Novel Gd2O2S: Tb3+at-CaF2 core / shell structure composite fluorescent material and preparation method thereof

Abstract

The invention discloses a novel Gd2O2S: Tb < 3 + >-coated CaF2 core / shell structure composite fluorescent material and a preparation method thereof. According to the composition of the material, Gd2O2S: Tb < 3 + > serves as a core, CaF2 is deposited on the surface of Gd2O2S: Tb < 3 + > fluorescent powder to serve as a shell, and the thickness of the shell is about 5-80 nm. The preparation technology of the fluorescent material comprises the following steps: preparing Gd2O2S: Tb < 3 + > fluorescent powder by a high-temperature solid-phase method, then adding the fluorescent powder into an absolute ethyl alcohol solution containing CaCl2 and NH4F, and heating and stirring for 3-4 hours in a water bath environment of 60-90 DEG C so as to finish coating treatment of CaF2. Finally, the Gd2O2S: Tb < 3 + > and CaF2 core / shell structure fluorescent material is successfully prepared through the steps of ultrasonic dispersion, deionized water washing, drying and the like. According to the Gd2O2S: Tb < 3 + > CaF2 core / shell structure fluorescent material prepared by the invention, the photoluminescence intensity and cathode ray luminescence intensity of Gd2O2S: Tb < 3 + > fluorescent powder are greatly improved.

Description

Technical Field

[0001] The present invention relates to a Gd2O2S:Tb 3+ @CaF2 core / shell structure composite fluorescent material and a preparation technology thereof. The core / shell structure composite material significantly improves the photoluminescence and cathodoluminescence intensities of the Gd2O2S:Tb 3+ fluorescent material, belonging to the field of optoelectronic functional materials. Background Art

[0002] Gd2O2S (GOS)-based rare earth luminescent materials have characteristics such as good luminescence performance, high conversion rate, strong absorption, and low phonon energy, and are an ideal luminescent material. Gd2O2S:Tb 3+ can emit light under the excitation of various excitation sources such as X-rays, cathode rays, ultraviolet rays, and high-energy particles, and plays an important role in many aspects such as high-resolution computed tomography detectors, low-light-level image intensifiers, neutron radiography technology, X-ray intensifying screens, and scintillation detectors. The luminescence performance of this material directly affects the luminescence efficiency, color uniformity, and resolution of the device. In order to meet the actual application requirements, it is necessary to prepare Gd2O2S:Tb 3+ phosphors with high luminescence performance.

[0003] In recent years, researchers at home and abroad have optimized the performance and enhanced the luminescence efficiency by means of process optimization, formulation regulation, material compounding, etc. Yujie Ding et al. synthesized Gd2O2S:Tb 3+ phosphors by the sulfide melting method. When adding Na2S2O3, the luminescence intensity of the Gd2O2S:Tb 3+ [[ID=–23]]phosphors is stronger than that of other sodium compound fluxes; Wu et al. synthesized the precursor of Gd2O2S:Tb 3+ by adjusting the ratio between H2SO4 and Gd2O3 in a water bath, and prepared Gd2O2S:Tb 3+ phosphors with high relative density and high brightness. Although the complex preparation method is beneficial to the preparation of Gd2O2S powders with high luminescence intensity, it increases the process difficulty and production cost. Wenhua zhang et al. developed a GOS:Tb 3+ ,Dy 3+ phosphor and explored the effect of Ta 5+ ions in GOS:Tb 3+ and GOS:Tb 3+ ,Dy 3+ , which promoted the improvement of the luminescence intensity of GOS:Tb 3+ . Ding Yu-Jie et al. successfully prepared Gd 3+ and Tb 3+micron-scale Gd2O2S:Tb with relatively high contents 3+ phosphors, which have good luminescent properties. Dengfeng Yang et al. designed a novel core / shell heterostructure with tunable size and composition based on the epitaxial growth of α-NaYF4 along the c-axis of Gd2O2S:Ln 3+ nanocrystals. Osseni et al. modified the surface of pre-prepared Gd2O2S:Eu 3+ nanoparticles with an amino-silica or mesoporous silica shell, and the luminescence intensity was significantly enhanced in Gd2O2S:Eu 3+ @mSiO2. Khursand E. Yorov et al. utilized the solution processability and optical properties of colloidal Gd2O2S:Tb 3+ to fabricate an X-ray scintillation screen with a high spatial resolution of 20 lp / mm, greatly exceeding that of commercial Gd2O2S:Tb 3+ scintillators with a resolution of only 5-10 lp / mm. There are various methods to enhance the luminescent properties of Gd2O2S:Tb 3+ In the present invention, a Gd2O2S:Tb 3+ @CaF2 core / shell structured composite phosphor material is developed by coating CaF2 on the surface of Gd2O2S:Tb 3+ phosphors, and this composite material can effectively enhance the luminescence efficiency of the phosphors. Summary of the Invention

[0004] The present invention discovers a novel Gd2O2S:Tb 3+ @CaF2 core / shell structured composite phosphor material and its preparation technology. The composition of this core / shell structured composite phosphor material is based on Gd2O2S:Tb 3+ phosphors as the core, and through the liquid-phase deposition method, CaF2 is coated on the surface of Gd2O2S:Tb 3+ phosphors as the shell, and the thickness of the shell is about 5-80 nm. This composite structured phosphor material can enhance the luminescent properties of Gd2O2S:Tb 3+ phosphors. The specific preparation process of the Gd2O2S:Tb 3+ @CaF2 core / shell structured composite phosphor material is as follows: First, using Gd2O2S:Tb 3+ phosphors as the core, the phosphor material can be synthesized by different methods, and then the surface of Gd2O2S:Tb 3+ phosphors is coated with CaF2 by the liquid-phase deposition method, with a coating amount of 2-10% (CaF2 relative to Gd2O2S:Tb 3 +Coated with a mass fraction of). Under a water bath environment of 60-90 °C, heat and stir for 3-4 h to complete the coating treatment of CaF2. Finally, through steps such as ultrasonic dispersion, washing with deionized water, and drying, the Gd2O2S:Tb 3+ @CaF2 core / shell structure composite fluorescent material was successfully prepared. Through this preparation process, on the one hand, the CaF2 coating layer can reduce the defects on the surface of Gd2O2S, reduce the probability of non-radiative transitions on the grain surface, and thus improve the luminescence performance of the fluorescent material. On the other hand, the CaF2 coating layer can form a protective film, reduce the direct bombardment of the electron beam on the powder surface, protect the crystal structure inside the powder, and avoid surface defects and energy loss caused by electron bombardment, further enhancing luminescence.

[0005] The technical effect of the present invention is obvious. By coating Gd2O2S:Tb 3+ fluorescent material with an appropriate amount of CaF2, the luminescence intensity of Gd2O2S:Tb 3+ fluorescent material has been greatly improved. There are two advantages of the present invention. One is to enhance the photoluminescence intensity of the fluorescent material, and the other is to improve the cathodoluminescence intensity of the fluorescent material. Description of the Drawings

[0006] Figure 1 is the XRD pattern of the Gd2O2S:Tb 3+ @CaF2 core / shell structure composite fluorescent material sample in the present invention.

[0007] Figure 2 is the TEM image of the Gd2O2S:Tb 3+ @CaF2 core / shell structure composite fluorescent material sample in the present invention.

[0008] Figure 3 is the photoluminescence emission spectrum of the Gd2O2S:Tb 3+ @CaF2 core / shell structure composite fluorescent material sample and Gd2O2S:Tb 3+ fluorescent material in the present invention.

[0009] Figure 4 is the photoluminescence excitation spectrum of the Gd2O2S:Tb 3+ @CaF2 core / shell structure composite fluorescent material sample and Gd2O2S:Tb 3+ fluorescent material in the present invention.

[0010] Figure 5 is the cathodoluminescence spectrum of the Gd2O2S:Tb 3+ @CaF2 core / shell structure composite fluorescent material sample and Gd2O2S:Tb 3+ fluorescent material in the present invention. Detailed Embodiments

[0011] Gd2O2S:Tb in the present invention 3+ The specific process of the @CaF2 core / shell structured composite fluorescent material is described as follows:

[0012] (1) Based on the Gd2O2S:Tb 3+ fluorescent material prepared by the high-temperature solid-phase method, coating is carried out according to a coating amount of 2% (mass fraction of CaF2 relative to Gd2O2S:Tb 3+ ), and the ingredients are calculated according to the chemical reaction formula CaCl2 + 2NH4F = 2NH4Cl + CaF2.

[0013] (2) Weigh the corresponding amounts of CaCl2 and NH4F using a precision electronic balance, dissolve the weighed drugs in absolute ethanol, and stir for 25 min in a water bath at 80 °C under air isolation. Then add the Gd2O2S:Tb 3+ fluorescent material into the absolute ethanol solution of CaCl2 and NH4F, and stir while heating in a water bath for 3 h.

[0014] (3) Finally, through steps such as ultrasonic dispersion, washing with deionized water, and drying, the Gd2O2S:Tb 3+ @CaF2 core / shell fluorescent material with excellent luminescent properties is successfully prepared.

[0015] Figure 1 For the XRD pattern of the prepared Gd2O2S:Tb 3+ @CaF2 core / shell structured composite fluorescent material, by comparing with the diffraction peaks of the standard card PDF#26 - 1422, it shows that the CaF2 coating will not affect the crystal structure of the Gd2O2S:Tb 3+ fluorescent material.

[0016] Figure 2 For the TEM image of the prepared Gd2O2S:Tb 3+ @CaF2 core / shell structured composite fluorescent material. It can be seen from the TEM image that after the CaF2 coating treatment, a relatively uniform and well-defined transparent coating layer will be formed on the surface of the grains, and its thickness is about 5 nm.

[0017] Figure 3 For the photoluminescence emission spectra of the prepared Gd2O2S:Tb 3+ @CaF2 core / shell structured composite fluorescent material and Gd2O2S:Tb 3+ fluorescent material. At 544 nm, the photoluminescence intensity of the Gd2O2S:Tb 3+ @CaF2 sample of the present invention is 25% higher than that of the Gd2O2S:Tb 3+ fluorescent material.

[0018] Figure 4 For the prepared Gd2O2S:Tb 3+ @CaF2 core / shell structured composite fluorescent material and Gd2O2S:Tb 3+ Photoluminescence excitation spectra of the fluorescent materials. The excitation spectrum of the sample is a broadband spectrum with a peak at 286 nm and can emit bright green light under ultraviolet excitation.

[0019] Figure 5 For the prepared Gd2O2S:Tb 3+ @CaF2 core / shell structured composite fluorescent material and Gd2O2S:Tb 3+ Cathodoluminescence spectra of the fluorescent materials. At 544 nm, under the excitation of cathode rays, the Gd2O2S:Tb 3+ @CaF2 sample of the present invention has a luminescence intensity that is 42% higher than that of the Gd2O2S:Tb 3+ fluorescent material.

Claims

1. A novel Gd2O2S:Tb 3+ @CaF2 core / shell structured composite fluorescent material, the composition of which takes Gd2O2S:Tb 3+ phosphor as the core and deposits CaF2 on the surface of Gd2O2S:Tb 3+ crystal grains as the shell, and the thickness of the shell is about 5 - 80 nm.

2. Based on Claim 1, Gd2O2S:Tb 3+ The preparation technology of the @CaF2 core / shell structured composite fluorescent material is to prepare Gd2O2S:Tb 3+ phosphor by high-temperature solid-phase method. Using the liquid-phase deposition method, add this phosphor into the absolute ethanol solution containing CaCl2 and NH4F, and under the water bath environment of 60-90 °C, heat and stir for 3-4 h to achieve the surface coating of CaF2 on the phosphor. Finally, through a series of steps such as ultrasonic dispersion, deionized water washing and drying, the Gd2O2S:Tb 3+ @CaF2 core / shell structured fluorescent material is successfully obtained.

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