abstract
Titanium-rich (Sr/Ti = 0.995) strontium titanate (ST) ceramics, air-sintered in a temperature range of 1400-1625 degrees C, were reported to possess anomalies in the grain growth and analogous anomalies in the grain boundary (GB) conductivity activation energy. However, these two interface-related phenomena, occurring at GBs, could not be associated with each other using a simple "brick-layer" model. In this work we revise the topic and advocate that the deviation from the model comes from the oxygen vacancies localized at GBs of the rapidly cooled ST ceramics. To verify this, we annealed the ceramics in oxygen and performed their systematic and comparative analysis using impedance spectroscopy. A levelling-off in the GB conductivity activation energy, which increases for <= 1.24 eV, and a four-fold decrease in the GB permittivity are observed after annealing. Thus, we confirm a key role of oxygen vacancies in relation between the grain growth and GB conductivity anomalies of as-sintered Ti-rich ST ceramics.
keywords
PHASE-TRANSITION; SRTIO3; CHEMISTRY; MICROSTRUCTURE; DEPENDENCE; CERAMICS; DEFECT; BULK
subject category
Materials Science
authors
Tkach, A; Amaral, L; Vilarinho, PM; Senos, AMR
our authors
Ana Maria de Oliveira e Rocha Senos
Collaborator
Oleksandr Tkach
Assistant Researcher
Paula Maria Lousada Silveirinha Vilarinho
Vice Directoracknowledgements
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 co-financed by FEDER under the PT2020 Partnership Agreement as well as within FCT independent researcher grant IF/00602/2013. L.A. acknowledges FCT for postdoctoral research grant SFRH/BPD/97453/2013. Thanks to Dr RC Pullar for assisting with the English language of this article.