Structure And Properties Of ZnO-B₂O₃-P₂O₅ System Low Melting Sealing Glass

In this paper,the development and propesrties of sealing glass were briefly reviewed.Sealing glass was mainly used for sealing of an opening or a joint in various kinds of electronic products for preventing entering of corrosive gas or moisture in order to ensure the operation stability. This glass material for use in sealing was made of low melting glass. Conventionally,mainly lead glass of PbO-B₂O₃ series was widely used as such a glass material for use in sealing.However,lead was a toxic substance,electronic products which contain lead could cause soil contamination or groundwater contamination,was prohibited under recent strict environmental regulations while limited application due to inclusion of lead makes recycling difficult.Against this background,developed a lead-free sealing glass which could substitute a conventional general purpose lead glass had been strongly demanded.In lead-free and low melting glass system,phosphate glass system had a great many of advantages at low melting and lead-free, mass of properties were correspond to lead glass and reduced the environment pollute greatly.Studied the properties and structure of the ZnO-B₂O₃-P₂O₅ system low melting sealing glasses,apprehended and utilized of the basic studying findings were worthwhile from theoretical and practical viewpoints.Designed for ZnO-B₂O₃-P₂O₅ system series compositions,twenty-two samples of the ZnO-B₂O₃-P₂O₅ system were prepared by cooling the melt from 1250℃in the compositional. Confirmed the glass forming region of the ZnO-B₂O₃-P₂O₅ system.A large glass forming region was found at the phosphate side of the ternary system with homogeneous glasses containing up to 0～20mol%of B₂O₃. Searched the proper materials and melting condition.The results of the experiments indicated that the thermal expansion coefficient increased first but decreased later with increasing P₂O₅content. This change point at about P₂O₅=43mol%,andαabout 93×10^-7/℃,Tg about 415℃.The glass transformation temperature of Tg increased with increasing B₂O₃ content,while densityρdecrease.It confirmed the optimal glass forming area:P₂O₅（35mol%～45mol%）,B₂O₃（10mol%～20mol%）,ZnO（25mol%～45mol%）.Adjusted composes of R_nO_m （Al₂O₃+Na₂O+Li₂O）in order to enlarge the glass forming region and improve the sealing properties of the glass,the thermal expansion coefficient,glass transformation temperature,density,chemical durability, resistance rate.Added 1wt%of the metal oxides such as Fe₂O₃,MnO₂, CuO and TiO₂,Fe₂O₃ could enhance the glass chemical durability most clearly,MnO₂ not only enhanced the chemical durability of the phosphate glass excellently,but also reduced the glass transformation temperature clearly,the influence of added CuO and TiO₂ to the sealing properties between the before-mentioned.