Stabilizing Thermoelectric Figure‐of‐Merit of Superionic Conductor Cu2Se through W Nanoinclusions

Cu2Se exhibits a high figure‐of‐merit (ZT) >1 due to the scattering of phonons by mobile Cu+ ions, but migration of the Cu+ ions leads to chemical instability at high temperature. It is demonstrated that the incorporation of W in the Cu2Se matrix results in peak ZT of 2.1 (ZTavg = 0.93) at 878 K. After the first thermal cycle, the peak ZT of the composite decreases to stable value of ≈1.5 (ZTavg = 0.97). The enhanced stability of the nanocomposite along with high ZTavg is attributed to the covering of Cu2Se grain boundaries with W that inhibits Cu+ migration, reduces Se loss, and improves charge carrier mobility. The incorporation of W in Cu2Se results in peak ZT of 2.1 (ZTavg = 0.93) at 878 K, which decreases to a stable value of ≈1.5 (ZTavg = 0.97) after the first thermal cycle. The improved stability is attributed to the presence of W at Cu2Se grain boundaries that reduces Se loss as well as inhibits Cu+ migration.