• PDF / 1,872,647 Bytes
• 8 Pages / 593.972 x 792 pts Page_size
• 60 Downloads / 193 Views

DOWNLOAD

REPORT

---

https://doi.org/10.1007/s11664-020-08566-0  2020 The Minerals, Metals & Materials Society

ORIGINAL RESEARCH ARTICLE

Synergistically Optimized Electrical and Thermal Transport Properties of CaMnO3 via Doping High Solubility Sr JING-WEN ZHANG,1 ZHEN-WANG WU,1 FEI-PENG ZHANG,2 XIN-YU YANG,1 and JIU-XING ZHANG 1,3 1.—School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009, China. 2.—Institute of Physics, Henan University of Urban Construction, Pingdingshan 467036, China. 3.—e-mail: [email protected]

Herein, we show that we can synergistically optimize the electrical and thermal transport properties of CaMnO3 via doping Sr. All the samples exhibit a single phase with an orthorhombic symmetry within the experimental doping range (0-10%). Sr doping significantly reduces resistivity while maintaining a relatively high absolute value of Seebeck coefficient, resulting in an effective enhancement in the electrical properties of the material. The maximum power factor ( 3.01 l W cm1 K2) is achieved at 873 K for Ca0.96Sr0.04MnO3, which is three times larger than that of the un-doped CaMnO3. The thermal conductivity governed by lattice thermal conductivity is notably decreased compared with the un-doped sample, which is mainly attributed to the decreased grain size and large mass and strain fluctuations caused by Sr doping, and the thermal conductivity decreases with increasing Sr doping level. The enhanced power factor and significantly reduced thermal conductivity lead to a maximum ZT value of 0.15 at 873 K in the Ca0.90Sr0.10MnO3 sample, indicating that CaMnO3 is a potential candidate for high-temperature application. Key words: CaMnO3, thermoelectric performance, Sr doping, lattice thermal conductivity

INTRODUCTION Thermoelectric (TE) materials, which can directly realize the conversion of heat and electricity, have attracted growing attention owing to their promising applications in waste-heat power generation and cryogenic refrigeration.1–3 The efficiency of energy conversation is correlated to the intrinsic properties of materials and is defined as the dimensionless figure of merit ZT = S2T/qj, where q is electrical resistivity, S is the Seebeck coefficient, T is absolute temperature, and j is thermal conductivity, respectively.4 It is obvious that the highperformance TE materials require a high S, low q and low j. However, owing to the complicated

(Received August 3, 2020; accepted October 13, 2020)

relationship among these three parameters, it is difficult to optimize the electrical and thermal properties simultaneously. So far, effective strategies for improving thermoelectric properties mainly emphasize two parts: one is the enhancement of power factor PF, including band engineering, energy filtering effect, and optimization of carrier concentration.5,6 The other is the reduction of lattice thermal conductivity jl, including defect engineering, nanostructure and all-scale hierarchical.7,8 In the past, most alloy-based TE materials such as PbTe, Bi2Te3 and GeTe, which have