Preparation Of Y₂O₃ Red Phosphors Doped With Rare-Earth Ions And Study On Its Luminescent Properties

In recent years, upconversion luminescence (UCL) dispalys have attracted much attention because of their advantages such as small volume, bright colorful and long lifetime, particularly their potential applicatons in real 3D-displays. For UCL displays with high brightness and high resolution, the fine tri-color UCL particles with high luminescent efficiency, high color purity and good morphology (the best morphology is spherical) are requisite. It is well known that Y2O3:Yb3+, Er3+ is one of the best candidates for the red phosphors. However, the commercial Y2O3:Yb3+,Er3+ phosphors are produced by a solid-state reaction at present, and show many disadvantages such as large particle size, agglomeration, irregular shape. As a result, this phosphor is limited in the application of UCL displays. On the other hand, Y2O3:Eu3+ as an efficient downconversion red phosphor has been widely used in the fields of cathode ray tube, tri-color fluorescent lamp, etc. With the development of high resolution displays technology, the phosphors with high luminescent efficiency, small particle size and spherical morphology are required. In view of the above, the preparation and improvement of luminescent efficiency of fineY2O3:Yb3+, Er3+ and Y2O3:Eu3+ red phosphors with spherical shape are investigated in this work. The main research contents and results are shown as follows:(1) The spherical Y2O3:Yb3+,Er3+ red UCL particles with the size in the range of 100-200nm were prepared using homogeneous precipitation method. The doping concentration of Yb3+ and Er3+ were optimized, and the sample with the optimal luminescent intensity and red color purity was obtain when the concentration of Yb3+ and Er3+ are 6mol% and 1.2mol%, respectively. The influences of urea concentration, aging time and calcining temperature on the UCL intensity of the particles were also studied, and the best technology parameters were obtained. It is found that the UCL intensity of the sample was enhanced remarkably by adding Li2CO3. The red light emission intensity can be increased about 13.6 times after adding 10wt% Li2CO3 and calcining at 850℃. By analyzing the upconversion mechanism of Y2O3:Yb3+,Er3+, it is determined that the red light (4F9/2â†'4I15/2 transition) and the green light(2H11/2,4S3/2â†'4I15/2 transition) emission were both originated from two photons upconversion process.(2) The spherical Y2O3:Eu3+ red downconversion luminescence particles with the size in the range of 100～200nm were prepared using homogeneous precipitation method. When the doping concentration of Eu3+ was 8mol%, the sample shown the highest luminescent intensity. The optimal excitation wavelength was determined to be 254nm. The effects of urea concentration, aging time and calcining temperature on the luminescent intensity of particles were studied, and the best technology parameters were confirmed. It is found that the red light emission intensity of the sample increased about 32% after adding Li2CO3. The optimal calcination temperature and the addition amount of Li2CO3 were 900℃and 8wt%, respectively. The result of concentration quenching curve revealed that the concentration quenching of Y2O3:Eu3+ is caused by exchange interaction.