resumo
X-ray diffraction (XRD) and Raman scattering in sol-gel derived Ph1-x CaxTiO3(PCT)thin films are studied as a function of Ca content x. It is found that Ca2+ addition to PbTiO3 films results in a gradual decrease of tetragonality of the perovskite lattice accompanied with a considerable modification of the Raman spectra. A significant difference in Raman spectra of PCT films and available reference data for single crystals (x = 0) is explained in terms of the large internal stress, small grain size, and structural disorder produced by Ca2+ substitution. It is found that the shift of the frequency of ferroelectric soft mode correlates well with the variation of tetragonality for x less than or equal to x(c) = 0.4. The concentration dependence of the shift is strongly non-linear being qualitatively different from that observed earlier in other A-site doped lead fitanate-based systems. According to XRD data, the averaged crystal structure for x(c) approximate to 0.4 appears as pseudo-cubic, while Raman scattering revealed short-range order tetragonal distortion. The structural characteristics of PCT films are linked to their electromechanical properties measured earlier by interferometric technique. (C) 2004 Elsevier B.V. All rights reserved.
palavras-chave
CHEMICAL-VAPOR-DEPOSITION; (PB,CA)TIO3 THIN-FILMS; LEAD TITANATE FILMS; PHASE-TRANSITION; CRYSTAL-STRUCTURE; SUBSTRATE; (PB
categoria
Materials Science
autores
Kholkin, AL; Bdikin, I; Yuzyuk, YI; Almeida, A; Chaves, MR; Calzada, ML; Mendiola, J
nossos autores
