Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1447284 | Acta Materialia | 2011 | 10 Pages |
Inelastic light scattering is used to study lattice dynamics of strontium titanate (STO) ceramics with several heterovalent dopants (La3+, Gd3+, Y3+), which substitute Sr2+ ions. An extraordinary shift of the antiferrodistortive transition temperature (Ta) is ascertained when just a small percentage of any of the dopants is used. Ta is dependent on the tolerance factor (t). In this work, it is clearly shown that, regardless of the dopant used, a common linear dependence of Ta vs. t is obtained if strontium vacancies are taken into account. A vacancy size of ∼1.547 Å was estimated, which is ∼7% larger than the Sr2+ radius. The vacancy size obtained can directly explain the increase in lattice parameter with increasing Bi3+ content in Bi-doped STO, as opposed to the dopants referred to above. Furthermore, the introduction of La3+, Gd3+ or Y3+ ions at the Sr site causes a considerable stiffening of the transverse optic TO1 mode at low temperatures, thereby decreasing the phonon contribution to the dielectric permittivity. Thus, no traces of a ferroelectric phase are found for any of the dopants used in this work.
Graphical abstractSr-substituents doping and compensation charge chemistry in SrTiO3 unraveled by giant tetragonality improvement. Sr-vacancy size is 1.547 Å.Figure optionsDownload full-size imageDownload high-quality image (142 K)Download as PowerPoint slide