The grain boundary (GB) microstructure influences and is influenced by the development of residual stresses during synthesis of polycrystalline thin films. Recent studies have shown that the frustration between the preferred growth direction and rotations of abutting crystals to local cusps in GB energies leads to internal stresses localized within nanoscopic surface layers around the valleys and ridges that form at emergent boundaries (eGBs). Using a combination of continuum frameworks, numerical analyses, and all-atom simulations of bicrystal $\ensuremath{\langle}111\ensuremath{\rangle}$ copper films, we show that eGBs tune their surface morphology and rotation extent in response to external strains. Compression favors rotation to and growth of low-energy GB phases (complexions) at eGB valleys while tension favors the transitions at eGB ridges, a reflection of the stress-induced mass efflux/influx that changes the energetic balance between interfacial and deformation energies. Molecular dynamics simulations of strained and growing bicrystal films reveal that the eGB phase transition is coupled to island formation at the surface triple junctions, providing a direct link between eGB phases and surface step flow. The interplay between eGB structure, morphology, and mechanics emerges as a crucial ingredient for predictive understanding of stress and morphological evolution during film growth, with broad implications for multifunctional response of polycrystalline surfaces in a diverse range of surface phenomena such as surface-mediated deformation, interfacial embrittlement, thermal grooving, stress corrosion, surface catalysis, and topological conduction.
The effect of 0~1mol% MnO 2 doping on microstructure and electrical properties of the Zn–Pr–Co–Cr–Mn-based varistor ceramics was investigated by means of SEM, XRD and standard current-voltage property tests. The increase of MnO 2 doping level strongly decreased the relative density (99%-91.5%) by the effect of pining of Pr 0.96 Mn 0.98 2O3. The nonlinear coefficient increased from 17.4 for MnO 2 -undoped sample to 54 for MnO 2 -doped sample up to 0.5 mol%, whereas the further doping resulted in decrease.
In order to develop infinite capacitive materials with high dielectric constant and low dielectric loss, influences of Y/Mn co-doping and ZrO 2 coating on the dielectric properties of barium strontium tinanate/polyvinylidene fluoride (BST/PVDF) composite films were systematically investigated with fixing Y concentration as 0.3 at.% and varying Mn concentration from 1 at.% to 4 at.%. The experimental results show that the dielectric constant of BST@ZrO 2 /PVDF composite increases by 50% relative to BST/PVDF and the dielectric loss is evidently depressed. In comparison with BST@ZrO 2 /PVDF sample, furthermore, the dielectric constant of Y/Mn co-doped BST@ZrO 2 /PVDF samples increases by about 60% and the dielectric loss further reduces at 1 kHz. The promoted dielectric performances of composite originate from the space charge separation formed by Y/Mn co-doping and the limitation of electronic mobility by coated ZrO 2 . Y/Mn co-doped BST@ZrO 2 /PVDF composite film with 3% Mn has a dielectric constant of 37.9, a dielectric loss of 0.0117, superior dielectric temperature stability (3.1% from −5[Formula: see text]C to 45[Formula: see text]C at 1 kHz), and a discharged energy density of 5.67 J/cm 3 at 600 kV/cm. The simultaneous optimization of dielectric constant and dielectric loss of BST/PVDF composite is realized in this experiment. The superior dielectric temperature stability suggests the application potential of Y/Mn co-doped BST@ZrO 2 /PVDF as wearable capacitors.
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