Compositions: ceramic – Ceramic compositions – Synthetic precious stones
Patent
1995-11-30
1997-11-04
Bell, Mark L.
Compositions: ceramic
Ceramic compositions
Synthetic precious stones
501153, 313636, C04B 3515
Patent
active
056839499
ABSTRACT:
A solid state method of converting a polycrystalline ceramic body to a single crystal body includes the steps of doping the polycrystalline ceramic material with a conversion-enhancing dopant and then heating the polycrystalline body at a selected temperature for a selected time sufficient to convert the polycrystalline body to a single crystal. The selected temperature is less than the melting temperature of the polycrystalline material and greater than about one-half the melting temperature of the material. In the conversion of polycrystalline alumina to single crystal alumina (sapphire), examples of conversion-enhancing dopants include cations having a +3 valence, such as chromium, gallium, and titanium. The polycrystalline body further can be inhomogeneously doped to form a first portion of the polycrystalline body that is doped to the selected level of the conversion-enhancing dopant and a second portion that is not doped such that heating the doped polycrystalline body causes conversion of first portion to a single crystal structure and the second portion retains a polycrystalline structure.
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Kaliszewski Mary Sue
Levinson Lionel Monty
Scott Curtis Edward
Bell Mark L.
Corwin Stanley C.
General Electric Company
Sample David
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