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A2: Medium temperature materials

Cu-Bi-Se-based pavonite homologue: a promising thermoelectric material with low lattice thermal conductivity

Mun, H.,1 Hwang, J.-Y.,2 Lee, K.H.,3* and Kim, S.W.1,2*
1Univ. of Sungkyunkwan, 2IBS, 3Univ. of Kangwon

The search for semiconducting materials with a low thermal conductivity (κ) is a key success factor to develop novel thermoelectric (TE) materials because their energy conversion efficiency from heat to electricity or vice versa is directly determined by κ. The structural complexity is basically linked to the lattice thermal conductivity (κlatt), thus exploring semiconducting materials with complex structure becomes one of the most promising routes for developing materials with intrinsically low κlatt.

Cu-Bi-Se-based pavonite homologues, Cux+yBi5-ySe8 (1.2 ≤ x ≤ 1.5, 0.1 ≤ y ≤ 0.4), in a polycrystalline bulk form have been synthesized using a conventional solid state sintering technique. Their thermal and electronic transport properties were evaluated for mid-temperature thermoelectric power generation applications. Structural complexity, based on unique substitutional and interstitial Cu atoms in the structure, makes this system attractive as an intrinsic low thermal conductivity material; also the band structure calculations revealed that interstitial Cu atoms generate n-type carrier conduction. Room temperature lattice thermal conductivities ranging between 0.41 W m-1 K-1 and 0.55 W m-1 K-1 were found for Cux+yBi5-ySe8; these values are comparable to those of the state-of-the-art low lattice thermal conductivity systems. These extremely low thermal conductivities combined with the power factors result in the highest ZT = 0.27 at 560 K for Cu1.9Bi4.6Se8 [1].

In low κ materials with complex structure, the engineering of electronic structure to control carrier transport is an essential paradigm for the realization of high ZT. Here we report that the structural components are strongly tangled with the transport properties in the complex structure and it is possible to control overall electronic and thermal transport properties by systematic doping at targeted atomic site considering structure-property relationships.

 

[1] J. Y. Cho, H. Mun, B. Ryu et al., “Cu-Bi-Se-based pavonite homologue: a promising thermoelectric material with low lattice thermal conductivity,” Journal of Material Chemistry A, vol. 1, no. 34, pp. 9768–9774, 2013.