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.

Hybrid inorganic–organic superlattice with an electron-transmitting but phonon-blocking structure has emerged as a promising flexible thin film thermoelectric material. However, the substantial challenge in optimizing carrier concentration without disrupting the superlattice structure prevents further improvement of the thermoelectric performance. Here we demonstrate a strategy for carrier optimization in a hybrid inorganic–organic superlattice of TiS₂[tetrabutylammonium] _x [hexylammonium] _y , where the organic layers are composed of a random mixture of tetrabutylammonium and hexylammonium molecules. By vacuum heating the hybrid materials at an intermediate temperature, the hexylammonium molecules with a lower boiling point are selectively de-intercalated, which reduces the electron density due to the requirement of electroneutrality. The tetrabutylammonium molecules with a higher boiling point remain to support and stabilize the superlattice structure. The carrier concentration can thus be effectively reduced, resulting in a remarkably high power factor of 904 µW m⁻¹ K⁻² at 300 K for flexible thermoelectrics, approaching the values achieved in conventional inorganic semiconductors.

Ceramic matrix composites containing two-dimensional graphene array show outstanding mechanical and frictional properties.

Graphene with excellent comprehensive properties has been considered as a promising filler to reinforce ceramics. While numerous studies have been devoted to the improvement of mechanical and electrical properties, incorporating graphene to ceramics also offers new opportunities for endowing ceramics with versatility. In this review, the recent development of graphene/ceramic bulk composites is summarized with the focus on the construction of well-designed architecture and the realization of multifunctional applications. The processing technologies of the composites are systematically summarized towards homogeneous dispersion and even ordered orientation of graphene sheets in the ceramic matrix. The improvement of composites in mechanical, electrical, electromagnetic, and thermal performances is discussed. The novel multifunctional applications brought by smart integration of graphene in ceramics are also addressed, including microwave absorption, electromagnetic interference shielding, ballistic armors, self-monitor damage sensors, and energy storage and conversion.

Two-dimensional (2D) materials have received extensive interest due to their exceptional properties. It is strongly required to assemble 2D materials in bulk quantities for macroscopic applications, but this is highly restricted by the aggregation of 2D materials. Constructing three-dimensional (3D) hybrid superlattices of alternating 2D materials and organic molecule layers provides a new path to access the exceptional properties of 2D materials in bulk quantities. In this tutorial review, the emerging concept of hybrid inorganic/organic superlattices is systematically illustrated. The abundant compositions and the various structures of inorganic and organic sublattices in hybrid superlattices are presented, followed by a summary of the chemical interactions between them. Many facile techniques have been developed for hybrid superlattices, enabling precise control of the structure. There are also various interesting mechanisms inside unique hybrid inorganic/organic superlattices that can help tune the properties, including electron transfer, quantum confinement, interlayer coupling, multiple interface effects, etc. The rich chemistry and abundant mechanisms of these hybrid superlattices can enhance the performance beyond the reach of existing materials, and provide new opportunities in various applications, including rechargeable batteries, catalysis, thermoelectrics, advanced electronics, superconductors, optoelectronics, etc.