Facile rapid synthesis of a nanocrystalline Cu₂Te multi-phase transition material and its thermoelectric performance

Abstract

A highly efficient facile method was used to synthesize Cu 2 Te via spark plasma sintering (SPS) of highenergy ball-milled elemental powders, followed by annealing, which dramatically reduced the whole process time. The multiple phase transitions of Cu 2 Te over an extensive temperature range were determined using a combination of high temperature X-ray diffraction (HTXRD) and differential scanning calorimetry (DSC). This merit endows Cu 2 Te with the ability to trigger multiple critical scatterings from room temperature up to 900 K. Microscopic investigation showed that the Cu 2 Te prepared by this rapid method possesses tiny dispersive precipitates, with sizes in the range of 50-100 nm, that could serve as obstacles for the transfer of mid-wavelength phonons. As a result, a ZT value of $0.52 at 1000 K was obtained for the sample annealed for 10 h after SPS.

Are Cu2Te‐Based Compounds Excellent Thermoelectric Materials?

“…However, at high temperature, the TE performance is greatly improved over a large temperature range, which can be traced to the suppressed phase transition temperature and the reduced carrier concentration. Specifically, the maximum zT value for pristine Cu 2 Te is only 0.4 and it is remarkably boosted to 1.8 for Cu 2 Te + 50% Ag 2 Te at 1000 K. This is a 323% improvement over Cu 2 Te itself and outperforms any other Cu 2 Te‐based material reported so far (Figure f) …”

“…However, the case is different in Cu 2 X‐based liquid‐like TE materials that are among the hottest materials in recent TE study. They possess exceptionally low thermal conductivity and excellent zT s with the values of 1.7–1.9 for Cu 2 S, 1.5–2.3 for Cu 2 Se, and 0.4–1.1 for Cu 2 Te (see Figure ) . It is quite abnormal and interesting that the zT in Cu 2 Te is lower than those in Cu 2 S and Cu 2 Se.…”

“…a) Electrical conductivity σ, b) Seebeck coefficient S , c) power factor PF, d) total thermal conductivity κ, and e) TE figure of merit zT . f) Comparison of zT values from 300 to 1000 K for several reported Cu 2 Te‐based TE materials …”

“…The other symbols are the data from refs. –. The dashed lines are derived from the single parabolic band (SPB) model with the weighted mobility µ 0 m *3/2 of 19.6 m e 3/2 cm 2 V −1 s −1 .…”

Measurement of electronic structure and surface reconstruction in the superionic Cu2−xTe

“…Recently, copper chalcogenides compounds Cu2X (X = S, Se, Te) have attracted lots of attention for their exceptionally low thermal conductivity and high TE performances [6,[9][10][11][12][13][14][15][16][17][18][19][20][21]. The achieved zT is as high as 1.5 in Cu2-xSe, 1.7 in Cu2-xS and 1.1 in Cu2-xTe at 1000 K, which are among the top values in bulk TE materials.…”