Department of Mechanical & Aerospace Engineering , West Virginia University , Morgantown , West Virginia 26506 , United States.
ACS Appl Mater Interfaces. 2018 Nov 14;10(45):39018-39024. doi: 10.1021/acsami.8b12710. Epub 2018 Nov 1.
This work presents a novel approach of dramatically increasing the energy conversion efficiency of thermoelectric CaMnO ceramics through the combination of lattice dopants substitution and secondary phase segregation at the grain boundaries. The oxide ceramic samples are with the nominal composition of Ca Bi MnCu O ( x = 0, 0.02, 0.03; y = 0.02, 0.04). When Cu is introduced into the CaBi MnCu O samples, the grain growth from Bi-doped CaMnO grains is accompanied by the limited solubility of Cu ions in the grain interior, whereas Cu mainly formed a CuO secondary phase at the grain boundaries. Cu nonstoichiometry addition subsequently resulted in the increase of the Seebeck coefficient and decrease of electrical resistivity simultaneously. The sample with designed chemistry of CaBiMnCuO exhibits the power factor of 2.4 mW m K at 337 K and figure of merit ZT of 0.67 at 773 K. This ZT of 0.67 is by far the highest ZT reported for various perovskites oxide ceramics. Such enhancements in electrical power factor and the overall ZT are attributed to the synergistic effect of decreasing the carrier concentration to increase the Seebeck coefficient and simultaneously increasing the carrier mobility through the existence of CuO phase at the grain boundaries.
这项工作提出了一种通过晶格掺杂取代和晶界二次相分离相结合来显著提高热电器件钙锰氧化物陶瓷能量转换效率的新方法。氧化物陶瓷样品的名义成分为 CaBiMnCuO（x=0、0.02、0.03；y=0.02、0.04）。当 Cu 被引入 CaBiMnCuO 样品中时，晶粒从 Bi 掺杂的 CaMnO 晶粒中生长，同时 Cu 离子在晶粒内部的溶解度有限，而 Cu 主要在晶界处形成 CuO 第二相。随后 Cu 的非化学计量添加导致 Seebeck 系数增加，同时电阻率降低。具有设计化学计量的 CaBiMnCuO 样品在 337 K 时的功率因子为 2.4 mW mK，在 773 K 时的品质因数 ZT 为 0.67。这一 0.67 的 ZT 值是迄今为止报道的各种钙钛矿氧化物陶瓷中最高的 ZT 值。电输运性能的提高和整体 ZT 值的提高归因于通过晶界处 CuO 相的存在来降低载流子浓度以提高 Seebeck 系数，并同时提高载流子迁移率的协同效应。
