Study On The Photoluminescence Properties Of Rare-earth-ions Co-doped Vanadates

The first generation white light-emitting diode (w-LED) has been already reported in 1996. This w-LED was made from InGaN chip and phosphor YAG:Ce. YAG:Ce which can emit yellow light after absorbing the blue light from the InGaN chip, and the white light can be achieved by adjusting the ratio of the yellow light from YAG:Ce to the blue light from the InGaN chip. This w-LED achieved by coating phosphor powder on the light-emitting diode (LED) have many advantages, such as high reliability, high luminous efficiency, long lifetime and low energy consumption. The w-LED has been paid many attentions because it possesses the wide prospect in the lighting, displaying, solid state laser and so on. The w-LED will become the fourth generation lighting sources to replace the incandescent and fluorescent lamps.In the dissertation, the authors co-dope two rare-earth ions into one matrix (vanadate) in order to obtain the white light-emitting phosphor as excited by a certain wavelength ultraviolet-light. The w-LED containing such a kind of phosphor has many advantages such as convenience in the device design and preparation, low cost, and enhancement of the luminescent stability, etc. The aim of this dissertation is to study the influence of the ratio between two rare earth ions on the luminous intensity. The main content of each chapter is summarized as follows:In the first and second chapters, several models of white-light have been sketched out. The LED light sources have many merits in contrast to thermal radiation and cathode-ray light sources. We then introduce several kinds of measurement techniques, and summarize the research progress and preparation methods of white-light emission phosphors by co-doping rare-earth-ions in vanadates. Presently the research on co-doping rare-earth ions into vanadates is in its beginning stage, and it is meaningful to study how to achieve the high purity and good color rendering white-light phosphors.In chapter three, we synthesize the Sr2.5Dy1/3-xEuxV2O8 (0≤x≤1/3) using the traditional solid state reaction method. Under excited by ultraviolet light, the samples can emit yellow light belongs to Dy3+ and red light belongs toEu3+. Moreover, the intensity ratio of yellow and red can be adjusted obviously by the tuning the concentration of Eu3+. So, we can obtain white light by changing europium's concentration. Furthermore, we dope the Bi3+ element into Sr2.5Dy1/3-xEuxV2O8 (0≤x≤1/3) to enhance the luminous intensity of Eu3+ and Dy3+In chapter four, we firstly synthesize Ba3(1-x)Ce2XV2O8(0≤x≤0.1) samples, and the luminescent results show that the phosphor with x=0.8 exhibits the strangest emission. Then, we synthesize series of samples Ba3(0.92-y)Ce0.16Eu2yV208 (0≤y≤0.1). In the emission spectrum, we can observe purple-light, blue-light and red-light. The intensity of cerium's emission varies hardly with the Eu3+ concentration but europium's emission changes greatly. So, we can obtain the white-light emission by changing the europium's concentration.In the end, we give out the brief summary and prospect of this dissertation.