DTA analysis on the solidification behavior of the Al_2O_2-Y_2O_3-ZrO_2 ternary oxide system and microstructural investigation

摘要

The well-aligned growth structures which derive from directional solidification of ceramic eutectics are of great interests due to their potential use in electronic devices and as structural materials at high temperatures. Because of the complexity of the component system and very high melting points, the solidification behavior on the oxide ceramic eutectic is still unclear up to date. In the presented paper, the Al_2O_2-Y_2O_3-ZrO_2 ternary eutectic ceramic is remelted by a DTA apparatus. The maximal heating temperature is 1950 ℃. The melting and solidification behavior are investigated by the DTA analysis. The solidification microstructure is investigated by scanning electron microscopy (SEM), energy disperse spectroscopy (EDS) and X-ray diffraction (XRD). The results show that solidus temperature and the liquidus temperature are 1738.4 ℃ and 1750.1 ℃, respectively. The formation path of eutectic phase is discussed. The microstructure of as-solidified eutectic ceramic shows a divorced ternary eutectic structure consisting of Al_2O_3, YAG and ZrO_2 phases with a random distribution. Furthermore, the microstructural comparison with directionally solidified ternary eutectic ceramic is presented and discussed.