Polycrystalline transluscent alumina for high intensity discharge lamps
AssigneeGeneral Electric Company
InventorsFangming Du, Thomas J. Boyle, Shuyi Qin, Zoltan Dobe
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Abstract
A polycrystalline body comprising a MgO/ZrO2-doped aluminum oxide in which alumina grains have an average size of at least 20 μm and wherein the magnesium oxide is present in an amount of at least 250 ppm and the zirconium oxide is present in an amount of at least about 20 ppm of the weight of the ceramic body, and the magnesium and zirconium oxides are present at a molar ratio of about 1:2 to about 15:1.
Claims23
A polycrystalline body comprising translucent, sintered magnesium oxide/zirconium oxide-doped alumina, in which at least 99.9% of the alumina grains of the body have a diameter of less than 75 μm, and wherein the molar ratio of MgO:ZrO2 in the body is 1:2 to about 15:1.
A high pressure sodium lamp comprising a sealed discharge tube including a sintered polycrystalline alumina body doped with MgO and ZrO2, wherein the sintered polycrystalline alumina body exhibits an average grain size of at least about 20 μm to about 40 μm, a molar ratio of MgO:ZrO2 in the body of 1:2 to about 15:1, and wherein the sealed discharge tube contains a fill comprising sodium and mercury.
A method of forming a translucent polycrystalline alumina body comprising:
- forming a mixture of ceramic-forming ingredients and an organic binder, the ceramic-forming ingredients including particulate alumina having an average grain size of at least 0.2 μm and additives, the additives being expressed in terms of their oxides in parts per million of a weight of the total ceramic forming ingredients as follows:
- magnesium oxide 350-600 ppm;
- and
- zirconium oxide 20-700 ppm;
- forming a shaped body from the mixture;
- firing the shaped body to form a translucent polycrystalline alumina body doped with MgO and ZrO2.
Dependencies are inferred from the claim text.