Study On The Crystallization Behavior Of Dy₂O₃-Al₂O₃-SiO₂ Glass Ceramic

Glass materials have good chemical compatibility with ceramic materials and are often used as solder in ceramic joining to solve problems in the manufacture of large size or complex shaped ceramic parts.Dy₂O₃-Al₂O₃-Si O₂（DAS）glass solder can be used for joining ceramic halide sodium lamps,ceramic microreactors and other components.However,the low softening temperature of pure DAS glass solder leads to low service temperature of joints.Therefore,this paper proposes the use of Ti O₂ or Zr O₂ as nucleation agents to promote the crystallization of DAS glass,which in turn improves the mechanical properties of DAS glass ceramics and increases its softening temperature.In this paper,the effects of Ti O₂ content on the crystallization kinetics,pore formation mechanism and mechanical properties of Dy₂O₃-Al₂O₃-Si O₂（DAS）glasses were firstly investigated.The results showed that the crystallization activation energy of microcrystalline glasses increased and then decreased with the increase of Ti O₂ content.The crystallization mode of all glass samples was surface crystallization.When the Ti O₂content was 0 wt.%,the crystalline phase of DAS microcrystalline glass was Dy₂Si₂O₇ and Al₂O₃.When the Ti O₂ content was 3 wt.%,the crystalline phase of DAS microcrystalline glass was Dy₂Si₂O₇.when the Ti O₂ content was 6-9 wt.%,the crystalline phase of DAS microcrystalline glass consisted of Dy₂Si₂O₇ and Al₂Si O₅.The morphology and distribution of the holes are influenced by the growth rate of the crystalline phase,the denseness of the crystalline phase and the morphology of the crystalline phase.The bending strength of the microcrystalline glass was reduced due to the pores generated by crystallization,and the bending strength of the microcrystalline glass was about 55 MPa.In this paper,the effects of Zr O₂ content on the crystallization kinetics,hole formation mechanism and mechanical properties of Dy₂O₃-Al₂O₃-Si O₂ glasses were further investigated.The results show that the crystallization activation energy of the microcrystalline glass gradually decreases with the increase of Zr O₂ content.When the Zr O₂ content increased from 0-3 wt.%to 6-9 wt.%,the crystallization mode of DAS glasses changed from surface crystallization to bulk crystallization.When the Zr O₂ content is 0-3 wt.%,the crystalline phase of DAS microcrystalline glass is Dy₂Si₂O₇ and Al₂O₃with the formation of cavities.at 6-9 wt.%Zr O₂ content,the DAS microcrystalline glass consists of Dy₂Si₂O₇,Al₂O₃ and Zr O₂ and no pore defects exist.Therefore,the formation of pores during crystallization can be attributed to the combined effect of the crystallization mode and the difference in density before and after crystallization.The ability of bulk crystallization to eliminate pore defects leads to an increase in the bending strength of the microcrystalline glass to 243.6 MPa.