Blue-white light conversion fluorescent powder on the basis of UV light excitation and preparation thereof

[0021] Example

[0022] 1. Prepare samples N1, N2, N3 and N4

[0023] Press NaSr 1-x MoO 4 Weigh a certain amount of sodium carbonate (Na 2 CO 3 ), strontium carbonate (SrCO 3 ), ammonium molybdate tetrahydrate ((NH 4 ) 6 Mo 7 O 24 ·4H 2 O), ammonium chloride (NH 4 Cl) (all of the above are analytically pure) and a certain amount of europium oxide (Eu 2 O 3 ) (99.99%), the Eu content was 0.02, 0.05, 0.1 and 0.15, respectively; corresponding to the sample numbers N1, N2, N3 and N4 (the same below). To prevent NH 4 Cl decomposes and evaporates during the heating process, so take 10% more when weighing. Put the weighed raw material in an agate mortar and grind it for 1.5 hours to make it evenly mixed, then put the ground raw material into a corundum crucible, roast it in a high temperature resistance furnace at 900°C for 3 hours, and cool it to room temperature with the furnace. Materials required.

[0024] 2. Sample testing and characterization

[0025] XRD analysis The powder X-ray diffraction analysis of the sintered powder was carried out using a DMAX-2500 X-ray diffractometer. The test parameters are: Cu(Kα) target, tube voltage 40Kv, tube current 250mA, scanning range 15-80°. The scanning step size was 0.02°, and the scanning speed was 10°/min.

[0026] Fluorescence spectrum analysis Hitachi F-4500 fluorescence spectrophotometer was used to measure the excitation spectrum and emission spectrum of the luminescent powder. The test conditions are xenon lamp source, voltage 400V, slit width 10nm, scanning speed 1200nm/min.

[0027] 3. Phase analysis

[0028] NaSr with different Eu content 1-x MoO 4 The X-ray diffraction pattern of Cl:xEu powder is shown in figure 1 shown. It can be seen from the figure that the main phase of the sample is SrMoO 4 structure, the diffraction peaks of this sample are consistent with JCPDS standard card 08-0482. SrMoO 4 It is a scheelite structure, belongs to the tetragonal system, and the space group is I4 1 /a, the unit cell parameters are: a=b=0.53944nm, c=1.202nm. According to the XRD pattern, NaSrMoO 4 Cl and SrMoO 4 The structure is similar, belonging to the tetragonal crystal system, the space group is I4 1 /a. Sr 2+ Radius 0.113nm, Eu 2+ (0.107nm) and Eu 3+ (0.095nm) radius is slightly smaller than Sr2+ Radius, into SrMoO 4 Lattice replaces Sr 2+. With the increasing Eu content, the XRD peak intensity is relatively weakened, this is because more Eu 2+ /Eu 3+ into the lattice, resulting in the matrix SrMoO 4 due to the decrease in the intensity of the diffraction peaks. In addition, the product contains a small amount of NaCl crystals, in figure 1 Marked with "◆" in the middle, it can be used as a flux in the process of phosphor baking.

[0029] 4. NaSr 1-x MoO 4 Cl:xEu Luminescence Properties

[0030] 4.1 Excitation and emission spectra

[0031] figure 2 for Sr 0.95 MoO 4 :0.05Eu 3+ Excitation spectrum at monitoring wavelength of 614 nm and emission spectrum excited at 287 nm wavelength. Broadband excitation at 225-325 nm from O 2- -Eu 3+ and O 2- →Mo 6+ charge migration; multiple narrow-band excitation peaks between 350-500 nm are Eu 3+ The 4f→4f forbidden transition of , corresponding to Eu 3+ ground state 7 F 0 to the excited state 5 D 4 (362nm), 5 L 7 (382nm), 5 L 6 (394nm), 5 D 3 (417nm), 5 D 2 (466nm) transition. The emission spectrum excited at 287 nm consists of a series of linear spectral lines corresponding to Eu 3+ of 5 D 0 arrive 7 F J (J=0-4) transition. 614nm (corresponding to Eu 3+ of 5 D 0 → 7 F 2 ) has the strongest electric dipole transition and is an ultrasensitive transition.

[0032] image 3 is NaSr 1-x MoO 4 Excitation and emission spectra of Cl:xEu. image 3 (a) is the excitation spectrum at the monitoring wavelength of 397 nm, the excitation spectrum is located at 250 nm, which is Eu 2+ and Eu 3+ the result of co-stimulation. image 3 (b) is the emission spectrum excited at 250 nm, the broadband emission between 350 nm and 500 nm originates from Eu 2+ 4f 6 5d-4f 7 transition, 468nm ( 5 D 2 → 7 F 0 ), 534nm ( 5 D 0 → 7 F 0 ),590mm( 5 D 0 → 7 F 1 ),614nm( 5 D 0 → 7 F 2 ), 652mm ( 5 D 0 → 7 F 3 ),700mm( 5 D 0 → 7 F 4 ) isolinear spectrum is the excitation of Eu 3+ The resulting broadband emission intensity is much larger than that of the linear spectrum, so, under excitation at 250 nm, the phosphor emits blue light. Eu 3+ In the emission spectrum of , the intensity at 614 nm is the largest, indicating that Eu 3+ Incorporation of ions induces lattice distortion in the matrix lattice, but Eu 3+ Does not occupy the center of symmetry. image 3 (c) is the excitation spectrum at the monitoring wavelength of 614 nm, and figure 2 In contrast, after 325nm, there is a strong broad excitation band, which must come from the addition of Cl; at the same time, with the addition of Cl, the broadband excitation peak positions between 225-325nm are located at 266nm, N1 at 289nm, and N3 at 289nm. 281nm, N4 is located at 272nm, relative to Sr 0.95 MoO 4 :0.05Eu 3+ The position of the peak line (287nm) of 3+ The 4f-4f low energy level is no longer excited, figure 2 Two faint excitation lines at 362nm ( 7 F 0 → 5 D 4 ), 416nm ( 7 F 0 → 5 D 3 ) does not appear. image 3 (d) is the emission spectrum of NaSr1-xMoO4Cl:xEu, which consists of a long broadband emission and a series of discrete line spectra. The broadband spectrum is composed of Eu 2+ emission, other linear spectra are determined by Eu 3+ emission. When the molar content of Eu (relative to Sr) is 0.02, the broadband emission peak is slightly stronger than that of Eu 3+ Emission peak at 614 nm; as the molar content of Eu increases, the broadband emission intensity decreases, Eu 3+ The emission intensity does not change much; when the content is 0.05-0.1, the broadband emission and Eu 3+ The launch is basically unchanged.

[0033] 4.2 Luminous performance

[0034] Table 1 shows the Sr calculated by CIE1931 software 0.95 MoO 4 :0.05Eu 3+ and NaSr 1-x MoO 4 The color coordinates of Cl:xEu with different x values ​​under excitation near 280nm and the color temperature at the coordinates, Figure 4 A chromaticity diagram drawn from the calculated color coordinates.

[0035] According to the calculated color coordinates and the target point analysis on the chromaticity diagram corresponding to the color coordinates, under UV excitation, Sr 0.95 MoO 4 :0.05Eu 3+ It emits orange-red light, and the color temperature is in a relatively moderate warm color area. Add Cl - Then, when the Eu concentration was in the range of 0.02 to 0.1, the NaSr 1-x MoO 4 Cl:xEu emits light in the white light region. When the value of x is around 0.05, its emission (0.311, 0.299) is closest to the white light center (0.333, 0.333), and the color temperature is close to the color temperature of white fluorescent lamps (6000K). Using CIE1931 calculation, the color coordinates of the series of materials under 250nm excitation are N1 (0.269, 0.212), N2 (0.261, 0.208), N3 (0.265, 0.214) and N4 (0.246, 0.192), and their corresponding luminescence dominant wavelengths are 442nm, 453nm, 452nm and 459nm are very close to the central wavelength of blue light at 440nm. It can be seen that the phosphor can be used as a blue light-emitting material or a potential substitute material for a new generation of white LEDs, and has broad application prospects.

[0036] Table 1 Color coordinates and color temperature

[0037]