Increasing energy demands require new materials, e.g., thermoelectrics, for efficient energy conversion of fossil fuels. However, their low figure of merit (ZT) limits widespread applications. Nanostructuring has been an effective way of lowering the thermal conductivity. However, grain growth at elevated temperature is still a big concern, for otherwise expected to be long-lasting thermoelectric generators. Here, we report a porous architecture containing nano- to micrometer size irregularly shaped and randomly oriented pores, scattering a wide spectrum of phonons without employing the conventional rattling phenomenon. Lattice thermal conductivity reaches the phonon glass limit. This design yields >100% enhancement in ZT, as compared to the pristine sample. An unprecedented and very promising ZT of 1.6 is obtained for Co23.4Sb69.1Si1.5Te6.0 alloy, by far the highest ZT ever reported for un-filled skutterudites, with further benefits, i.e. rare-earth-free and improved oxidation resistance enabling simple processing

A transition of the deformation mode from heterogeneous, localized deformation to homogeneous deformation was observed in Zr₅₀Cu₄₀Al₁₀ bulk metallic glass (BMG) by giant straining using the high-pressure torsion (HPT) method. The transition is accompanied by a pronounced decrease in hardness and elastic modulus as measured by nanoindentation. Annealing of the deformed BMG resulted in the restoration of the localized deformation, hardness, and elastic modulus; thus, the transition is reversible. The observed reversible transition can be attributed to a change in the local atomic environment in the rejuvenated volume and the relaxed one.