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Doctoral Thesis
DOI
https://doi.org/10.11606/T.76.2006.tde-14012008-170719
Document
Author
Full name
André Luiz Martinez
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2006
Supervisor
Committee
Hernandes, Antonio Carlos (President)
Baldochi, Sonia Licia
MPeko, Jean Claude
Schneider, Jose Fabian
Silva, Elson Longo da
Title in Portuguese
Síntese e crescimento de cristal da fase BiNbO4
Keywords in Portuguese
BiNb04
Crescimentos de cristais
Czochralski
LHPG
Abstract in Portuguese
Muitos trabalhos científicos têm sido publicados relatando os diferentes métodos de preparação e as propriedades de corpos cerâmicos e filmes finos de niobato de bismuto (BiNbO4 - BN). Provido de características como alta permissividade dielétrica e excelentes propriedades ferroelétricas, esse composto tem despertado o interesse da comunidade científica. No entanto, uma literatura restrita e conflitante é encontrada sobre esse composto na forma de monocristais. A ocorrência de transições de fase estrutural mostrou-se a maior dificuldade na preparação desses compostos como monocristais. A potencial aplicação como material de dispositivos eletrônicos, devido suas propriedades ferroelétricas, assim como o desafio da preparação de materiais que apresentam transição estrutural de fase, serviram de motivação para a realização desse estudo. O objetivo desse trabalho foi a realização do estudo da síntese e do crescimento de cristais de BiNbO4. Para isso foram utilizadas as técnicas de Czochralski (CZ), Laser Heated Pedestal Growth (LHPG) e fluxo. As dificuldades encontradas quando utilizada cada uma das técnicas, assim como suas variações, foram discutidas. A transição estrutural de fase ('alfa'-BiNbO4 - 'beta'-BiNbO4) mostrou-se uma barreira na preparação desse tipo de material com qualidade óptica. O comportamento da permissividade dielétrica ('épsilon') e fator de perda (tg'teta') em função da temperatura e freqüência foram determinados através de estudos de espectroscopia de impedância.
Title in English
Synthesis and crystal growth of BiNbO4 phase
Keywords in English
BinNbO4
Cristal growth
Czochralski
LHPG
Abstract in English
Many scientific works have been published reporting different procedures to the preparation and properties of ceramic bodies and thin films of bismuth niobate (BiNbO4 - BN). Characterized by high dielectric permittivity and excellent ferroelectric properties, this compound has attracted the interest of the scientific community. However, a restricted and conflict literature is found about this compound in the single crystal form. The appearance of structure phase transitions was demonstrated in the most difficulty for the preparation of this compounds as single crystals. The potential applications as electronic device material, due its ferroelectrics properties, as well as the challenge to preparation materials which indicate structural transition were used as motivations to the development of this work. The main purposes of this work were to make synthesis and the crystal growth of BiNbO4. For this propose, techniques as Czochralski (CZ), Laser Heated Pedestal Growth (LHPG) and self-flux were used. The difficulties found when used each one of the techniques and their variations are discussed. The structural phase transition ('alfa'-BiNbO4 - 'beta'-BiNbO4) was the principal barrier in the preparation of this material with optical quality. The behavior of dielectric permittivity ('épsilon' ) and lost factor (tg' teta') by the temperature and frequency were determined through studies of Impedance Spectroscopy
 
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Publishing Date
2008-01-28
 
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