FIZIKA A 13 (2004) 1 , 11-22

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STRUCTURAL AND DIELECTRICAL PROPERTIES OF NANO-STRUCTURE BaTiO3 POWDERS DOPED WITH Eu3+ IONS PREPARED BY SOL-GEL PROCESS

M. BETTINELLIa, A. SPEGHINIa, S. I. SELIMANb and I. K. BATTISHAc

aDipatimento Scientifico e Tecnologico, Universita di Verona and INSTM, UDR Verona, Italy
bAin Shams University, Faculty of Girls, Cairo, Egypt
cNational Research Center, Department of Solid Satate Physics, Guiza, Egypt

Received 6 July 2003;  revised manuscript received 18 November 2004
Accepted 22 November 2004        Online 23 December 2004

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, e, 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.

PACS numbers: 77.84.-s, 42.70.Mp, 77.22.-d
UDC 537.226.4, 538.911, 537.226.2

Keywords: Eu3+-doped BaTiO3, powders, nano-crystalline, sol-gel, XRD, TEM, luminescence, dielectric properties

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