Niu Na, He Fei, Wang Liuzhen, Wang Lin, Wang Yan, Gai Shili, Yang Piaoping
J Nanosci Nanotechnol. 2014 May;14(5):3509-14. doi: 10.1166/jnn.2014.7976.
In this paper, well-defined tetragonal-phase LiYF4:Yb3+,Er3+/Tm3+/Ho3+ micro-crystals with octahedral morphology were successfully prepared through a surfactant-free molten salt process for the first time. By gradually increasing the LiF content in the NaNO3-KNO3 reaction medium, the crystal phase transforms from a mixture of YF3 and LiYF4 to pure tetragonal-phase LiYF4. The possible formation process for the phase and morphology evolution is also presented. Moreover, upon 980 nm laser diode (LD) excitation, the lanthanide ions (Yb3+, Er3+/Tm3+/Ho3+) doped LiYF4 crystals exhibit intense upconversion emission lights. By tuning the sensitizer concentrations of Yb3+ ions in LiYF4:Yb3+,Er3+, the relative intensities of green and red emissions can be precisely adjusted under single wavelength excitation. Consequently, multicolor upconversion emissions can be obtained. On the other hand, UC mechanisms were also given based on the emission spectra and the plot of luminescence intensity to pump power.
在本文中，首次通过无表面活性剂熔盐法成功制备了具有八面体形态的晶型明确的四方相LiYF4:Yb3+、Er3+/Tm3+/Ho3+微晶。通过逐渐增加NaNO3-KNO3反应介质中LiF的含量，晶相从YF3和LiYF4的混合物转变为纯四方相LiYF4。还介绍了相和形态演变的可能形成过程。此外，在980 nm激光二极管（LD）激发下，镧系离子（Yb3+、Er3+/Tm3+/Ho3+）掺杂的LiYF4晶体呈现出强烈的上转换发射光。通过调节LiYF4:Yb3+、Er3+中Yb3+离子的敏化剂浓度，在单波长激发下可以精确调整绿色和红色发射的相对强度。因此，可以获得多色上转换发射。另一方面，还根据发射光谱以及发光强度与泵浦功率的关系图给出了上转换机制。
