STRUCTURAL AND LUMIENESCENT STUDY OF EUROPIUM (III) DOPED TUNGSTATES

Abstract

Motivated by the need of new red phosphor for white - light - emitting diodes (WLEDs) application, Eu³⁺ doped Sc_2-xIn_x(WO₄)₃ (x = 0, 1, 2) solid solutions were synthesized by high temperature solid - state reaction. Structural and luminescent properties were obtained by using X - ray diffraction (XRD), infrared and photoluminescence spectroscopic techniques. IR spectrum of the ScIn(WO₄)₃ doped with Eu³⁺ contains the characteristic vibrations of the WO₄ and MeO₆ , (Me = Sc, In) polyhedral, building the Sc₂(WO₄)₃ and In₂(WO₄)₃ structures. An effective energy transfer from the tungstate matrix to the active Eu³⁺ ion was observed. Intense red luminescence was obtained in these samples under excitation at 394 nm using the sharp 7F0 → 5L6 transition of Eu³⁺. The calculated asymmetric ratio ( 5D0 → 7F2 / 5D0 → 7F1 ) was about 7.5, suggesting that the obtained materials are characterized with distorted environment around the rare earth ion and with high red emission intensity. The prepared ScIn(WO₄)₃ solid solution demonstrates the highest emission intensity. The obtained chromaticity coordinates of the Eu³⁺ doped Sc_2-xIn_x(WO₄)₃ solid solutions were very close to the red standard recommended by National Television Standards Committee (NTSC).