Strontium titanate-based ceramics processed by laser floating zone: Effects of processing atmosphere and Sr/Ti ratio

abstract

Strontium titanate (SrTiO3) is a well-known perovskite oxide with a simple crystalline structure and well-documented redox sensitivity, making it a versatile material for a wide range of functional applications, including thermoelectrics, photocatalysis and electronics. In this work, SrTiO3-based ceramics with varied Sr/Ti ratios (Sr0.95TiO3-delta, SrTiO3-delta, and Sr1.05TiO3 +/-delta) were processed using the laser floating zone (LFZ) technique under oxidising and reducing atmospheres, enabling a controlled study of the effects of non-equilibrium processing conditions on phase composition and microstructure. Despite the simplicity of the system, the combination of LFZ and composition variation led to pronounced changes in phase evolution behaviour, grain morphology, and local structural order. Secondary phase segregation, including TiO2 and SrO, was observed to depend on stoichiometry and processing atmosphere, with some precipitates showing preferred orientation along the growth direction. Raman spectroscopy revealed distinct signatures of lattice distortion in air-processed samples, in contrast to the more symmetric structures formed under reducing conditions. The thermogravimetric analysis confirmed the formation of only minimal Ti3+, underscoring the need for further defect engineering strategies to achieve functional properties such as enhanced electronic conductivity. These results highlight the potential of LFZ processing, combined with tailored composition, as a versatile tool for tuning the microstructure of SrTiO3-based ceramics for various functional applications.

keywords

THERMOELECTRIC PERFORMANCE; DEFECT CHEMISTRY; SRTIO3; INSIGHT; ENERGY; RAMAN

subject category

Materials Science

authors

Lopes, D; Ferreira, NM; Yaremchenko, AA; Constantinescu, G; Fernandes, AJS; Costa, FM; Kovalevsky, A

Groups

G3 - Electrochemical Materials, Interfaces and Coatings

Projects

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)

Thermoelectric oxide composites: design through controlled interactions (TEOsINTE)

acknowledgements

This work was developed within the scope of the project i3N, LA/P/0037/2020, UIDB/50025/2020 & UIDP/50025/2020, financed by national funds through the FCT/MEC. The authors also acknowledge 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 project UID 00481 Centre for Mechanical Technology and Automation (TEMA) . Gabriel Constantinescu acknowledges the support of the TEOsINTE project (Grant agreement ID: 101003375) , funded under the H2020-EU.4. Programmes (Funding Scheme: MSCA-IF-EF-ST-Standard EF) , and of the 2021.09690.CBM project (FCT-DAAD bilateral mobility) , funded by the FCT. Diogo Lopes acknowledges the PhD scholarship by FCT (grant https://doi.org/10. 54499/2020.06454.BD) .This work was also funded by national funds (OE) , through FCT-Fundacao para a Ciencia e a Tecnologia, I.P., in the scope of the framework contract foreseen in the numbers 4, 5 and 6 of the article 23, of the Decree-Law 57/2016, of August 29, changed by Law 57/2017, of July 19.