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Entering New Era of Thermoelectric Oxide Ceramics with High Power Factor through Designing Grain Boundaries



Cesar-Octavio Romo-De-La-Cruz, Yun Chen, Liang Liang, Sergio Paredes-Navia, Winnie Wong-Ng, Mark Williams, Xueyan Song


Thermoelectric (TE) oxide ceramics could play a significant role in waste heat recovery using TE generators, accelerating clean energy generation and achieving net-zero emissions. In 2003, the TE performance of single-crystal Ca3Co4O9+δ was evaluated with an extrapolated dimensionless thermoelectric figure of merit of 0.87. Polycrystalline Ca3Co4O9+δ ceramics are typically only about 30 % as efficient as single crystals since they have low electrical conductivity and low Seebeck coefficient. To improve the TE performance of polycrystalline Ca3Co4O9+δ, we have developed a unique approach to driving dopants segregation at the grain boundaries (GBs) to dramatically increase the Seebeck coefficient and electrical conductivity and overall energy conversion efficiency of oxide. This review exploited our pertinent results from five sets of dopants to elucidate that the GBs can be engineered to reverse their detrimentally impact on electrical properties and provide the design domain to improve the electrical transport properties instead significantly. The selection of two dopants with appropriate size results in the oxide ceramics with a peak ZT of 0.9 at 1073 K, outperforming single-crystal. In addition, this is the highest ZT value of oxide ceramics of any type at an elevated temperature of over 1000 K. The present review unveils the atomic structure origin of the dopants' segregation at GBs and presents a feasible and valuable approach for treating the GBs as a two-dimensional secondary phase complexion that is independently tunable to decouple the strongly correlated physical parameters and simultaneously enhance the Seebeck coefficient, electrical power factor, and ZT over a wide range of temperatures.
Renewable & Sustainable Energy Reviews


Grain boundary, thermoelectric, Seebeck coefficient, oxide, segregation, dopant


Romo-De-La-Cruz, C. , Chen, Y. , Liang, L. , Paredes-Navia, S. , Wong-Ng, W. , Williams, M. and Song, X. (2023), Entering New Era of Thermoelectric Oxide Ceramics with High Power Factor through Designing Grain Boundaries, Renewable & Sustainable Energy Reviews, [online], , (Accessed April 24, 2024)
Created January 12, 2023, Updated April 24, 2023