Effects of alkali and alkaline-earth oxides on thermal, dielectrical, and optical properties of zinc borate glasses for transparent dielectric

Abstract

The development of a transparent dielectric layer with a low dielectric constant is essential for improving the luminous efficacy of plasma display panels (PDPs). In this study, a ZnO-B2O3-SiO2-Al2O3 glass containing alkaline-earth oxides and an alkali oxide was fabricated as a candidate Pb- and Bi-free transparent dielectric layer with a low dielectric constant. The thermal, electrical, and optical properties of these glasses were characterized. The changes in the properties in this glass system were investigated according to the alkalineearth oxides (RO)/alkali oxide (R2O) ratio. The glass transition temperature (Tg), the coefficient of thermal expansion (CTE), and the dielectric constant of the glasses varied from 480°C to 540 °C, 7.9 to 10.6 × 10−6 /K, and 7.4–8.2, respectively. As the RO/R2O ratio was increased, the Tg value increased, the CTE and transmittance decreased, and the dielectric constant increased slightly. The Tg or CTE can be calculated from other known values in these system glasses without requiring numerous experiments. The Tg and CTE are inversely proportional to each other and a constant was obtained by multiplying the two values.