-
本文以覆盖Nb薄膜的半赫斯勒合金Nb 0.8CoSb为研究对象, 成功利用原位加热透射电镜技术在高温下诱导Nb扩散, 致使Nb 0.8CoSb转变为有序度更高的Nb 0.8+δCoSb, 即倒空间漫散带代表的短程有序结构转变为超结构衍射点代表的长程有序结构. 进一步的分析表明, 这种超结构的调制波矢为
$ q= ({a}^{*}+{b}^{*}-{c}^{*})/{3} $ , 其形成主要源自于Sb和Nb组分的变化. 与离位合成的Nb 0.84CoSb的微观结构进行对比, 发现二者中超结构不同, 这种超结构的调制波矢为$ q= ({2a}^{*}-2{c}^{*})/3 $ , 主要源自于Nb组分的变化. 此项研究揭示了组分导致超结构的多样性以及半赫斯勒合金结构相变的复杂性, 丰富了对半赫斯勒合金材料的理解, 对相变材料的设计以及功能调控具有重要指导意义.This study focuses on the investigation of Nb 0.8CoSb half-Heusler alloy covered with Nb films. By employing in-situheating transmission electron microscopy (TEM) technique, diffusion of Nb is observed at high temperature, showing the ordering transformation from Nb 0.8CoSb to Nb 0.8+δCoSb. Through observations of high-angle annular dark-field (HAADF) images and selected-area electron diffraction (SAED) patterns, it is found that under elevated temperatures, the diffuse streaks representing short-range disorder in Nb 0.8CoSb sample transform into superlattice diffraction spots representing long-range order. The modulation wave vector of this superstructure is determined to be $ q={1}/{3}({a}^{*}+{b}^{*}-{c}^{*}) $ . This structural evolution primarily arises from the diffusion of Nb atoms from the Nb film into the Nb 0.8CoSb sample at high temperature, leading to compositional changes in Sb and Nb.Further comparative analysis reveals significant differences between in-situsynthesized Nb 0.8+δCoSb samples and ex-situsynthesized Nb 0.84CoSb samples despite both exhibiting superstructures. In the ex-situsynthesized Nb 0.84CoSb, the modulation wave vector of the superstructure is $ q={1}/{3}({2a}^{*}-2{c}^{*}) $ , which is mainly attributed to Nb compositional variations. Moreover, the superstructure in Nb 0.84CoSb sample can remain stable from room temperature to high temperature, whereas in Nb 0.8+δCoSb samples, it only exists at elevated temperatures and gradually weakens as the temperature decreases, suggesting that it may be a metastable structure between Nb 0.8CoSb and Nb 0.84CoSb.This study reveals the diversity of superstructures induced by compositional variations and the complexity of structural phase transitions in half-Heusler alloys, enriching the understanding of these materials and providing important guidance for the design and functional control of phase-change materials. 
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] -
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29]
下载:
计量
- 文章访问数:929
- PDF下载量:47
- 被引次数:0