Study On Crystallization Behavior Of Yttrium Aluminosilicate Glass

Yttrium aluminum silicate（YAS）glass has a low thermal expansion coefficient,good chemical resistance and high concentration of rare earth,so it has broad application prospects in the field of SiC ceramic bonding,medicine and luminescence.In order to improve the performance of glass and prepare new materials,glass can be prepared into glass ceramics.Some studies have been carried out on the crystallization behavior of yttrium aluminosilicate glass.However,there are few studies on the crystallization behavior of yttrium aluminosilicate glass with high yttrium content.In this paper,Y₂O₃-Al₂O₃-SiO₂ base glass and glass doped with ZnO,La₂O₃ and YF₃were selected as the research object,using differential scanning calorimeter（DSC）,X-ray diffraction（XRD）,scanning electron microscopy（SEM）,infrared spectroscopy（IR）,thermal expansion,Vickers hardness tester,high temperature viscometer and other means studied the structure,thermal expansion coefficient,hardness,crystallization activation energy,viscous activation energy and qualitative and semi-quantitative analysis of precipitated crystals of YAS glass.Obtained the following main findings:In the Y₂O₃-Al₂O₃-SiO₂ glass system,the lower the liquidus temperaturecorresponding to the basal glass composition in the ternary system,the higher the crystallization peak temperature of the glass.The glass composed of22Y₂O₃-19Al₂O₃-59SiO₂ promotes glass crystallization by phase separation,and only y-Y₂Si₂O₇ crystals are precipitated.The glass composed of 25Y₂O₃-25Al₂O₃-50SiO₂precipitated only Y_4.67（SiO₄）₃O apatite crystal at 1112°C,and only y-Y₂Si₂O₇ crystal was precipitated at 1344°C.Except for 25Y₂O₃-25Al₂O₃-50SiO₂（y-Y₂Si₂O₇）glass ceramics,the crystallization mechanism of other glass compositions belongs to surface crystallization.The sorghum content of YAS glass and glass ceramics is harder than the high silicon content base glass,the thermal expansion coefficient of the former is larger.The effect of doping ZnO,La₂O₃ and YF₃ on the crystallization properties of glass was studied based on the glass composition of 22Y₂O₃-19Al₂O₃-59SiO₂.After ZnO was doped,y-Y₂Si₂O₇ and ZnAl₂O₄ crystals were precipitated in the glass,and a part of ZnO enters the glass network to form[ZnO₄],which enhances the degree of glass network connection and inhibits the phase separation of the base glass.With the increase of La₂O₃doping amount,the crystallization peak temperature and melting temperature of glass firstly increased and then decreased,and the degree of glass network connection also increased first and then weakened.The y-Y₂Si₂O₇ and Y₃Si₃O₁₀F crystals were precipitated in the glass after doping with YF₃.The introduced F ions preferentially replaced the positions of free oxygen and non-bridged oxygen,and did not cause much damage to the glass network structure.After doping ZnO with 22 Y₂O₃-19Al₂O₃-59SiO₂ base glass,the viscous activation energy of glass increases and the crystallization activation energy increases.After La₂O₃doping,the viscous activation energy of glass decreases,and the crystallization activation energy decreases.After the YF₃ was mixed,the viscous activation energy of the glass was lowered,and the crystallization activation energy was increased.Further,the smaller the kind of crystals precipitated in the glass,the larger the crystallinity of the glass.