| Autor: |
Almeida, A., Teles, Pedro, Chaves, M. R., Vilarinho, P. M., Baptista, J. L. |
| Předmět: |
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| Zdroj: |
Ferroelectrics; 2003, Vol. 294 Issue 1, p49-59, 11p |
| Abstrakt: |
Raman spectra and pyroelectric studies in bismuth doped SrTiO 3 ceramics, with general formulae Sr (1 - 1.5x) Bi x TiO 3 , were undertaken. For x = 0.0053, the low frequency Raman spectra exhibit striking similarities with the spectra of the undoped ceramics also revealing the existence of a polar soft-mode TO 1 , that obeys the classical Cochran softening law. The sample with x = 0.133 presents a very different dynamics, and its Raman spectra give evidence for the inexistence of an anti-ferrodistorsive phase transition, that occurs in the undoped ceramics at 104 K. Pyroelectric measurements disclose the existence of small electrical dipoles probably due to polar grain boundaries, off-centre positions of Bi 3+ and Ti 4+ ions, and Sr vacancies, that strongly influence the behaviour of these systems with temperature variation. There is a strong evidence for the existence of a relaxor state in the x = 0.133 ceramic at low temperatures. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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