Soft Chemical Preparation And Properties Of Phosphor For White LEDs

Blue LEDs chip excited yellow phosphors is the main way for the achievementof white LEDs. The defects of lower color rendering index (CRI), higher colortemperature, unstable performance limit the development and application of whiteLEDs. However, the doping of red phosphors plays an important role in adjusting theCRI and color temperature of white LEDs.Yellow phosphors with three different matrixes (MYG: Ce3+(M=Y, Lu, Tb))were prepared by hydrothermal pyrolysis method. The results indicated that thismethod could not only decrease the sintering temperature of high temperaturesolid-stated method, but also uniformize the particle size and morphology of products.YAG: Ce (6%) are spherical-like particles with the particle size of10?m. Theexcitation wavelength (460nm), emission wavelength (530nm) and color coordinates(0.43,0.55) of YAG: Ce (6%) all meet the commercial standard.Red phosphors with three different matrixes (MMoO4:Pr3+(M=Sr?Ba?Ca))were prepared by hydrothermal pyrolysis method. The results showed that the effectof molybdenum calcium matrix was better. The CaMoO4: Pr3+obtained with1.5%Pr3+were evenly distributed as spherical-like particles with the particle size of5?m.The main excited peaks were at453nm,477nm and490nm, respectively. And theemission peak was at654nm. This material possessed of a broad excitation range ofblue light. The emission position and intensity of red light could better match the blueLED chip. The results indicated that the luminous intensity were increased by thedoping of alkali metal ions as charge compensators. Among these ions, the dopingeffect of Li+was best. When the pH was7.0, the products were spherical-like particles with the color coordinates of (0.43,0.55) and emitted pure red light.NaY(MoO4)2: Eu3+(Sm3+, Pr3+) phosphors with bimetallic molybdate wereprepared by hydrothermal pyrolysis method. The results showed that NaY(MoO4)2:Pr3+phosphors possessed of better glowing effect. NaY0.94(MoO4)2:0.06Pr3+with thecolor coordinators of (0.65,0.34) emitted pure red light. These results revealed thatacidity was the main impact factor of morphology. For example, when the pH valuewas7.0, the products were uniform sphere; when the pH value was9.0, the productswere changed into irregular sphere; when the pH value was11.0, the products weresheet with obvious reunion; when the pH value was13.0, the products were needle.The addition of additive was the main method to control the morphology of products.NaY(MoO4)2: Pr3+phosphors with regular shape of octahedron were successfullyprepared using glutamic acid as the surfactant.The results indicated that the red phosphors doped with Pr possessed of the bestperformance among those prepared by hydrothermal pyrolysis method. Themorphology and particle size of the products could be effectively controlled bychanging the pH value and adding the surfactant.