Influence of CaO–ZrO2–Al2O3–SiO2 glass-ceramic frits on the technological properties of porcelain stoneware bodies

In the present work, the effect of the addition to a porcelain stoneware body of glass-ceramic frits belonging to the CaO–ZrO2–Al2O3–SiO2 (CZAS, containing 1, 3, 5, and 10 mol% of Al2O3) system as replacement of the “state of the art” frit belonging to CaO–ZrO2–SiO2 system (CZS) was evaluated. The firing process was performed in a furnace able to complete the thermal cycle in 50 min, in order to simulate the industrial process. Technological properties such as water absorption, firing shrinkage, flexural strength, and thermal expansion behaviour were measured. Aesthetical properties were also evaluated. X-ray diffraction and scanning electron microscopy studies were also carried out to analyse the microstructure and the phase compositions of the studied samples. It was found that the sample containing the CZAS frit with 5 mol% of Al2O3 shows, in general, the best combination of properties in term of mechanical, physical and aesthetical properties.