Enhanced Thermoelectric Properties and Increased Thermal Stability of Superionic Cu 2S by Excessive Iodine Doping
32 Pages Posted: 13 Dec 2018 Sneak Peek Status: Under ReviewMore...
Highly disordered superionic phases lead to high thermoelectric performance (ZT~1.5) for Cu2M (M=S, Se, Te) alloys but bring challenges concerning thermal instability. Here we demonstrate that enhanced thermoelectric properties and improved thermal stability could be simultaneously realized in Cu2S upon excessive I doping. The addition of excessive I beyond stoichiometric ratio not only induces higher Cu deficiency and thus better electrical properties for the prepared Cu2SIx (x=0–0.15) alloys, but also leads to ultra-low thermal conductivity ascribed to multiple superionic phases and abundant nano-crystals. As a result, a ZT value of 1.62 at 700°C is achieved for the sample x=0.10 (Cu2SI0.1), which is nearly twice the value of undoped Cu2S. Moreover, I doping eliminates the ultrafast phase transformation that results in abrupt volume changes in pristine Cu2S and suppresses the rest transformations to be very sluggish. The high ZT value together with significantly suppressed phase transitions and impeded copper segregation enable the excessively I-doped samples more beneficial for practical thermoelectric power generation.
Keywords: Superionic phase, thermal stability, phase transformation, thermoelectric properties, Cu2S
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