在YbGaGe系统中,在5K时存在价值不稳定性,相位过渡和急剧格子扩张
Serena Margadonna1, Kosmas Prassides, Andrew N Fitch
1Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, UK. sm413@cam.ac.uk
Journal of the American Chemical Society
|April 9, 2004
概括
混合价值YbGa1.05Ge0.95表现出负热膨胀,原因是5K的Yb价值突然过渡. 高温导致结构障碍和最终崩.
科学领域:
- 材料科学 材料科学 材料科学
- 凝聚物质物理学 凝聚物质物理学
- 固态化学 固态化学
背景情况:
- 混合价值化合物具有复杂的电子和结构性质.
- 多层材料具有独特的热膨胀特性.
- 基于伊特 (Yb) 的化合物已知存在价值波动.
研究的目的:
- 研究YbGa1.05Ge0.95从3-1123 K.的热膨胀情况.
- 用温度来描述相位转换和结构变化.
- 了解Yb价值状态在物质行为中的作用.
主要方法:
- 使用粉末同步射线X射线衍射.
- 温度依赖的测量是在广泛的范围 (3-1123 K) 中进行的.
主要成果:
- 在5K时观察到带有负热膨胀的突然同对称相位过渡.
- 这种转变是由Yb的价值转移驱动的,从+(2+epsilon) 转向+2.2.
- 在1123K,该结构转化为AlB2型,具有同Yb和无序的Ga/Ge平面.
结论:
- Yb的价值状态显著影响YbGa1.05Ge0.95.5的热膨胀.
- 该材料在低温下表现出独特的负热膨胀行为.
- 观察到高温结构不稳定性和最终的崩.
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