High-Temperature Thermoelectric Properties of Na_xCoO_2-δ Single Crystals

Abstract

We measure the high-temperature thermoelectric properties of the Na x CoO 2−δ single crystal for the first time. The Na x CoO 2−δ single crystals are prepared by a flux technique, and the resulting flaky single crystals are very thin on the c-axis. The inplane electrical resistivity (ρ), the thermoelectric power (S) and the in-plane thermal conductivity (κ) are measured in the range of 300 K to 800 K. The estimated power factor (PF = S 2 ·ρ −1 ) and the figure-of-merit (Z = S 2 ·ρ −1 κ −1 ) are about 2.4 mW m −1 K −2 and 0.12 mK −1 at 300 K, respectively. These factors increase with temperature, and reach the value of PF = 7.7 mW m −1 K −2 and Z = 1.5 mK −1 at 800 K, and the dimensionless value of Z T exceeds the criterion of 1. The PF and Z exceed the values of typical "high-temperature thermoelectric materials", such as p-type FeSi 2 and Si 0.7 Ge 0.3 . These results suggest that Na x CoO 2−δ could be a very promising material for use in high-temperature thermoelectric power generation devices.

Promising Thermoelectric Bulk Materials with 2D Structures

“…[80] According to solid state physical principles, the ZT value for bulk mate rials with a single parabolic band (SPB) along a certain direc tion can be given as: [4] The timeline for thermoelectric bulk materials with 2D structures, showing data from a superlattice, [8] SnSe, [11,[19][20][21] Bi 2 Te 3 , [12,14,16,17,[22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] BiCuSeO, [12,[42][43][44][45][46][47][48][49][50][51][52][53][54][55][56] Na x CoO 2 , [57,58] Ca 3 Co 4 O 9 , [5...…”

Data-Driven Review of Thermoelectric Materials: Performance and Resource Considerations

“…Material family References Mn oxide [49][50][51][52][53][54][55][56][57][58][59][60] ZnO, SrTiO 3 33, [61][62][63][64][65][66][67][68][69][70][71][72] Co oxide 34,35,[73][74][75][76][77] other oxide 28,63,[78][79][80][81][82][83][84][85][86][87][88][89][90][91][92][93][94][95][96] Si-Ge …”

Observation of Bulk Superconductivity inNaxCoO2·yHJin1, Sales2, Khalifah3 et al. 2003Phys. Rev. Lett.984610View full textAdd to dashboardCite

“…1). For single crystal growth, both the floating-zone technique and flux method [7] were employed. In the latter case, thin plate-like single crystals were obtained with surface areas up to 5×5 mm 2 .…”