Tubular discharge envelope composed of a polycrystalline transparent alumina and a high-pressure vapor discharge lamp using the same

摘要

A tubular discharge envelope and a high-pressure vapor discharge lamp using the same are disclosed. The envelope is composed of a polycrystalline transparent alumina having an average crystal grain size of 20-60 mu m and crystal grains of 20 mu m or less which occupy not more than 30% per unit area of the envelope.