The relationship between composition-sintering behaviour of porcelain stoneware tile

In this thesis, the relationship between composition-sintering behaviour of porcelain stoneware tile formulations is investigated in order to lower sintering temperatures and/or firing cycles. Furthermore, different particle size and distribution of porcelain tile slurries and its effects on the sintering behaviour and the technological properties of the final product were investigated. Experimental trials were performed under industrial conditions in Toprak Seramik Tile Company. At first, glassy phase composition of a standard porcelain tile was taken as a reference and modifications of the glassy phase composition were made by using Seger formula. Hot stage microscopy was used to analyze thermal behaviour of the glassy phases, and according to the results glassy phase compositions which are formed extremely rapidly and have low viscosities developed. It was found that the softening points and viscosities decreased by increasing the amount of total alkali oxide and decreasing MgO/CaO and Na2O/Li2O ratio in glassy phase compositions. New porcelain stoneware body formulations were prepared based on these glassy phase compositions. According to results, it was observed that it was possible to lower maximum temperature of porcelain tiles down to 1185 ? C and also shorten the firing cycle to 35 minutes. Addition of small amount of Li2O and high total alkaline amount reduce the glassy phase viscosity during sintering and increase the sintering rate. Especially, addition of Li2O increased the amount of elongated needle shape mullite crystals due to the reduced glassy phase viscosity. This phenomenon could have contributed to further increase technical characteristics of porcelain stoneware tiles and decrease the deformation. Moreover, CaO addition to body compositions favours the crystallization of anorthite. Therefore a considerable degradation of the sintering performances was seen by decreasing MgO/CaO ratio. Additionally, the achievement of a lower thermal expansion coefficient value in the experimental compositions in comparison to the reference composition suggests that the residual quartz content is lower in the experimental compositions. Finally, the investigated bodies had lead to produce in short grinding cycle as well as with high sieve residue.