High thermoelectric and mechanical performance achieved by a hyperconverged electronic structure and low lattice thermal conductivity in GeTe through CuInTe2 alloying

초록

GeTe-based thermoelectric materials have a very high hole carrier concentration (similar to 10(21) cm(-3)), and thus, improving the figure of merit, ZT, is substantially challenging. In this work, we foremost dope Bi to lower the majority carrier concentration, followed by alloying CuInTe2 to further adjust the hole concentration to an optimal level (0.5-2.0 x 10(20) cm(-3)). This strategy also improves the structural symmetry and leads to hyperconverged valence sub-bands and resonance levels, increasing the effective mass from 1.42 m(0) to 1.95 m(0). Consequently, a high power factor of similar to 23 mu W cm(-1) K-2 at room temperature and similar to 41 mu W cm(-1) K-2 at 623 K in the (Ge0.93Bi0.05Te0.98)(CuInTe2)(0.01) sample is reported. Moreover, the introduced point defects and nano-deposits reduce the lattice thermal conductivity to amorphous levels. As a result, the (Ge0.93Bi0.05Te0.98)(CuInTe2)(0.01) sample has a peak ZT value of similar to 2.16 at 623 K and an average ZT value of similar to 1.42 at 300-773 K. A record high hardness value (similar to 277 Hv) is achieved. Simultaneous Bi doping and CuInTe2 alloying appear to be an effective strategy for increasing the ZT values of GeTe-based compounds.

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