Abnormal Grain Growth as a Method To Enhance the Thermoelectric Performance of Nb-Doped Strontium Titanate Ceramics


Driven by the need for high-temperature n-type thermoelectrics for energy-harvesting sectors, SrTi0.8Nb0.2O3 +/-delta ceramics are prepared here from powders with average particle sizes of 270 and 800 nm by the conventional sintering in air at 1450 degrees C and further in H-2/N-2 at 1400 degrees C. In contrast to coarse particle powders, the use of fine particle powders under these conditions leads to abnormal grain growth and thereby bimodal grain size distribution in SrTi0.8Nb0.2O3 +/- ceramics. As a result, a 3-fold increase in the thermoelectric figure of merit to 0.36 at 970 K is achieved, thus establishing the record value for bulk Nb-doped strontium titanate up to this temperature.




Chemistry; Science & Technology - Other Topics; Engineering


Tkach, A; Resende, J; Saravanan, KV; Costa, ME; Diaz-Chao, P; Guilmeau, E; Okhay, O; Vilarinho, PM

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This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT ref UID/CTM/50011/2013), financed by national funds through the FCT/MEC and when appropriate cofinanced by FEDER under the PT2020 Partnership Agreement as well as within FCT independent researcher grant IF/00602/2013. We thank Krzysztof Orlinski and Dorota A. Pawlak from the Institute of Electronic Materials Technology (ITME), Warsaw, Poland, for the heat capacity measurements.

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