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A BiFeO₃film is grown epitaxially on a PrScO₃single crystal substrate which imparts ~ 1.45% of biaxial tensile strain to BiFeO₃resulting from lattice misfit. The biaxial tensile strain effect on BiFeO₃is investigated in terms of crystal structure, Poisson ratio, and ferroelectric domain structure. Lattice resolution scanning transmission electron microscopy, precession electron diffraction, and X-ray diffraction results clearly show that in-plane interplanar distance of BiFeO₃is the same as that of PrScO₃with no sign of misfit dislocations, indicating that the biaxial tensile strain caused by lattice mismatch between BiFeO₃and PrScO₃are stored as elastic energy within BiFeO₃film. Nano-beam electron diffraction patterns compared with structure factor calculation found that the BiFeO₃maintains rhombohedral symmetry, i.e., space group ofR3c. The pattern analysis also revealed two crystallographically distinguishable domains. Their relations with ferroelectric domain structures in terms of size and spontaneous polarization orientations within the domains are further understood using four-dimensional scanning transmission electron microscopy technique.

 

Cu3Sn, a well-known intermetallic compound with a high melting temperature and thermal stability, has found numerous applications in microelectronics, 3D printing, and catalysis. However, the relationship between the material's thermal conductivity anisotropy and its complex anti-phase boundary superstructure is not well understood. Here, frequency domain thermoreflectance was used to map the thermal conductivity variation across the surface of arc-melted polycrystalline Cu3Sn. Complementary electron backscatter diffraction and transmission electron microscopy revealed the thermal conductivity in the principal a, b, and c orientations to be 57.6, 58.9, and 67.2 W/m-K, respectively. Density functional theory calculations for several Cu3Sn superstructures helped examine thermodynamic stability factors and evaluate the direction-resolved electron transport properties in the relaxation time approximation. The analysis of computed temperature- and composition-dependent free energies suggests metastability of the known long-period Cu3Sn superstructures while the transport calculations indicate a small directional variation in the thermal conductivity. The ∼15% anisotropy measured and computed in this study is well below previously reported experimental values for samples grown by liquid-phase electroepitaxy.