2024/06/09 by Gbadebo Taofeek Yusuf, Yusuf, Gbadebo Taofeek, Sukhwinder Singh +7
Materials Science · #Advanced Thermoelectric Materials and Devices #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Solidification and crystal growth phenomena
paper · pdf · doi:10.48550/arxiv.2406.05769
openalex publication_date 2024/06/09 · openalex created_date 2024/06/12 · openalex updated_date 2026/07/28
Grain-boundary-limited charge transport remains a key bottleneck in polycrystalline thermoelectric materials, where reduced carrier mobility degrades electrical conductivity and suppresses the power factor. Here we present a semi-empirical mobility model that integrates three dominant grain-boundary mechanisms: (i) weighted mobility linked to carrier effective mass and concentration, (ii) thermionic emission across grain-boundary barriers, and (iii) geometric suppression arising from a finite mean free path (ℓ). The model is validated against a diverse set of polycrystalline thermoelectric materials -- including Bi2Te3, PbTe, Mg2Si, and SnSe -- showing excellent agreement with experiment (R2 = 0.93--0.99) and yielding physically consistent parameters: 0 \lesssim ΦGB \lesssim 0.15 eV and ℓ ≈ 15--60 nm. The model captures the non-monotonic mobility trends produced by the interplay between barrier activation and phonon scattering. We further apply the model to Al-doped ZnO, revealing that combined grain-boundary passivation (reducing ΦGB from 0.15 eV to 0.05 eV) and moderate grain growth (increasing ℓ from 5 nm to 25 nm) can raise the power factor by ∼ 6× (from ∼ 4 to ∼ 26 mW m-1 K-2) and the electronic quality factor B by nearly 7× (from ∼ 0.15 to >1.0 × 10-3 m2 V-1 s-1 kg3/2), approaching values achieved in leading chalcogenide thermoelectrics. The model therefore provides a transparent and practical framework for grain-boundary engineering in oxide-based thermoelectrics.