Synthesis And Luminescence Properties Of Rare-earth (Eu³⁺,La³⁺,Gd³⁺ And Y³⁺)-Doped Layered Mica Phosphors

Layered silicate phosphors have many advantages in optical fields due to their large inner surface,superior cation exchange ability,high chemical and thermal stability,which has attracted many researchers'attention.Mica is a typical layered silicate minerals,but the luminescent properties of rare-earth-doped mica phosphors are not so good.In this paper,the rare-earth ions were attempted to introduce into the mica lattices,and then the system of co-doped mica matrix with rare-earth ions was prepared.The crystal field effect was used to break the forbidden transition and enhance the luminescence of the phosphor.Besides,the optical properties and the energy transfer process between rare-earth ions were investigated.In this paper,a series of rare-earth single doped and co-doped(Eu³⁺;La³⁺,Eu³⁺;Gd³⁺,Eu³⁺;Y³⁺,Eu³⁺)fluorophlogopite and fluorosilicone mica phosphors were prepared.The elements,morphology and structure of the samples were characterized by scanning electron microscopy and X-ray diffraction.Their luminescent properties and lifetime were analyzed by fluorescence spectra,color coordinates and fluorescence decay curves.It was found that in the rare-earth single-doped samples,the structure of mica was little changed except for the interlayer spacing became smaller.The results showed that the K⁺between the mica lattice layers was replaced by rare-earth Eu³⁺.The main fluorescence emission peak of the samples belonged to the ⁵D₀?⁷F₂ characteristic red emission of rare-earth Eu³⁺.In the rare-earth co-doped mica samples,the fluorescent lifetime and luminescence intensity are higher than that of the single-doped mica samples,implying the presence of La³⁺?Eu³⁺,Gd³⁺?Eu³⁺and Y³⁺?Eu³⁺energy transfer phenomenon.If the fluorophlogopite mica is used as a substrate,the Gd,Eu co-doped samples have the optimal light-emitting effect.As the fluorosilicone mica is used as a substrate,the La,Eu co-doped samples show the strongest luminescence.After the optimatization,the samples can reach the quantum efficiency more than 30%under the excitation of near-UV light.This means that the change of micro-environment in mica has a great influence on the luminescence.Therefore,a pure red phosphors with better luminescence can be obtained by controlling the concentration of rare-earth ions,doping species,and adjusting the substrate,and may be used in solid state lighting and other optical fields.