Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-06-09T23:48:16Z No. of bitstreams: 1 PauloAntonioMacedoSilva_TESE.pdf: 3938129 bytes, checksum: 33a58d5ed902b34a959919327356aca8 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-06-10T20:54:26Z (GMT) No. of bitstreams: 1 PauloAntonioMacedoSilva_TESE.pdf: 3938129 bytes, checksum: 33a58d5ed902b34a959919327356aca8 (MD5) / Made available in DSpace on 2016-06-10T20:54:26Z (GMT). No. of bitstreams: 1 PauloAntonioMacedoSilva_TESE.pdf: 3938129 bytes, checksum: 33a58d5ed902b34a959919327356aca8 (MD5) Previous issue date: 2015-10-26 / No presente trabalho mostra que a s?ntese por combust?o, destaca-se como uma t?cnica alternativa para obten??o dos p?s-cer?micos de ?xidos superiores, nanoestrutrurados e de alta pureza, como as ferritas de f?rmulas Co(1-x)Zn(x)Fe2O4 e Ni(1-x)Zn(x)Fe2O4 com x variando de 0,2 mols, num intervalo de 0,2 ? x ? 1,0 mol, que apresentam propriedades, magn?ticas, em que ocorre ? coexist?ncia de estado ferroel?trico e ferrimagn?tico, as quais podem ser utilizadas em antenas de micro fitas e superf?cies seletivas de frequ?ncias em faixas de micro-ondas miniaturizadas, sem perda de desempenho. A obten??o ocorreu atrav?s do processo de combust?o e de processos f?sicos adequados a utiliza??o ao m?todo de sinteriza??o do substrato, resultando um material cer?mico, de elevado grau de pureza nanom?trico. An?lises no Magnet?metro de Amostra Vibrante (MAV) mostraram que estes materiais ferriticos apresentam par?metros como histereses de materiais que possuem comportamento pr?prio dos materiais magn?ticos de boa qualidade, em que os estados de magnetiza??o podem ser mudados bruscamente com uma varia??o relativamente pequena da intensidade do campo, tendo assim grandes aplica??es no campo de eletroeletr?nicos. A caracterizaram dos p?s-cer?micos sinterizados a 900?C, como suas propriedades estruturais, geom?tricas, tamanho do cristalito e dist?ncia Interplanar, foram feitas por Difra??o de Raios-X (DRX). Foram feitas outras an?lises, como a Microscopia Eletr?nica de Varredura (MEV), Fluoresc?ncia de Raios-X (FRX) , a permissividade el?trica e a tangente de perda, em altas frequ?ncias, atrav?s do aparelho ZVB - 14 Vector Network Analyzer 10 MHz-14 GHz, da ROHDE & SCHWART. / This work shows that the synthesis by combustion is a prominent alternative to obtain ceramic powders of higher oxides, nanostructured and of high purity, as the ferrites of formulas Co(1-x)Zn(x)Fe2O4 e Ni(1-x)Zn(x)Fe2O4 with x ranging from 0.2 mols, in a range from 0.2 ? x ? 1.0 mol, that presents magnetic properties in coexistence of ferroelectric and ferrimagnetic states, which can be used in antennas of micro tapes and selective surfaces of low frequency in a range of miniaturized microwaves, without performance loss. The obtainment occurred through the combustion process, followed by appropriate physical processes and ordered to the utilization of the substrate sinterization process, it gave us a ceramic material, of high purity degree in a nanometric scale. The Vibrating Sample Magnetometer (VSM) analysis showed that those ferritic materials presents parameters, as materials hysteresis, that have own behavior of magnetic materials of good quality, in which the magnetization states can be suddenly changed with a relatively small variation of the field intensity, having large applications on the electronics field. The X-ray Diffraction (XRD) analysis of the ceramic powders synthesized at 900 ?C, characterize its structural and geometrical properties, the crystallite size and the interplanar spacing. Other analysis were developed, as Scanning Electron Microscopy (SEM), X-ray Fluorescence (XRF), electric permittivity and the tangent loss, in high frequencies, through the equipment ZVB - 14 Vector Network Analyzer 10 MHz-14 GHz, of ROHDE & SCHWART.