Thermoelectric properties and low thermal conductivity of nanocomposite ZrTe5 under magnetic field

Zirconium pentatelluride (ZrTe5) single crystal has recently received significant attention because of its quantum electronic transport properties and is regarded as a promising candidate for low-temperature thermoelectric cooling and spintronic applications. However, single crystal of ZrTe5 has generally small sizes and can only be produced in small quantities using a complicated process, whereas ZrTe5 polycrystals are easily produced and their properties are easily adjusted. In this study, we focus on the magneto-transport properties at low temperatures of nanocomposites of ZrTe5 produced using both hand-milling and ball-milling processes to investigate the impact of microstructure. The ball-milled sample shows a low thermal conductivity of 1 W.m-1.K-1, which is almost a constant below 300 K. However, due to its small grain sizes, the electron mobility is significantly decreased, thus their thermoelectric performances are not as good as that of the hand-milled sample. Also, below 25 K, the resistivity and the Seebeck coefficient of the ball-milled sample are decreased, which is associated with the energy barrier at their grain boundaries. Due to the larger grain sizes and fewer defects in the hand-milled sample, the external magnetic field shows a significant influence on its thermoelectric properties at low temperatures. These results indicate that polycrystalline ZrTe5 with large grain sizes may exhibit similar quantum properties as those of single crystals.