Thermoelectric performance of Ni, Co, and Fe nanoparticles incorporated into their metal borates glassy matrices

Abstract

AbstractHere, we present our current attempt to intrinsically dope Ni0, Co0, and Fe0 nanoparticles within NiII‐, CoII‐, and FeII‐borate glassy matrices, respectively. The system was prepared by one‐pot reaction of the desired MTII salt with excess NaBH4 through an in‐situ reduction and hydrolysis processes to afford metallic MT0 nanoparticles dispersed into the MT‐BO3 matrix. The composition and structural characteristics of these MT0:MT‐BO3 materials were identified by thermal oxidation, ATR‐IR, X‐ray powder diffraction, and magnetic techniques as glassy/amorphous borate matrices containing magnetic nanoparticles. The electrical conductivity (σ) of cold‐pressed discs of these metal‐doped composites shows that they behave as nonohmic semiconductors within the temperature range of 303 ≤ T ≤ 373 K suggesting a mixed electronic‐ionic conduction. However, their thermal conductivity (κ) occurs through phonon lattice vibration dynamics rather than electronic. The σ/κ ratio shows a steep non‐linear increase from 9.4 to 270 KV−2 in Ni0:Ni‐BO3. In contrast, a moderate‐weak increase is observed for Co0:Co‐BO3 and Fe0:Fe‐BO3 analogs. The obtained materials are examined for thermoelectric (TE) applications by determining their Seebeck coefficient (S) power factor (PF), figure of merit (ZT), and conversion efficiency (η%). All the TE data shows that Ni0:Ni‐BO3 (S, 80 μVK−1; PF, 97.7 mWm−1 K−1; ZT 0.54; η, 2.15%) is a better TE semiconductor than the other two MT0:MT‐BO3. This finding shows that Ni0:Ni‐BO3 is a promising candidate to exploit low‐temperature waste heat from body heat, sunshine, and small domestic devices for small‐scale TE applications.