Microstructure evolution of sputtered BiSb-Te thermoelectric films during post-annealing and its effects on the thermoelectric properties

► We examined the microstructure evolution of BiSb-Te films during post-annealing. ► The microstructure of the BiSb-Te was nano-crystalline in the as-deposited state. ► The grains of nano-crystalline were found to be the stable Bi2Te3-type phase. ► The BiSb-Te thin film was based on the grain growth process. ► The grain growth influenced the ZT value in the positive direction.