Preparation and Luminescence Characteristics of Eu-doped Nanocrystalline Zinc Oxide

Preparation and Luminescence Characteristics of Eu-doped Nanocrystalline Zinc Oxide
　　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 a material to produce a lot of luminous products such as dope, printing ink, concrete, plastic, paper, ceramic, glass, in dustrial artwork and clock. Therefore photoluminescence material plays an important role in the following fields: archietcture, decoration, transportation, military, light chemical Block neodymium magnet 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 http://www.chinamagnets.biz/ 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 is used as the sensitive components.Direct precipitation, homogeneous precipitation and microemulsion method are adopted to prepare the red photoluminescence material ZnO:Eu3+. The microshape and the structure of crystal can be determined by the X-ray diffraction (XRD) and SEM (scaning electron microscope).The results of the present study are listed as follows:(1) With solution precipitation method by using urea or ammonia as precipitator and microemulsion method by using cetyl trimethyl ammonium bromide(CTAB) as surfactant, the red photoluminescence material ZnO:Eu3+ can be fabricated from two main materials Zn(NO3)2·6H2O and Eu2O3.
　　There are also two main emission peak at 595nm and 612nm in ZnO:Eu3+ samples prepared by precipitation method, furthermore, red-shift phenomenon is found in the sample prepared by the homogeneous precipitation and the most stong peak is http://www.chinamagnets.biz/ at 592nm. In the case of intensity of emission, the sample prepared by direct precipitation is little better than that by homogeneous precipitation. But there is no found 595nm emission peak in the ZnO:Eu3+ sample prepared by the microemulsion method, which has only one emission peak at 615nm and eradiate red luminescence.(2)The crystalline structure of samples from solution precipitation and microemulsion method, is the same as that of pure ZnO, which shows that the most adulterated elements Eu3+ have been mixed into the ZnO crystal lattices. Through the analyse of XRD, the red photoluminescence material ZnO:Eu3+ samples prepared by the microemulsion method contains impurity Eu2O3.(3)The luminous mechanism of samples can be described as follows: Eu3+ mixed into the ZnO crystal lattices forms many centers of luminescence.(4) Through direct precipitation or homogeneous precipitation can prepared ZnO: Eu3+ nano-powders, and varying degrees of reunion phenomenon also exists. The size distribution of ZnO: Eu3+ sample prepared by the direct precipitation method is between the 300nm-1μm, and particles shows column or flake state, otherwise, that prepared by the homogeneous precipitation method is between 100nm-200nm and particles shows short column state. The rod-shaped particles can be fabricated by the microemulsion method, which dispersed well and the distribution of particle size is between 50nm-100nm .(5) The results indicate that the homogeneous precipitation method and the microemulsion method can be regard as better methods for the preparation of the red photoluminescence material ZnO:Eu3+ than the direct precipitation method.