Influence of P₂O₅/TeO₂ composition ratio on the physical properties of V₂O₅–P₂O₅–TeO₂ glasses for lead-free low-temperature sealing

Abstract

We examined how the composition ratio of P₂O₅ to TeO₂ affected the physical properties and the structure of the semiconductive vanadate glasses in a low-melting V₂O₅–P₂O₅–TeO₂ glass system containing 57 mol % V₂O₅. It was found that increasing the P₂O₅ content and correspondingly decreasing the TeO₂ content raised the glass transition temperature and the deformation temperature as well as the fraction of the reduced V ions ([V⁴⁺]/[V_total]) and the average interionic distance of the V ions. In addition, the increase in P₂O₅ content from 7 to 32 mol % lowered the thermal expansion coefficient, volume resistivity, and density by 27, 42, and 14%, respectively, and also lowered the apparent molar volume of O ions and crystallization tendency. Furthermore, the infrared (IR) spectra suggested that the TeO₂-enriched glasses had a layered structure similar to crystalline V₂O₅, whereas the P₂O₅-enriched glasses had a denser layered structure as a result of the increased packing density of the O ions due to the reduction of the V ions.