Popuri Srinivasa R, Redpath Debbie, Chan Gavin, Smith Ronald I, Cespedes Oscar, Bos Jan-Willem G
Institute of Chemical Sciences and Centre for Advanced Energy Storage and Recovery, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, UK.
Dalton Trans. 2015 Jun 21;44(23):10621-7. doi: 10.1039/c4dt03307h. Epub 2014 Dec 15.
Structure analysis using X-ray and neutron powder diffraction and elemental mapping has been used to demonstrate that nominal A-site deficient Sr(2-x)FeMoO(6-δ) (0 ≤x≤ 0.5) compositions form as Mo-rich Sr(2)Fe(1-y)Mo(1+y)O(6) (0 ≤y≤ 0.2) perovskites at high temperatures and under reducing atmospheres. These materials show a gradual transition from the Fe and Mo rock salt ordered double perovskite structure to a B-site disordered arrangement. Analysis of the fractions of B-O-B' linkages revealed a gradual increase in the number of Mo-O-Mo linkages at the expense of the ferrimagnetic (FIM) Fe-O-Mo linkages that dominate the y = 0 material. All samples contain about 10-15% antiferromagnetic (AF) Fe-O-Fe linkages, independent of the degree of B-site ordering. The magnetic susceptibility of the y = 0.2 sample is characteristic of a small domain ferrimagnet (T(c)∼ 250 K), while room temperature neutron powder diffraction demonstrated the presence of G-type AF ordering linked to the Fe-O-Fe linkages (m(Fe) = 1.25(7)μ(B)). The high temperature thermoelectric properties are characteristic of a metal with a linear temperature dependence of the Seebeck coefficient, S (for all y) and electrical resistivity ρ (y≥ 0.1). The largest thermoelectric power factor S(2)/ρ = 0.12 mW m(-1) K(-1) is observed for Sr(2)FeMoO(6) at 1000 K.
利用X射线和中子粉末衍射以及元素映射进行的结构分析已被用于证明，名义上A位缺陷的Sr(2-x)FeMoO(6-δ)（0≤x≤0.5）组合物在高温和还原气氛下形成富含Mo的Sr(2)Fe(1-y)Mo(1+y)O(6)（0≤y≤0.2）钙钛矿。这些材料显示出从Fe和Mo岩盐有序双钙钛矿结构到B位无序排列的逐渐转变。对B - O - B'键分数的分析表明，Mo - O - Mo键的数量逐渐增加，而以在y = 0的材料中占主导的亚铁磁性（FIM）Fe - O - Mo键为代价。所有样品都含有约10 - 15%的反铁磁性（AF）Fe - O - Fe键，与B位有序程度无关。y = 0.2样品的磁化率是小畴亚铁磁体的特征（居里温度T(c) ∼ 250 K），而室温中子粉末衍射表明存在与Fe - O - Fe键相关的G型AF有序（铁磁矩m(Fe) = 1.25(7)μ(B)）。高温热电性质是一种金属的特征，其塞贝克系数S（对于所有y）和电阻率ρ（y≥0.1）具有线性温度依赖性。在1000 K时，Sr(2)FeMoO(6)的最大热电功率因子S(2)/ρ = 0.12 mW m(-1) K(-1)。
