Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-11-22T20:32:41Z No. of bitstreams: 1 AlcineyMirandaCabral_TESE.pdf: 9055485 bytes, checksum: 069ff7e30ae747a94ed4317fcd5f7186 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-11-23T22:39:21Z (GMT) No. of bitstreams: 1 AlcineyMirandaCabral_TESE.pdf: 9055485 bytes, checksum: 069ff7e30ae747a94ed4317fcd5f7186 (MD5) / Made available in DSpace on 2017-11-23T22:39:21Z (GMT). No. of bitstreams: 1 AlcineyMirandaCabral_TESE.pdf: 9055485 bytes, checksum: 069ff7e30ae747a94ed4317fcd5f7186 (MD5) Previous issue date: 2017-06-20 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / O desafio inovador deste trabalho foi aplicar o m?todo qu?mico de S?ntese por Rea??o de Combust?o adaptada ?s perovskitas multiferr?icas BiFeO3, nas suas formas monof?sicas. Inicialmente, foi realizado a s?ntese para o BFO nas temperaturas ap?s a rea??o (BFOP.C.), a 700 oC (antes da Temperatura de Curie, BFO700) e a 830oC (pr?xima a Temperatura de Curie, BFO830). Na segunda etapa da s?ntese, foi definida a temperatura de 700 oC no sistema de dopagens LaxBi1-xFeO3 (x= 0.00, 0.10, 0.20 e 0.30), formando BFO700, L0.10BFO700, L0.20BFO700 e L0.30BFO700. Os materiais sintetizados foram caracterizados por Refinamento de Rietveld (DRX ? Rietveld), Espectroscopia no Infravermelho M?dio com Transformada de Fourier (FTIR), Microscopia Eletr?nico de Varredura com Espectroscopia por Energia Dispersiva (MEV/EDS/MAPEAMENTO), An?lises T?rmicas (TG/DTA), Propriedades Magn?ticas e El?tricas (???,??,??? ? ??? ?). Os resultados das an?lises dos par?metros estruturais, el?tricos e magn?ticos das perovskita de BiFeO3 (BFO) nas fases monof?sicas, indicaram simetria/grupo espacial Rombo?drica/?3? (BFOP.C.), Rombo?drica/?3? (BFO700) e Tricl?nica/?1 (BFO830) nas cer?micas. As dopagens por La3+ nas amostras BFO700, L0.10BFO700, L0.20BFO700 e L0.30BFO700 proporcionam diferentes valores Magn?ticos de Satura??es e resultaram Romboedral/?3? - 0.011314 ??.[?.?.]?1, Ortorr?mbico/???? - 0.006516 ??.[?.?.]?1, Ortorr?mbico/???? - 0.011503 ??.[?.?.]?1e Ortorr?mbico/???? - 0.009509 ??.[?.?.]?1respectivamente. As an?lises por FTIR/DRX ? Rietveld evidenciaram vibra??es caracter?sticas em 530.34, 531.61 e 551.51cm-1 que atribu?dos s?o ?s perovskitas de BiFeO3 com distor??o octaedral (FeO6). O estudo das estruturas sintetizadas apontaram para as cer?micas antiferromagneticas com distor??o octaedral. Na faixa 0 ? 0.5 GHz a dieletricidade das cer?micas foi maior que 6 e a tangente de perdas menores que -0.13. O fator de qualidade da antena com as amostras cer?micas apresentaram valores entre -10 dB e -25dB. Os resultados indicaram o alto potencial do BFO e LBFO como substratos cer?micos qu?micos em antenas magnetoferr?icas. / The innovative challenge of this work was to apply the chemical synthesis method by combustion reaction adapted to multiferroic perovskite in the forms BiFeO3 single. Initially, the synthesis of the BFO in temperatures after the reaction (BFOP. C.), 700 oC (before to curie temperature, BFO700) and 830 oC (near to curie temperature, BFO830). Secondly, the synthesis was defined the temperature of 700 oC in the doping system LaxBi1-xFeO3 (x= 0.00, 0.10, 0.20 and 0.30), forming BFO700, L0.10BFO700, L0.20BFO700 and L0.30BFO700. The sintetized materials were characterized by Rietveld Refinement (DRX ? Rietveld), Medium Fourier Transform Infrared Spectroscopy (FT ? IR), Scanning Electron Microscopy and Energy Dispersive X ? ray Spectroscopy (SEM/EDX/MAPPING), Thermical Analysis (TG/DTA), Magnetic and Electrical Properties (???,??,??? and ??? ?). The analytical results of the structural parameters, eletrics and magnetics of the perovskites of BiFeO3 (BFO), in the single phases, indicated symmetry/space group Rhombohedral/?3? (BFOP.C.), Rhombohedral/?3? (BFO700) and Triclinic/?1 (BFO830) in the ceramics. The doping by La3+ in the samples BFO700, L0.10BFO700, L0.20BFO700 and L0.30BFO700 showed different magnetic saturation of materials, resulting in Rhombohedral/?3? - 0.011314??.[?.?.]?1, Orthorhombic/???? - 0.006516 ??.[?.?.]?1, Orthorhombic/???? - 0.011503 ??.[?.?.]?1and Orthorhombic/???? - 0.009509 ??.[?.?.]?1 respectively. The analysis by FT ? IR/XRD ? Rietveld showed vibration characteristics in 530.34, 531.61 and 551.51cm-1 that are attribute to perovskites of BiFeO3 with octahedral distortion (FeO6). The study of the sintetized structures pointed for the antiferromagnetic ceramics with an behaviour octaedral distortion. In the range 0 ? 0.5 GHz, the dielectricity of the ceramics was more that 6 and the smaller loss tangent that -0.13. The quality factor of the antenna with the ceramic samples presented value between -10 dB and -25dB. The results indicated the potential high of the BFO and LBFO as substrates chemical ceramics in magnetoferroic antennas.