摘要
本文以覆盖Nb薄膜的半赫斯勒合金Nb_(0.8)CoSb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_(0.8)CoSb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_(0.8)4CoSb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~*-2c~*)/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 Nb0.8CoSb half-Heusler alloy covered with Nb films.By employing in-situ heating transmission electron microscopy(TEM)technique,diffusion of Nb is observed at high temperature,showing the ordering transformation from Nb0.8CoSb to Nb0.8+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 Nb0.8CoSb sample transform into superlattice diffraction spots representing long-range order.The modulation wave vector of this superstructure is determined to be.This structural evolution primarily arises from the diffusion of Nb atoms from the Nb film into the Nb0.8CoSb sample at high temperature,leading to compositional changes in Sb and Nb.Further comparative analysis reveals significant differences between in-situ synthesized Nb0.8+δCoSb samples and ex-situ synthesized Nb0.84CoSb samples despite both exhibiting superstructures.In the ex-situ synthesized Nb0.84CoSb,the modulation wave vector of the superstructure is,which is mainly attributed to Nb compositional variations.Moreover,the superstructure in Nb0.84CoSb sample can remain stable from room temperature to high temperature,whereas in Nb0.8+δCoSb samples,it only exists at elevated temperatures and gradually weakens as the temperature decreases,suggesting that it may be a metastable structure between Nb0.8CoSb and Nb0.84CoSb.This study reveals the diversity of superstruc-tures 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.
作者
李其柱
范浩涵
高梓恒
南鹏飞
朱铁军
葛炳辉
Li Qi-Zhu;Fan Hao-Han;Gao Zi-Heng;Nan Peng-Fei;Zhu Tie-Jun;Ge Bing-Hui(Information Materials and Intelligent Sensing Laboratory of Anhui Province,Institute of Physical Science and Information Technology,Anhui University,Hefei 230601,China;State Key Laboratory of Silicon and Advanced Semiconductor Materials,School of Materials Science and Engineering,Zhejiang University,Hangzhou 310027,China)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2024年第11期273-279,共7页
Acta Physica Sinica
基金
国家自然科学基金(批准号:11874394,92163203)资助的课题。
关键词
固态相变
原位加热
短程有序
半赫斯勒合金
solid-state phase transition
in-situ heating
short-range ordering
half-Heusler alloy
