以氟化钾(KF)作为助熔剂,选用70~90℃/cm的固液界面温度梯度,通过改进的助熔剂-布里奇曼方法生长出了Dy3+离子掺杂的α-NaYF4单晶体.测试了样品的X射线粉末衍射,吸收光谱,激发光谱,以及在不同紫外光激发下的发射光谱,分析了样品的的物相和光谱特性.应用色度学理论计算了Dy3+离子掺杂α-NaYF4单晶的色度坐标和色温.结果表明:当原料组份配比为30NaF-18KF-52YF3时,有利于大尺寸晶体生长.原料中KF的加入起到助熔剂作用,它改变了NaF-YF3二元系相图并且降低了α-NaYF4的熔点,使得α-NaYF4能从熔融的NaF-KF-YF3混合物中结晶出来,最后生长出透明的α-NaYF4单晶体.实验发现大多KF被排析在生长后期的晶体顶端,KF的加入没有对α-NaYF4单晶体的结构产生影响.在348 nm紫外光激发下,单晶体可发射出蓝光约479 nm,黄光约571 nm以及弱的红光约659 nm.其中1.299 mol% Dy3+掺杂浓度的α-NaYF4单晶体发射的蓝、黄与红光可耦合出色坐标x=0.285,y=0.338以及色温为8 065 K的白光.这些新型材料在紫外激发的白光二极管领域具有潜在的应用.

The Dy3+ doped α-NaYF4 single crystals were synthesized by a modified Bridgman method under the conditions of taking KF as an assistant flux and a temperature gradient (70~90 ℃/cm) at the solid-liquid interface.X-ray diffraction,absorption spectra,excitation spectra,and emission spectra were measured to investigate the phase and spectrum properties of the crystals.The chromaticity coordinates and color temperature of crystals were calculated based on Colorimetry theories.Many growing experiments demonstrate that the chemical compositions of 30NaF-18KF-52YF3 (molar ratio) are beneficial to obtain big α-NaYF4 single crystals.The introduction of KF changed the phase equilibrium between NaF and YF3 completely and lowered the melting point of α-NaYF4,resulting into crystallization of α-NaYF4 just from the mixture when it is cooled.Most of KF was excluded on the top of crystals which grew at the final stage of crystal growth.The introduction of flux KF did not change the structure of α-NaYF4 single crystals.The emission blue 479 nm,yellow 571 nm and weak red 659 nm could be obtained simultaneously under the excitation of ultraviolet lights.A white light emission from the coupling of the above three lights with chromaticity coordinates of x=0.285,y=0.338,color temperature Tc=8 065 K could be obtained from 1.299 mole% Dy3+ doped α-NaYF4 single crystal when excited by a 348 nm light.This indicates that Dy3+ doped α-NaYF4 single crystals can be a potential candidate for white light emitting diode excited by ultraviolet light.