High thermoelectric power factor in Cu–Ni alloy originate from potential barrier scattering of twin boundaries

Abstract

Constantan alloy (Cu-Ni) has been known for a long time in thermocouples due to its thermal power property. In this study, we show an enhancement in thermoelectric performance of Cu 56 Ni 42 Mn 2 alloy by introducing nanoscale twins into its microstructure. Comparing to arcmelted ingot (without nanoscale twins), the ball milled and hot pressed (BM-HP) samples with twinning showed a higher Seebeck coefficient of $ À72.5 μV K À 1 (an increase of $ 12% at 873 K), a larger power factor of $102 μW cm À 1 K À 2 (an increase of $21% at 873 K), and hence a higher ZT of $0.19 (an increase of $ 34% at 873 K). A high output power density of $ 53.4 W cm À 2 is calculated from the high power factor even though the conversion efficiency is lower than 3% due to the low ZT. TEM characterization shows there is a large quantity of nanoscale twins with spacing of 50-200 nm. It is very likely that low-energy carriers are selectively scattered by the twin boundaries (i.e., potential barrier scattering) thus lead to http://dx.enhanced Seebeck coefficient. The improved thermoelectric performance of nano-twinned CuNi alloy suggests constantan could be promising in thermoelectric power generation where the power output density is more important than the conversion efficiency.

Achieving high power factor and output power density in p-type half-Heuslers Nb 1-x Ti x FeSb

“…Such an unusually high power factor has previously been observed only in metallic systems such as YbAl 3 and constantan (26,27). Furthermore, a record output power density of ∼22 W·cm −2 with a leg length ∼2 mm is experimentally obtained with T C = 293 K and T H = 868 K. We also observe that the lattice thermal conductivity hardly changes within the range of grain sizes studied in this work.…”

“…Similar results were also reported by Fu et al (12) with Zr and Hf doping. (27). These materials possess peak power factors of at least 100 μW·cm −1 ·K −2 .…”

Investigation of the bipolar effect in the thermoelectric material CaMg2Bi2 using a first-principles study

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] The TE conversion efficiency and performance-price ratios of TE devices developed so far and those under development are insufficient to compete with fossil fuel based energy resources. Some intrinsic issues need to be solved for TE materials design and synthesis, and some of them have been lasting for decades.…”

Ultrahigh figure‐of‐merit of Cu2Se incorporated with carbon coated boron nanoparticles

“…The nanometric grains are proposed to be nucleated from C/B‐NPs hetero‐surface, while the much larger grains should be the agglomeration of Cu 2 Se during melting process. Meanwhile, large density of twins are observed as presented in Figure C, which could scatter the phonons to reduce thermal conductivity …”

“…Meanwhile, large density of twins are observed as presented in Figure 2C, which could scatter the phonons to reduce thermal conductivity. 37,38 F I G U R E 2 A, Scanning electron microscope (SEM) image of the cross-section of the Cu 2 Se incorporated with 0.10 wt% carbon-coated-boron nanoparticles. B, BSE image with enlargement shown in inset.…”