کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1607065 | 1516232 | 2016 | 8 صفحه PDF | دانلود رایگان |
• Two novel Mn-containing double perovskites were obtained by citrate method.
• Their crystallographic structures were determined by XRPD and NPD.
• The electronic configurations are Mn2+(3 d5)–Mo5+(4 d1) deduced from XANES and NPD.
• The Impedance Spectroscopy evidences the localized behaviour of 4 d1 electrons in Mo.
Sr3MnMo2O9 and Ba3MnMo2O9 double perovskites with Mo5+ valence states have been prepared in polycrystalline form by thermal treatment, in reducing atmosphere (H2/N2 flow), of previously decomposed citrate precursors. These materials have been studied by X-ray and neutron powder diffraction (XRPD, NPD), magnetic and transport measurements. At room temperature, the crystal structure of Sr3MnMo2O9 is monoclinic, space group P21/n, with a = 5.6564(1) Å, b = 5.6383(1) Å, c = 7.9765(2) Å, β = 89.994(7)º; whereas Ba3MnMo2O9 presents a cubic lattice, space group Fm 3¯m, with a = 8.14900(8) Å. These samples present a frustrated magnetic interaction below to 12 and 9 K for Sr3MnMo2O9 and Ba3MnMo2O9, respectively. Semiconductor behaviour, observed either from d.c. or a.c. measurements, was modelled by a variable-range hopping mechanism. This transport behaviour is in accord with the electronic configurations Mn2+(3 d5)–Mo5+(4 d1) and supports the absence of mixed valence states in both double perovkites.
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Journal: Journal of Alloys and Compounds - Volume 661, 15 March 2016, Pages 411–418