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Magnesium doping on brownmillerite Ca2FeAlO5 |
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| Authors: | J. Malveiro L.P. Ferreira M.R. Nunes M.D. Carvalho |
| Affiliation: | a CCMM, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal b CFMC-UL, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa; Dep. Física, Faculdade de Ciências e Tecnologia, Universidade de Coimbra, 3004-516 Coimbra, Portugal c Dep. Química, ITN/CFMC-UL, Estrada Nacional 10, P-2686-953 Sacavém, Portugal d CCMM/Dep. Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, C8, 1749-016 Lisboa, Portugal e CFMC-UL/Dep. Física, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal |
| Abstract: | Ca2FeAl1−xMgxO5 (x=0, 0.05 and 0.1) compounds adopting the brownmillerite-type structure were prepared by a self-combustion route using two different fuels. Characterisation was performed using X-ray powder diffraction, Mössbauer spectroscopy, magnetisation measurements, chemical analysis, scanning electron microscopy and 4-point dc conductivity measurements. Global results indicate that the solubility limit was reached for x=0.1. An antiferromagnetic behaviour was detected for all studied compositions, with magnetic ordering temperatures of 340 and 290 K for x=0 and 0.05, respectively. Mg doping increases the number of iron cations in tetrahedral sites, which induces magnetisation enhancement at low temperatures through the coupling between octahedral iron cations in different octahedral planes. The compounds exhibit semiconductor behaviour and Mg2+ doping yields a significant enhancement of the total conductivity, which can be essentially attributed to the presence of Fe4+ ions. |
| Keywords: | Brownmillerite Self-combustion synthesis Mö ssbauer spectroscopy |
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