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Doctoral Thesis
DOI
10.11606/T.43.1997.tde-27022014-154140
Document
Author
Full name
Maria Cláudia Cerchiari Custódio
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 1997
Supervisor
Committee
Hernandes, Antonio Carlos (President)
Baldochi, Sonia Licia
Balzuweit, Karla
Leite, Jose Roberto
Missell, Frank Patrick
Title in Portuguese
Síntese e Crescimento de Materiais Termoelétricos: Bi2Te3 e Soluções Sólidas de (Bi(1-x)Sbx)2 Te3
Keywords in Portuguese
Matéria condensada
Termoeletricidade
Abstract in Portuguese
Neste trabalho desenvolvemos um estudo detalhado do processo de síntese e preparação de cristais de Bi IND 2 Te IND 3 e (Bi IND (l-x)Sb IND x) Te IND 3, bem como uma abordagem qualitativa sobre a variação do coeficiente Seebeck em função do comprimento destes cristais. Preparamos cristais com condutividade tipo-p e tipo-n pela técnica de Bridgman em um sistema com gradiente de temperatura axial fixo (29 °C/cm), e em outro em que este parâmetro poderia ser alterado facilmente. Os cristais de telureto de bismuto tipo-p preparados no primeiro equipamento foram axialmente homogêneos em composição e coeficiente Seebeck, cuja intensidade média medida foi de 220 V/K. Os tipo-n apresentaram uma fase rica em telúrio em todo o seu comprimento e uma diminuição gradativa do coeficiente Seebeck. O aparecimento desta fase pode ser associado à instabilidade da interface sólido-líquido ou a um processo de superresfriamento constitucional localizado. Por outro lado, em nenhum dos cristais de Bi IND 2 Te IND 3 e (Bi IND (l-x)Sb IND x) Te IND 3, com condutividade tipo-p e n preparados no segundo sistema, houve presença da fase rica em telúrio e o máximo valor do coeficiente Seebeck foi superior ao relatado na literatura.
Title in English
Synthesis Growth Thermoelectric Materials Bi2Te3 Solid Solutions (Bi (1-x) Sbx)2 Te3
Keywords in English
Condensed matter
Thermoelectricity
Abstract in English
ln this work, a detailed study on the synthesis and crystal growth process of Bi2Te3 e (Bi(l-x)Sbx)2 Te3 was carried out. The dependence of the Seebeck coefficient variation on the length crystal has been discussed in a qualitative way. P-type and n-type crystals were grown by the Bridgman technique using two different systems. In one system the axial temperature gradient was fixed, while in the other it could be adequately changed. The p-type bismuth tellurides grown in the first equipment were axially homogeneous in composition and Seebeck coefficient. Its average measured value was about 220 V/K. The n-type bismuth telluride presented a tellurium-rich phase in all of its extension and a decreasing Seebeck coefficient. The tellurium-rich phase can be related to solid-liquid interface instability or a constitucional supercooling. On the other hand, no Te-rich phase was detected in Bi2Te3 e (Bi(l-x)Sbx)2Te3 crystals grown in the second equipment. The maximum measured Seebeck coefficient of these materials was higher than the literature reported ones.
 
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Publishing Date
2014-02-28
 
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