Improvement of morphology and luminescence properties of powellite type red phosphors CaGd1 xNbMoO8: xEu3+ synthesized via citrate gel route

Abstract

Powellite type molybdate-based red phosphors CaGd1 xNb-MoO8: xEu3+ (x = 0.05, 0.1, 0.15, 0.20, 0.25, and 0.30) were synthesized by a solid-state reaction (SSR) route, and a citrate gel (CG) route. The crystalline structure, morphology, absorbance, and luminescent properties of these phosphors were characterized using powder X-ray diffraction, scanning electron microscopy, UV visible absorption spectroscopy, and photoluminescence spectroscopy. The solid solution formation of the phosphor effectively takes place at a lower temperature by the CG route than the SSR route. Particle morphology of the phosphors prepared by the CG route reveals that they are less agglomerated, more spherical, and homogenous in nature with uniform particle size. Investigations on photoluminescence properties show that these phosphors emit strong red light(614 nm) under both near UV (395 nm), and blue (465 nm)excitations. The morphological variation of the developed phosphors with respect to synthesis method and heat treatment played an important role in their luminescence enhancement.The red phosphors prepared via CG route were characterized by enhanced and sharper red emission with longer life time compared to that of phosphors synthesized via SSR route. The CIE color coordinates of the developed red phosphors are (0.65, 0.34) that are closer to NTSC standard red phosphor. Thus, these phosphors could be a promising red candidate for the phosphor converted white light emitting diode applications