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

• Tipo: Artigo em Revista Científica Internacional
• Data: 2011

Autores

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

Revista

Título: Acta Materialia

Vol. 59

Páginas: 5388-5397

ISSN: 1359-6454

Editora: Elsevier

Indexação

ISI Web of Knowledge - 37 Citações

Scopus - 40 Citações

Classificação Científica

FOS: Ciências da engenharia e tecnologias > Engenharia dos materiais

Outras Informações

ID Authenticus: 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.

Idioma: Inglês

Tipo (Avaliação Docente): Científica

Nº de páginas: 10