Lead-Free Low-Melting and Semiconductive Vanadate Glass Applicable to Low-Temperature Sealing

We optimized the fundamental composition and additives in a semiconducting V₂O₅–P₂O₅–TeO₂ glass system to develop lead-free low-melting glass suitable for low-temperature sealing below 400 °C. Glass with a composition of 55.7V₂O₅–19.8P₂O₅–23.5TeO₂ (mol %) has a low glass transformation temperature (T_g < 300 °C) as well as hard crystallization, and it is desired as a low-temperature sealing material. The effects of adding BaO, Sb₂O₃, MnO₂, or Fe₂O₃ to the fundamental composition of 55.7V₂O₅–19.8P₂O₅–23.5TeO₂ (mol %) on the thermal properties and water-vapor resistance were then characterized. Adding 11.7 mol % Fe₂O₃ improved the water-vapor resistance drastically and decreased the thermal expansion coefficient without increasing T_g. Sealing at 360 °C with our lead-free Fe₂O₃-added vanadate glass enabled practical airtight packaging on an electronic device.