Preparation method of Ce < 3 + >-doped calcium hafnate fluorescent material

Abstract

The invention particularly relates to a preparation method of a Ce < 3 + >-doped calcium hafnate fluorescent material. CaHfO3: Ce < 3 + > powder is synthesized by adopting a hydrothermal method, a hydrothermal product does not need to be roasted, and CaHfO3: Ce < 3 + > can be directly synthesized in one step by adopting the hydrothermal method. The preparation method comprises the following steps: carrying out hydrothermal reaction for 24 hours at the temperature of 200 DEG C under the conditions that the molar ratio of Ca to Hf is 1.1: 1 and the pH value is 13.5 to obtain the polygonal single-phase CaHfO3: Ce < 3 + > powder with the particle size of about 0.5-1 mu m and the optimal luminescence property. The morphology of the powder can be controlled by adjusting the pH value, when the pH value is 13.5, polygonal powder particles are obtained, and the reaction time is prolonged, so that the crystal form development of the powder tends to be regular and complete.

Description

Technical field:

[0001] The present invention belongs to the technical field of scintillation ceramic materials, and particularly relates to a Ce 3+ A method for preparing a calcium hafnium oxide-doped fluorescent material. Background technology:

[0002] In recent years, scintillating materials have been widely used in the medical field. Nuclear medicine electronic imaging technology is an important means of medical diagnosis. The core of this advanced imaging technology is scintillators. For example, an X-CT machine requires thousands of scintillators to capture information in all directions, which puts more stringent requirements on the optical properties of scintillating materials.

[0003] Transmittance is one of the key factors in the preparation of transparent scintillators for scintillating ceramics. The performance of the scintillating material must be able to minimize the path length of visible photons or ultraviolet light, and to reduce the reflection, scattering, and absorption of the emitted wavelength during the transmission process. Materials with cubic crystal structures are easy to achieve optical isotropy and transparency, but when there are residual pores at the grain boundaries or in the grains, and their size is close to the wavelength of visible light, they will become efficient scattering centers, reducing transparency. Similarly, when second phase particles or other impurity phases appear in the matrix composition, the transmittance of the material will also be reduced.

[0004] CaHfO3:Ce 3+ It is an excellent ceramic scintillator material, which produces high-intensity and rapid fluorescence, greatly reduces afterglow, and improves luminous efficiency. However, the preparation of ceramic scintillators is the key to powder preparation. Based on this, the present invention adopts a wet chemical hydrothermal reaction method to prepare a Ce-doped 3+ By controlling the hydrothermal parameters, when the Ca / Hf molar ratio was 1.1:1 and the pH value was 13.5, and the reaction was carried out at 200°C for 24 hours, a single-phase CaHfO3:Ce with a particle size of about 0.5-1μm, a polygonal shape and the best luminescence performance was obtained. 3+ Ultrafine powder. The powder prepared by the hydrothermal method can achieve controllable morphology through reaction conditions, and can obtain slender needle-shaped, rod-shaped, and granular crystal forms. At the same time, the powder preparation process does not require calcination and has low energy consumption, so it is widely used. Summary of the invention:

[0005] The present invention aims to provide a Ce 3+ Preparation method of calcium hafnium oxide doped fluorescent material. For the first time, CaHfO3:Ce was successfully prepared by wet chemical hydrothermal reaction method. 3+ The ultrafine powder prepared by the invention has the advantages of good crystallinity, low agglomeration, controllable components and grain morphology, relatively simple process and less environmental pollution, and is convenient for industrial production.

[0006] The technical solution adopted by the present invention is as follows:

[0007] The present invention provides a scintillating ceramic material, which can obtain CaHfO3:Ce with different morphologies by adjusting the pH value. 3+ Powder, with the increase of pH value, CaHfO3:Ce 3+ The crystal morphology gradually changes from slender needles to granules. When the pH value is 13.5, polygonal powder particles are obtained. Adjusting the reaction time can make the powder crystal development tend to be regular and complete.

[0008] According to the present invention, the hydrothermal reaction method is used to prepare CaHfO3:Ce 3+ Nano powder, the specific steps are as follows:

[0009] S1: To obtain 1g of CaHfO3 powder (Ce doping concentration is 1mol%), use Ca(NO3)2 and HfOCl2·8H2O raw materials with a purity of 99.99%, Ce(NO3)3·6H2O raw materials with a purity of 99.99%, and KOH solution with a purity of ≥85%, and weigh various raw materials on an electronic balance after calculating the precise stoichiometric ratio.

[0010] S2: Prepare solutions of Ca(NO3)3, HfOCl2·8H2O and Ce(NO3)3·6H2O respectively and mix them evenly under constant stirring;

[0011] S3: After adding KOH solution (2 mol / L) dropwise to the solution in S2 to adjust the pH value, stirring was continued for 1 h to obtain a precursor;

[0012] S4: the precursor obtained in S3 is placed in a reactor after ultrasonic treatment, with a filling degree of 70% to 80%, and subjected to hydrothermal reaction at 120 to 200° C. for 6 to 36 hours;

[0013] S5: The hydrothermal product obtained in S4 was filtered, washed with deionized water for 2-3 times, and then washed with anhydrous ethanol (purity 99.7%) for 2-3 times, placed in a constant temperature drying oven at 120°C for 12 hours, ground with a mortar, and sieved with 200 mesh to obtain CaHfO3:Ce 3+ Powder.

[0014] Beneficial effects:

[0015] The present invention adopts wet chemical hydrothermal synthesis method to prepare CaHfO3:Ce for the first time. 3+Nanopowder. The solvent (water) in the hydrothermal synthesis system is generally in a near-critical, critical or supercritical state, and the entire reaction system is in a non-equilibrium state. The low-medium temperature heating adopted by the present invention realizes the control of the liquid phase, has low energy consumption, and has a wide range of applications; the reaction raw materials are relatively cheap and easy to obtain, the process is simple, and the target product is directly obtained without high-temperature treatment; the reaction temperature, pressure, reaction time and pH value, type of raw materials and concentration of the starting solution in the hydrothermal process have a great influence on the reaction rate, the crystal form, particle size and morphology of the product, and controllable powders are obtained by controlling the experimental conditions; the reaction is carried out in a closed state to avoid the volatilization of components and the mixing of impurities. Description of the drawings:

[0016] Figure 1 The different hydrothermal temperatures of CaHfO3:Ce 3+ XRD pattern of powder;

[0017] Figure 2 The CaHfO3:Ce synthesized at the same pH value of the present invention 3+ XRD pattern of powder;

[0018] Figure 3 The CaHfO3:Ce with different pH values ​​in the present invention 3+ SEM morphology of powder;

[0019] Figure 4 The CaHfO3:Ce powder synthesized at different pH values ​​in the present invention 3+ Emission spectrum of powder. Specific implementation method:

[0020] In order to explain the preparation method of the present invention more clearly, the present invention is described in detail below in conjunction with the accompanying drawings.

[0021] The present invention provides a Ce 3+ The preparation method of calcium hafnium oxide doped fluorescent material, when the Ca / Hf molar ratio is 1.1:1 and the pH value is ≥13, a single-phase CaHfO3:Ce can be obtained by hydrothermal reaction at 200°C for 24h. 3+ The luminescence intensity of the sample increases with the increase of pH value, because the morphology of CaHfO3 powder obtained under different pH conditions changes from slender needles to particles. The specific implementation plan is as follows:

[0022] Example 1:

[0023] (1) According to the experimental raw materials in Table 1, 1g CaHfO3 powder (Ce 3+ The doping concentration is 1 mol%), 2 mol / L KOH (100 ml) is prepared, and the molar ratio of Ca to Hf is 1.1:1;

[0024] Table 1 shows the raw materials and purity of the present invention.

[0025] raw material <![CDATA[Ca(NO3)2]]> <![CDATA[HfOCl2·8H2O]]> <![CDATA[Ce(NO3)3·6H2O]]> KOH Molecular weight 164.02 409.517 434.2225 56.1056 purity 99.5％ 99.99％ 99.99％ ≥82％

[0026] (2) According to the data in Table 2, Ca(NO3)3, HfOCl2·8H2O, and Ce(NO3)3·6H2O were prepared into aqueous solutions respectively, and mixed evenly under constant stirring;

[0027] Table 2 is the calculation data of the present invention

[0028] Chemical formula <![CDATA[CaHfO3]]> <![CDATA[HfOCl2·8H2O]]> <![CDATA[x*Ca(NO3)2]]> <![CDATA[Ce(NO3)3·6H2O]]> Molecular weight 266.97 409.517 x*164.02 434.2225 Mass / g 1g 1.126 0.794 0.012

[0029] (3) KOH solution (2 mol / L) was added dropwise, the pH value was adjusted to 13.5, and stirring was continued for 1 h to obtain a precursor solution;

[0030] (4) After ultrasonic treatment, the mixture was placed in an autoclave with a filling degree of 80% and subjected to hydrothermal reaction at 200°C for 24 hours;

[0031] (5) The hydrothermal product was first washed with deionized water and then with anhydrous ethanol, and then dried in a constant temperature drying oven at 120°C for 12 h. After grinding with a mortar, it was sieved with 200 mesh to obtain CaHfO3:Ce with a particle size of about 0.5 to 1 μm. 3+ Powder with regular crystal shape.

[0032] Figure 1 The different hydrothermal temperatures of CaHfO3:Ce 3+ XRD spectrum of the powder. It can be seen from the figure that when the hydrothermal temperature is further increased to 200℃, the peak values ​​of each peak gradually increase, the half-width height becomes narrower, and the baseline of the diffraction peak is stable, and a well-crystallized single-phase CaHfO3:Ce 3+ Powder.

[0033] Figure 2 The CaHfO3:Ce synthesized at the same pH value of the present invention 3+ XRD spectrum of the powder. Hydrothermal reaction is usually carried out under alkaline conditions. When the pH value of the solution increases, a large amount of OH - It will replace the H2O in the hydration layer on the surface of the growth unit, accelerate the dehydration reaction between the growth units, and is beneficial to CaHfO3:Ce 3+ So when pH value is ≥13, CaHfO3:Ce 3+ Phase powder.

[0034] Figure 3 The CaHfO3:Ce with different pH values ​​in the present invention 3+SEM morphology of the powder. Different pH values ​​have obvious effects on the morphology and size of the synthesized samples. CaHfO3:Ce with different morphologies can be obtained by adjusting the pH value of the hydrothermal system. 3+ Powder.

[0035] Figure 4 The CaHfO3:Ce powder synthesized at different pH values ​​in the present invention 3+ Emission spectrum of the powder. It can be seen that with the increase of pH value, the luminescence intensity of the sample continues to increase. Figure 3 The morphology of the synthesized powders under different pH conditions is given. It is found that with the increase of pH value, slender needle-shaped, rod-shaped, and granular grains can be obtained. The difference in powder morphology may be the reason why the intensity of powder luminescence changes with different pH values.

[0036] Example 2:

[0037] (1) According to the data in Table 2, Ca(NO3)3, HfOCl2·8H2O, and Ce(NO3)3·6H2O were prepared into aqueous solutions respectively, and the solutions were mixed evenly after continuous stirring;

[0038] (2) adjusting the pH value to 13 by dropwise addition of KOH solution (2 mol / L), and continuing stirring for 1 h to obtain a precursor solution;

[0039] (3) placing the precursor solution into a reactor after ultrasonic treatment with a filling degree of 80% and conducting a hydrothermal reaction at 200° C. for 24 h;

[0040] (4) The hydrothermal product was first washed with deionized water and then with anhydrous ethanol, and then dried in a constant temperature drying oven at 120°C for 12 h. After grinding with a mortar, it was sieved with 200 mesh to obtain CaHfO3:Ce with a particle size of about 0.5 to 1 μm. 3+ Powder.

[0041] Example 3:

[0042] (1) According to the data in Table 2, Ca(NO3)3, HfOCl2·8H2O, and Ce(NO3)3·6H2O were prepared into aqueous solutions respectively, and the solutions were mixed evenly after continuous stirring;

[0043] (2) adjusting the pH value to 12 by dropwise addition of KOH solution (2 mol / L), and continuing stirring for 1 h to obtain a precursor solution;

[0044] (3) placing the precursor solution into a reactor after ultrasonic treatment with a filling degree of 75% and conducting a hydrothermal reaction at 200° C. for 24 h;

[0045] (4) The hydrothermal product was first washed with deionized water and then with anhydrous ethanol, and then dried in a vacuum constant temperature drying oven at 120°C for 12 h. After grinding with a mortar, it was sieved with 200 mesh to obtain CaHfO3:Ce with a particle size of about 0.5 to 1 μm. 3+ Powder.

[0046] Example 4:

[0047] (1) According to the data in Table 2, Ca(NO3)3, HfOCl2·8H2O, and Ce(NO3)3·6H2O were prepared into aqueous solutions respectively, and the solutions were mixed evenly after continuous stirring;

[0048] (2) adjusting the pH value to 12.5 by dropwise addition of KOH solution (2 mol / L), and continuing stirring for 1 h to obtain a precursor solution;

[0049] (3) placing the precursor solution into a reactor after ultrasonic treatment with a filling degree of 70% and conducting a hydrothermal reaction at 200° C. for 36 h;

[0050] (4) The hydrothermal product was first washed with deionized water and then with anhydrous ethanol, and then dried in a vacuum constant temperature drying oven at 120°C for 12 h. After grinding with a mortar, it was sieved with 200 mesh to obtain CaHfO3:Ce with a particle size of about 0.5 to 1 μm. 3+ Powder.

[0051] In summary, the present invention adopts wet chemical hydrothermal synthesis method to prepare CaHfO3:Ce 3+ Ultrafine powder, the powder synthesized under the above parameters has uniform and stable distribution of each phase, low cost, simple operation, and no need for high-temperature calcination to directly obtain the target product. This low-cost method can easily synthesize other hafnium salt material systems and is easy to realize industrial production.

[0052] The above description of the specific examples and drawings of the present invention is only for illustrating the technical route of the present invention and is not intended to limit the present invention. Any replacements, modifications, etc. made within the core principles of the present invention shall be protected by the present invention.

Claims

1. A Ce 3+ A method for preparing a calcium hafnium oxide doped fluorescent material, characterized in that The wet chemical hydrothermal synthesis method does not require high-temperature calcination of the hydrothermal product. The hydrothermal method can directly synthesize CaHfO3:Ce in one step. 3+ By controlling the hydrothermal parameters, when the Ca / Hf molar ratio is 1.1:1 and the pH value is 13.5, a single-phase CaHfO3:Ce with a particle size of about 0.5 to 1 μm, a polygonal morphology, and the best luminescence performance can be obtained after reacting at 200 °C for 24 hours. 3+ Powder.

2. A Ce according to claim 1 3+ The method for preparing a calcium hafnium oxide doped fluorescent material is characterized in that: The specific steps are as follows: S1: Prepare Ca(NO3)3, HfOCl2·8H2O, Ce(NO3)3·6H2O aqueous solutions respectively, heat and stir continuously until the mixture is uniform; S2: adjusting the pH value by dropping KOH solution into the mixed solution in step S1; S3: the solution in S2 is continuously stirred and then ultrasonically treated and then added into a reactor for hydrothermal reaction; S4: The hydrothermal product obtained in S3 is filtered, washed, and dried in a vacuum constant temperature drying oven. After grinding with a mortar, it is sieved with 200 mesh to obtain CaHfO3:Ce3+ powder.

3. A Ce according to claim 2 3+ The preparation method of the calcium hafnium oxide doped fluorescent material is characterized by: The aqueous solution described in step S1, its raw materials are Ca(NO3)2, HfOCl2·8H2O, Ce(NO3)3·6H2O, KOH, anhydrous ethanol. Taking 1g of CaHfO3 powder (Ce doping is 1mol%) as an example, the calculation is shown in Table 1.

4. A Ce according to claim 2 or 3 3+ The preparation method of the calcium hafnium oxide doped fluorescent material is characterized by: The KOH solution in step S2 is prepared by preparing 100 ml of KOH solution (2 mol / L), wherein the molar ratio of Ca to Hf is 1.1:1, and the pH value is adjusted to 12-13.

5.

5. A Ce according to claim 2 3+ The preparation method of the calcium hafnium oxide doped fluorescent material is characterized by: The hydrothermal reaction in step S3 has a filling degree of 80% and is carried out at 200° C. for 24 hours.

6. A Ce according to claim 2 3+ The preparation method of the calcium hafnium oxide doped fluorescent material is characterized by: The hydrothermal product in step S4 is first washed with deionized water for 2 to 3 times, then washed with anhydrous ethanol for 2 to 3 times, and then placed in a vacuum constant temperature drying oven at 120° C. for 12 hours.

Images