A transparent strontium fluoride ceramic based on low-temperature sintering, its preparation method and application
By combining low-temperature sintering with strontium acetate additive, high-density, high-transparency strontium fluoride transparent ceramics were prepared, solving the energy consumption and material composite problems caused by high-temperature sintering, and realizing the fabrication of high-performance optoelectronic devices.
Patent Information
- Application Number
- CN202610195769.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-11
- Publication Date
- 2026-06-30
Smart Images
Figure CN122301559A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of optical materials, and specifically relates to a transparent strontium fluoride (SrF2) ceramic based on low-temperature sintering, its preparation method, and its application. Background Technology
[0002] Transparent ceramics, such as strontium fluoride, are considered ideal fluorescent matrices and encapsulation materials for next-generation high-power LEDs and laser devices due to their excellent optical transmittance, high thermal conductivity, and good mechanical strength. However, the sintering temperature of traditional transparent ceramics is extremely high (typically >1000 °C), which leads to huge energy consumption and prevents the direct composite with many high-performance but thermally unstable optical functional materials (such as perovskite quantum dots and organic-inorganic hybrid nanoclusters), severely limiting their applications. In existing technologies, hot pressing or spark plasma sintering techniques are commonly used to lower the sintering temperature, but these still require relatively high temperatures (>800 °C). Some studies have also used liquid-phase sintering aids, but these often introduce amorphous phases at grain boundaries, reducing the thermal conductivity and optical quality of the ceramic. Furthermore, commonly used acid-base sintering aids can damage the luminescent material. Therefore, developing a ceramic preparation technology that can achieve high density, high transparency, and clean grain boundaries at extremely low temperatures, and effectively composite with thermosensitive luminescent materials, is a pressing technical challenge in this field. Summary of the Invention
[0003] The technical problem to be solved by the present invention is to provide a transparent strontium fluoride ceramic based on low-temperature sintering, its preparation method and application, so as to overcome the defects of the prior art where high or low sintering temperature of ceramics leads to a reduction in the thermal conductivity and optical quality of the ceramic.
[0004] This invention provides a transparent strontium fluoride ceramic based on low-temperature sintering, wherein the transparent strontium fluoride ceramic is composed of 95-99% strontium fluoride matrix and 1%-5% thermosensitive luminescent material by mass percentage.
[0005] Preferably, the strontium fluoride matrix is strontium fluoride nanoparticles with a particle size of 10-30 nm.
[0006] Preferably, the thermosensitive luminescent material includes, but is not limited to, any one of hybrid cuprous iodide clusters, quantum dots, and phosphors.
[0007] This invention provides a method for preparing the above-mentioned transparent strontium fluoride ceramic based on low-temperature sintering, comprising the following steps:
[0008] (1) At room temperature, strontium nitrate solution was added dropwise to potassium fluoride solution, stirred to obtain a suspension, and after standing, it was washed with water, centrifuged and dried to obtain strontium fluoride nanopowder;
[0009] (2) Strontium fluoride nanoparticles are mixed with thermosensitive luminescent materials, and the mixed powder is ground evenly with strontium acetate solution. The mixture is then placed in a mold, uniaxial pressure is applied and the sintering temperature is controlled. After the heat preservation is completed, the ceramic block is taken out and polished to obtain strontium fluoride transparent ceramic.
[0010] Preferably, in step (1), the concentration of the strontium nitrate solution or potassium fluoride solution is 0.05-0.5 mol / L; the molar ratio of strontium nitrate to potassium fluoride is 1:2; and the dripping rate of the strontium nitrate solution is 1-5 mL / min.
[0011] Preferably, the settling time of the suspension in step (1) is 12-24 h.
[0012] Preferably, in step (2), the strontium acetate solution is the only sintering aid, with a concentration of 1-1.5 mol / L and an addition amount of 5-15 wt% of the mass of the strontium fluoride nanoparticles; the grinding time is 5-10 min.
[0013] Preferably, in step (2), the uniaxial pressure is 250-375 MPa, the heating rate is 5-15 ℃ / min, the sintering temperature is 100-150 ℃, and the holding time is 0.5-2 h.
[0014] The present invention also provides an application of the above-mentioned strontium fluoride transparent ceramic based on low-temperature sintering in optoelectronic devices.
[0015] Preferably, the application includes, but is not limited to:
[0016] a. By directly using the aforementioned strontium fluoride transparent ceramic as a phosphor conversion layer and encapsulator on LED chips, high-performance white LEDs can be fabricated. Thanks to the high thermal conductivity of the strontium fluoride transparent ceramic, the device exhibits excellent heat dissipation performance, avoiding the aging and yellowing problems of traditional organic encapsulants, and achieving a high color rendering index (CRI > 92).
[0017] b. It can be used as a scintillator material for X-ray imaging.
[0018] Beneficial effects
[0019] This invention offers a universally applicable method suitable for various high-temperature sensitive materials, breaking through the limitations of traditional sintering methods. The innovative use of a mild cationic sintering aid lowers the sintering temperature of strontium fluoride ceramics to 150 °C while maintaining a density of up to 99%. The mild strontium acetate aid, after participating in the reaction, generates SrF2 consistent with the matrix, resulting in high ceramic transmittance. This achieves efficient composite bonding of thermistor materials, maintaining their high luminous efficiency and addressing the industry's pain point of poor stability. The prepared LED devices exhibit high color rendering index, uniform light color, and good reliability, demonstrating significant commercial potential. The entire preparation process is simple, generates no toxic byproducts, has low energy consumption, is environmentally friendly, and suitable for large-scale industrial production. Attached Figure Description
[0020] Figure 1 Transmission electron microscopy (TEM) scan of strontium fluoride nanoparticles prepared in Example 1; (a) morphology image; (b) microstructure elemental distribution map.
[0021] Figure 2 The internal quantum yield of the strontium fluoride-based optical ceramic in Example 1 during the sintering process is shown.
[0022] Figure 3 This is a diagram illustrating the LED device based on strontium fluoride optical ceramics in Example 1.
[0023] Figure 4 The image shows the optical performance of the LED device based on strontium fluoride optical ceramics in Example 1.
[0024] Figure 5 This is an X-ray imaging illustration of the strontium fluoride-based optical ceramic in Example 2.
[0025] Figure 6 The density curves of strontium fluoride ceramics obtained by adding different sintering aids in Comparative Example 1 are shown.
[0026] Figure 7 The image shows the transmittance of strontium fluoride ceramics obtained by different sintering methods in Comparative Example 2, as well as actual images of strontium fluoride ceramics obtained by low-temperature sintering. Detailed Implementation
[0027] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.
[0028] Example 1
[0029] The preparation method of strontium fluoride transparent ceramic in this embodiment includes the following steps:
[0030] (1) Weigh 13.23 g of strontium nitrate (Sr(NO3)2) powder and dissolve it in 200 mL of deionized water. Set the rotation speed to 500 rpm and stir for 10 minutes to obtain a completely dissolved clear solution A. Weigh 11.77 g of potassium fluoride dihydrate (KF·2H2O) powder and dissolve it in 250 mL of deionized water. Set the rotation speed to 500 rpm and stir for 10 minutes to obtain a completely dissolved clear solution B. Slowly add solution A to solution B at a dropping rate of 3 mL / min, while keeping the mixture stirred during the dropping process. After titration, continue stirring for 1 hour. After stirring, let the mixture stand for 12 hours to age. Wash the precipitate with deionized water and centrifuge five times at a speed of 9000 rpm for 10 min. After centrifugation, dry the precipitate in a vacuum oven at 60 ℃ for 24 hours to obtain strontium fluoride (SrF2) nanoparticles. The morphology and elemental distribution diagram are shown in the figure. Figure 1 As shown in ab.
[0031] (2) Weigh 0.5 g of SrF2 nanoparticles, add 0.01 g of hybrid CuI clusters, grind and mix them evenly, add 50 μL of 1.5 mol / L strontium acetate solution, and grind for 10 minutes to mix thoroughly. Place the mixture into a specific tungsten carbide alloy mold, apply a uniaxial pressure of 350 MPa, heat to 150 °C at 10 °C / min, and hold for 60 minutes. After furnace cooling, a ceramic sheet with a diameter of 10 mm is obtained. After polishing, a strontium fluoride-based optical ceramic with a thickness of 1 mm is obtained, with a density of 99% and a transmittance of 79% at 700 nm. The internal quantum yield at different temperatures during sintering is measured using a quantum efficiency testing device as follows: Figure 2 As shown, at a sintering temperature of 150 °C, its internal quantum yield is 80%, which is 90% of that of the initial powder, further illustrating its excellent performance at this sintering temperature. After encapsulating the ceramic with an LED UV chip, the results were tested as follows... Figure 3 As shown, when lit, the device emits warm white light. Its electroluminescence spectrum is as follows: Figure 4 As shown, its relative color temperature is 3925 K, and its color rendering index is 93.4%. Through the preparation method of this embodiment, a strontium fluoride-based optical ceramic suitable for use in warm white LEDs was obtained.
[0032] Example 2
[0033] The preparation method of the strontium fluoride transparent ceramic in this embodiment is the same as in Example 1, except that:
[0034] (2) Weigh 0.4 g of the SrF2 nanoparticles prepared in Example 1, add 0.02 g of hybrid CuI clusters, grind and mix them evenly, add 50 μL of 1.5 mol / L strontium acetate solution, and grind and mix thoroughly. Place the mixture into a specific tungsten carbide alloy mold, apply a uniaxial pressure of 350 MPa, heat to 150 °C at 10 °C / min, and hold for 60 minutes. After furnace cooling, a ceramic sheet with a diameter of 10 mm is obtained. After polishing, a strontium fluoride-based optical ceramic with a thickness of 0.5 mm is obtained; its density is 99%, and its transmittance at 700 nm is 52%. This ceramic sheet is used as a scintillator material in a self-made X-ray imaging system. The system irradiates a capsule containing a metal spring through an X-ray source. The light passes through the ceramic scintillator, converting the X-rays into visible light, which is then collected by a camera. The effect is as follows: Figure 5 As shown, the spring inside the capsule can be clearly observed. Samples prepared by this method have imaging capabilities and application potential.
[0035] Comparative Example 1
[0036] Different strontium fluoride ceramics were prepared by adding different sintering aids during low-temperature sintering.
[0037] Weigh 0.5 g of the SrF2 nanoparticles prepared in Example 1, add 50 μL of a 1.5 mol / L strontium acetate solution, and grind thoroughly. Place the mixture into a specific tungsten carbide alloy mold, apply a uniaxial pressure of 350 MPa, and heat to 150 °C at a rate of 10 °C / min, holding for 60 minutes. After furnace cooling, a transparent strontium fluoride ceramic (low-temperature sintered - SrF2) with a diameter of 10 mm is obtained. Figure 6 As shown, the relative density is 99.2%; ceramics such as Figure 7 As shown in the image, its excellent optical transmittance is evident, with a linear transmittance of 79% at 700 nm.
[0038] Using the same method described above, strontium fluoride ceramics were prepared as a comparison using acetic acid, water, and without the addition of sintering aids. Figure 6 As shown, the density of strontium fluoride ceramics prepared using acetic acid, water, and without sintering aids is significantly lower than that of transparent strontium fluoride ceramics prepared using strontium acetate sintering aids. This demonstrates the important role of the cationic solution in the sintering aid of the present invention in ceramic densification, and that its mild sintering aid solution avoids damage to the material from strong acids and alkalis, making it widely applicable.
[0039] Comparative Example 2
[0040] As a comparison, strontium fluoride ceramics were prepared using a conventional hot-pressing sintering method (sintering temperature 800 °C). Figure 7As shown, the transmittance of strontium fluoride ceramics (hot-pressed SrF2) prepared by conventional hot-pressing sintering is only 65% at 700 nm, while the strontium fluoride transparent ceramics prepared by the low-temperature sintering method of this invention have a linear transmittance of 79% at 700 nm, and the preparation temperature is only 150 °C, which is much lower than that of conventional hot-pressing sintering. These results demonstrate that the low-temperature sintering method can reduce energy efficiency while ensuring high transmittance, and can be combined with various thermosensitive luminescent materials, greatly expanding its application range.
Claims
1. A transparent strontium fluoride ceramic based on low-temperature sintering, characterized in that, The strontium fluoride transparent ceramic, by weight percentage, consists of 95-99% strontium fluoride matrix and 1%-5% thermosensitive luminescent material.
2. The strontium fluoride transparent ceramic based on low-temperature sintering according to claim 1, characterized in that, The strontium fluoride matrix is strontium fluoride nanoparticles with a particle size of 10-30 nm.
3. The strontium fluoride transparent ceramic based on low-temperature sintering according to claim 1, characterized in that, The thermosensitive luminescent material includes any one of hybrid cuprous iodide clusters, quantum dots, and phosphors.
4. A method for preparing strontium fluoride transparent ceramics based on low-temperature sintering as described in any one of claims 1-3, comprising the following steps: (1) At room temperature, strontium nitrate solution was added dropwise to potassium fluoride solution and stirred to obtain a suspension. After standing, the suspension was washed with water, centrifuged and dried to obtain strontium fluoride nanopowder. (2) Strontium fluoride nanoparticles are mixed with thermosensitive luminescent materials, and the mixed powder is ground evenly with strontium acetate solution. The mixture is then placed in a mold, uniaxial pressure is applied and the sintering temperature is controlled. After the heat preservation is completed, the ceramic block is taken out and polished to obtain strontium fluoride transparent ceramic.
5. The preparation method according to claim 4, characterized in that, In step (1), the concentration of the strontium nitrate solution or potassium fluoride solution is 0.05-0.5 mol / L; the molar ratio of strontium nitrate to potassium fluoride is 1:2; and the dripping rate of the strontium nitrate solution is 1-5 mL / min.
6. The preparation method according to claim 4, characterized in that, The settling time of the suspension in step (1) is 12-24 h.
7. The preparation method according to claim 4, characterized in that, In step (2), the concentration of strontium acetate solution is 1-1.5 mol / L, and the amount added is 5-15 wt% of the mass of strontium fluoride nanoparticles; the grinding time is 5-10 min.
8. The preparation method according to claim 4, characterized in that, In step (2), the uniaxial pressure is 250-375 MPa, the heating rate is 5-15 ℃ / min, the sintering temperature is 100-150 ℃, and the holding time is 0.5-2 h.
9. The application of a low-temperature sintered strontium fluoride transparent ceramic as described in any one of claims 1-3 in optoelectronic devices.