Počet záznamů: 1

Role of trivalent Sr substituents and Sr vacancies in tetragonaland polar states of SrTiO.sub.3./sub..

  1. 1.
    0366112 - FZU-D 2012 RIV GB eng J - Článek v odborném periodiku
    Tkach, A. - Correia, T.M. - Almeida, A. - Moreira, J.A. - Chaves, M. R. - Okhay, O. - Vilarinho, P. M. - Gregora, Ivan - Petzelt, Jan
    Role of trivalent Sr substituents and Sr vacancies in tetragonaland polar states of SrTiO3.
    Acta Materialia. Roč. 59, č. 14 (2011), 5388-5397 ISSN 1359-6454
    Grant CEP: GA AV ČR KAN301370701
    Výzkumný záměr: CEZ:AV0Z10100520
    Klíčová slova: phase transformations * dynamic phenomena * Raman spectroscopy * lattice defect vacancies * perovskites
    Kód oboru RIV: BM - Fyzika pevných látek a magnetismus
    Impakt faktor: 3.755, rok: 2011

    Raman scattering is used to study strontium titanate (STO) ceramics with several heterovalent dopants(La3+, Gd3+, Y3+), which substitute Sr2+ ions. Extraordinary shift of the antiferrodistortive transition temperature (Ta) is observed when a small percentage these dopants is used. A common linear dependence of Ta vs. tolerance factor t is obtained if strontium vacancies are taken into account. A vacancy size of ~1.547 A˚ was estimated, ~7% larger than the Sr2+ radius. This vacancy size can directly explain the increase in lattice parameter with increasing Bi3+ content in Bi-doped STO. 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. No traces of a ferroelectric phase are found for any of the dopants used.
    Trvalý link: http://hdl.handle.net/11104/0201197