Investigação das propriedades dielétricas da matriz ortoniobato de itrio (YNbO4) sob efeitos da adição de TiO2

• Ano de defesa: 2021
• Autor(a) principal: Abreu, Tallison Oliveira
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Palavras-chave em Português: Niobato de ítrio; Propriedades dielétricas; Compósitos; Antenas
• Link de acesso: http://www.repositorio.ufc.br/handle/riufc/58849

Due to technological development in the area of engineering and materials science, advanced ceramics prove to be promising materials, mainly for applications in devices that operate in the microwave (MW) and radiofrequency (RF) range. In this work, the structural characteristics and dielectric properties of the YNbO4 yttrium orthoniobate (YNO) with the addition of TiO2 in the molar proportions of 20, 37, 40, 60 and 80% were studied. The ceramics were prepared using the solid-state reaction method, followed by calcination at a temperature of 1200 ºC. After calcination, these materials were sintered at 1200 °C and the ceramic pieces obtained were characterized in terms of their structure and morphology by X-Ray Diffraction and Scanning Electron Microscopy, respectively. The X-ray Diffraction analysis proves the obtaining of the YNO matrix, as well as the identification of the yttrium and niobium Y(Nb0.5Ti0.5)2O6 (YNT) phase, formed by the addition of TiO2. The morphological study and the analysis of the micrographs revealed that the addition of TiO2 modified the morphology of the materials leading to an increase in the grains and the appearance of pores of varying sizes. Through the pycnometry test it was also observed that the densification of the pieces obtained was around 70%. The study of the dielectric properties of ceramics carried out in the MW range suggests that the composites of the (YNO)1-x - (TiO2)x series have properties for application as a dielectric resonant antenna (DRA). The composition with 37 mol% of TiO2 (YNO63) presented the best antenna parameters with a gain of 5.768 dB, radiation efficiency of 99.39% and a temperature coefficient of resonance frequency close to zero (-8.96 ppm /°C). Such results indicate this material as promising for devices that operate in the microwave range and that require thermal stability. For the results in the RF range, the impedance spectroscopy analyzes reveal that the increase in temperature promotes greater mobility to the load carriers inside the samples. Regarding the results of activation energy (Ea), the addition of TiO2 favored not only the formation of the YNT phase, but also the increase in Ea and with that, there was an increase in the insulating character for all compositions, except for YNO20. In addition, the samples YNO, YNT and YNO63 demonstrated that they can present thermal stability in radiofrequency in the range of 100 kHz to 1 MHz as shown by the analysis of the capacitance temperature coefficient (TCC).