Preparation And Properties Studies Of R₂O-Bi₂O₃-B₂O₃-SiO₂Low Melting Glasses

Low softening point glass, as a sealing material, has been widely used in electronicvacuum technology, micro-electronic technology, laser and infrared technology, automotivetechnology and aerospace industry. For a long time, compositions with high PbO contentswere widely used in commercial sealing glass. However, PbO is toxic to human and animalsand PbO-containing electronic waste is damaging to the environment, therefore, free-lead hasbecome an important indicator of the low softening point glass and extensive interest has beengiven to free-lead glass system owing to the improvement of the environmental protectionconsciousness. It is well known that Bi3+ions are highly polarizable, and the polarizability ofthe glasses increase with the increase in Bi2O3content. Bismuth oxide cannot be consideredas a glass network former due to small field strength of the Bi3+ions. However, incombination with the B2O3glass former it is possible to obtain glasses in a relatively largecompositional range. Therefore, as the study of this subject, R2O-Bi2O3-B2O3-SiO2systems oflow melting sealing glasses have been investigated.The Bi2O3-B2O3-SiO2system glasses with Sb2O3were fabricated by melt quenchingmethod. The effects of Sb2O3addition on the structure, thermo-physical properties andchemical durability of R2O-Bi2O3-ZnO-B2O3-SiO2glasses were analyzed employing varioustechniques. The analysis results indicated that the glass network had a tiny change with theintroduction of Sb2O3. There is no crystalline phase in the reheated glasses. When the Sb2O3content was less than4wt.%, the density decreased with the further increase of Sb2O3content,and then increased with the further increase of Sb2O3content, but Tfwas just on the contrary.The appropriate addition of Sb2O3was helpful to improve the chemical durability of the glass,and the introduction lowered the devitrification resist ability.The R2O-Bi2O3-B2O3-SiO2system glasses with Fe2O3were fabricated by meltquenching method. The effects of Fe2O3on the structure, thermal behavior and chemicaldurability of the samples were studied. The CTE of the glass increases first and then decreases with the increasing of Fe2O3contents. Comparing with the CTE, the tendencies of the TgandTfare just on the contrary. There is no apparent effect on the structure of glasses with theincreasing of Fe2O3contents and Fe2O3enhances the glass network as glass network modifier.The chemical durability of the glasses is improving with the increasing of Fe2O3contentsobviously, but excess Fe2O3will reduce glass-forming ability.The R2O-Bi2O3-B2O3-SiO2system glasses with Y2O3were fabricated by melt quenchingmethod and the effects of Y2O3addition on the structure, thermo-physical properties andchemical durability of R2O-Bi2O3-B2O3-SiO2glasses were analyzed employing varioustechniques. The analysis results indicate that the glass network has a tiny change with theintroduction of Y2O3. The CTE increases with the increasing of Y2O3content when thecontent is less than0.6wt.%, and then decreases with the further increasing of Y2O3content.The tendencies of the variation of the Tgand Tfare consistent. It can be seen that the Tgdecreases when Y2O3is first introduced. However, it increases with the further increasing ofY2O3content. It can be seen that an increase of Y2O3leads to a decrease of chemicaldurability, but the trend becomes weaker when the addition over1.4wt.%. In general, thedensity of the glasses decreases with the increasing of Y2O3owing to the higher characteristicof concentration of Y3+, but excess Y2O3will breaks the glass network structure resultingdensity decreases.