Molten Salt Synthesis and Luminescent Properties of GdVO4:Eu3+ Nanophosphors

摘要:

以等摩尔的硝酸钠和硝酸钾作为反应介质，氢氧化钠作为碱化剂，采用熔盐法制备了GdVO4:Eu3+纳米晶。利用X射线衍射（XRD）仪、傅里叶变换红外光谱（FT-IR）、透射电子显微镜（TEM）、荧光光谱（PL）和荧光寿命（Lifetime）等手段对产物的相态、结晶度、结构、形貌和发光性能等进行了表征与研究。X射线衍射结果表明，产物在250 °C时开始结晶，400 °C时结晶完全，控制反应体系碱度和温度可获得纯四方相GdVO4:Eu3+晶体。透射电镜观察结果显示，产物为粒径20 nm左右的立方形颗粒，分散良好，形貌均一。依据XRD数据计算结果表明，GdVO4:Eu3+纳米晶的晶胞参数和晶胞体积相对于体相材料均有所减小，归因于纳米晶表面大量悬键的存在，并通过FT-IR得到验证。315 nm波长光的激发下，GdVO4:Eu3+纳米晶呈现Eu3+的特征发射光谱，表明了能量由VO43-向Eu3+的传递。发射强度和荧光寿命研究表明，Eu3+的最佳掺杂浓度为5%(摩尔分数)

Abstract:

GdVO4:Eu3+ nanophosphors were prepared via molten salt synthesis. Equal moles of NaNO3 and KNO3 were used as reaction medium, rare earth nitrates and NH4VO3 as precursors, and NaOH as alkalizer. X-ray diffraction (XRD), Fourier transform infrared (FT-IR), transmission electron microscopy (TEM), photoluminescence (PL) spectrum and lifetime were used to characterize the nanophosphors. XRD demonstrates that NaOH concentration and the sintering temperature play important roles in the crystallinity and the phase purity of the products. The optimum NaOH concentration and sintering temperature are 2:40 and 400 °C, respectively. TEM micrographs show that the GdVO4:Eu3+ nanocrystals exhibit a cubic morphology and have a mean size of about 20 nm, which is in good agreement with that calculated by Scherrer’s formula. Both the cell parameters and the volume of GdVO4:Eu3+ nanocrystals decrease due to the existence of big quantity of dangling bonds on the particle surface. Upon excitation at 315 nm, the GdVO4:Eu3+ nanocrystals show the strong characteristic emission of Eu3+, which indicates the efficient energy transfer from VO43- groups to Eu3+. The best doping concentration of Eu3+ in GdVO4 is determined to be 5 mol%.