Concentration driven size optimization of ZnO nanoinclusions in Bi₂Te₃: Thermoelectric enhancement and modelled device performance

A scalable and cost-effective approach (with inherent simplicity of processing route) is employed to engineer ZnO nanoinclusion with controlled size and distribution to improve thermoelectric (TE) efficiency of n-type Bi 2 Te 3 . The effects of ZnO content (0, 2, 5, and 10 wt%), nanoinclusion size and its distribution on thermoelectric properties are systematically investigated. Structural and microscopic analysis confirm the formation of well dispersed ZnO inclusion in Bi 2 Te₃ matrix with average sizes (∼3 nm) at 2 wt%, a bimodal (∼ 4 nm and ∼13 nm) size distribution at 5 wt%, and agglomerated particles (∼30–40 nm) at 10 wt% ZnO . The 2 wt% ZnO composition exhibits an ∼46% increase in power factor compared to pristine Bi 2 Te 3 , while increasing the ZnO content to 5 wt% results in ∼ 71% reduction in lattice thermal conductivity, leading to an overall thermal conductivity reduction of ∼ 25%. The combined effect of nanoinclusion size and bimodal distribution synergistically may play the role to suppress phonon transport while preserving charge carrier transport, might be attributed to energy dependent carrier filtering and enhanced phonon interface scattering. Consequently, a ∼ 50% enhancement in TE figure of merit (ZT ∼ 0.46 at 370 K) is achieved. Furthermore, using experimentally measured thermoelectric parameters, the device level figure of merit and conversion efficiency are estimated, yielding a computed device ZT ∼0.43 over 300–500 K and a maximum efficiency ∼3.8%. These findings highlight the potential of economically efficient facile approach to optimized ZnO content in Bi 2 Te 3 matrix for near room temperature TE materials fabrication with modelled device level implications for day to day energy conversion applications.