Preparation Of Large-sized Novel Oxide Glass Through Containerless Solidification And Hot-pressing

The novel oxide glass lacking glass network formers e.g.SiO₂,B₂O₃,P₂O₅ and GeO₂has excellent optical properties such as ultra-high refractive index,low dispersion,wide-band and optical window owe to its special structural composition.It has broad application prospects in the fields of laser,lens,imaging,and scintillation.But these novel oxide glass is hard to be prepared by conventional melt cooling method for its low glass forming ability and high melting point.Luckily the containerless solidification method could effectively suppress the inhomogeneous nucleation caused by the contact of the container wall,making the melt reach a deep supercooling state and achieve rapid solidification to prepare the novel oxide glass material lacking glass forming network.However,the sample size obtained by the containerless solidification method is extremely small,usually 3-5 mm,which limits its development and application.In order to obtain a large-sized novel lacking-network-former glass,this study adopts the method of amorphous powder sintering.Firstly,the glass beads were prepared by the containerless solidification method,and then the amorphous powder was obtained by crushing and grinding the beads.A large-sized novel oxide glass was obtained by hot-pressed sintering within the temperature dynamics window?T.In this study,La₂O₃-TiO₂-SiO₂,La₂O₃-TiO₂-ZrO₂ and Al₂O₃-Y₂O₃ systems large-sized glass were prepared successfully.Differential scanning calorimeter?DSC?,X-ray diffractometer?XRD?,spectroscopic ellipsometer,scanning electron microscopy?SEM?,UV-Vis-infrared spectrophotometer and fourier infrared spectrometer were used to characterize the samples.The effects of sintering aids,sintering pressure,sintering temperature and other factors on sintering were investigated.Hot pressing mechanism of amorphous oxide was investigated according to the sintering shrinkage curve.A small amount of SiO₂ was added as a sintering aid in La₂O₃-TiO₂,and a large-sized colorless transparent La₂O₃-TiO₂-SiO₂ glass was obtained by hot pressing sintering.The glass forming ability of the sample increases with the increase of SiO₂ content.The transparency of the sample obtained by hot pressed sintering also increases with the increase of SiO₂ content.When the SiO₂ content is 15%,the transmittance of the sample can reach54%and 72%at 800 nm and in the near-infrared bands respectively?sample thickness is 1mm?.The refractive index of the sample decreased with the increase of SiO₂ content,but the sample still showed an ultra-high refractive index.When the SiO₂ content was 15%,the refractive index of the sample exceeded 2.14 in the visible range.La₂O₃-TiO₂-ZrO₂ large-sized glass without network formers was prepared by hot pressed sintering.The addition of ZrO₂ is beneficial to increase the glass forming ability of the sample while keep high refractive index of the sample,which can reach 2.33.When the sintering temperature is too high,the sample would devitrify.When the sintering temperature is too low,the densification of the sample would be low.The large-sized La₂O₃-TiO₂-ZrO₂glass obtained by hot pressing at 900°C has highest density and maintains completely amorphous.And appropriate increase of sintering pressure can effectively increase the density of the sample.Large-sized Al₂O₃-Y₂O₃ glass host materials were prepared by hot pressing sintering that the samples were colorless and transparent.The most suitable sintering temperature is925°C,and the increase in sintering pressure can effectively increase the density and transparency of the sample.A transparent ceramic material is obtained by heat treatment further.The precipitated crystal phase is YAG phase,and the sample is also colorless and transparent.The hot pressed sintering mechanism of the novel oxide amorphous bulks was studied according to the sintering shrinkage curve of the samples.The hot pressing sintering mechanism of the amorphous powder within the dynamics window?T is consistent with the plastic flow.