This paper has put forward a high-temperature quantitative X-ray powder diffraction analysis method for the determination of an isothermal section of a ternary system in comparison with a conventional method. In a three-phase region of the isothermal section at 1150 °C of Cu2O(CuO)-Al2O3-SiO2 pseudo-ternary system, the compositions of the solid phase points of three system points are determined according to the quantitative analysis of the crystalline phases in the samples carried out by Rietveld method. Then the liquid phase point of the three-phase region is determined according to the crosspoints of the tie lines of every pair of system point and solid phase point. The precisions of the analytical results have reached to be 0.1 ~ 5.0 %. By comparison, a good result is obtained for the determination of the liquid phase point of the three-phase region in the isothermal section at 1150 °C when the analytical results of high-temperature RQA analysis are used in determination of the isothermal section of the pseudo-ternary system.
Cu2O-Al2O3-SiO2 ternary system of given compositions can be used as a kind of thermal shock resistance sealing materials for electronic devices. So far, little systematic work was reported on the phase behavior and phase equilibrium at a high temperature, except the isothermal section of a CuO-Al2O3–SiO2 ternary system at 950 and 1150°C. We have investigated the thermodynamic behavior and the microstructure of the compositions in the miscibility gap of the Cu2O-Al2O3-SiO2 pseudo-ternary system on the basis of the reported isothermal section of this system at 1150°C based on the analyzing of the differential scanning calorimeter and the observing of the scanning electronic microscope. The eutectic point of the Cu2O-Al2O3-SiO2 pseudo-ternary system was determined by the thermal analysis. Then, the changing rule of the microstructures with different compositions was investigated. The results indicated that large differences existed among the different compositions in the miscibility gap of Cu2O-Al2O3-SiO2 ternary system.
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