Tm /Dy doped LiYF4 monocrystal for white light LED (Light Emitting Diode) and preparation method thereof

The invention discloses a Tm /Dy doped LiYF4 monocrystal for white light LED (Light Emitting Diode) and a preparation method thereof. The LiYF4 crystal contains two rare earth ions, namely, Tm and Dy , the molecular formula of a product is LiY(1-alpha-beta)Tm alpha Dy beta F4, wherein alpha is not smaller than 0.0020 but not larger than 0.0300, and beta is not smaller than 0.0076 and not larger than 0.01140. Blue green light and yellow light emitted by Dy are mixed with blue light emitted by Tm to emit white light. When the atom concentration proportion of Tm /Dy in the crystal reaches to 3.7-3.9, the chromaticity coordinates of white light are optimal under the excitation of 350nm light, and the chromaticity coordinates x and y are basically close to the ideal 0.33. The doping concentration of rare earth in the lithium yttrium fluoride monocrystal is large, and the lithium yttrium fluoride monocrystal has excellent thermal, mechanical and chemical stability. The light emitting efficiency of the Eu and Dy rare earth ions doped in the monocrystal is high; and oxygen-free and water-free sealed Bridgman-Stockbarger method is adopted in the preparation method, and a high temperature fluorination treatment is performed on the raw material to obtain a fluoride crystal with high quality.