微波辅助溶胶-凝胶法合成红色发光材料NaLa(MoO_4)_2:Eu^(3+)及其发光性能研究

Synthesis and Luminescent Properties of Red-emitting Phosphors NaLa( MoO_4)_2:Eu^(3+) by Microwave-assisted Sol-gel Method

以柠檬酸为络合剂,采用微波辅助溶胶-凝胶法制备了红色荧光粉NaLa(MoO4)2∶Eu3+,运用热重-差热分析仪、红外光谱、X射线粉末衍射仪、扫描电子显微镜和荧光分光光度计等对样品进行了分析和表征。结果表明:前驱体经700～900℃焙烧均能得到目标产物NaLa(MoO4)2∶Eu3+,且具有四方晶系白钨矿结构;样品由尺寸约1～3μm类球形小颗粒组成。激发光谱在250～350 nm处有一宽的吸收带,峰值位于290 nm,属于Mo-O,Eu-O的电荷迁移带;350～500 nm范围内的系列尖峰是由Eu3+的4f-4f跃迁所致;发射光谱由一系列发射峰组成,主峰位于616nm处,属于5D0→7F2电偶极跃迁发射。同时研究了焙烧温度和时间、柠檬酸和乙二醇的摩尔比,以及助熔剂等对样品发光性能的影响。

The red-emitting phosphors NaLa（MoO 4） 2 ∶ Eu 3 ＋ was synthesized by microwave-assisted sol-gel method using citric as complexing agent.These compounds were characterized by means of thermo gravimetric-differential thermal analysis,fourier transform infrared spectroscopy,X-ray diffraction,scanning electron microscope and fluorescence spectrophotometer.The results show that the target products NaLa（MoO 4） 2 ∶ Eu 3 ＋ have been synthesized by calcining precursor at the temperature from 700 ℃ to 900 ℃.The obtained products are of pure scheelite type molybdate with tetragonal crystal structure.The particles of NaLa（MoO 4） 2 ∶ Eu 3 ＋ are spherical in shape with a diameter of 1-3 μm.The excitation spectrum of NaLa（MoO 4） 2 ∶ Eu 3 ＋ has a broad band in the range of 250-350 nm,and the main peak is at 290 nm.The broad band can be ascribed to the charge transfer band of Mo-O and Eu-O.The sharp lines in 350-500 nm range are due to 4f-4f transitions of Eu 3 ＋.The emission spectrum contains a series of narrow peaks,with the main peak at 616 nm originated from the electric dipole transition of 5 D 0 → 7 F 2 of Eu 3 ＋.Meanwhile,the influences of reaction temperature and time,molar ratio of citric and EG,and flux on the fluorescent properties of as-prepared samples were also investigated. The red-emitting phosphors NaLa（MoO 4） 2 ∶ Eu 3 ＋ was synthesized by microwave-assisted sol-gel method using citric as complexing agent.These compounds were characterized by means of thermo gravimetric-differential thermal analysis,fourier transform infrared spectroscopy,X-ray diffraction,scanning electron microscope and fluorescence spectrophotometer.The results show that the target products NaLa（MoO 4） 2 ∶ Eu 3 ＋ have been synthesized by calcining precursor at the temperature from 700 ℃ to 900 ℃.The obtained products are of pure scheelite type molybdate with tetragonal crystal structure.The particles of NaLa（MoO 4） 2 ∶ Eu 3 ＋ are spherical in shape with a diameter of 1-3 μm.The excitation spectrum of NaLa（MoO 4） 2 ∶ Eu 3 ＋ has a broad band in the range of 250-350 nm,and the main peak is at 290 nm.The broad band can be ascribed to the charge transfer band of Mo-O and Eu-O.The sharp lines in 350-500 nm range are due to 4f-4f transitions of Eu 3 ＋.The emission spectrum contains a series of narrow peaks,with the main peak at 616 nm originated from the electric dipole transition of 5 D 0 → 7 F 2 of Eu 3 ＋.Meanwhile,the influences of reaction temperature and time,molar ratio of citric and EG,and flux on the fluorescent properties of as-prepared samples were also investigated.