CN1249198C - Perofskite aluminic gadolinium-base fluorescent powder and preparing method thereof - Google Patents

Abstract

The invention relates to a nanoscale perovskite type gadolinium aluminate-based fluorescent powder and a preparation method thereof. Using the selected raw materials and the process conditions provided by the present invention, the GAP powder doped with active ions can be obtained at a temperature of 900 ° C. The chemical expression of the powder is Gd _1-x AlO ₃ : Re _x , Re is a rare earth Elements such as one or any two of Eu, Pr, Ce or Tb; X is the molar weight of doping, 0.01<x<0.1. The main feature of the invention is that metal nitrate is used as raw material, citric acid is used as chelating agent and fuel, and precursor powder is obtained through sol-gel and combustion processes. The single-phase perovskite-type gadolinium aluminate-based fluorescent powder prepared by the invention emits visible fluorescence under the excitation of ultraviolet light, and has high luminous color purity and high luminous intensity. In addition, the prepared powder also has the advantages of uniform particle size distribution, ranging from 40 to 100 nm, simple and easy process, and cheap and easy-to-obtain raw materials.

Description

Perovskite-type gadolinium aluminate-based fluorescent powder and preparation method thereof

technical field

The invention relates to a rare earth-activated perovskite-type gadolinium aluminate-based fluorescent powder and a preparation method thereof, more precisely, a fluorescent powder in which rare earth-activated ions replace gadolinium in the aluminate matrix and its preparation, which belongs to the luminescent powder field of preparation.

Background technique

Perovskite gadolinium aluminate (GdAlO ₃ , referred to as GAP) has excellent optical properties, mechanical properties and stable physical and chemical properties, and its application as a new optical matrix material is attracting people's attention. GAP belongs to the orthorhombic crystal system, with fast growth rate, relatively small inner core, ideal distribution coefficient for doping, and large absorption coefficient. Its crystal is an ideal solid-state laser matrix material. The powder doped with other ions (mainly rare earth element ions and transition metal ions) in GAP emits visible light under the excitation of ultraviolet and vacuum ultraviolet light, X-rays and high-energy particles, and is expected to be used in cathode ray tubes (CRT), field Launch flat panel display (FED), plasma flat panel display and other fields to improve device resolution. As a new material, there are few studies on the preparation of GAP. JWM Verweij et al. synthesized GAP powder (Chemical Physics Letters 239 (1995) 51-55) by solid reaction method, uniformly mixed Gd ₂ O ₃ and Al ₂ O ₃ powders, and performed heat treatment at a high temperature above 1450°C. The method has simple process and is easy to produce in batches. The disadvantage is that the heat treatment temperature is high, and impurities are easily introduced during the ball milling process. The impurities come from the calcined product, except for the main crystal phase GAP, often remaining a small amount of intermediate phases Gd ₄ Al ₂ O ₉ (GAM for short) and Gd ₃ Al ₅ O ₁₂ ( Abbreviated as GAG). In recent years, wet chemical methods have been successfully applied to the synthesis of Y ₃ Al ₅ O ₁₂ powders. Such as Japan's IKEGAMI TAKAYASU et al. invented "Method for preparing YAG powder" (Patent No. JP2001270714), use yttrium carbonate and dawsonite as raw materials to make a solution containing carbonate and sulfide ions, and adjust the pH value of the solution A precipitate is formed, and the precipitate is heat-treated to obtain a single-phase YAG powder with a particle size of 40-400 nm. "Preparation method of ion-doped yttrium aluminum garnet nano-powder" (CN1398817A) proposed by Zhang Junji and Ning Jinwei uses nitrate aqueous solution of Y and Al as raw material, citric acid as chelating agent and spontaneous combustion The obtained gel is calcined at 800-1300°C to obtain YAG powder with a particle size in the range of 40-100nm. Both of the above two methods belong to the preparation method of YAG crystal phase powder. However, in the GdAlO ₃ (GAP) matrix involved in the present invention, the atomic radius of gadolinium is greater than that of yttrium (the rare earth element involved in the above two patents), and this feature makes the luminescent rare earth ions (such as europium and terbium) with larger atomic radius also available The incorporation into the matrix or the doping concentration in the matrix increases, so that new luminescent phases may be formed. In addition, the crystal phase (orthorhombic phase) of GAP is also completely different from the crystal phase (cubic phase) of YAG.

Contents of the invention

On the basis of the above-mentioned technical principle, the present invention proposes a new method for preparing perovskite-type gadolinium aluminate-based fluorescent powder. The chemical expression of the prepared fluorescent powder is:

Gd _1-x AlO ₃ :Re _x

Wherein the activated rare earth ion Re is one or any two composites of rare earth elements Eu, Pr, Ce or Tb, X is the molar weight of doping, 0.01<x<0.1, when X=0, it is pure GdAlO ₃ (ultraviolet fluorescence Spectral analysis revealed that pure _GdAlO3 has no fluorescent properties).

The invention adopts the method of combining the sol-gel process and the combustion synthesis process to prepare the fluorescent powder, and the preparation involves solization, gelation, and calcining heat treatment processes. First, rare earth oxides are dissolved in concentrated nitric acid to form metal nitrates. Citric acid is used as a chelating agent to complex with metal ions to form a clear sol; the xerogel obtained after the sol loses water contains citrate and nitrate, which is combustible and can provide additional heat. During the calcination heat treatment process The processing temperature can be lowered to help form nano-powders.

Rare earth oxides such as Gd ₂ O ₃ , Eu ₂ O ₃ , Pr ₆ O ₁₁ , and CeO ₂ with a purity of 99.99% and nitrates of Al(NO ₃ ) ₃ 9H ₂ O and Gd with a purity of analytical purity are used as raw materials. . Water is the solvent, nitric acid is used to dissolve the oxide raw material, citric acid is the gelling agent and fuel, and the purity is analytically pure.

The preparation process is as follows: according to the stoichiometric ratio, the above-mentioned one or more oxides are dissolved in a container with concentrated nitric acid, and an appropriate amount of citric acid is added to the mixed solution (the molar ratio of the amount of citric acid to the metal ion is 1-2:1) , adjust the pH value of the solution to 3-7. Place the container containing the mixed solution on a magnetic stirrer, stir and heat at 70-80°C, the sol can be obtained in several hours, and continue to heat until a transparent gel is obtained. Put the gel into a box furnace for pre-calcination at 400-500°C to obtain gray-black precursor powder. The resulting precursor powder was heat-treated at 800-1300°C for 2 hours to obtain the final powder. As the calcination temperature increased, the luminous intensity of the powder increased, but the luminous intensity remained basically unchanged after 1200°C. Moreover, the particle size increases slightly with the increase of calcination temperature.

The phosphor powder prepared by the invention emits red fluorescence under the excitation of ultraviolet light, has high luminous color purity, high luminous intensity, uniform powder particle size distribution (ranging from 40 to 100 nm), simple and easy preparation process, and cheap and easy raw materials. have to.

Description of drawings

The XRD spectrum of the product of Fig. 1 embodiment 1 shows that the product is a single GAP crystal phase.

The XRD spectrum of the product of Fig. 2 embodiment 2 shows that the product is a single GAP crystal phase.

Fig. 3 is the fluorescence spectrum of the Eu:GAP nanopowder prepared according to Example 3 under the excitation of ultraviolet light, the abscissa is the wavelength (nm), and the ordinate is the luminous intensity.

Fig. 4 is the fluorescence spectrum of the Pr:GAP nanopowder prepared according to Example 4 under ultraviolet excitation, the abscissa is the wavelength (nm), and the ordinate is the luminous intensity.

Fig. 5 is the fluorescence spectrum of the Eu, Ce:GAP nanopowder prepared according to Example 5 under the excitation of ultraviolet light, the abscissa is the wavelength (nm), and the ordinate is the luminous intensity.

Fig. 6 is the fluorescence spectrum of the Tb:GAP nanopowder prepared according to Example 6 under the excitation of ultraviolet light, the abscissa is the wavelength (nm), and the ordinate is the luminous intensity.

Detailed ways

The present invention will be specifically described below in conjunction with the embodiments and the accompanying drawings.

Example 1

Take 15.006g of aluminum nitrate (Al(NO ₃ ) ₃ 9H ₂ O), 7.252g of gadolinium oxide (Gd ₂ O ₃ ), 33.4g of citric acid, and an appropriate amount of concentrated nitric acid, dissolve in 200ml of deionized water, stir to form a uniform solution and Adjust the pH of the solution to 7. The beaker containing the solution was placed on a magnetic stirrer, heated to 70°C and kept stirring, and a sol was formed after several hours. Continue stirring to form a transparent gel. Put the gel into a box furnace preheated to 400°C, and burn it to form a gray-black precursor powder. The precursor powder was heat-treated at 900°C for two hours to obtain a light pink final product. Accompanying drawing 1 is the XRD spectrum of powder, and the spectrum shows that GAP nano powder forms a single crystal phase.

Example 2

Take 15.006g of aluminum nitrate (Al(NO ₃ ) ₃ 9H ₂ O), 7.252g of gadolinium oxide (Gd ₂ O ₃ ), 16.7g of citric acid, and an appropriate amount of concentrated nitric acid, dissolve in 200ml of deionized water, stir to form a uniform solution and Adjust the pH value of the solution to 3. Thereafter process is the same as example 1. Figure 2 is the XRD pattern of the synthesized powder under this condition, which shows that the GAP nanopowder also forms a single crystal phase under this condition.

Example 3

Take 15.006g of aluminum nitrate (Al(NO ₃ ) ₃ 9H ₂ O), 7.252g of gadolinium oxide (Gd ₂ O ₃ ), 0.352g of europium oxide (Eu ₂ O ₃ ), 33.4g of citric acid, and an appropriate amount of concentrated nitric acid, dissolve In 200ml deionized water, stir to form a homogeneous solution and adjust the pH value of the solution to 7. Thereafter technological process is with example 1. A pinkish final product of GdAlO ₃ :Eu (5% molGd) was obtained. Accompanying drawing 3 is the fluorescence spectrum of GdAlO ₃ :Eu ³⁺ nanopowder under the excitation of ultraviolet light, indicating that the luminescent ion Eu has entered the GAP lattice in solid solution form, and emits red fluorescence under the excitation of ultraviolet light (254nm).

Example 4

Take 15.006g aluminum nitrate (Al(NO ₃ ) ₃ 9H ₂ O), 7.252g gadolinium oxide (Gd ₂ O ₃ ), 0.339g praseodymium oxide (Pr ₆ O ₁₁ ), 33.4g citric acid, appropriate amount of concentrated nitric acid, dissolve in 200ml of deionized water, stirred to form a homogeneous solution and adjusted the pH value of the solution to 7. Thereafter technological process is with example 1. A pale pink final product of GdAlO ₃ :Pr (5% molGd) was obtained. Figure 4 is the fluorescence spectrum of GdAlO ₃ :Pr ³⁺ nanopowder excited by ultraviolet light, which shows that the luminescent ion Pr has solid-dissolved into the GAP lattice, and emits red fluorescence under the excitation of ultraviolet light (254nm).

Example 5

Take 15.006g aluminum nitrate (Al(NO ₃ ) ₃ 9H ₂ O), 7.252g gadolinium oxide (Gd ₂ O ₃ ), 0.352g europium oxide (Eu ₂ O ₃ ), 0.034g cerium oxide (CeO ₂ ), 33.4g Citric acid and an appropriate amount of concentrated nitric acid were dissolved in 200ml deionized water, stirred to form a uniform solution and the pH value of the solution was adjusted to 7. Thereafter technological process is with example 1. A pale pink final product of GdAlO ₃ :Eu, Ce (5% molGd for Eu, 10% molEu for Ce) was obtained. Accompanying drawing 5 is the fluorescence spectrum (red light) of GdAlO ₃ :Eu, Ce nanopowder excited by ultraviolet light.

Example 6

Take 15.006g aluminum nitrate (Al(NO ₃ ) ₃ 9H ₂ O), 7.252g gadolinium oxide (Gd ₂ O ₃ ), 0.374g terbium oxide (Tb ₄ O ₇ ), 33.4g citric acid, appropriate amount of concentrated nitric acid, dissolve in 200ml of deionized water, stirred to form a homogeneous solution and adjusted the pH value of the solution to 7. Thereafter technological process is with example 1. A white final product of GdAlO ₃ :Tb (5% molGd) was obtained. Accompanying drawing 6 is the fluorescence spectrum (green light) of GdAlO ₃ : Tb nanopowder under the excitation of ultraviolet light.

Table 1 is the stoichiometry and main parameters of each comparative example example Al(NO ₃ ) ₃ 9H ₂ O(g) Gd ₂ O ₃ (g) Eu ₂ O ₃ (g) Pr ₆ O ₁₁ (g) CeO ₂ (g) Tb ₄ O ₇ (g) Citric acid (g) pH Particle size (nm) Luminous color 1 15.006 7.252 0 0 0 0 33.4 7 40 no light 2 15.006 7.252 0 0 0 0 16.7 3 45 no light 3 15.006 7.252 0.352 0 0 0 33.4 7 60 red 4 15.006 7.252 0 0.339 0 0 33.4 7 50 red 5 15.006 7.252 0.352 0 0.034 0 33.4 7 80 red 6 15.006 7.252 0 0 0 0.374 33.4 7 90 green

Claims (6)

1. A perovskite-type gadolinium aluminate-based nano-phosphor powder activated by rare earth ions, characterized in that the chemical composition of the rare earth ion-activated gadolinium aluminate base is: Gd _1-x AlO ₃ :Re _x In the formula, the activated rare earth ion Re is one or any two of Eu, Pr, Ce or Tb compounded, X is the molar weight of doping, and 0.01<x<0.1. 2. The perovskite-type gadolinium aluminate-based nano-phosphor powder according to claim 1, characterized in that the particle size of the powder is 40-100 nm. 3. The method for preparing the perovskite-type gadolinium aluminate-based nano-fluorescent powder as claimed in claim 1, including solization, gelation, and heat treatment process, characterized in that: first, according to the chemical composition ratio of claim 1 Dissolve one or more oxides as raw materials in a container with concentrated nitric acid, then add citric acid to the mixed solution to adjust the pH value of the solution to 3-7; stir and heat at 70-80°C to obtain a sol, and continue heating Get a transparent gel at 80-100°C; then put the gel into a box furnace and pre-fire at 400-500°C to obtain a gray-black precursor powder; finally, heat-treat the obtained precursor powder at a temperature of 800-1300°C for 2 Hour. 4. The method for preparing perovskite-type gadolinium aluminate-based nano-fluorescent powder according to claim 3, characterized in that the molar ratio of the amount of citric acid added to metal ions is 1-2:1. 5. The method for preparing the perovskite-type gadolinium aluminate-based nano-phosphor powder according to claim 3, characterized in that the mixing solution container is placed on a magnetic stirrer when stirring and heating the sol. 6. The method for preparing the perovskite-type gadolinium aluminate-based nano-phosphor powder according to claim 3, characterized in that Al, Gd, and Re elements are introduced in the form of corresponding metal nitrates or oxides.

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