resumo
Donor-substituted strontium titanate is known as one of the best highly performing n-type oxide thermoelectrics. In the present work, structural, microstructural, and thermoelectric properties of Sr1-xPrxTiO3 +/-delta, Sr1-1.5x PrxTiO3 +/-delta, and Sr1-yTi0.8Nb0.2O3 +/-delta (x = 0.05-0.30, y = 0-0.10) perovskite-type titanates were assessed to identify the impact of nominal A-site deficiency on thermoelectric performance. A large increase in power factor was observed for A-site nonstoichiometric materials at high donor-substitution level, provided by the favorable changes in electronic structure, defect chemistry, and microstructure. Complex dependence of the total conductivity and Seebeck coefficient on strontium deficiency suggests effects of microstructure on the electrical properties of Pr-and Nb-substituted ceramic samples. Formation of oxygen vacancies was found to suppress lattice thermal conductivity at low and intermediate temperatures, whereas the electronic part of the heat transfer increases for cation-deficient materials. For both Pr- and Nb-substituted titanates, introducing nominal A-site deficiency represents a promising strategy for improving performance.
palavras-chave
NB-DOPED SRTIO3; TRANSPORT-PROPERTIES; CERAMICS; OXIDES; CONDUCTIVITY; TEMPERATURE; BEHAVIOR; SENSORS; PHASES; DEFECT
categoria
Chemistry; Science & Technology - Other Topics; Materials Science
autores
Kovalevsky, AV; Yaremchenko, AA; Populoh, S; Weidenkaff, A; Frade, JR
nossos autores
Aleksey Yaremchenko
Investigador Principal
Andrei Kavaleuski
Investigador principal
Jorge Ribeiro Frade
Professor(a) Jubilado(a)agradecimentos
This work was supported by the FCT, Portugal (projects SFAH/BPD/85619/2012, PEst-C/CTM/LA0011/2013, and FCT Investigator program, Grants IF/00302/2012 and IF/ 01072/2013). Financial support from the SNF-NCCR Manep and the DfG-SPP 1386 is greatly acknowledged. The authors are thankful to K. Galazka (EMPA) and S. Mikhalev, M.J. de Pinho Bastos (UA) for their experimental assistance.