Polymerized Complex Sol-Gel Synthesis, Structural and Optical Properties of Monoclinic Eu3+ Doped KGd(WO4)2 Crystalline Red Phosphors

1% Eu3+ doped KGd(WO4)(2) (KGW) was synthesized through Pechini sol-gel process and crystallized by subsequent annealing at high temperature. Potassium nitrate, gadolinium nitrate and ammonium para tungstate precursors were mixed with citric acid and ethylene glycol to synthesis the polymerizable complex gel. The gel was heated to 250 degrees C for decomposition of polymer, which after the brownish white powder was used to synthesis the pure form of 1% Eu:KGW. The pre-fired powder was further heated at high temperature's (550, 600, 650 and 700 degrees C) for calcination. The properties of heat treated samples were characterized by powder XRD, FT-IR, Raman, FESEM and fluorescence analysis to understand the crystallinity, organic liberation, tungstate ribbon formation, surface morphology and emission nature, respectively. Phase evaluation from the amorphous pre-fired sample to well crystalline KGW powder formation was confirmed with powder XRD analysis. Powders calcined at 600 degrees C show the appearance of monoclinic phase of KGW. Crystalline peaks without intermediate compound peaks were observed for samples calcined at 700 degrees C. Gel degradation and formation of double tungstate was clearly seen in the FT-IR spectrum. FT-IR spectrum of synthesized gel also, confirms the citrate formation and etherification. FESEM analysis reveals the size and morphology of the powder. Double tungstate formation from the amorphous powder was analyzed using laser Raman spectral analysis. The emission property of the europium doped KGW was analyzed using fluorescence. Changes in emission intensity was observed for samples calcined at different temperatures.