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首页> 外文期刊>Zeitschrift fur Anorganische und Allgemeine Chemie >Site Preference of Rare Earth Doping in Palladium-Iron-Arsenide Superconductors
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Site Preference of Rare Earth Doping in Palladium-Iron-Arsenide Superconductors

机译：钯-铁-砷超导体中稀土掺杂的位置偏好

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摘要

The solid solutions (Ca1-yREyFe1-xPdxAs)(10)PdzAs8 with RE = La, Ce, and Pr were synthesized by solid state methods and characterized by X-ray powder diffraction with subsequent Rietveld refinements [(CaFeAs)(10)Pt3As8-type structure ("1038 type"), P (1) over bar, Z = 1]. Substitution levels (Ca/RE, Fe/Pd, and Pd/square) obtained from Rietveld refinements coincide well with the nominal values according to EDS and the linear courses of the lattice parameters as expected from the ionic radii. The RE atoms favor the one out of five calcium sites, which is eightfold coordinated by arsenic. This leads to significant stabilization of the structure, and especially prevents palladium over-doping in the iron-arsenide layers as observed in the pristine compound (CaFe1-xPdxAs)(10)PdzAs8. While the stabilization energy is estimated to about 40 kJ.mol(-1) by electronic structure calculations, the reason for the diminished Fe/Pd substitution through RE doping is still not yet understood. We suggest that the electrons transferred from RE3+ to the (Fe1-xPdx) As layer makes higher palladium concentrations unfavorable. Anyway the reduced palladium doping enables superconductivity with critical temperatures up to 20 K (onset) in the RE doped Pd1038 samples, which could not be obtained earlier due to palladium over-doping in the active iron-arsenide layers.
机译：通过固态方法合成具有RE = La，Ce和Pr的固溶体（Ca1-yREyFe1-xPdxAs）（10）PdzAs8，并通过X射线粉末衍射和随后的Rietveld精制[（CaFeAs）（10）Pt3As8-类型结构（“ 1038类型”），横条上的P（1），Z = 1]。从Rietveld精炼获得的取代水平（Ca / RE，Fe / Pd和Pd /平方）与根据EDS的标称值和离子半径所期望的晶格参数的线性变化过程非常吻合。 RE原子偏爱五个钙位中的一个，这是砷配比的八倍。如原始化合物（CaFe1-xPdxAs）（10）PdzAs8中所观察到的那样，这将导致结构的显着稳定，并特别防止钯在砷化铁层中的过度掺杂。虽然通过电子结构计算估计稳定能约为40 kJ.mol（-1），但仍不清楚通过RE掺杂减少Fe / Pd取代的原因。我们建议电子从RE3 +转移到（Fe1-xPdx）As层会使较高的钯浓度不利。无论如何，减少的钯掺杂可在RE掺杂的Pd1038样品中在高达20 K（起始）的临界温度下实现超导性，这是由于有源砷化铁层中的钯超掺杂而无法较早获得的。

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