Navegando por Palavras-chave "Polyphase System"

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    Influência Do Processamento Na Formação De Cerâmicas Eletrônicas Polifásicas E Suas Propriedades Elétricas
    (Universidade Federal de São Paulo (UNIFESP), 2017-12-08) Boaventura, Andre Luis [UNIFESP]; Antonelli, Eduardo [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    The general objective of this work was to investigate the influence of processing on the electrical properties (dielectric and piezoelectric) of ceramics of the barium-zirconate titanate system (BT+BZ) as well as the barium zirconate-titanate/barium calcium-titanate (BZT-BCT). Studies indicate that intrinsic and extrinsic factors influence the dielectric and piezoelectric properties of electronic ceramics. The methodology consisted in obtaining monophase materials of barium-zirconate titanate (BZT), calcium titanate (BCT), barium titanate (BT) and barium zirconate (BZ). New materials were made through mixture of calcined powders of BZT with BCT and BZ, forming polyphase ceramics of BZT-BCT and BT-BZ respectively. The ceramics were sintered at 1380 ºC at different times (10 min, 2h, 3h and 24h). The results showed that polyphase ceramics presented the phase coexistence in the temperature range studied, forming polymorphic phase behavior (PPB). The intrinsic and extrinsic factors were influenced by the stage of sintering. For the BZT-BCT polyphase system, the extrinsic factors (average grain size, texture, density, grain boundary) and intrinsic factors (coexistence of symmetries, polarization, tetragonal phase stabilization) increased because of the stages of sintering e and consequently improved the piezoelectric responses of this system. As for the polyphase system BT-BZ, the intrinsic factors (coexistence of symmetries and the stabilization of the cubic phase) increased because of the stages of sintering, while the extrinsic factors (average grain size, homogeneity and phase segregation) decreased because of the increase of stages of sintering. For sintered BT-BZ ceramics with a time interval of 10 mins, the balance between the intrinsic and extrinsic factors, caused the dielectric properties to be more stable than the single-phase solid solution (BZT). This result is a promising choice for the production of dielectric materials for the purpose of usage in the capacitors. Therefore, it was possible to demonstrate that the processing routes of the mixtures, BZT-BCT and BT-BZ formed polyphase materials with PPB, and that the time of stages influenced the intrinsic and extrinsic factors that led to the responses in the electrical, dielectric properties and piezoelectric properties of the ceramics investigated