The Study For The ZnO-doped Red Photoluminescence Material

Luminescence is a process during which the absorbed energy is converted to optical radiation in some way. The photoluminescence is a phenomenon that some objects shine in some certain conditions after absorbing and storing the light energy. The photoluminescence material can be widely used in many fields such as the screen of TV, computer and fluorescent lamps. It also can be used as an material to produce a lot of luminous products such as dope, printing ink, concrete, plastic, paper, ceramic, glass, industrial artwork and clock. Therefore photoluminescen--ce material plays an important role in the following fields: architecture, decoration, transportation, military, light chemical industry, emergency lighting, and anti-forged sign. Although a great progress has been made after about 10-year researches and applications of photoluminescence material, the study evolvement of the red photoluminescence material is quite slow in comparison with the mature manufacture techniques of the green and blue photoluminescence material. The main raw materials of the traditional red photoluminescence materials are the costly rare earth oxides such as Y₂O₃ and Eu₂O₃. However, ZnO is adopted as the main raw material in this paper. ZnO is a cheap oxide, which can intensively absorb the ultraviolet light and has the properties of stability in physics and chemistry. The red photoluminescence material used ZnO as the matrix material can be applied to various abominable nature conditions such as cold north, fervent south and tableland with strong ultraviolet radiation. It can be also widely used in the field of the palette of aircraft coating. In this experiment the rare earth element Eu and the alkali metal element Li are used as the sensitive components. High temperature solid phase method and sol-gel method are adopted to prepare the red photoluminescence material ZnO:Eu,Li. The calcinations temperature can be confirmed through thermogravimetric (TG-DTA) analysis, the microshape and the structure of crystal can be determined by the X-ray diffraction (XRD) and SEM, the distribution of granularity can be ascertained by the laser granularity analysis, the luminous property can be analyzed by the PL-PLE. The results of the present study are listed as follows: (1) With the high temperature solid phase method and sol-gel method, the red photoluminescence material ZnO:Eu,Li can be fabricated from three kinds of materials Zn(Ac)2·2H2O (or ZnO), LiAc·H2O (or LiOH) and Eu2O3 respectively for the first time. (2) The crystalline structure of samples from the high temperature solid phase method and the sol-gel method is the same as that of pure ZnO, which shows that adulterated elements Li and Eu have been mixed into the ZnO crystal lattices. (3) The luminous mechanism of samples can be described as follows: Eu3+ mixed into the ZnO crystal lattices forms many centers of luminescence. Firstly ZnO absorbs light energy, then transfers the energy to Eu3+, during this process Li+ can be served to have double effects, assisting solvent and compensating charge. (4) For the high temperature solid phase method and sol-gel method, the calcinations temperatures of precursors should be 600 οC～1000 οCand 600 οC～800 οC respectively. (5) The optimized experimental conditions for the preparation of the red photoluminescence material ZnO:Eu,Li are that the ratio of Eu and Li is 3:1 (in molar), the calcinations temperatures of precursors are 600 οC and 800 οC respectively for the two synthetic methods. (6) Nanosized powders with the value of the grain size between 0.05μm-0.1μm can be prepared by high temperature wet solid phase method and the sol-gel method. It is proved that the distribution of the grain size prepared by the sol-gel method is more homogenous, while the agglomerate is more obvious when using the high temperature solid method. (7) The high temperature solid phase wet method and the sol-gel method can be regard as better methods for the preparation of the red photoluminescence material ZnO:Eu,Li than the high solid phase dry method.