Enhanced thermoelectric performance of In2O3-based ceramics via Nanostructuring and Point Defect Engineering

Abstract

The issue of how to improve the thermoelectric figure of merit (ZT) in oxide semiconductors has been challenging for more than 20 years. In this work, we report an effective path to substantial reduction in thermal conductivity and increment in carrier concentration, and thus a remarkable enhancement in the ZT value is achieved. The ZT value of In2O3 system was enhanced 4-fold by nanostructuing (nano-grains and nano-inclusions) and point defect engineering. The introduction of point defects in In2O3 results in a glass-like thermal conductivity. The lattice thermal conductivity could be reduced by 60%, and extraordinary low lattice thermal conductivity (1.2 W m−1 K−1 @ 973 K) below the amorphous limit was achieved. Our work paves a path for enhancing the ZT in oxides by both the nanosturcturing and the point defect engineering for better phonon-glasses and electron-crystal (PGEC) materials.

Substitution effect of tetravalent and pentavalent elements on thermoelectric properties in In₂O₃-SnO₂ system

“…The single element substitution of Co [6], Sn [7], and co-substitution of Zn+Nd [8], Zn+Ge [9], Zn+Ce [10], M+Sn (M=Zn, Cu, Ni) [11] for the indium site has been recently investigated and ZT values as high as 0.3 can be obtained at high temperatures. The approaches of fine-grained and high packing were also performed to decrease the thermal conductivity [12,13].…”

In2O3-Based Thermoelectric Materials: The State of the Art and the Role of Surface State in the Improvement of the Efficiency of Thermoelectric Conversion

“…[28,178] demonstrated that in nanostructured In 2 O 3 :MO x (M = Cr, Mn, Ni, Zn, Sn) ceramics, the thermal conductivity decreased to k~1.58-1.75 W/m·K at RT irrespective of the chemical nature of the second phase. Lan et al [166] reported on the thermal conductivity k~1.2 W/m·K at 973 K in sintered In 2 O 3 doped by Zn and Ce that is below the amorphous limit [142]. Approximately in the same range was the minimum thermal conductivity of In 2 O 3 doped with Ge [70].…”

“…For In 1.92 (ZnCe) 0.08 O 3 this regularity is shown in Figure 8. The rapid decrease of thermal conductivity in comparison with bulk values takes place with the reduction of grain size [38,166,177]. For example, Ohtaki and co-workers.…”

“…Therefore, bulk-like ITO with tightly-packed large grains (~5 µm) possesses a relatively high total thermal conductivity k~10 W/m·K at room temperature (RT) [70,166], which limits the achievement of the required efficiency of thermoelectric conversion. Therefore, the problem of reducing the thermal conductivity of In 2 O 3 -based oxides is an important task in terms of using these oxides as thermoelectric materials.…”

Understanding Phonon Interactions with Defects in Functional Oxide Materials

“…Even in the mid-1900's, the thermoelectric properties of TiO 2 were being investigated with modification of extrinsic and intrinsic defect levels to alter the thermopower [15,130] Aside from point defect scattering, common strategies to reduce thermal conductivity for thermoelectrics lie in nano-structuring [49,117,118] and introduction of nano-particles [114,135]. Advances with respect to complex oxide thermoelectrics have been made in superlattice structures with interrupted interfaces [51] as well as incorporation of nano-scale grain boundaries and inclusions into already defected oxides [127].…”