ICT2014 Abstracts

We report promising thermoelectric performance in n-type nanocrystalline BiAgSeS, a lead-free material with earth abundant elements. The electrical conductivity is significantly improved by partially substituting S^2- by Cl^-, from 3.3 Scm^-1 (BiAgSeS) to 33 Scm^-1 (BiAgSeS_0.95Cl_0.05) at 300K. Enhanced electrical conductivity coupling with moderate Seebeck coefficients leads to a maximum value of power factor ~5 μWcm⁻¹K⁻² for BiAgSeS_0.97Cl_0.03 at 823K. Moreover, BiAgSeS shows very low thermal conductivity in the temperature ranges from 300K (~0.46 Wm^-1K^-1) to 823K (~0.29 Wm^-1K^-1). The combination of the optimized power factor and the intrinsically low thermal conductivity gives a high ZT of ~1.0 at 823K for BiAgSeS_0.97Cl_0.03, and indicates BiAgSeS system is promising for thermoelectric power generation applications. Transmission electron microscopy results show the micro-features of BiAgSeS including meso-scale grain boundaries, lamellar structures and nano-scale laminated endotaxial precipitates.