Phase Equilibria and Properties of Glasses in the Al2O3-Yb2O3-SiO2 System

Phase diagrams of the Al2O3-Yb2O3-SiO2 system and the properties of glasses in this system were investigated. The results are summarized as follows:(1) Phase diagram of the 3-component Al2O3-Yb2O3-SiO2 system at 1550°C and those of the three types of 2-component Yb2Si2O7-Al6Si2O13, Al1.25Yb0.75O3-SiO2 and Al1.44Yb0.56O3-SiO2 systems were established and the region where the liquid phase exist at a high temperature was clarified. The lowest solidus temperature in the present system is 1500°C.(2) The glass-forming region of the Al2O3-Yb2O3-SiO2 system was clarified by quenching the melt in an infrared image furnace(3) The glass transition temperature of the present glasses is in a range of 880-895°C. The onset and peak temperatures for crystallization are in a range of 975-1040°C and 1070-1230°C, respectively. They tend to increase as the SiO2 concentration is increased.(4) In the 2-component Yb2Si2O7-Al6Si2O13 system, the peak temperature for crystallization and the activation energy for crystal growth attain a maximum at a composition near the eutectic composition.(5) Analyzing the infrared spectra of glasses, it is suggested that Yb ion is mainly a network modifier in glassses.(6) Solidus temperature of the Ln2Si2O7-Al6Si2O13-SiO2 system (Ln=Dy, Er, Gd, La, Nd, Sm, Y, Yb) tend to increase as the radius of rare-earth ion decreases. The system with Yb has the highest solidus temperature among them.