Thermoelectric property of doped LiNb02

Abstract

Using first-principles calculations, we investigated the electronic and t hermoelectric (TE) properties of doped LiNb02. vVe show that LiNb02 is a direct bandgap ma terial and the bonding between Nb and 0 atoms is covalent . Seebeck coefficient, electrical conductivity, power factor, and figure of merit of LiNb02 are optimized under electron and hole carrier concentrations, using the Boltzman transport the ory. Electron carrier concentrations can give larger figure of merit. The effect of 0 and Li vacancies on the electronic and TE properties are also studied, and we show that Li (0) vacancy in LiNb02 generates holes (electrons). Though T/,-type LiNb0 2 is expected to have superior TE proprieties over p-type LiNb02, but the defect formation energy of 0 vacancy is larger than the Li vacancy in LiNb02. The elec tronic structures and TE properties of Lh_xAxNb02(A= Ta,Ni) and LiNb1_ x Tax O2 (x=O.0625) as a function of temperature are also investigated. Doping of Ta at Nb site is energetically more favourable as compared with Ni doping in LiNb02. Hence, we believe that Nb-doped LiNb02 could be a possible candidate material for ther moelectric applications. Our calculations also agree with the available experimental TE data of LiNb02.