Czochralski single crystal growth, modeling, and characterization of ilmenite /
Ilmenite is a wide band gap material, and could be used for electronic applications. Since ilmenite is stoichiometric at its melting point, the single crystals are grown using Czochralski crystal growth method. Earlier research in ilmenite uses ceramic material, and smaller size single crystals....
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1998.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=733039501&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Ilmenite is a wide band gap material, and could be used for electronic applications. Since ilmenite is stoichiometric at its melting point, the single crystals are grown using Czochralski crystal growth method. Earlier research in ilmenite uses ceramic material, and smaller size single crystals. In this research large size single crystals of ilmenite are grown. To grow large size single crystals it is essential to have a Czochralski growth system with minimum imperfections. Since Czochralski crystal growth is highly nonlinear any imperfection in the system would lead to instability, and the growth might terminate. Crucible placement and seed-rod rotation are the main source of eccentricity in the Czochralski system. In this research the crystal growth equipment is modified to overcome the eccentricities caused by crucible placement and seed-rod rotation. The modifications could be easily implemented to improve most Czochralski crystal growth systems. Ilmenite crystals of diameter greater than twenty-five millimeters are grown using the modified crystal growth system. As the crystal growth dimension, and the quality requirement of eletronic material increases, the need for modeling the process becomes important. Various models have been developed using the physicl principles of crystal growth. These models are limited by the crystal growth technique and the type of material used. In this research empirical modeling approaches are used to model the thermal dynamics of the ilmenite crystal growth process. Linear and nonlinear techniques are used in the modeling study. The nonlinear modeling method uses artificial neural networks to model the crystal growth process. Both the linear and nonlinear models predict the crucible temperature for different ilmenite crystal growth experiments to within the accuracy limits of the pyrometer sensor. Characterization studies on the ilmenite specimen from the top of the boule revealed that the grown crystals are single crystalline. Phase separation of iron and titanium oxide are observed on the ilmenite specimen cut from the middle of the boule. Phase separation occurs while ilmenite cools from its melting point to room temperature. Quenching the grown boule of ilmenite might reduce the phase separation. |
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| Item Description: | Vita. "Major Subject: Electrical Engineering". |
| Physical Description: | xiii, 101 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 89-94). |