Detrimental effects of impurity phases on the thermoelectric performance of Nb0.8Ti0.2Fe1.02Sb synthesized by arc-melting

Abstract We demonstrate the detrimental impacts of impurity phases on thermoelectric (TE) performance in Nb0.8Ti0.2Fe1.02Sb system that instigate performance irreproducibility that may impede rapid and progressive performance improvement of compounds synthesized by arc-melting. Three samples prepared by arc-melting are annealed at 700 °C, 850 °C and 1000 °C. The optimal homogeneity is achieved in the sample annealed at 850 °C with ~ 0.8 % impurity phases’ quantity, relative to ~ 4 % and ~ 10 % in the samples annealed at 700 °C and 1000 °C, respectively. The samples with increased impurities depict a significantly decreased Seebeck coefficient and increased lattice thermal conductivity, which intimately impairs the TE performance. The highest ZT is achieved in the sample with the least impurities, ~ 0.73 at 873 K, which is 49% higher than the inhomogeneous samples. This stresses the pertinence of minimizing the impurities in a bid to reproduce the optimal TE performance from this system.