中文摘要：

采用水热法成功制备了Er^3＋/Yb^3＋/共掺杂的NaYF构,而四方相LiYF4微米晶体则为八面体结构.在近红外光980 nm激发下,Na YF4：Yb^3＋//Er^3＋/和Li YF4：Yb^3＋//Er^3＋/微米晶体均展现出很强上转换荧光发射.且NaYF4：Yb^3＋//Er^3＋/微米晶体的荧光发射强度大约是Li YF4：Yb^3＋//Er^3＋/微米晶体的2倍,但红绿比明显较低.根据荧光光谱,并借助激光光谱学及发光动力学深入探讨基质变化及表面修饰剂乙二胺四乙二酸（EDTA）对荧光特性的影响.实验结果发现：影响荧光强度的主要因素是基质环境的局域对称性,而导致不同红绿比则是由于样品表面较多的EDTA分子所引起.Er^3＋/掺杂的NaYF4和LiYF4微米晶体呈现出很强的绿光发射可被应用于全色显示,荧光粉和微光电子器件中.

英文摘要：

Lanthanide-doped upconverting fluoride nano- and micro-materials have aroused much research interest due to their potential applications in phosphors, color displays, optical storages, solid-state lasers, solar cells and biomedical imaging. In order to synthesize L^（3＋doped crystals with favorable optical properties, such as high upconversion（UC）efficiency and controllable emission profile, the two major parameters that affect luminescence processes including host materials and lanthanide activator ions should be selected appropriately in the synthesis process. Majority of scientists deem that lanthanide doped fluoride nano- and micro-materials with low phonon energy are currently the efficient UC host materials. In this work, Yb^3＋and Er^3＋ions codoped Na YF4 and Li YF4 microcrystals are synthesized by a facile hydrothermal method with ethylene diamine tetraacetic acid（EDTA） as a chelator. The Na YF4：Yb^3＋/Er^3＋and Li YF4：Yb^3＋/Er^3＋microcrystals are characterized by X-ray diffraction（XRD）, scanning electron microscope（SEM）, and the photo-luminescence spectra method. The influences of EDTA on the crystal phase, shape and upconversion luminescence are explored in detail. According to the results of XRD and SEM, the pure hexagonal phased Na YF4：Yb^3＋/Er^3＋rod-like microcrystals each with smooth surface are all around 12 μm in the length. While the pure tetragonal phased Li YF4：Yb^3＋/Er^3＋microcrystals each with smooth surface are octahedral in shape, and their average size is around12 μm. Under near infrared（NIR） 980 nm excitation, the two dominant emission peaks of Er^3＋ions at 544 nm and at 650 nm are observed in Na YF4 and Li YF4 microcrystals, which can be assigned to the transitions of（2~H（11/2）/4~S（3/2））→4~I（15/2）and4~F（9/2）→4~I（15/2）, respectively. It is found that the upconversion luminescence intensity of Na YF4：Yb^3＋/Er^3＋microcrystals is about two times that of Li YF4：Yb^3＋/Er^3＋microcrystals under the same e