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Ag2Se到KAg3Se2:通过缩小维度来抑制秩序-混乱过渡
Alexander J E Rettie1, Christos D Malliakas2, Antia S Botana1
1Materials Science Division , Argonne National Laboratory , Argonne , Illinois 60439 , United States.
Journal of the American Chemical Society
|June 28, 2018
概括
我们在二维半导体KAg3Se2中发现了一种秩序-混乱相位转换, 这种转变影响其热和电子特性,为设计新材料提供了洞察力.
科学领域:
- 材料科学
- 固态物理
- 晶体学
背景情况:
- 缩小尺寸是一种调整材料特性的策略.
- 银化物 (Ag2Se) 呈现出有趣的相变和离子导电性.
- 对于新型应用来说,了解缩小维度材料的相位过渡至关重要.
研究的目的:
- 研究二维半导体KAg3Se2的相位转换和特性.
- 将KAg3Se2的行为与其3D父化合物Ag2Se进行比较.
- 探索材料设计中的尺寸缩小的潜力.
主要方法:
- 在现场依赖温度的X射线衍射以研究相位过渡.
- 紫外线光谱测量以确定光带间隙.
- 电子结构计算
- 电子运输测量
主要成果:
- 在~695 K时,KAg3Se2从单临床 (β) 阶段转变为六角 (α) 阶段.
- 观察到显著的Ag+离子干扰,类似于3D Ag2Se中的超离子过渡.
- 在有序β-阶段的超低导热率 (~0.4 W m-1 K-1).
- β-KAg3Se2 的间接光学带间隙为~1 eV.
- 在300 K时具有高电子流动性的n型行为 (~400 cm2 V-1 s-1).
结论:
- 在KAg3Se2的尺寸缩小导致了具有显著的Ag+离子障碍的秩序-障碍相位过渡.
- 即使在有序阶段,无调的Ag运动也会导致超低的导热率.
- 由于其降低的维度,KAg3Se2显示出有前途的电子特性 (n型,高流动性).
- 尺寸缩小可以作为控制相位转换的策略,同时保持理想的电子和热性质.
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