The role of defects on the structural and magnetic properties of Nb2O5
| Autor: | Ernesto C. Pereira, Ariano De Giovanni Rodrigues, Marcio P.F. de Godoy, Adilson J.A. de Oliveira, L. K. S. Herval, Adriano C. Rabelo, Driele von Dreifus, Yara Galvão Gobato |
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| Rok vydání: | 2015 |
| Předmět: |
Phase transition
Materials science Magnetic moment Annealing (metallurgy) Mechanical Engineering Anharmonicity Metals and Alloys symbols.namesake Paramagnetism Magnetization Nuclear magnetic resonance Mechanics of Materials Materials Chemistry symbols Physical chemistry Orthorhombic crystal system Raman spectroscopy |
| Zdroj: | Journal of Alloys and Compounds. 653:358-362 |
| ISSN: | 0925-8388 |
| DOI: | 10.1016/j.jallcom.2015.09.019 |
| Popis: | Defects play a fundamental issue on physical properties of wide bandgap materials. We present here the effect of preparation and annealing conditions on the properties of Nb 2 O 5 synthesized by Pechini method. Structural characterization, Raman spectroscopy and magnetic measurements show significant experimental fingerprints related to the presence of oxygen defects in the system. The increase of oxygen vacancies causes an irreversible phase transition from pseudohexagonal (TT-phase) to orthorhombic phase (T-phase). The critical temperature range around 400 °C during thermal annealing is derived by in-situ Raman measurements applying the theory of phonon anharmonicity. We observed that the values of Nb 2 O 5 Curie constants as (4.37 ± 0.06)10 −4 emu K/mol and (20.50 ± 0.08)10 −4 emu K/mol for TT- and T-phases respectively. The oxygen vacancies are the responsible for 10 21 –10 22 effective magnetic moments per mol related to paramagnetic behavior. |
| Databáze: | OpenAIRE |
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