Patent ID: 7061182

Claim:
A metal halide lamp comprising an arc tube having an arc tube container as an envelope that is made of oxide-based translucent ceramic material and comprises a discharge arc tube portion, the arc tube being filled with sodium iodide, cerium halide as a luminescent material, and a halide of a rare earth element that is more reactive with the ceramic material than is the cerium halide, wherein a filling amount of the halide of a rare earth element is in a range from 1.5 molar parts to 100 molar parts when a filling amount of the cerium halide is 100 molar parts and wherein the oxide-based translucent ceramic material is at least one ceramic selected from the group consisting of polycrystalline alumina ceramic, Al 2 O 3 (alumina), Y 3 Al 5 O 3 , BeO, MgO, Y 2 O 3 , Yb 2 O 3 , and ZrO 2 .