Properties of Lead-Free Sealing Glasses Composed of V₂O₅–H₂WO₄–KPO₃–Sb₂O₃

Abstract

Lead-free glasses with a low glass transition temperature, low coefficient of thermal expansion, high fluidity and high durability against water are desirable for sealing of electrical devices. In this study, V₂O₅, H₂WO₄, and KPO₃ were used to develop a novel sealing glass. We investigated the glass transition temperature, softening temperature, glass crystallization temperature, coefficient of thermal expansion and ratio of weight loss of glasses after waterproof testing. Amorphous glasses were obtained by melting of mixtures of V₂O₅ (10–60 mol%), H₂WO₄ (10–50 mol%), and KPO₃ (30–70 mol%). Two types of glass (40 mol% V₂O₅–20 mol% H₂WO₄–40 mol% KPO₃ and 40 mol% V₂O₅–10 mol% H₂WO₄–50 mol% KPO₃) had low glass transition temperature and good fluidity. Addition of Sb₂O₃ (2.5, 5 or 10 wt%) to the glasses enhanced their durability against water. The coefficient of thermal expansion of the glass composed of 39.0 mol% V₂O₅–9.7 mol% H₂WO₄–48.7 mol% KPO₃–2.6 mol% Sb₂O₃ was lowered by incorporation of Zr₂(WO₄)(PO₄)₂, a low-thermal-expansion ceramic filler. The glass showed comparable bonding strength with a commercial lead glass.