Journal
JOURNAL OF MATERIALS CHEMISTRY C
Volume 6, Issue 4, Pages 738-744Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/c7tc03975a
Keywords
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Funding
- Deutsche Forschungsgemeinschaft [WE 4972/2, FR 3718/1-1]
- Feodor Lynen Research Fellowship Program of the Alexander von Humboldt Foundation
- Hessen State Ministry of Higher Education, Research and the Arts via LOEWE RESPONSE
- DFG [MO 3010/3-1]
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Point defects largely determine the properties of functional oxides. So far, limited knowledge exists on the impact of cation vacancies on electroceramics, especially in (Na1/2Bi1/2) TiO3 (NBT)-based materials. Here, we report on the drastic effect of A-site non-stoichiometry on the cation diffusion and functional properties in the representative ferroelectric (Na1/2Bi1/2) TiO3-SrTiO3 (NBT-ST). Experiments on NBT/ST bilayers and NBT-ST with Bi non-stoichiometry reveal that Sr2+-diffusion is enhanced by up to six orders of magnitude along the grain boundaries in Bi-deficient material as compared to Bi-excess material with values of grain boundary diffusion similar to 10(-8) cm(2) s(-1) and similar to 10(-1)3 cm(2) s(-1) in the bulk. This also means a nine orders of magnitude higher diffusion coefficient compared to reports from other Sr-diffusion coefficients in ceramics. Bi-excess leads to the formation of a material with a core-shell microstructure. This results in 38% higher strain and one order of magnitude lower remanent polarization. In contrast, Bi-deficiency leads to a ceramic with a grain size six times larger than in the Bi-excess material and homogeneous distribution of compounds. Thus, the work sheds light on the rich opportunities that A-site stoichiometry offers to tailor NBT-based materials microstructure, transport properties, and electromechanical properties.
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