Effective governance of thermal conductivity and other properties is of significant interest for science, including the fields of thermal barrier coatings, thermoelectric materials, and limit alloys. In this study, we investigated the impact of entropy engineering on properties of fluorite RE3NbO7, and limit thermal conductivity and strengthened mechanical properties are achieved. The solution strengthening mechanism leads to an 80% increase in toughness when the intrinsic stiffness and Young's modulus of the fabricated samples are identified via nanoindentation. Thermal conductivity is as low as 1.03–1.17 W m−1 K−1 at 25–900 °C, drastically reducing the gap between experimental results and theoretical limit values of fluorite RE3NbO7. The limit thermal conductivity as well as enhanced thermal expansion coefficients (11.2 × 10−6 K−1) and mechanical properties imply that the working performance of RE3NbO7 is evidently promoted by entropy engineering.

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The regioselective derivatization of the monocarba-closo-dodecaborate anion via catalytic B-H bond activation is reported. Amide directing groups in combination with rhodium and iridium catalysts allowed for the direct functionalization of cage boron vertices. Products comprising B-C, B-N and B-Cl bonds were synthesized. As a key intermediate of the B-H activation step, an iridium complex with a direct B-Ir interaction was isolated and fully characterized by spectroscopic methods as well as X-ray crystallography.

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