Síntese e estudo das propriedades estruturais e dielétricas de matrizes cerâmicas compósitas (CMC) baseadas em : (Fe1/4Cu1/8Ti3/8)2O3 / (Fe5/8Cr3/8)2O3 / Pb(Fe1/2Nb1/2)O3 / CaTiO3 para uso em dispositivos eletrônicos

• Ano de defesa: 2008
• Autor(a) principal: Freire, Francisco Nivaldo Aguiar
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Palavras-chave em Português: Síntese; Propriedades estruturais; Compósitos; Cerâmicas
• Link de acesso: http://www.repositorio.ufc.br/handle/riufc/61312

In this work the solid state procedure was used, with success, in the production of ceramic matrix composites based in Cr0,75Fei,2503(CRF0100), Fe0 , 5Cu0 , 75Ti0 , 7503 (FCT0100), Pb(Fe0 , 5Nb0 , 503) (PFN100) e CaTiO3 (CTO), for the study of the structural and electrical properties of these composites for the possible use in electronic, radio-frequency and microwave circuitry. The first two series Cr0,75Fei,2503(CRF0100)--Feo,sCuo,75Tio,7503 (FCT0100), and Pb(Feo,5Nbo,503) (PFN100)--Cro,75Fei,2503 (CRF0100), were studied by the X-ray, MEV, EDSX, Mõssbauer spectroscopy and electrical properties as a function of temperature . The study of the electrical properties at the microwave region was done using the Hakki-Coleman technique and operating the samples as a dielectric resonator antenna. The series Cr0 , 75Fe1 , 2503 (CRF0100)--CaTiO3 (CTO) was studied by all the mentioned techniques, except for the techniques MEV, EDSX and Môssbauer spectroscopy. This work has the objective to synthesize and to characterize new composite materials for use in electronic, microwave and radio-frequency devices. After the synthesis of the samples the formation of the composites in the following series: (CRFO)x-(FCTO)100-x, with x — 0, 17, 34, 50, 66, 83 and 100% in mass; (PFN)x - (CRFO)100-x, with x = 0, 10, 50, 90 and 100 in mass % and xCRFO - (1-x)CTO with x = 0, 10, 50, 90 and 100 in moi %. The identification and the subsequent refinement of the data for the first series revealed a trigonal structure for the CRF0100 and a cubic structure for the FCT0100. In the case of the second series, the PFN100 present a tetragonal structure and in the third series, the CTO present an ortorhombic structure. The MOssbauer spectroscopy confirmed in the case of the first two series, the state of oxidation of the iron (Fe34) and it's coordination in all composites. Except for the PFN100, the morphology of the grains in the samples was characterized by the diversity in the form and size for all the samples of the first two series. The elementary chemical analysis supplied quantitative resqlts concerning of the present elements in the investigated samples. It was observed by the RF measurements a dispersion which is characteristic of the process of dipolar polarization. The dielectric properties with temperature was also studied. The TCC (Temperature Coefficient of Capacitance) and activation energy associated to the modulus formalism was obtained in a temperature interval of 25°C to 100°C. Measurements in the microwave region (300 MHz <f<30 GHz) were accomplished in the case of the first series for the samples CRF0100, CRF050 and FCT0100. For the CRFO-CTO series, a possibility to obtain a composite with TCC=0 was observed. Samples in the tree series are presenting high value of the dielectric permittivity (E>1 0) and low loss, which is necessary to the miniaturization of components to be used in microwave devices, and in telecommunications.