D. Balaji

Synthesis, vibrational and luminescence studies on Eu3+:KY(WO4)2 red phosphors

Eu3+:KY(WO4)2 (Eu3+:KYW) phosphors were synthesized by sol-gel method using citric acid as a chelator and ethylene glycol as a binder. The crystallinity, organic liberation and tungstate bridge formation and excitation and emission properties of the synthesized phosphors were characterized by powder XRD, FT-IR, Raman and fluorescence analysis respectively. Powder XRD confirms the formation of monoclinic crystalline structure with space group C2/c. Organic liberation with respect to thermal treatments was analyzed in FT-IR. Raman results indicate different vibration mode related to monoclinic structure. The strong red emission at 615 nm (5D0→ 7F2) of the phosphors under the near UV excitation was examined by the fluorescence studies.

Investigation on the luminescence properties of Eu3+/Tb3+:Y3Al5O12 phosphors

Eu3+/Tb3+ singly and co-doped Y3Al5O12 (YAG) phosphors were synthesized by the modified sol-gel method. The prepared phosphors were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscope (FE-SEM) and luminescence analysis. Cubic YAG formation was confirmed by XRD. A strong characteristic emission from Eu3+ and Tb3+ ions was identified and the influence of doping concentration was studied. Energy transfer mechanism was observed from Tb3+ to Eu3+ ions in the co-doped phosphor. The CIE co-ordinates cover orange-red to green with increasing the Tb3+ion concentration.

Synthesis structural and luminescence analysis of NaGd1−XTbx(WO4)2 solid solution for white LED application

NaGd1−xTbx(WO4)2 (Tb:NGW) green phosphor were synthesised by high temperature solid state reaction. Synthesised powders were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and spectroflorimeter analysis. The formation of NGW scheelite structure was conformed by XRD. FE-SEM images clearly show the surface morphology of synthesized powder. From excitation spectrum, the charge transfer band (CTB) of O-W elucidated at 270 nm and emission spectrum has shown green emission at 545 nm under 270 nm (UV light) excitation. The optimum dopant concentration of Tb has been found to be 15 at%.

Synthesis and characterization of Eu3+:YAG nanopowder by precipitation method

Eu3+:Y3Al5O12 (Eu3+:YAG) nanopowder has been synthesized by reverse co-precipitation method. Cubic YAG structure was obtained at 850 °C calcination. FE-SEM micrographs confirm that YAG:Eu3+ particles are homogeneous sphere like morphology with average particle size of 50-70 nm. The crystalline phosphors showed orange - red emission with magnetic dipole transition 5D0→7F1 (590 nm) as most prominent group than forced electric dipole transition 5D0→7F2 (610nm).

Synthesis and vibrational characterization of KLa(WO4)2 crystalline powders by modified pechini method

KLa(WO4)2 crystalline powders were synthesized by modified Pechini method using metal nitrates as starting materials, citric acid and ethylene glycol were used as chelating and binding agents respectively. Synthesized gel was pre-fired at 250°C and calcined at 700°C using resistive furnace in air. The properties of the high temperature calcined powders were characterized by powder XRD, FT-IR, and Raman analysis to understand the crystalline nature, organic liberation, and tungstate ribbon formation respectively. Powder XRD confirms the tetragonal structure of the synthesized KLa(WO4)2 powders. Organic liberation from the samples was analyzed using FT-IR. Different vibrational modes of W-O bonds in higher frequency region were observed in Raman spectrum.