Exploring the potential for enhancing the thermoelectric properties of barium titanate-based materials through the B-site-specific doping and nominal A-site deficiency

abstract

This study explores the potential for enhancing the thermoelectric performance of barium titanate through simultaneous Ta doping at the B-site and introducing barium deficiency, under various sintering conditions. The Taguchi method was employed to systematically assess the impacts of doping level, A-site stoichiometry, and sintering temperature on the thermoelectric properties using an L9 (27) orthogonal array, reducing the number of experiments to 9. XRD and SEM/EDS studies confirmed that the Ta-substituted BaTiO3 samples are nearly single phase in terms of composition, with only minor traces of TiO2 detected. The coexistence of cubic and tetragonal symmetries observed in the XRD patterns reflects structural polymorphism within the perovskite phase, rather than the presence of multiple chemical phases. The results demonstrate that Ta substitution at the Ti-site significantly improves electrical conductivity, reaching nearly 40 S/cm at 900 degrees C with 0.10 mole Ta doping. The lowest thermal conductivity of 1.05 W/m/K was observed for BaTi0.9Ta0.1O3, which represents the best value reported in the literature. This sample also exhibited the highest ZT value (similar to 0.4 at 900 degrees C), sintered at 1450 degrees C, attributed to enhanced electrical conductivity and a moderate Seebeck coefficient. Notably, this ZT value is the highest reported in the literature for the BaTiO3 family. Analysis of the correlation matrix emphasized the positive impact of Ta doping on electrical conductivity and its adverse effect on the Seebeck coefficient. These trends were also confirmed by multivariate linear regression provided a large positive coefficient of Ta doping on electrical conductivity while showing a large negative fitting coefficient for the Seebeck coefficient.

keywords

PERFORMANCE; SRTIO3; LA; SUBSTITUTION; IMPROVEMENT; EVOLUTION; BATIO3; FIGURE; MERIT; OXIDE

subject category

Materials Science

authors

Amirkhizi, P; Rasekh, S; Dura, OJ; Mikhalev, SM; Frade, JR; Kovalevsky, AV

Groups

G3 - Electrochemical Materials, Interfaces and Coatings

Projects

Collaboratory for Emerging Technologies, CoLab (EMERGING TECHNOLOGIES)

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)

acknowledgements

Sh. Rasekh acknowledges the support of the Research Employment Contract FCT - CEECIND/02608/2017. This work was also developed within the scope of the PhD project of P. Amirkhizi (grant 2020.08051. BD funded by FCT) and the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 (DOI 10.54499/UIDB/50011/2020) , UIDP/50011/2020 (DOI 10.54499/UIDP/50011/2020) & LA/P/0006/2020 (DOI 10.54499/LA/P/0006/2020) , financed by national funds through the FCT/MCTES (PIDDAC) . This article was supported by the projects UIDB/00481/2020 and UIDP/00481/2020-Fundaca o para a Cie ncia e a Tecnologia, DOI 10.54499/UIDB/00481/2020 (https://doi.org/10.544 99/UIDB/00481/2020) and DOI 10.54499/UIDP/00481/2020 (https://doi.org/10.54499/UIDP/00481/2020) .