Soft chemical control of superconductivity in lithium iron selenide hydroxides Li(1-x)Fe(x)(OH)Fe(1-y)Se.
Soft chemical control of superconductivity in lithium iron selenide hydroxides Li(1-x)Fe(x)(OH)Fe(1-y)Se.
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DOI：
10.1021/ic5028702
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发表时间：
2014-08
影响因子：
4.6
通讯作者：
Hualei Sun;D. Woodruff;S. Cassidy;Genevieve M. Allcroft;S. Sedlmaier;A. Thompson;P. Bingham;S. Forder
中科院分区：
文献类型：
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作者：
Hualei Sun;D. Woodruff;S. Cassidy;Genevieve M. Allcroft;S. Sedlmaier;A. Thompson;P. Bingham;S. Forder
描述了在硒化铁层中具有宽范围的铁位空位浓度的层状锂铁硒化氢氧化物Li（1-x）Fe（x）（OH）Fe（1-y）Se（x ≤ 0.2; 0.02 < y < 0.15）的水热合成。铁空位浓度是唯一重要的组成变量，也是控制晶体结构和电子性质的关键参数。单晶X射线衍射、中子粉末衍射和X射线吸收光谱测量结果表明，当铁空位浓度较低时，在水热合成的样品中观察到高达40 K的超导性（y < 0.05）并且当铁的氧化态降低到略低于+2时，而具有较高空位浓度和相应较高铁氧化态的样品不是超导的。通过证明样品的还原合成后锂化通过从Li（1-x）Fe（x）（OH）储层置换铁原子以填充硒化物层中的空位而在临界温度超过40 K时开启超导性，强调了将低铁氧化态与低空位浓度的铁硒化物层相结合的重要性。
Hydrothermal synthesis is described of layered lithium iron selenide hydroxides Li(1-x)Fe(x)(OH)Fe(1-y)Se (x ∼ 0.2; 0.02 < y < 0.15) with a wide range of iron site vacancy concentrations in the iron selenide layers. This iron vacancy concentration is revealed as the only significant compositional variable and as the key parameter controlling the crystal structure and the electronic properties. Single crystal X-ray diffraction, neutron powder diffraction, and X-ray absorption spectroscopy measurements are used to demonstrate that superconductivity at temperatures as high as 40 K is observed in the hydrothermally synthesized samples when the iron vacancy concentration is low (y < 0.05) and when the iron oxidation state is reduced slightly below +2, while samples with a higher vacancy concentration and a correspondingly higher iron oxidation state are not superconducting. The importance of combining a low iron oxidation state with a low vacancy concentration in the iron selenide layers is emphasized by the demonstration that reductive postsynthetic lithiation of the samples turns on superconductivity with critical temperatures exceeding 40 K by displacing iron atoms from the Li(1-x)Fe(x)(OH) reservoir layer to fill vacancies in the selenide layer.