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arXiv 2201.13116cond-mat.mtrl-sci
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AgInTe$_2$在常压与高压下的NMR研究

NMR study of AgInTe$_2$ at normal and high pressure

Robin Guehne, Carsten Kattinger, Marko Bertmer, Simon Welzmiller, Oliver Oeckler, Jürgen Haase

AI总结:

本文利用$^{115}$In和$^{125}$Te NMR研究AgInTe$_2$在常压及高压下的局域结构与电子性质,揭示阳离子无序、四极相互作用突变及高压相变,并证实卸压后出现高度无序的亚稳态常压相。

摘要:

三元半导体AgInTe$_2$是一种具有黄铜矿型结构的热电材料,在高压下可逆地转变为岩盐型结构。核磁共振(NMR)被认为能够在原子间长度尺度上提供对材料性质的独特认识,尤其是在结构相变的背景下。本文利用$^{115}$In和$^{125}$Te NMR研究了AgInTe$_2$在常压及高达5 GPa压力下的行为。$^{125}$Te的磁场依赖实验和魔角旋转(MAS)实验证明存在显著增强的核间耦合,以及各向同性化学位移的分布,表明存在一定程度的阳离子无序。$^{115}$In的间接核耦合较小,化学位移分布也较小,与晶体结构一致。$^{115}$In NMR进一步受较小的四极相互作用($ν_\mathrm{Q} \approx$ 90 kHz)支配,并且其核弛豫速度比$^{125}$Te快数个数量级。在约3 GPa压力下,$^{115}$In四极相互作用急剧增加至约2400 kHz,表明发生了向具有明确但非立方局域对称性结构的相变,而$^{115}$In的位移表明电子结构没有显著变化。在约5 GPa以上(至少到约10 GPa),NMR信号消失。然而,在释放压力后信号恢复,指向已报道的具有高度无序的亚稳态常压相。

英文摘要:

The ternary semiconductor AgInTe$_2$ is a thermoelectric material with chalcopyrite-type structure that transforms reversibly into a rocksalt-type structure under high pressure. Nuclear magnetic resonance (NMR) is considered to provide unique insight into material properties on interatomic length scales, especially in the context of structural phase transitions. Here, $^{115}$In and $^{125}$Te NMR is used to study AgInTe$_2$ for ambient conditions and pressures up to 5 GPa. Magnetic field dependent and magic angle spinning (MAS) experiments of $^{125}$Te prove strongly enhanced internuclear couplings, as well as a distribution of isotropic chemical shifts suggesting a certain degree of cation disorder. The indirect nuclear coupling is smaller for $^{115}$In, as well as the chemical shift distribution in agreement with the crystal structure. The $^{115}$In NMR is further governed by a small quadrupolar interaction ($ν_\mathrm{Q} \approx$ 90 kHz) and shows an orders of magnitude faster nuclear relaxation in comparison to that of $^{125}$Te. At a pressure of about 3 GPa, the $^{115}$In quadrupole interaction increases sharply to about 2400 kHz, indicating a phase transition to a structure with a well defined, though non-cubic local symmetry, while the $^{115}$In shift suggests no significant changes of the electronic structure. The NMR signal is lost above about 5 GPa (at least up to about 10 GPa). However, upon releasing the pressure a signal is recovered that points to the reported metastable ambient pressure phase with a high degree of disorder.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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