Caracterizações óptica e elétrica de cristais de Bi2TeO5 crescidos por um método de duplo cadinho
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2015-01-22
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Universidade Federal de Goiás
Resumo
Bismuth tellurite, Bi2TeO5, here labeled BTeO has a lot of properties like
improper ferroelectricity, photochromic, photorefractive, with two optical axes large
optical window and another interesting optical and electrical properties, as recently
we discovered, photovoltaic effect.
BTeO single crystal growth and processing has two inherent difficulties, high
vapor pressure of tellurium oxide close to bismuth tellurite melting point and BTeO
cleavage plane parallel to (100) plane. So, BTeO factory good sample for material
characterization require singular precautions and depends on researcher
experience invariably.
Present work is dedicated to detailed study of BTeO single crystals growth
parameters in a modified Czochralski method with unpublished concept double
crucible system. In our case, we used oxides mix on external crucible with volatile
oxide bigger quantity related to internal crucible to create a supersaturated
atmosphere used to control crystal growth liquid phase stoichiometry reducing
tellurium oxide evaporation. We also highlighted important details about good
quality samples production, like crystal cut and polish enclosed in acrylic resin to
avoid cleavages during this processes.
Finally, we characterized BTeO by optical spectroscopy (optical absorption,
Raman scattering and luminescence) and electrical properties (conductivity,
photoconductivity and impedance spectroscopy). We measured BTeO
photorefractive properties with 633 nm wavelength for the first time and results
suggested that material could be photovoltaic, hypothesis tested and confirmed in
the present work.
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FABRIS, Z. V. Caracterizações óptica e elétrica de cristais de Bi2TeO5 crescidos por um método de duplo cadinho. 2015. 98 f. Tese (Doutorado em Fisica) - Universidade Federal de Goiás, Goiânia, 2015.