Enhancement of the Figure of Merit in Bi-microwire Arrays

Enhanced thermopower and low thermal conductivity in p-type polycrystalline ZrTe5

“…Figure 3(a) shows T dependence of thermal conductivity (), with the room temperature value of 2.2 W/m-K, which is lower in comparison 8 W/m-K for the reported ZrTe5 single crystal 29 . Our  values are comparable to high density hot-pressed polycrystalline ZrTe5, HfTe5, Hf0.5Zr0.5Te5 compounds 26 . Low value of  could be associated with large number of atoms presents in unit cell of this pentatelluride with weak van der Waals bonding 29 .…”

“…Low value of  could be associated with large number of atoms presents in unit cell of this pentatelluride with weak van der Waals bonding 29 . It is possibly related to the purity and stoichiometry of samples, pure sample will have less number of defects and impurities, this fact seems consistent with reduced size of maxima (5.6 W/m-K) at 19 K in comparison to single crystal (20 W/m-K) at the same T, because peak maxima 26 , however it is almost 4 times smaller than the high density hot pressed polycrystalline ZrTe5 and Zr0.5Hf0.5Te5 26 . Hot pressing increases the density of material and enhances  which consequently improves the zT value.…”

“…The thermopower of ZrTe5 (Figure 2 (b)) is positive, indicating holes as the dominant carriers in T range 2 -340 K. The room temperature value of S in our polycrystalline compound, 458 V/K is almost two time higher than in comparison to reported S for ZrTe5 and HfTe5, where maximum S values ranges from 75 -250 V/K 4, 12,14-21, 26 . Previous reports have shown the change in sign of S from negative (n-type) to positive (p-type) 4,12,14-21 .…”

“…Zhou et al reported the suppression of resistivity anomaly on application of pressure and emergence of superconductivity with the TC ~ 4 K at 14 GPa pressure 11 . The latest report by H. Xiong et al 13 has suggested 3D nature of band structure and estimated the gap of [18][19][20][21][22][23][24][25][26][27][28][29] meV between valence and conduction band by photoemission study 13 . It is suggested that the electronic transport anomaly in ZrTe5 is mediated by Lifshitz transition in the Dirac band, and strongly depends on the carrier concentration 12 .…”