Precipitation Synthesis And Luminescence Properties Of Rare Earth Eu³⁺-doped Gadolinium Tungstate/molybdate Phosphors

In 1993, Shuji Nakamura in Japan Nichia Corporation invented wide-bandgap semiconductor materials GaN and In GaN blue light-emitting-diodes(LEDs) with commercial values. Afterwards, the white LEDs were invented though improvement and exploration. With high luminous efficiency, long luminous life, energy-saving and environmentally friendly and so many other advantages, the white LEDs, as the fourth generation of the light source, has a wide range of applications. This white LED is coated by yellow phosphor(YAG: Ce3+) in the original blue LED chip to achieve white light. However, this method makes the luminous efficiency of the white LED reduced greatly, If a kind of red phosphor as the complementary color is added,the fluorescence efficiency of white LED will enhance greatly.In this work, a series of Eu3+-doped Gd2(MoO4)3, Gd2(WO4)3 and Gd2(WO4)x(MoO4)y powders were synthesized by co-precipitation method,respectively. Co-precipitation method results in high-purity powder due to some water-soluble ions can be eliminated after filtration and washing. Moreover, the reaction can carry out completely during the formation of precipitation. Through stirring timely, the powder appearance can be effectively improved, and the luminescence efficiency is affected. Finally, the precursor powders are suitably heat-treated to obtain the products.The main contents of this paper can be divided into three parts, molybdate gadolinium, tungstate gadolinium and tungstate/molybdate gadolinium 。 The experimental design in the three systems is the same, which involves in Eu3+ ion concentration, heat treatment temperature, and the amount of surfatcant polyethylene glycol(PEG400) and polyvinyl alcohol(PVA). The final purpose of the study is to seek the optimum system with more efficiency. The phosphor samples were characterized by fluorescence spectrophotometer, X-ray diffraction, scanning electron microscopy and fluorescence lifetime. The optimal system is tungstate/molybdate gadolinium, and the optimal Eu3+,the proportion of molybdate and tungstate and heattreat temperature is 0.6, n(MoO42-:n(WO42-) =1.25:0.75 and 900℃, respectively.The as-prepared red light-emitting tungstate/molybdate gadolinium phosphors has a higher luminous efficiency. The powder shows high brightness and translucent red under the UV light. In short, this work provides a new way of thinking and rationale for researching the red phosphor in the future.