Study On The Structure And Melt Properties Of Bi₂O₃-B₂O₃-ZnO Low-melting Lead-free Sealing Glass

Glass used as the sealing materials long before, it was the inreplaceable materials in sealing industry because of its anticorrosion properties which excelled macromolecule materials, as well as its isolated performance which excelled metal materials. With development of the electric industry, the investigation of the sealing glass were on the fields of low-melting, high chemical stability, well isolated performance and gas tightness, so that meet with the no-scathe and low-melting sealing on electric materials. Nowadays, the materials mainly contained with Pb, with the use of Pb contained materials becoming forbidden because of its pollution, then empolder lead-free materials to make the satisfaction of sealing glass industry becoming more and more important.As a kind of lead-free low-melting system, the structure and melting properties of Bi2O3-B2O3-ZnO glass were studied。As well as its ternary glass-formation area, low-melting structure parameter, viscosity of the fused mass and sintering and free-running property of the glass powder were studied, so as to got appropriate low-melting sealing glass to supply reasonable reference for practical application.The ternary glass-formation area of Bi2O3-B2O3-ZnO system were studied which characterized by XRD, the results showed that the glass-formation area were mainly converge the center of ternary area and lean on the part of B2O3, the glass-formation area in Bi2O3-B2O3 were more wide than ZnO-B2O3 area, and the total glass-formation area is x(B2O3)=15%-70%, x(ZnO)=0-65%,x(Bi2O3)=0-70%. Bi2O3 and B2O3 were the main factor which affect the low-melting properties of the glass system characterized by DSC and thermal expansion, it showed that with the content of Bi2O3 increased the characteristic temperatures were decreased and the thermal expansion coefficient increased, and B2O3 made a contrary result.The structure of Bi2O3-B2O3-ZnO glass system was characterized by Infrared spectrum, Raman spectrum and XRD. The results showed that Bi2O3 and B2O3 were the glass network formation oxide and ZnO was network modifier oxide in the glass system. With the content of Bi2O3 increased, the content of [BiO3] and [BiO6] units increased and [BO4] units tend to [BO3] units which made glass structure looser, on the other hand with the content of B2O3 increased, [BO4] and [BO3] units increased and [BiO3] and [BiO6] units decreased correspondingly which made the glass structure becoming compact. The XRD patterns of the glass in different heat treatment temperature showed that with the content of Bi2O3 increased, the temperature of separate crystals out decreased and becoming easier, however, B2O3 made a opposite result.The studies on viscosity of the fused mass and sintering and free-running property of the glass powder showed that the addition of Bi2O3 content could make the viscosity of the fused mass decreased obviously, and addition of B2O3 content made the viscosity of the fused mass increased in the same temperature. The characteristic temperatures which calculated by the line fit by Arrhenius formula were very approach with experiment. At the same time, the sintering temperature was decreased with the content of Bi2O3 increased, and the increased B2O3 content made the sintering temperature increased. So control the content of Bi2O3 and B2O3 were in favor of getting well properties lead free low-melting sealing glass.