Patent ID: 6955579

Claim:
A method of making a seal for a high pressure discharge lamp comprising the steps of: providing a tube made of sapphire with an exterior surface; providing in a presintered state, an end cap made of unsintered doped polycrystalline alumina, the end cap shaped to have an interior surface substantially conformal with the exterior wall, placing the presintered end cap adjacent the sapphire tube, heating the sapphire tube and end cap to sinter the end cap, to shrink the end cap into tight coupling with the sapphire tube, and to induce a liquid phase in the end cap at least adjacent the sapphire tube; holding the sapphire tube and end cap in a heated state sufficiently long to induce growth of the sapphire tube into the end cap; and cooling the sapphire tube and end cap to preserve the crystalline growth from the sapphire tube into the end cap.