Thermoelectric (TE) materials have captured extensive attention because of their potential use in direct thermal-to-electrical energy conversion and solid-state refrigeration. The performance of thermoelectric materials can be quantified by a dimensionless figure of merit ZT. Currently, ZT value is too low to be used in large scale. Hence, it is a great challenge how to raise their ZT value.

-Zn4Sb3 is a promising moderate-temperature thermoelectric material with cheap constituent elements. The experimental studies conducted by Prof. Xiaoying QIN and his team show that Gd-doping causes resonant distortion of DOS near the Fermi level of -(Zn1-xGdx)4Sb3, which is manifested by a large increase in DOS effective mass and verified by low-temperature heat capacity. First-principles calculations further reveal that a high sharp resonant peak in the DOS locating near the valence band maximum of -Zn4Sb3 originates largely from contribution of the d-orbit of Gd. This resonant distortion of DOS results in an increase of thermopower by ~40 V K-1 for -(Zn1-xGdx)4Sb3(x = 0.002 and 0.003); additionally, this Gd-doping gives rise to ~15% reduction of thermal conductivity k at x = 0.002 content.As a result, a largest value of ZT =1.2 is achieved at 655 K for -(Zn1-xGdx)4Sb3 (x= 0.002), which is~60% larger than that (ZT= 0.75) of the un-doped one. The present result demonstrates that Gd doping is a promising way to elevate thermoelectric performance of -Zn4Sb3 via bringing about resonant distortion of DOS. For details please see their recent published paper (J. Mater. Chem. A, 2015, 3, 11768)

Thermoelectric materials, such as BiSbTe, with thermoelectric figure of merit, ZT, being much larger than unit at near room temperatures is vital for power generation by using low-grade waste heat. Prof. Xiaoying Qin and his coworkers show that by incorporating very small proportion (1 vol.%) of Cu3SbSe4 nanoparticles into BiSbTe matrix to form nanocomposites, besides large (~50%) reduction of lattice thermal conductivity, both enhanced thermopower through energy-dependent scattering and alleviated reduction of carrier mobility via carrier scattering at heterojunction potentials occur at elevated temperatures, which allow thermoelectric power factor of the composite material to reach ~37?W/(cm?K2) at 467 K. Consequently, a largest value of ZT = 1.6 is achieved at 476 K. Moreover, it has excellent performance in broad temperature range (say, ZT=1.0 at 300 K and ZT=1.5 at 500 K), which makes this material attractive for cooling and power generation.

Further details were published in J. Mater. Chem. A entitled Enhancement of thermoelectric performance of [small beta]-Zn4Sb3 through resonant distortion of electronic density of states doped with Gd and Enhanced thermoelectric performance through carrier scattering at heterojunction potentials in BiSbTe based composites with Cu3SbSe4 nanoinclusions.

Contact:

Prof. QIN Xiaoying

Institute of Solid State Physics, Chinese Academy of Sciences

Hefei, Anhui 230000, China

Tel: 0551-65592750

E-mail: xyqin@issp.ac.cn