First fabrication of a Ta₆-based nanocomposite coating, for energy saving applications, by an EPD solution process.

Understanding the mechanism that connects heat transport with crystal structures and order/disorder phenomena is crucial to develop materials with ultralow thermal conductivity (κ), for thermoelectric and thermal barrier applications, and requires the study of highly pure materials. We synthesized the n-type sulfide CuPbBi₅S₉ with an ultralow κ value of 0.6–0.4 W m^–1 K^–1 in the temperature range 300–700 K. In contrast to prior studies, we show that this synthetic sulfide does not exhibit the ordered gladite mineral structure but instead forms a copper-deficient disordered aikinite structure with partial Pb replacement by Bi, according to the chemical formula Cu_1/3□_2/3Pb_1/3Bi_5/3S₃. By combining experiments and lattice dynamics calculations, we elucidated that the ultralow κ value of this compound is due to very low energy optical modes associated with Pb and Bi ions and, to a smaller extent, Cu. This vibrational complexity at low energy hints at substantial anharmonic effects that contribute to enhance phonon scattering. Importantly, we show that this aikinite-type sulfide, despite being a poor semiconductor, is a potential matrix for designing novel, efficient n-type thermoelectric compounds with ultralow κ values. A drastic improvement in the carrier concentration and thermoelectric figure of merit have been obtained upon Cl for S and Bi for Pb substitution. The Cu_1–x□_xPb_1–xBi_1+xS₃ series provides a new, interesting structural prototype for engineering n-type thermoelectric sulfides by controlling disorder and optimizing doping.

This study deals with the nanoarchitectonic concept applied to the design of photoelectrodes built on two types of cluster core building blocks, namely, {Re₆Sⁱ ₈} and {Re₆Seⁱ ₈}. The effect of the nature of the metal/ligand on photoinduced conductivity properties is thus investigated through an in‐depth photoelectrochemical study and it is rationalized by the establishment of an energy diagram using a set of complementary optical (ultraviolet–vis–near infrared), electrochemical and spectroscopic (X‐ray photoelectron spectroscopy) characterization techniques. The optical and electronic properties of {Re₆Qⁱ ₈}‐based films (Q = S or Se) are drastically dependent on the composition. The sulfide‐based photoelectrodes exhibit ambipolar behavior with an n‐type domination whereas the selenide‐based photoelectrodes have a p‐type semiconducting behavior. Such electronic properties can be exalted by increasing the interactions between the cluster building blocks by heating. The design of mixed {Re₆Qⁱ ₈}‐based photoelectrodes combining the two n‐{Re₆Sⁱ ₈} and p‐{Re₆Seⁱ ₈} cluster core‐based building blocks is explored. The physical properties of the heterostructures can be tuned by controlling the {Re₆Sⁱ ₈}:{Re₆Seⁱ ₈} ratio and the interaction between the clusters. The creation of such nanoarchitectonic p–n junctions allows the optimization of the photocurrents generated by increasing the separated charge state lifetime that turns out to be attractive for solar cell applications.