Luminescence properties of Eu3+ -activated SrWO4 nanophosphors- Concentration and Annealing effect.

Abstract

Eu3+ (2, 5, 7 and 10 at.%) activated SrWO4 phosphors were prepared via a polyol synthesis route at low temperature (∼150 °C) under urea hydrolysis. X-ray diffraction studies of all Eu3+ doped samples corroborate good crystallinity with a tetragonal scheelite-type structure of the SrWO4 phase. The value of strain was obtained in the range ∼0.003 to 0.004 for as-prepared (ASP) and samples annealed at 900 °C. Vibrational modes were studied using IR and Raman Spectroscopy. Photoluminescence studies of Eu3+ doped SrWO4 samples were carried out under 266, 394 and 464 nm excitations. An intense red emission was observed with a strong peak at ∼613 nm due to 5D0 → 7F2 transition under 266 nm. Effect of annealing at 900 °C on the photoluminescence properties of samples has been studied and it was found that luminescence intensity increases up to ∼9 times (for 10 at.% Eu3+-doped SrWO4) on annealing as compared to the corresponding as-prepared sample. High asymmetric ratios (A21) ∼ 6–13 were observed demonstrating it to be a red emitter. Calculated CIE co-ordinates of these Eu3+ doped samples under 266 nm excitation for ASP and annealed at 900 °C are x = 0.65 & y = 0.34, which are closer to the standard of NTSC (x = 0.67 & y = 0.33). These studies reveal that SrWO4:Eu3+ nano-phosphors can be used as potential red emitting phosphors for the development of white LEDs.