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