Dislocations are commonly present and important in metals but their effects have not been fully recognized in oxide ceramics. The large strain energy raised by the rigid ionic/covalent bonding in oxide ceramics leads to dislocations with low density (∼106 mm−2), thermodynamic instability and spatial inhomogeneity. In this paper, we report ultrahigh density (∼109 mm−2) of edge dislocations that are uniformly distributed in oxide ceramics with large compositional complexity. We demonstrate the dislocations are progressively and thermodynamically stabilized with increasing complexity of the composition, in which the entropy gain can compensate the strain energy of dislocations. We also find cracks are deflected and bridged with ∼70% enhancement of fracture toughness in the pyrochlore ceramics with multiple valence cations, due to the interaction with enlarged strain field around the immobile dislocations. This research provides a controllable approach to establish ultra-dense dislocations in oxide ceramics, which may open up another dimension to tune their properties.

The localized vibration in SrTi11O20 forms low-lying optical phonon bands that distort acoustic phonon branches through the avoided crossing effect. The electrical and thermal transport are decoupled to achieve phonon-glass electron-crystal behaviour.

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The flexible thermoelectric (TE) generator has emerged as a superior alternative to traditional batteries for powering wearable electronic devices, as it can efficiently convert skin heat into electricity without any safety concerns. MXene, a highly researched twodimensional material, is known for its exceptional flexibility, hydrophilicity, metallic conductivity, and processability, among other properties, making it a versatile material for a wide range of applications, including supercapacitors, electromagnetic shielding, and sensors. However, the low intrinsic Seebeck coefficient of MXene due to its metallic conducting nature poses a significant challenge to its TE application. Therefore, improving the Seebeck coefficient remains a primary concern. In this regard, a flexible MXene/organics/TiS 2 misfit film was synthesized in this work through organic intercalation, exfoliation, and re-assembly techniques. The absolute value of Seebeck coefficient of the misfit film was significantly enhanced to 44.8 μV K −1 , which is five times higher than that of the original MXene film. This enhancement is attributed primarily to the weighted effect of the Seebeck coefficient and possibly to energy-filtering effects at the heterogeneous interfaces. Additionally, the power factor of the misfit film was considerably improved to 77.2 μW m −1 K −2 , which is 18 times higher than that of the original MXene film. The maximum output power of the TE device constructed of the misfit film was 95 nW at a temperature difference of 40 K, resulting in a power density of 1.18 W m −2 , demonstrating the significant potential of this technology for driving low-energy consumption wearable electronics.

Thermoelectric (TE) generators are a kind of clean energy technology that can harvest electrical energy from waste heat. However, scant attention has been paid to the potential influence of the bonding orbitals on TE properties, which has severely hindered the exploitation of TE materials. Herein, a simple but effective strategy based on crystal field theory was proposed here to sift out potential TE materials based on the orbital degeneracy engineering that comprises the electronic bands. A typical p-type material Cu 8 SiS 6 composed of CuS 4 tetrahedra−units was selected and investigated. When the ligands−sulfur atoms get close to the center copper ion in a unit CuS 4 , the degeneracy of the d orbital would split due to the static electric field, leading to a high density of state at the top of the valence band, thus enhancing the Seebeck coefficient. It was found that Cu 7.92 SiS 6 shows a zT of 0.24 at 850 K. The orbital degeneracy engineering approach is promising to extend to other class of TE materials, thereby substantially accelerating the screening and design of novel TE materials.