Journal of The Australian Ceramic Society Volume 52[2], 2016, 82 – 86 82 The Effect of Nepheline Syenite Addition on the Sintering Behaviour of Sanitaryware Bodies Nazım Kunduraci 1* , Tuna Aydin 2 and Atamer Akbay 3 1) Bulent Ecevit University, Engineering Faculty, Metallurgy and Material Engineering Department, Zonguldak, Turkey 2) Kirikkale University, Engineering Faculty, Metallurgy and Material Engineering Department, Kirikkale, Turkey 3) Canakcılar Ceramic Co., Gokcebey, Zonguldak, 67670 Turkey Email: n.kunduraci@creavit.com.tr Available Online at: www.austceram.com/ACS-Journal Abstract In this study, the effect of nepheline syenite addition on the sintering and material properties of sanitaryware porcelain bodies was investigated. Three ceramic sanitaryware bodies were prepared by substituting Na feldspar (max. 30 wt %) with nepheline syenite. The sintering behaviour was evaluated using an optical dilatometer. Samples were sintered at 1300 °C using step-by-step processing. In addition the linear shrinkage, water absorption and bending strength were measured. Results showed that the addition of nepheline syenite enhanced the material properties of sanitaryware bodies, had a positive effect on the formation of the liquid phase during sintering and improved overall the sintering and mechanical properties. Keywords: Nepheline syenite, sintering behaviour, sanitaryware INTRODUCTION Today, sanitaryware technology is well known and described in different textbooks and papers. Sanitary wares are made of clay, quartz and feldspar and are fired at temperatures ranging from 1200 o C to 1300°C [1]. However, the optimization of sanitaryware porcelain production requires further improvement with regard to ceramic structures and their properties [1–3]. This study investigates the effect of nepheline syenite addition on the sintering behaviour of sanitaryware porcelains. Nepheline syenite is a light-coloured, medium to coarse-grained holocrystalline, silica-deficient, feldspathic, plutonic igneous rock, which is largely made up of sodium feldspar (albite) and alkali feldspar (orthoclase, microcline), but no quartz. Nepheline syenites are essentially syenites that are undersaturated with respect to silica. Crystallization from magma undersaturated with respect to silica results in the formation of nepheline instead of albite feldspar [4]. In this study, three ceramic sanitaryware compositions were prepared. Samples were prepared by substituting Na feldspar (max. 30 wt %) with nepheline syenite. METHODS AND PROCEDURES Samples were prepared under industrial conditions. All sanitaryware body compositions contain clay, kaolin, quartz and feldspar. The chemical compositions of these raw materials were determined using an X-ray fluorescence analyser (Rigaku, ZSX Primus). A formulation used in industrial production was selected as the standard body (ST) composition. The composition containing nepheline syenite was named as NC. The mixture of raw materials was ground in a ball mill with alumina balls for 7 h. The particle size distribution of the mixture was measured using a laser particle-size analyser (Malvern, Hydro 2000G). The mean particle size of ST and NC was 17.4 µm. The litre weight of the ST and NC slips was measured using a pycnometer and held at 1800 g/L. Viscosity of the slips was measured using a Ford Cup viscometer. Thixotropy was measured using a Gallenkamp-type torsion viscometer. The samples were prepared using the slip casting method in a plaster mould in order to easily measure deformation, strength, firing shrinkage and water absorption and to perform the Harkort analysis. After shaping, the samples were dried at 110 °C for 1 h. All samples were fired under industrial conditions after which the material properties were measured. The sintering behaviour was investigated using an optical dilatometer