Plastic Sintering Behavior of Large-sized La2O3-TiO2-ZrO2 Amorphous Bulk

La2O3-TiO2-ZrO2 glass has great potential applications in lens and upconversion host materials for its ultrahigh refractive index. However, due to its low glass forming ability, it can only be prepared by some extremely rapid melt cooling method, which is hard to produce large-sized materials. On the basis of amorphous plastic behavior above the glass transition temperature T-g, large-sized La2O3-TiO2-ZrO2 bulk glasses were obtained by hot pressed sintering within the thermodynamic window Delta T. 30.8% LaO3/2-59.2% TiO2-10% ZrO2 amorphous spheres were firstly prepared by aerodynamic levitation furnace. Whereafter, these spheres were smashed and ground into powders. Then these glass powders were hot pressed into a bulk glass with dimension of phi 20 mmx1 mm. The effects of sintering temperature and pressure on the process of hot pressed sintering were investigated. Microstructures and phase compositions of samples were studied by SEM and XRD. The results show that the samples sintered above 910 degrees C contain a few La4Ti9O24 crystal phases, while the samples sintered below 900 degrees C are totally amorphous. When the sintering temperature is below 900 degrees C, the increase of sintering temperature in a certain range can reduce the number of pores apparently to improve the density of samples. And with the increase of pressure from 20 MPa to 60 MPa, the density of bulk glass prepared by hot pressing at 900 degrees C increases from 4.8797 g/cm(3) to 5.1178 g/cm(3). The large-sized La2O3-TiO2-ZrO2 glass displays excellent optical performance with refractive index of 2.33 at the wavelength of 587.6 nm and the abbe number of 13.2. By analyzing the shrinkage curve of the samples, it is confirmed that the plastic flow is the main mass transfer way during densification process.