Unraveling Thermodynamic and Kinetic Contributions to the Stability of Doped Nanocrystalline Alloys using Nanometallic Multilayers (Adv. Mater. 27/2022)

Gibbs Adsorption and Zener Pinning Enable Mechanically Robust High‐Performance Bi2Te3‐Based Thermoelectric Devices

“…The propensity of grain growth depends on the GB velocity ( v ), as described by [ 42 ] $$$$\begin{equation}v\ = {M}_{{\mathrm{GB}}}P\ = {M}_0{{\mathrm{e}}}^{\frac{{ - Q}}{{RT}}}\frac{{2{\gamma }_{{\mathrm{GB}}}}}{r}\end{equation}$$$$where M GB is the GB mobility determined by the activation energy for GB migration ( Q ), and P is the driving force for grain growth determined by the GB energy ( γ GB ) and the principal radius of curvature ( r ). Equation () demonstrates that the GB velocity and thus the grain growth can be inhibited by reducing the GB energy thermodynamically and suppressing the GB migration kinetically.…”

Strain‐Driven Thermal and Optical Instability in Silver/Amorphous‐Silicon Hyperbolic Metamaterials

“…Here, the anisotropic elastic strain energy due to thermal expansion mismatch is identified as the predominant driving force. Most previous literature on multilayer instabilities disregards this effect and treats the morphological redistribution in the context of interfacial energy minimization, including work on sputtered Ag/a‐Si multilayers, [ 44,45 ] other systems with high CTE missmatch, [ 46–48 ] predictive models, [ 39,49 ] and reviews. [ 50 ] It should be noted that these conclusions are often based on experiments using transmission electron microscopy (TEM).…”

“…Our results indicate that the main driving force is the inhomogeneous elastic strain energy caused by a mismatch in thermal expansion between the metallic phase of the metamaterial and the substrate. This contribution has often been disregarded [ 39,47 ] or assumed to be homogeneous. [ 38 ] Notably, the observed instability is tightly related to the HMM design, as co‐sputtered Ag/a‐Si [ 55 ] thin films preserve their structural integrity in the studied temperature range.…”

Enthalpy‐Driven Self‐Healing in Thin Metallic Films on Flexible Substrates

“…[30,54,56] Due to the combination of highly positive mixing enthalpy (H mix ) [34] and the low segregation enthalpy (H seg ) (positive for Mo-rich, negative for Ag-rich) [34] for both the Mo-rich and Ag-rich alloys, the metastable alloy should decompose into separated polycrystals given enough temperature and time. [33] The negative H seg for Ag-rich alloys indicates that, as for Ni impurities in Cu, [57] the solute (Mo) is even repelled from the grain boundary. [34,57] The phase separation is shown by the polycrystalline Ag fillings of the cracks (Figure 3a), the surface segregations (Figure 2) and the homogeneous distribution of Ag inside Mo in the TEM-EDX image (Figure 3b).…”

“…[32] The nanoparticles formation in the metastable Mo-Ag system is driven by phaseseparation into polycrystals due to highly positive enthalpy of mixing (H mix ) that outweighs the enthalpy of segregation (H seg ) significantly. [33,34] Due to the biocompatibility, hydrophilicity and particle formation of the Mo 1-x Ag x (18≤x≤58.9) system, it can be used to create an effective substrate for surface-enhanced Raman scattering. [32,[35][36][37] With high Ag contents (87 at%), the binary system is known to have strong light-trapping properties.…”