Thermal and Electrical Transport Properties of Novel Metal Oxychalcogenides for Thermoelectrics

Up to 50 % of global energy production is lost as waste heat.¹ Harvesting or recycling this energy could provide a new source of energy or increase the efficiency of extant operations, contributing to the green energy transition. High efficiency thermoelectric materials typically contain rare or toxic materials such as Pb, unsuitable for widespread use, so the discovery of nontoxic, earth-abundant but nevertheless efficient thermoelectrics are necessary to fulfil their potential.<br/>Following the recent proposal of the mixed anion system Y₂Ti₂O₅S₂ as an n-type thermoelectric,² we investigate the electronic and thermal and transport properties of its family, the Ln₂M₂O₅Ch₂ oxychalcogenides (Ln = Sc, Y, La; M = Ti, Zr, Hf and Ch = S, Se, Te) as thermoelectrics. We first identify which materials are kinetically and thermodynamically stable, before demonstrating via band alignment they share a preference for n-type doping with Y₂Ti₂O₅S₂. We then assess the electronic transport properties using the momentum relaxation time approximation (MRTA) as implemented in AMSET³ to identify the most effective candidates for which to calculate the lattice thermal conductivity, in order to assess their dimensionless figure of merit, ZT.<br/><br/>[1] Firth, A. et al, <i>Appl. Energy</i>, 2019, <b>235</b>, 1314<br/>[2] Brlec, K. et al., <i>J. Mat. Chem. A</i>, 2022, <b>10</b>, 16813<br/>[3] Ganose, A. M. et al, <i>Nat. Commun.</i>, 2021, <b>12</b>, 2222