Forming and Surface-Finishing Technologies for Translucent Polycrystalline Alumina (TL-PCA)

抄録

Translucent polycrystalline alumina (TL-PCA) was one of the earliest modern ceramic materials used for practical applications as the material of the thin-wall straight tube of high-pressure sodium (HPS) lamps. To improve the brightness and save energy, the optical mechanical and chemical properties of the tubes under mass production manufacturing conditions have been investigated focusing on the sintering behavior of TL-PCA. With the development of manufacturing technologies for cylindrical and bulgy tubes, TL-PCA has been applied to light bulbs for ceramic metal halide lamps. In particular, the new forming process of gel-casting enables the precise duplication of three-dimensional (3D) cavities using a metal mold. The dimensional accuracies attained by such net-shape forming processes are sufficient for emitting light tubes; however, for the substrates of electronic devices, subnanometer-precision planarization finishing technologies are required. In this paper, the net-shape technologies for light tubes and the surface-finishing technology for TL-PCA to use as the substrates of electronic devices developed by NGK Insulators are reported.