Investigation of the effect of type and grain size of feldspar on thermal properties of ceramic sanitaryware

Ceramic sanitaryware products are produced using inorganic and non-metallic raw materials such as clay, kaolin, quartz and feldspar at certain rates. After mixing and grounding process, the slip is obtained. The products are shaped in gypsum or synthetic resin moulds. Green bodies are fired at 1250 °C for 16–18 h, and their water absorption values are less than 0.5%. Nowadays the most important issues are raw materials and energy costs. In this study, the sintering behaviour of Na-feldspar and K-feldspar, which are widely used in ceramic sanitaryware, is analysed by reducing to different grain sizes. The grain sizes of the samples containing Na-feldspar were reduced under 63 µm. It was found that the decrease in grain size of Na-feldspar contributed to the decrease in sintering temperature. Potassium feldspar was also added instead of Na-feldspar in order to develop deformation behaviour at higher temperature. The increase in the amount of K-feldspar contributed to the decrease in deformation values. However, the flexural strength of the bodies decreased. A decrease in grain size of Na-feldspar resulted in a reduction of 10 °C at the sintering temperature. The decrease in sintering temperature will provide a cost advantage of around 3%. It was also found that technical properties such as firing shrinkage, bulk density, and flexure strength increased as the grain size of Na-feldspar decreased.