Identifying insulating to metallic complexion transitions in NbFeSb

Electrical resistance from grain boundary phases (complexions) is detrimental to thermoelectric performance. A promising strategy for mitigating this resistance is altering the composition at a grain boundary through complexion transitions. In NbFeSb, increasing the Ti content has been shown to result in Ti-rich boundaries that effectively eliminate boundary resistance and make Ti-doped NbFeSb a high performing thermoelectric. In this study, a model based on the average band offset between the grain boundaries and grain is used to identify a resistive to nonresistive complexion transition in NbFeSb. This method can be applied to any material with thermoelectric transport data and grain size measurements.