Phase separation-induced nanoscale heterogeneity in Gd5Si1.5Ge2.5. (15th September 2020)

• Record Type: Journal Article
• Authors: Kou, Ronghui; Chen, Zhongwei; Ouyang, Sheng; Gao, Jianrong
• Is Part Of: Acta materialia. Volume 197(2020)
• Page Start: 163
• Page End: 171
• Publication Date: 2020-09-15
• Subjects: Gd5(Si, Ge)4 -- High resolution transmission electron microscopy -- Heterogeneity -- Nanodomains -- Phase separation; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2020.07.044
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: Pseudobinary Gd5 (Si, Ge)4 compounds show a giant magnetocaloric effect due to an intriguing structure-magnetism interplay. Here, we report a high resolution transmission electron microscopic study of microstructure in a melt-grown compound of Gd5 Si1.5 Ge2.5 . Electron diffraction showed that mesoscopic microstructure of the compound consists of crystals of a monoclinic structure and two kinds of orthorhombic structure. However, atomic-level imaging revealed a coexistence of mosaic-like nanodomains of these structures in each crystal. The nanodomains have twin-like interfaces along the b axis of the crystal but have semicoherent interfaces along a perpendicular axis due to stacking faults. Such a nanoscale structural heterogeneity is due to covalent bond-controlled phase separation at elevated temperatures. This finding offers insights into phase relations and abnormal magnetic behavior of Gd5 (Si, Ge)4 compounds and points out a route of synthesizing bulk nanocomposites via nanoscale phase separation. Graphical abstract: Image, graphical abstract