CN102660273A - Preparation method of rare earth doped nano zirconia up-conversion phosphor powder - Google Patents

Abstract

The invention provides a preparation method of rare earth-doped nano zirconia up-conversion fluorescent powder. Dissolve Zr(NO ₃ ) ₄ and Zr(NO ₃ ) ₃ in deionized water respectively according to the molar ratio of Er(NO ₃ ) ₃ to Zr(NO ₃ ) ₄ at a ratio of 0.05-0.2:1, and stir until clear to obtain Mix the solution, add citric acid with a cation ratio of 4:1 in the mixed solution, then add ammonia water to adjust the pH value of the solution to 6.5-7.5, stir to form a sol; dry the sol at 130°C to form a xerogel, Then sintering at 800°C to obtain white precursor phosphor powder, and finally calcining the precursor phosphor powder at 1100°C-1400°C to obtain rare earth-doped nano zirconia up-conversion phosphor powder. The invention is a scheme for effectively weakening the concentration quenching effect of highly doped rare earth ions, and has the advantages of simple synthesis process, low cost, high luminous efficiency of finished products, and the like.

Description

Preparation method of rare earth doped nano zirconia up-conversion phosphor

technical field

The invention relates to a preparation method of a rare earth-doped nano-luminescent material. the

Background technique

Since the laser has a high energy density, excellent collimation and monochromaticity, since the laser was invented in 1960, it has attracted widespread attention. High-performance lasers made of different materials and methods have always been The focus of people's research. At present, the technology of using rare earths as active ions to achieve laser output is relatively mature, including Er, Nd plasma doped LiYF ₄ , NaYF ₄ , YAlO ₃ and Y ₃ Al ₅ O ₁₂ crystals emitting near 1000nm, near 1310nm and near 1550nm Laser output. The current development of rare earth lasers has two general directions: one is to develop into the infrared long-wave field that is safe for human eyes and has less loss in the atmosphere and optical fibers; the other is to develop into the short-wave field with higher energy. Among them, the research on infrared long-wave is in its infancy, and the cost of various detection equipment is very high, which greatly limits the development of this direction. On the other hand, since the performance of the current near-infrared semiconductor laser is quite stable, the output power is high, and the cost is relatively low, the method of using the relatively mature near-infrared semiconductor laser to excite rare earth doped materials to generate visible light has great potential. potential. Since this method uses near-infrared low-energy photons to excite high-energy photons in the visible band, it is called upconversion luminescence.

Up-conversion phenomenon has attracted extensive attention of researchers from various countries in recent decades due to its great application potential in the fields of short-wavelength all-solid-state lasers, information processing, stereoscopic displays, and fluorescent labels. Rare earth ions, especially Er ions, have the advantages of rich radiation bands and long lifetimes of excited state levels, and are very suitable as luminescent centers for upconversion fluorescent materials. the

Various applications of rare earth ion-doped materials for upconversion fluorescence require high luminous efficiency as a basis, but the efficiency of various rare earth doped luminescent materials is not very high, which greatly limits the practical application of upconversion fluorescence. Therefore, one of the main research directions of upconversion luminescence of rare earth ion doped materials is how to improve the upconversion efficiency of materials. the

Among all the factors affecting the upconversion efficiency, the choice of substrate is one of the most important factors. In fact, quite a lot of materials can be used as substrates to achieve upconversion luminescence, but many of them have low upconversion efficiency due to their high phonon energy, and have little practical value. the

Rare earth-doped nanocrystalline powder matrix has attracted widespread attention due to the advantages of both rare earth materials and nanomaterials. Common powder matrixes are mainly oxides, including ZnO, Gd ₂ O ₃ , ZrO ₂ , Y ₂ O ₃ , Lu ₂ O ₃ and TiO ₂ etc. Among them, zirconia has the advantages of rich mineral resources, heat resistance, corrosion resistance, strong plasticity, and low phonon energy (about 470 cm ^-1 ), making it a very potential up-conversion matrix material.

In addition, the upconversion intensity of rare earth ions generally increases with the increase of doping concentration. But when the doping concentration is too high, because the distance between rare earth ions is shortened and the interaction is enhanced, the rare earth ions at a high energy level can easily transfer their energy to the host material through surface defects, thereby reducing the fluorescence emission intensity, which is concentration quenching phenomenon. In order to achieve high-efficiency upconversion radiation, how to weaken the concentration quenching effect under the condition of higher doping concentration has become a hot spot of concern. the

Contents of the invention

The purpose of the present invention is to provide a method for preparing rare earth-doped nano-zirconia up-conversion phosphors that can effectively reduce the concentration quenching effect of rare earth ions, thereby improving fluorescence efficiency by increasing the doping concentration of rare earth ions. the

The object of the present invention is achieved in this way: Zr(NO ₃ ) ₄ and Zr(NO ₃ ) ₃ are dissolved respectively according to the molar ratio of Er(NO 3 ) ₃ and Zr( _{NO 3 ) 4} at a ratio of 0.05-0.2:1 In deionized water, stir until clarification to obtain a mixed solution, add citric acid with a cation ratio of 4:1 in the mixed solution, then add ammonia water to adjust the pH value of the solution to 6.5-7.5, stir to form a sol; put the sol in Dried at 130°C to form a xerogel, then sintered at 800°C to obtain a white precursor phosphor, and finally calcined the precursor phosphor at 1100°C-1400°C to obtain a rare earth-doped nano-zirconia up-conversion phosphor.

The realization principle of the present invention is: according to the luminescence theory of rare earth ions, the fluorescence intensity emitted by rare earth ions is closely related to the number of surface defects, and the fewer surface defects, the higher the fluorescence efficiency. By calcining the rare earth-doped up-conversion phosphors synthesized by conventional methods, the surface defects of nanocrystals can be effectively reduced. Specifically, O-H bonds and C-O bonds adsorbed on the surface of nanocrystals can be removed more effectively after secondary high-temperature calcinations. In addition, the grain size of nanocrystals also increases with the increase of sintering temperature, which is equivalent to reducing the specific surface area of nanocrystals, thereby reducing the surface defects of nanocrystals. the

The beneficial effects of the present invention are mainly reflected in: 1. The preparation process is simple. 2. Low cost. 3. The fluorescence efficiency of the finished product is high. the

Description of drawings

Figure 1 is the preparation process of rare earth-doped zirconia nanocrystalline high-efficiency phosphor;

Fig. 2 is 5mol%Er ³⁺ : ZrO ₂ is synthesized by conventional sol-gel method (5Er800) and is calcined (5Er1300) under the condition of 1300 degrees Celsius for the second time up-conversion spectral comparison;

Figure 3 is a comparison of the XRD data of 10mol% Er ³⁺ : ZrO ₂ synthesized by a conventional sol-gel method (10Er800) and secondary calcined (10Er1300) at 1300 degrees Celsius;

Fig. 4 is a comparison of the up-conversion spectra of 10mol% Er ³⁺ : ZrO ₂ synthesized by conventional sol-gel method (10Er800) and calcined twice at 1300 degrees Celsius (10Er1300).

Detailed ways

The basic method of the present invention is: select Zr(NO ₃ ) _{4 and} Zr(NO ₃ ) ₃ of analytical grade according to the molar ratio of Er(NO 3 ) 3 and Zr(NO ₃ ) ₄ being 0.05-0.2 _: 1 Dissolve in deionized water respectively, stir vigorously until the solution is clear, add citric acid with a ratio of 4:1 to the cations in the solution, then add ammonia water to adjust the pH value of the solution to about 7, and stir for 2 hours to form a sol. Put the above sol in a drying oven and dry at 130°C for 20 hours to form a xerogel. Put the sample in a muffle furnace and sinter at 800°C for 2 hours to obtain a white precursor phosphor. Finally, put the precursor at 1100°C Calcining at -1400°C for 2 hours to obtain high-efficiency rare earth-doped phosphors. Specifically, it can be realized through the following specific implementation methods:

Embodiment 1: according to formula ratio (mol ratio):

The xerogel of the 0.05Er(NO ₃ ) ₃ : 1Zr(NO ₃ ) ₄ synthetic sample was sintered at 800°C for 2 hours to obtain the precursor phosphor, and then calcined at 1100°C for 2 hours.

The basic formula remains unchanged, only the proportion of Er(NO ₃ ) ₃ is changed, and several different implementation modes are obtained as follows:

Embodiment 2: The xerogel is prepared according to the formula ratio of 0.1Er(NO ₃ ) ₃ : 1Zr(NO ₃ ) ₄ , the same as Embodiment 1 below.

Embodiment 3: The xerogel is prepared according to the formulation ratio of 0.15Er(NO ₃ ) ₃ : 1Zr(NO ₃ ) ₄ , the same as Embodiment 1 below.

Embodiment 4: The xerogel is prepared according to the formulation ratio of 0.2Er(NO ₃ ) ₃ : 1Zr(NO ₃ ) ₄ , the same as Embodiment 1 below.

Embodiment 5: According to the formula ratio in Embodiment 1, the second calcination is carried out at 1200 degrees Celsius for 2 hours. the

Embodiment 6: Prepare xerogel according to the formulation ratios in Embodiments 2, 3, and 4, and the following is the same as Embodiment 5. the

Embodiment 7: According to the formula ratio in Embodiment 1, the second calcination is carried out at 1300 degrees Celsius for 2 hours. The up-conversion spectrum data of the precursor and the phosphor powder after secondary calcination are shown in Fig. 2 . the

Embodiment 8: Prepare xerogel according to the formula ratio in Embodiments 2, 3, and 4, and the following is the same as Embodiment 7. The XRD data of the precursor and the phosphor powder after secondary calcination are shown in FIG. 3 , and the up-conversion fluorescence data are shown in FIG. 4 . the

Embodiment 9: According to the formula ratio in Embodiment 1, the second calcination is carried out at 1400 degrees Celsius for 2 hours. the

Embodiment 10: The xerogel is prepared according to the formulation ratios in Embodiments 2, 3, and 4, and the following is the same as Embodiment 9. the

The specific embodiments described above have described the purpose, principle, technical solution and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific examples of the present invention, and are not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. the

In the present invention, the rare earth ions are Er ions, of course, Yb ions, Tm ions, Ho ions, Eu ions, Tb ions, Nd ions, etc. can also be selected, and the doping concentration is greater than 5 mol.%. the

In the present invention, the rare-earth doped matrix that achieves fluorescence enhancement through secondary calcination is zirconia. Of course, other rare-earth doped matrix that achieves fluorescence enhancement through secondary calcination can also be selected, such as yttrium oxide, lutetium oxide, aluminum oxide, gadolinium oxide, Sodium yttrium fluoride, etc. the

Claims (5)

_1. A preparation method for rare earth _- doped nano-zirconia up-conversion phosphor, characterized _in that: Zr ₍ NO ₃ ) ₄ and Zr(NO ₃ ) ₃ were respectively dissolved in deionized water, stirred until clarified to obtain a mixed solution, citric acid with a ratio of 4:1 to the cation in the mixed solution was added, and ammonia water was added to adjust the pH value of the solution to 6.5-7.5, stirring to form a sol; drying the sol at 130°C to form a xerogel, and then sintering at 800°C to obtain a white precursor phosphor, and finally calcining the precursor phosphor at 1100°C-1400°C to obtain Rare earth doped nano zirconia up-conversion phosphor. 2. The preparation method of rare earth-doped nano-zirconia up-conversion phosphor according to claim 1, characterized in that: the drying time for drying the sol at 130° C. to form a xerogel is 20 hours. 3. The preparation method of rare earth-doped nano-zirconia up-conversion phosphor according to claim 1 or 2, characterized in that the sintering time at 800° C. is 2 hours. 4. The preparation method of rare earth-doped nano-zirconia up-conversion phosphor according to claim 1 or 2, characterized in that the calcination time at 1100°C-1400°C is 2 hours. 5 . The method for preparing rare earth-doped nano zirconia up-conversion phosphor according to claim 3 , wherein the calcination time is 2 hours at 1100° C.-1400° C.

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