Conversion of polycrystalline alumina to single crystal sapphire using molybdenum doping
AssigneeGeneral Electric Company
InventorsJames Anthony Brewer, Charles David Greskovich, Curtis Edward Scott
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Abstract
A process for converting a polycrystalline ceramic material to a single crystal material includes the steps of doping at least a first portion of the polycrystalline ceramic material with a conversion-enhancing dopant having a +6 valence state in the unfired ceramic material and heating the polycrystalline ceramic material to convert at least a second portion of the polycrystalline ceramic material to a single crystal ceramic material. Preferably, the ceramic material is alumina and the conversion-enhancing dopant is molybdenum or tungsten.
Claims26
A process for converting a polycrystalline ceramic material to a single crystal ceramic material, comprising:
- doping at least a first portion of the polycrystalline ceramic material with a conversion-enchancing dopant having a +6valence state in the ceramic material, the conversion-enhancing dopant comprising at least one of molybdenum and tungsten in a first concentration, wherein the first concentration is ≧30 wppm;
- and
- heating the polycrystalline ceramic material to convert at least a second portion of the polycrystalline ceramic material to a single crystal ceramic material.
A process for converting polycrystalline alumina to sapphire, comprising:
- immersing at least a first portion of a polycrystalline bisque-fired alumina body containing at least 150 wppm of magnesium oxide in a liquid solution containing molybdenum or tungsten in a concentration equal to or greater than 5 wppm and allowing the molybdenum or tungsten to penetrate into said alumina body;
- sintering the alumina body;
- decreasing the concentration of magnesium oxide in the sintered alumina body to a concentration of 60 wppm or less;
- and
- heating the sintered alumina body to a temperature above one-half of a melting temperature of alumina but below the melting temperature of alumina to convert at least the first portion of the sintered alumina body to single crystal sapphire.
A ceramic material body comprising at least a first single crystal sapphire portion containing a first concentration of molybdenum or tungsten sufficient to enhance a conversion of polycrystalline alumina to the single crystal sapphire wherein the first concentration comprises at least 30 wppm.
Dependencies are inferred from the claim text.