Original scientific paper
Structural and dielectrical properties of nano-structure BaTiO3 powders doped with Eu3+ ions prepared by sol-gel process
M. Bettinelli
; Dipatimento Scientifico e Tecnologico, Universita di Verona and INSTM, UDR Verona, Italy
A. Speghini
; Dipatimento Scientifico e Tecnologico, Universita di Verona and INSTM, UDR Verona, Italy
S. I. Seliman
; Ain Shams University, Faculty of Girls, Cairo, Egypt
I. K. Battisha
; National Research Center, Department of Solid Satate Physics, Guiza, Egypt
Abstract
Nano-structure BaTiO3 powders doped with Eu3+ ions have been prepared by a sol-gel technique. X-ray diffraction (XRD) results indicate that BaTiO3 gel powders crystallize into tetragonal symmetry on heat treatment at 750 ◦C. Particle sizes as small as 3.5 nm were measured for pure BaTiO3 powders. The XRD data were confirmed by transmission electron microscope. Room-temperature luminescence spectra of BaTiO3:0.5% Eu3+, BaTiO3:1% Eu3+ and BaTiO3:2% Eu3+ powders have been measured. The luminescence spectra of prepared ultrafine powders are dominated by the 5D0 →7F2 transition in Eu3+, suggesting a strong distortion of the Eu3+ sites. The foreign ions are mainly accommodated in Ba2+ tetragonal sites, which are then distorted by the occurrence of different ionic charge of the two cations Ba2+ and Eu3+. The dielectric constant, ε, of BaTiO3, BaTiO3:0.5% Eu3+, BaTiO3:1% Eu3+ and BaTiO3:2% Eu3+ powders at frequency 100 Hz was found to be equal to 1000, 1211, 1455 and 1800, respectively. This high dielectric constant is believed to arise from the increase of the crystallite size, when increasing the concentration of Eu3+ ions. After annealing in argon at 400 ◦C for two hours, at 100 Hz, the dielectric constant of the pure sample was 625 and the AC resistivity also decreased. The room temperature (RT) AC resistivity of the samples depends on the concentration of Eu3+ ions in BaTiO3 powders, and was found to decrease as the concentration of Eu3+ ions increased.
Keywords
Eu3+-doped BaTiO3; powders; nano-crystalline; sol-gel; XRD; TEM; luminescence; dielectric properties
Hrčak ID:
301681
URI
Publication date:
1.3.2004.
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