The impact of Ni and Zn doping on the thermal durability and thermoelectric variables of pristine CuSe nanoparticles

Abstract

Copper selenide nanomaterials are recognized to possess thermoelectric characteristics, becoming a strong contender to unite materials science and energy technology with effective use in practical applications in extreme environments. Nanoparticles of pure CuSe, as well as Ni- and Zn-doped CuSe, are synthesized via an elementary co-precipitation strategy, with their structural and compositional verification achieved through preliminary characterization. In this endeavor, the authors embark on a first-of-its-kind investigation of the thermal attributes of as-synthesized Ni and Zn-doped CuSe nanoparticles. The thermogravimetric profiles for pristine, Ni- and Zn-doped CuSe nanoparticles are acquired under neutral nitrogen (N₂) conditions spanning ambient temperature to 793 K. The assessment demonstrated that all nanoparticles tested went through a two-step breakdown, showcasing a maximum weight reduction of 26.08% for pristine CuSe and the lowest weight decrement of 16.87% for Zn-doped CuSe nanoparticles. The experimental assessment of thermal stability is substantiated through a comprehensive theoretical analysis of phonon dynamic stability that provides profound insight into the thermal characteristics of the as-synthesized nanoparticles. Density functional theory is employed to scrutinize the phonon dynamic stability within CuSe with Ni and Zn as dopants. The Kissinger framework is employed to estimate the thermodynamic coefficients conveying the non-spontaneous disintegration of all nanoparticles. All five samples are proven to be semiconductors based on the variations in Seebeck coefficient (S), dc electrical conductivity (σ), and thermal conductivity (κ) from ambient temperature to 523 K. The investigation of temperature-induced variations in the power factor (S²σ) and figure of merit (ZT) elucidated that Ni- and Zn-doped nanoparticles exhibit superior values in comparison to pure CuSe nanoparticles. The optimum ZT metric of 1.28 is attained for 10% Zn-doped CuSe nanoparticles at 523 K. A detailed discussion of the findings is provided.