Thermoelectric properties of copper selenide with ordered selenium layer and disordered copper layer

Thermoelectric figure-of-merit (ZT) of ∼1.6 at 700 °C is achieved in β-phase copper selenide (Cu2Se) made by ball milling and hot pressing. The β-phase of such material possesses a natural superlattice-like structure that combines ordered selenium (Se) and disordered copper (Cu) layers in its unit cell, resulting in a low lattice thermal conductivity of 0.4–0.5 W m−1 K−1. A λ-shaped specific heat peak indicates a phase transition from cubic β-phase to tetragonal α-phase at around 140 °C upon cooling and vice versa. An abnormal decrease in specific heat with increasing temperature was also observed due to the increased random motion of disordered Cu atoms. These features indicate that β-phase Cu2Se could be potentially an interesting thermoelectric material, competing with other conventional thermoelectric materials.

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► β-Phase Cu2Se with a combination of ordered and disordered layers in its unit cell was studied.
► The natural superlattice-like structure promises to achieve a low lattice thermal conductivity.
► Increased random motion of disordered Cu atoms at high temperature results in reducing Cp values.
► High thermoelectric figure-of-merit (ZT) values of ∼1.6 at 700 °C were obtained.