Impact\nof Boron Nitride\non the Thermoelectric Properties\nand Service Stability of Cu<sub>2–<i>x</i></sub>Se

Improving the thermoelectric performance\nand service\nstability\nis essential for the effective use of cuprous selenide (Cu<sub>2–<i>x</i></sub>Se). In this study, hexagonal boron nitride (h-BN)\nwas incorporated into nano-Cu<sub>2–<i>x</i></sub>Se, with the goal of enhancing thermoelectric performance and service\nstability. It was found that Cu<sub>2–<i>x</i></sub>Se-0.005 wt % BN showed a higher thermoelectric figure of merit (<i>zT)</i> value (∼1.76 at 923 K), which was 11% greater\nthan that of pure Cu<sub>2–<i>x</i></sub>Se, mainly\ndue to a significant reduction in lattice thermal conductivity (<i>k</i><sub>L</sub>) to about 50% (0.13 W m<sup>–1</sup> K<sup>–1</sup>). Additionally, the formation of an ion-blocking\ninterface by hexagonal boron nitride effectively shortens the migration\npath of Cu<sup>+</sup> ions, improving service stability while maintaining\nthe contribution of Cu<sup>+</sup> transitions to thermal conductivity.\nFinally, an increase in hardness of ∼11.1% was observed, reaching\n0.7 GPa in Cu<sub>2–<i>x</i></sub>Se-0.02 wt % BN.\nThis research is a feasible approach to improving the service stability\nof Cu<sub>2–<i>x</i></sub>Se.