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Title: Optical phonon modes and dielectric behavior of Sr1-3x/2CexTiO3 microwave ceramics
Authors: Moreira, R L
Lobo, R P S M
Subodh, G
Sebastian, M T
Matinaga, F M
Dias, A
Keywords: SRTIO3 Thin films
Strontium titanate
Homologous series
Phase transition
Raman spectrum
Issue Date: 2007
Publisher: American Chemical Society
Citation: Chemistry of Materials 19(26):6548-6554;25 Dec 2007
Abstract: Sr1-3x/2CexTiO3 dielectric ceramics (with x varying from 0.133 to 0.400) were investigated by Raman and infrared spectroscopies. The observed features could be related to SrTiO3 phonon modes. The Raman spectra show first-order modes-which are modes either activated by polar defects or due to local symmetry lowering-together with classical second-order modes of SrTiO3. The infrared spectra are dominated by the three predicted polar phonons of SrTiO3, although a faint terragonal distortion confirmed by low-temperature measurements was observed for all compositions. For increasing Ce content, the infrared spectra show a continuous hardening of the TO modes and the softening of the highest frequency LO mode. Together with the broadening of the TO phonon lines, these phonon energy evolutions explain the 7 observed dielectric behavior of the material: namely, the decreasing of the dielectric constant and temperature coefficient of the resonance frequency (tau(f)) with x. The quality factor is maximized for x = 0.25. Compared to pure SrTiO3, chemically substituted Sr1-3x/2CexTiO3 ceramics present more adequate dielectric properties at microwave frequencies for technological applications.
ISSN: 0897-4756
Appears in Collections:2007

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