Growth And Optical Properties Of Doped YAG Crystals

Yttrium aluminum garnet (YAG) is a kind of important functional materials, which widely used for laser devices, scintillation detector and LED, etc. The melting point of YAG crystal is high, closed to 2000 ℃.The traditional growth method of YAG crystals, such as the CZ method, due to high cost, is not suitable for industrialization. However, the Bridgman method is considered to suit for industrialization of crystals, because it can realize poly-crucibles’growth technology at the same time. This is expected to reduce the cost of crystal growth and apply to high power white LED, scintillation detector, etc. Thus, the research of YAG crystals growth method is of great significance.Ce:YAG single crystals with transparent and pale yellow, were grown firstly by the Bridgman method. Spectrum analysis showed that the excitation peak is located in broad band around 500-680nm, which has two fitting emission peaks (530nm and 580nm) by double Gaussian peak fitting. The white LED was prepared by Ce:YAG single crystal sample coupling with blue chip, and its luminous efficiency is gradually increasing with the increase of drive current. Above 100 mA, the white LED color rendering index starts to reduce.Dy3+:YAG and 0.06Dy3+, Eu3+:YAG nanopowders were synthesized by sol-gel method. The character emission peaks of Dy3+ and Eu3+ are 582、677nm and 596nm、649nm, respectively. The chromaticity coordinate of Dy3+:YAG nanopowder (0.385,0.384) was very closed to that of the white energy saving lamp (0.380,0.380), The that of Dy3+,Eu3+:YAG nanopowder (0.3263,0.3334) was closed to the ideal white light (0.3333,0.3333). Thus, they have a potential application in simulating the sunlight artificially through fabricating white light LED.Ce,Pr:YLuAG and Ce,Tm:YLuAG crystals were grown by the floating zone method. Ce,Pr:YLuAG crystal with transparent and pale yellow exists some cracks. The FWHM is 14" of Ce,Pr:YLuAG crystal. The transmittances of Ce,Pr:YLuAG and Ce,Tm:YLuAG crystals are over 80%(>500nm), which are close to the theoretical value 84.2%. Lu3+ partly replaces Y3+ entering into YAG matrix, this changes the original YAG crystal field. It prompted the excitation and emission peaks of Ce3+ and Pr3+ shift. The color coordinate was located at (0.474,0.495) under 487nm excitation, which shifts to red zone compared with commercial Ce:YAG yellow phosphor. As a result, the Ce,Pr:YLuAG crystal is more suitable to fabricate white LED.