Entropy engineering is one of the powerful approaches to suppress phase transitions.

Hierarchical microstructures lead to high thermoelectric performance in Cum+nPb100SbmTe100Se2m (CLAST) through synergistically optimizing carrier and phonon transport.

Perovskite-related materials with various dimensionalities have attracted sustained attention owing to their extraordinary electronic and optoelectronic properties, but it is still challenging in the synthesis of compounds with desired compositions and structures. Herein, a two-dimensional (2D) CsPb 2 I 5 perovskite has been synthesized by the conversion of CsPbI 3 at high-pressure and high-temperature (high P−T) conditions, which is quenchable at ambient conditions. In situ synchrotron X-ray diffraction shows that high-pressure monoclinic CsPbI 3 converts into tetragonal CsPb 2 I 5 and cubic CsI at 8.7 GPa upon heating from 644 to 666 K. Keeping the tetragonal structure stable, CsPb 2 I 5 exhibits tunable optical properties with the bandgap changing from ∼2.4 eV at ambient pressure to ∼1.4 eV at 36.9 GPa. Further experiments demonstrate similar structural evolution in the typical three-dimensional CsPbBr 3 perovskite into 2D CsPb 2 Br 5 at high P−T conditions, indicating that the conversion of CsPbX 3 (X = Br and I) into CsPb 2 X 5 is ubiquitous.

Determination of the structures of materials involving more light elements such as boron-rich compounds is challenging and technically important in understanding their varied compositions and superior functionalities. Here we resolve the long-standing uncertainties in structure and composition about the highest boride (termed MoB4, Mo1–x B3, or MoB3) through the rapid formation of large-sized boron-rich molybdenum boride under pressure. Using high-quality single-crystal X-ray diffraction analysis and aberration-corrected scanning transmission electron microscopy, we reveal that boron-rich molybdenum boride with a composition of Mo0.757B3 exhibits P63/mmc symmetry with a partial occupancy of 0.514 in 2b Mo sites (Mo1), and direct observations reveal the short-range ordering of cation vacancies in (010) crystal planes. Large anisotropic Young’s moduli and Vickers hardness are seen for Mo0.757B3, which may be attributed by its two-dimensional boron distributions. Mo0.757B3 is also found to be superconducting with a transition temperature (T c) of ∼2.4 K, which was confirmed by measurements of resistivity and magnetic susceptibility. Theoretical calculations suggest that the partial occupancy of Mo atoms plays a crucial role in the emergence of superconductivity.

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Temperature-or pressure-driven n−p conductiontype switching has been described as an emerging phenomenon for potential applications as transistors, switches, and memory devices.The key challenge in the development of such n−p conductiontype switching materials is to establish maneuverable and controllable methods to achieve easy convertibility and nonvolatility. Herein, we report the first example of rewritable pressure and temperature dual-controlled n−p conduction-type switching in marcasite-type CrSb 2 . At room temperature, CrSb 2 exhibits an unexcepted pressure-driven n−p conductivity-type switching around 12 GPa accompanied by a marcasite-to-arsenopyrite structural transition and a semiconductor-to-metal transition. The dramatic conduction-type switching is irreversible after pressure releasing at room temperature but reversible by annealing at a relatively low temperature (>80 °C). Accordingly, a multicycle bistability switching process is established under the dual regulation of both pressure and temperature. The underlying structure− property mechanism is revealed by in situ/ex situ characterization and analyses of the atomic-level microstructure, local lattice distortion, and residual stress induced by compression. This demonstration provides a new platform for the rational design of rewritable temperature/pressure-responsive photoelectric conversion devices.

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