High temperature investigation of SiO2-Al2O3-ZnO-Na2O glass for ceramic-glaze: in‐situ/ex-situ synchrotron diffraction and conventional approaches

The temperature dependent behaviour of a complex aluminosilicate glass (SiO2-Al2O3-ZnO-Na2O system), which is a reference for ceramic glaze technology, has been determined, by combining techniques that cover a scale ranging from atomistic to macroscopic. The system shows a linear thermal expansion up to about 600 °C. The glass transition temperature is at 620 °C, as observed from Differential Scanning Calorimetry. Ex situ synchrotron diffraction experiments found a further transformation consisting of albite crystallization above 810 °C. This reaction is very slow and induces permanent structural modifications in the material at both intermediate and short ranges, as shown by in situ synchrotron diffraction experiments. These observations explain why ceramic glaze technology still faces challenges for large scale manufacturing and show the critical thermal range where interventions should be focussed. Eventually, melting takes place at 1190 °C, from hot stage microscopy.