Phase relations in the Cu-O-Al2O3-SiO2 system at 1150 °C and 1300 °C in air

Phase equilibria of the Cu-O-Al2O3-SiO2 system are important in the processing of copper aluminosilicate glasses, mullite ceramics and in non-ferrous metallurgy. We experimentally investigated the phase equilibria of this system at 1150 degrees C and 1300 degrees C in air atmosphere using equilibration and quenching method. Chemical compositions of the liquid and solid phases in the quenched samples were determined by Electron Probe Microanalysis (EPMA). Based on the results, we constructed an isothermal section containing the liquidus contours of various primary phases at 1300 degrees C. Comparison of these results with previous experimental work confirms that oxygen pressure affects phase stability and composition of the liquidus in this system. The experimental liquidus determined in this work disagrees by up to 50 wt% with the calculated values of MTDATA 6.0 software and Mtox database version 8.2. Concentration of 'Cu2O' in mullite ranged from 0.46 wt% to 1.25 wt %. The results of this work will enable improvement of thermodynamic descriptions for this system.