order to satisfy the molar ratio of K2O : B2O3 : SiO2 = 1 : 2 : 3 known as the Seger formula. A batch having a composition of 50 % kaolin, 35 % wollastonite and 15 % frit was prepared. The differential thermal analysis (DTA) and linear dilatometry (LD) curves of this batch were determined. The firing schedule (FS) curve which shows the variation of temperature as a function of time was derived from the LD and DTA curves. The batch was fired for 210 min. including cooling, such that the maximum temperature was 1050 °C according to the FS and a self glazing porcelain was obtained. From the X-ray diffraction pattems it was determined that anorthite phase was formed in the porcelain. It was concluded that a great amount of energy would be saved by the production of a single firing porcelain which depends on the formation of the anorthite phase instead of the production of a double-stepped firing porcelain which depends on the formation of the muhite phase (3A12O3.2SİO2)