ملخص
The influence of mechanical milling and subsequent sintering of a 2:1 molar mixture of SrCO 3 and Cr-Fe 2O 3 on the formation of SrFeO 3-δ pervoskite-related nanocrystalline particles is investigated. The structural evolution during the formation process is systematically investigated using X-ray diffraction, thermal analysis, X-ray photoelectron spectroscopy and Mössbauer spectroscopy. Premilling the mixture in air for 120 h leads to the incorporation of Sr 2+ in the α-Fe 2O 3 crystal structure thus facilitating the formation of a 2:1 nanocrystalline mixture of SrFeO 3 and SrFeO 2.875 by sintering the pre-milled mixture in air at 800°C (12 h). This temperature is ∼300°C lower than those at which SrFeO 3-δ phases are synthesized by the conventional ceramic techniques. Pre-milling the precursors was found to result in a smaller oxygen deficiency (δ) relative to conventional ceramic synthesis of SrFeO 3-δ. Rietveld refinement of the X-ray diffraction shows the interatomic distances in the resulting SrFeO 2.875 nanocrystalline phase to be slightly different from those of the conventionally prepared bulk leading, in turn, to a crystal structure with tilted polyhedral cationic sites. This structural distortion is related to both small-size and surface effects in the nanoparticles that have no counterparts in the corresponding bulk material. The surface structure of the attained SrFeO 3-δ nanocrystalline particles shows a significant partial reduction of Fe 4+ to Fe 3+ due to ambient conditions and the presence of an appreciable amount of SrCO 3 as well.
اللغة الأصلية | English |
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الصفحات (من إلى) | 2510-2517 |
عدد الصفحات | 8 |
دورية | Journal of Nanoscience and Nanotechnology |
مستوى الصوت | 9 |
رقم الإصدار | 4 |
المعرِّفات الرقمية للأشياء | |
حالة النشر | Published - أبريل 2009 |
ASJC Scopus subject areas
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