Thermal characterisation of raw aluminosilicate glazes in SiO2–Al2O3–CaO–K2O–Na2O–ZnO system with variable content of ZnO

Abstract

Thermal properties of raw aluminosilicate ceramic glazes in the multicomponent system of SiO2–Al2O3–CaO–K2O–Na2O–ZnO modified by ZnO addition were studied by differential thermal analysis (DTA), dilatometry (DIL), hot-stage microscopy (HSM), X-ray diffraction and fourier transform infrared spectroscopy (FTIR). Using the method of differential thermal analysis, the ways in which zinc oxides affect the temperature of transition (T g), crystallisation (T c) were determined. An analysis of the DTA data obtained during thermal tests showed that an increase in ZnO content results in decreasing the T g value. Also, the influence of ZnO on characteristic temperatures and viscosity of glazes was checked. The introduction of zinc oxide (ZnO) into the glaze composition contributes to the decrease in viscosity of such glazes. An increasing ZnO content in the glazes also causes the reduction in softening (T s), half-sphere (T half-sphere) and fusion (T fusion) temperatures. The mid-infrared spectroscopy showed that the thermal properties of glazes in SiO2–Al2O3–CaO–K2O–Na2O–ZnO system modified by addition of ZnO can be associated with the depolymerising influence of zinc ions on the structure of the tested glazes.