Frömling, Till ; Steiner, Sebastian ; Ayrikyan, Azatuhi ; Bremecker, Daniel ; Dürrschnabel, Michael ; Molina-Luna, Leopoldo ; Kleebe, Hans-Joachim ; Hutter, Herbert ; Webber, Kyle G. ; Acosta, Matias (2018)
Designing properties of (Na1/2Bix)TiO3-based materials through A-site non-stoichiometry.
In: Journal of Materials Chemistry C, 6 (4)
doi: 10.1039/C7TC03975A
Artikel, Bibliographie

Kurzbeschreibung (Abstract)

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 ∼10−8 cm2 s−1 and ∼10−13 cm2 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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