In situ study on atomic mechanism of melting and freezing of single bismuth nanoparticles

• Published in: Nature communications Vol. 8; no. 1; p. 14462
• Main Authors: Li, Yingxuan, Zang, Ling, Jacobs, Daniel L., Zhao, Jie, Yue, Xiu, Wang, Chuanyi
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 13-02-2017; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301/357/354; 639/638/440/950; 639/766/119/2795; 639/925/930/328/2082; Crystallization; Humanities and Social Sciences; multidisciplinary; Nanoparticles; Phase transitions; Point defects; Science; Science (multidisciplinary); United States > US; China; Utah
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms14462

Experimental study of the atomic mechanism in melting and freezing processes remains a formidable challenge. We report herein on a unique material system that allows for
in situ
growth of bismuth nanoparticles from the precursor compound SrBi
2
Ta
2
O
9
under an electron beam within a high-resolution transmission electron microscope (HRTEM). Simultaneously, the melting and freezing processes within the nanoparticles are triggered and imaged in real time by the HRTEM. The images show atomic-scale evidence for point defect induced melting, and a freezing mechanism mediated by crystallization of an intermediate ordered liquid. During the melting and freezing, the formation of nucleation precursors, nucleation and growth, and the relaxation of the system, are directly observed. Based on these observations, an interaction–relaxation model is developed towards understanding the microscopic mechanism of the phase transitions, highlighting the importance of cooperative multiscale processes.
The atomic mechanisms of reversible phase transitions are challenging to probe experimentally. Here, the authors induce melting and freezing processes in bismuth nanoparticles inside a high-resolution electron microscope, observing the atom-level stages of this phase transition pathway in real time.