Síntese e caracterização da manganita La0,7-xEuxSr0,3MnO3: estudo das propriedades magnéticas, térmicas, estruturais e luminescentes
Data
2024-06-03
Orientadores
Molina, Celso 
Tipo
Trabalho de conclusão de curso
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Manganitas são óxidos de manganês que desempenham um importante papel tecnológico devido às suas propriedades magnetocalóricas e de magnetorresistência colossal. Neste trabalho, as manganitas La0,7Sr0,3MnO3 e La0,4Eu0,3Sr0,3MnO3 foram preparadas por síntese no estado sólido pela mistura dos óxidos de lantânio, manganês, estrôncio e európio. Foi feito um estudo das propriedades luminescentes, estruturais, magnéticas e comportamento frente à aplicação de conformação mecânica uniaxial para formação de pastilhas desta manganita. Foram realizadas caracterizações por
espectroscopia vibracional na região do infravermelho com transformada de Fourier (FTIR-ATR), microscopia eletrônica de varredura (MEV), difratometria de raios X (DRX), espectroscopia por dispersão de energias de raios X (EDX), por medidas de magnetização em função do campo aplicado e temperatura, e as luminescentes por espectroscopia eletrônica de fotoluminescência. Os principais resultados mostraram que a magnetização de saturação da manganita reduziu em aproximadamente 50 vezes com a inserção do íon európio na estrutura e a manganita com európio apresentou luminescência quando excitada na banda de transição de carga ligante-metal (TCLM). Além disso, as manganitas foram submetidas a diferentes conformações mecânicas sobre corpos de prova na forma de pastilhas. A magnetização de saturação do material aumentou em torno de 10 vezes após a aplicação dessas conformações mecânicas para a manganita contendo európio na estrutura. Também houve um aumento dos tempos de vida experimentais obtidos (decaimento a partir do estado emissor 5D0). Pequena variação no ambiente local do íon Eu3+ foi observada em função da conformação
mecânica aplicada, indicando maior assimetria em seu entorno.
Manganites are manganese oxides that play an important technological role due to their magnetocaloric properties and colossal magnetoresistance. In this work, the manganites La0.7Sr0.3MnO3 and La0.4Eu0.3Sr0.3MnO3 were prepared by solidstate synthesis by mixing lanthanum, manganese, strontium and europium oxides. A study was carried out on the luminescent, structural, magnetic properties and behavior when applying uniaxial mechanical conformation to form tablets of this manganite. Characterizations were carried out by vibrational spectroscopy in the infrared region with Fourier transform (FTIR-ATR), scanning electron microscopy (SEM), X-ray diffractometry (XRD), X-ray energy dispersion spectroscopy (EDX), by measurements of magnetization as a function of applied field and temperature, and luminescence by photoluminescence electronic spectroscopy. The main results showed that the saturation magnetization of manganite reduced by approximately 50 times with the insertion of the europium ion in the structure and the manganite with europium showed luminescence when excited in the ligand-metal charge transition band (TCLM). Furthermore, the manganites were subjected to different mechanical conformations on test specimens in the form of tablets. The saturation magnetization of the material increased by around 10 times after applying these mechanical conformations to the europiumcontaining manganite in the structure. There was also an increase in the experimental lifetimes obtained (decay from the 5D0 emitting state). Small variation in the local environment of the Eu3+ ion was observed as a function of the applied mechanical conformation, indicating greater asymmetry in its surroundings.
Manganites are manganese oxides that play an important technological role due to their magnetocaloric properties and colossal magnetoresistance. In this work, the manganites La0.7Sr0.3MnO3 and La0.4Eu0.3Sr0.3MnO3 were prepared by solidstate synthesis by mixing lanthanum, manganese, strontium and europium oxides. A study was carried out on the luminescent, structural, magnetic properties and behavior when applying uniaxial mechanical conformation to form tablets of this manganite. Characterizations were carried out by vibrational spectroscopy in the infrared region with Fourier transform (FTIR-ATR), scanning electron microscopy (SEM), X-ray diffractometry (XRD), X-ray energy dispersion spectroscopy (EDX), by measurements of magnetization as a function of applied field and temperature, and luminescence by photoluminescence electronic spectroscopy. The main results showed that the saturation magnetization of manganite reduced by approximately 50 times with the insertion of the europium ion in the structure and the manganite with europium showed luminescence when excited in the ligand-metal charge transition band (TCLM). Furthermore, the manganites were subjected to different mechanical conformations on test specimens in the form of tablets. The saturation magnetization of the material increased by around 10 times after applying these mechanical conformations to the europiumcontaining manganite in the structure. There was also an increase in the experimental lifetimes obtained (decay from the 5D0 emitting state). Small variation in the local environment of the Eu3+ ion was observed as a function of the applied mechanical conformation, indicating greater asymmetry in its surroundings.