Abstract
Ternary diamondlike semiconductors Cu2Ge1+xSe 3 have been synthesized by direct-melting the constituent elements under several different synthetic conditions. The Hall effect and thermoelectric properties of Cu2Ge1+xSe3 were measured. All samples show positive Hall coefficients (RH) for the whole temperature range studied, and a positive Seebeck coefficient of 360 μV K-1 was observed at 300 K for Cu2GeSe3. Low thermal conductivities were also observed for all samples; the lowest value reaches 1.0 Wm-1 K-1 at 745 K.
| Original language | English |
|---|---|
| Article number | 073713 |
| Journal | Journal of Applied Physics |
| Volume | 108 |
| Issue number | 7 |
| DOIs | |
| State | Published - Oct 1 2010 |
Funding
J.Y.C., X.S., J.R.S., and J.Y. would like to thank J. Herbst and M. Verbrugge for their continued support and encouragement. Elemental analysis provided by Richard Waldo and x-ray powder diffraction measurements provided by Richard Speers, Jr. are highly appreciated. The work is supported by GM and by DOE under corporate agreement under Grant No. DE-FC26-04NT42278, by the assistant secretary for Energy Efficiency and Renewable Energy, Office at Oak Ridge National Laboratory managed by the UT-Battlelle LLC, and the Department of Energy under Contract DEAC05000OR22725. Table I. Synthesis, nominal, and actual composition (determined by EPMA) of Cu 2 Ge 1 + x Se 3 . Synthesis condition Nominal ratio (Cu:Ge:Se) EPMA a (Cu:Ge:Se) S1 (orthorhombic) ⋯ 2:1:3 2.00(1):0.96(1):2.82(1) S2 (orthorhombic) Se excess 2:1:3.03 2.00(2):0.93(2):2.79(1) S3 (cubic) Ge excess 2:1.55:3 2.00(30):1.54(31):2.94(14) a Composition is normalized to copper. FIG. 1. XRD patterns of Cu 2 Ge 1 + x Se 3 . Samples 1 and 2 crystallize in the orthorhombic I m m 2 (No. 44) space group. Sample 3 shows the cubic F 4 ¯ 3 m (No. 216) phase. FIG. 2. Temperature dependence of electrical resistivity (a), carrier concentration (b), and Hall mobility (c) for Cu 2 Ge 1 + x Se 3 . The solid and dotted lines with slopes T − 3 / 2 and T 3 / 2 , respectively, are guides for the eye. FIG. 3. (a) Hall coefficient vs 1 / T (experimental values ●) black solid line is the fit to the two band model. (b) Resistivity vs 1 / T (experimental values ●) and black line is the fit. E i and E a are shown for the regions of activated behavior, the inset shows the linear behavior of ln ( ρ ) vs T − 1 / 4 indicative of Mott variable range hopping. FIG. 4. Temperature dependence of Seebeck coefficient (a), thermal conductivity (b), and Z T (c) of Cu 2 Ge 1 + x Se 3 .
| Funders | Funder number |
|---|---|
| Energy Efficiency and Renewable Energy, Office at Oak Ridge National Laboratory | |
| UT-Battlelle LLC | |
| U.S. Department of Energy | DE-FC26-04NT42278, DEAC05000OR22725 |
| Office of Energy Efficiency and Renewable Energy |