EFFECT OF DIFFERENT METAL OXIDES ON VICKERS HARDNESS OF THE FRIT BASED CRYSTALLINE GLAZES

Frit based glaze is a thin glassy surface coating which gives technical and aesthetic value to the ceramic product after firing. Crystalline glazes are one of the most important type of artistic glazes formed through a controlled crystallization of glass during a special heat treatment. Crystals are visible to the naked eye and the product can have only a few single crystals on the surface or the entire surface can be coated with crystals. The preferred clay substrate for crystalline glazes is porcelain and in some cases may be used for the macrocrystallines. Usage of these types of glazes as porcelain tile coatings is an alternative choice for relevant ceramic industry and these glazes strongly enhance the visual quality of the final products. When designing crystalline glazes for porcelain tiles; besides the chemical composition, mechanical properties such as hardness is also an important factor. Within the scope of experimental studies, frit based crystalline glazes which consist of different nucleating agents such as MnO, Fe 2 O 3 , NiO, CoO, CuO and Cr 2 O 3 were applied on the raw porcelain bodies and then subjected to a special heat treatment cycle. The aim of this study was to investigate the effect of different metal oxides on crystallization capacity of newly developed fritted glaze compositions and Vickers hardness of the final products. Micro hardness of the glazes was measured with Vickers hardness test method. Characterization of crystalline glazes was done by x-ray diffraction (XRD) technique.