Microstructure and mechanical behavior of alumina–zirconia–mullite refractory materials

The synthesis of Al2O3–ZrO2–SiO2 (AZS) refractory materials for use in furnace chambers for glass melting has been studied in this work. Several mixtures with different alumina–zirconia–silica ratios, corresponding to compositions selected within the ternary phase diagram Al2O3–ZrO2–SiO2, were processed by attrition milling followed by pressing and reactive sintering at different temperatures (1450, 1550 and 1650 °C). The density of the sintered samples varied significantly with respect to that of the green materials, with increases of up to 90% in this property after sintering at 1650 °C. The X-ray diffraction patterns revealed the formation of the predicted phases (ZrO2, Al6Si2O13 and Al2O3) according to the ternary phase diagram for all compositions studied, with varying amounts of each formed phase. SEM characterization showed that the sintering temperature employed made a significant difference regarding the final microstructure of the sintered materials. For the studied compositions, the maximum resistance to fracture (MRF) was 185 MPa, with the highest values of fracture toughness obtained at 1650 °C.