Role of trivalent Sr substituents and Sr vacancies in tetragonal and polar states of SrTiO3

• Type: Article in International Scientific Journal
• Date: 2011

Authors

Tkach, A (Author) Other; Correia, TM (Author) Other; Almeida, A (Author) FCUP; Agostinho Moreira, JA (Author) FCUP; Chaves, MR (Author) Other; Okhay, O (Author) Other; Vilarinho, PM (Author) Other; Gregora, I (Author) Other; Petzelt, J (Author) Other

Journal

Title: Acta Materialia

Vol. 59

Pages: 5388-5397

ISSN: 1359-6454

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 37 Citations

Scopus - 40 Citations

Scientific classification

FOS: Engineering and technology > Materials engineering

Other information

Authenticus ID: P-002-P42

DOI: 10.1016/j.actamat.2011.05.011

Abstract (EN): Inelastic light scattering is used to study lattice dynamics of strontium titanate (STO) ceramics with several heterovalent dopants (La3+, Gd3+, Y-3+), which substitute Sr2+ ions. An extraordinary shift of the antiferrodistortive transition temperature (T-a) is ascertained when just a small percentage of any of the dopants is used. T-a 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 T-a vs. t is obtained if strontium vacancies are taken into account. A vacancy size of similar to 1.547 angstrom was estimated, which is similar to 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.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 10