Structure and thermoelectric performance of β-Cu2Se doped with Fe, Ni, Mn, In, Zn or Sm

• Doping of Zn, Ni, Fe, Mn or Sm decreased the resistivity and Seebeck coefficient of Cu1.99A0.01Se.
• Power factor is optimized.
• Lattice thermal conductivity is reduced.
• ZT value is improved at 823 K.
• High ZT value of 1.51 is obtained for the sample of x = 0.075 and 0.10 at 823 K in Cu2−xNixSe system.

Cu1.99A0.01Se (A = Fe, Ni, Mn, In, Zn or Sm) alloys with high thermoelectric performance were prepared through a conventional melting, ball milling and quenching route, followed by a spark plasma sintering technique. Elemental doping did not change the structure type of Cu2Se. All the samples showed p-type conduction. All the doping elements except Indium reduced the electric resistivity and modified the carrier concentration, leading to a significant increase in the power factor. The lattice distortion and point defects due to the substitution of Cu became new phonon scattering centers, leading to a significant decrease in thermal conductivity. All the samples except the In-doped sample obtained better thermoelectric properties compared with the undoped Cu2Se sample. The values of the figure of merit ZT of the samples doped with Zn, Mn, Ni, Fe and Sm were 1.25, 1.28, 1.51, 1.07 and 1.07 at 823 K, respectively. In Cu2−xNixSe system, High ZT value of 1.51 is obtained for the sample of x = 0.0075 and 0.010 at 823 K.

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