A rare earth doped layered stannate-based white light fluorescent powder material and a preparation method thereof

Abstract

The application relates to the technical field of inorganic photoluminescence materials, and discloses a rare earth doped layered stannate-based white light fluorescent powder material and a preparation method thereof, a chemical molecular formula of which is A1-xSn2-xO6:Eu3+, wherein 0 < x <= 0.05, A is one or more divalent alkali earth metal ions in Ca, Sr and Ba, and is doped in different proportions, the A provides a red light emission component, the A provides a blue and yellow light emission component, the emission intensity of the red light and the blue and yellow light can be adjusted by regulating and the doping proportion, the ionic radius of the A is similar to that of the A, and the A substitutes the lattice position. Through the synergic doping of the A and the A and the proportion regulation, the charge compensation and the lattice position optimization of the A and the A are combined, the accurate matching of the red light and the blue and yellow light emission intensity of the fluorescent powder is realized, white light emission effects with excellent color rendering and stable color tone are obtained, and the problems of red light loss or light emission efficiency decay caused by the mixing of multi-color fluorescent powder in traditional white light LED fluorescent powder are effectively overcome.

Description

Technical Field

[0001] This invention relates to the field of inorganic photoluminescent materials technology, specifically to a rare earth-doped layered stannate-based white phosphor material and its preparation method. Background Technology

[0002] With its significant advantages of low energy consumption, long lifespan, no pollution, and high safety, LED lighting technology has rapidly achieved large-scale application in various fields such as general lighting, display backlighting, and special lighting, gradually replacing traditional incandescent and fluorescent lamps and becoming the mainstream technology in the modern lighting field.

[0003] As the core functional material of white LEDs, phosphors directly determine the luminous efficiency, color rendering index, color temperature stability, and lifespan of white LEDs. Therefore, the research and development of high-performance phosphors has always been a research hotspot and core issue in the field of LED technology. Currently, the realization of white LEDs mainly relies on two technical paths: the first is the "blue LED chip + yellow phosphor" combination scheme. In this scheme, the yellow phosphor absorbs the blue light emitted by the chip and converts it into yellow light. The yellow light then combines with the unabsorbed blue light to form white light. However, this technical approach has inherent flaws. Because yellow phosphors lack red light components in their emission spectrum, the resulting white light suffers from a high color temperature and poor color rendering, making it difficult to meet the demands of applications requiring high color fidelity, such as indoor lighting, medical lighting, and high-end displays. The second approach is a combination of "violet LED chip + red / yellow / green phosphors." This scheme utilizes the three phosphors to absorb violet light and then emit red, yellow, and green light respectively. The three monochromatic lights combine to form white light. While this effectively improves the color rendering of white light, it still faces several technical bottlenecks: Firstly, when multiple phosphors are mixed, photon absorption occurs between them, leading to light energy loss. Secondly, the different light decay rates of different colored phosphors vary, resulting in color temperature drift and decreased color rendering after long-term use, severely affecting the long-term stability of white LEDs. Furthermore, the complex preparation, screening, and proportioning processes of multiple phosphors significantly increase the production cost of white LEDs, limiting their widespread application in the low-to-mid-range lighting market.

[0004] The performance of luminescent materials is determined by the synergistic effect of the matrix material and the activator. Selecting a high-performance matrix material is a crucial prerequisite for developing high-performance phosphors. Stannate compounds, due to their stable physicochemical properties, good thermal stability, and excellent optical inertness, have become an important research direction for phosphor matrix materials. Among them, layered stannates, represented by Ca2SnO4, possess a typical Ruddlesden-Popper (RP) phase-like perovskite structure. In their crystal structure, [SnO6] octahedra are interconnected to form a unique one-dimensional chain structure. This unique crystal structure not only provides a stable lattice environment for activator ions but also promotes their smooth entry into the lattice and the formation of suitable energy traps within the band gap, thereby achieving efficient luminescence transitions. Simultaneously, the [SnO4] in the Ca2SnO4 matrix... 4- The presence of functional groups further enhances the optical stability of the material, making it an ideal matrix choice for rare-earth-doped luminescent materials.

[0005] Despite the numerous advantages of stannate matrix materials, there are still pressing technical challenges to be addressed in the preparation of white phosphors using rare earth doping: Firstly, the rare earth ions (such as Eu)... 3+ Dy 3+ (etc.) are mostly trivalent ions, while the A site in the stannate matrix (such as Ca) 2+ The A-site is a divalent cation site. When trivalent rare earth ions replace the divalent A-site cation, an electrochemical imbalance occurs, leading to defects in the crystal structure and consequently affecting the luminescence intensity and stability of the phosphor. Secondly, rare earth ions react with Sn in the matrix. 4+ The ionic radii differ, and some rare earth ions may occupy Sn. 4+ Lattice sites disrupt the integrity of the matrix's crystal structure, adversely affecting luminescence performance; thirdly, single rare earth ion doping makes it difficult to achieve full-spectrum white light emission, while how to achieve synchronous and efficient excitation of different ions and intensity matching of different emitted light components when multiple rare earth ions are co-doped is the core technical challenge for controlling high-quality white light.

[0006] In summary, existing phosphors for white LEDs still have many shortcomings in terms of color rendering, stability, and cost control. Furthermore, the technical challenges encountered in the preparation of stannate-based rare-earth-doped phosphors, such as charge imbalance, lattice site interference, and multi-ion synergistic excitation, have not yet been effectively resolved. Therefore, developing a rare-earth-doped layered stannate-based white phosphor material that combines high luminous efficiency, excellent color rendering, good stability, and low cost is of significant practical importance and application value for promoting the upgrading and popularization of white LED lighting technology. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a rare-earth-doped layered stannate-based white phosphor material and its preparation method, thus solving the problems mentioned in the background section.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a rare-earth-doped layered stannate-based white phosphor material with the chemical formula A. 2- x(Eu 3+ / Dy 3+ )xYxSn 1- xO4, where 0 < x ≤ 0.05, A is one or more divalent alkaline earth metal ions selected from Ca, Sr, and Ba, and Eu 3+ and Dy 3+ Doping was carried out in different proportions.

[0009] Preferably, the Eu 3+ Provides red light emitting components, Dy 3+ Provides blue and yellow light emission components, by modulating Eu 3+ and Dy 3+ The doping ratio can be adjusted to control the emission intensity of red and blue-yellow light.

[0010] Preferably, the Y 3+ The ionic radius of Sn 4+ The ionic radii are similar, Y 3+ Replace Sn 4+ The lattice position.

[0011] Preferably, the Y 3+ It is used to compensate for the valence imbalance caused by trivalent rare earth ions replacing divalent alkaline earth metal ions at the A site, and to ensure the conservation of molecular formula and valence in the material.

[0012] Preferably, the excitation wavelength is Eu. 3+ The corresponding excitation spectrum and Dy 3+ The wavelength at the intersection of the corresponding excitation spectra can simultaneously excite high-intensity Eu. 3+ Feature emission and Dy 3+ Feature emission.

[0013] A method for preparing a rare-earth-doped layered stannate-based white phosphor material includes the following steps: According to the chemical formula A 2- x(Eu 3+ / Dy 3+ )xYxSn 1- The raw materials for xO4 are weighed according to their stoichiometric ratio. The raw materials include compounds containing A, compounds containing Sn, Eu2O3, Dy2O3, and Y2O3, where 0 < x ≤ 0.05, and A is one or more divalent alkaline earth metal ions selected from Ca, Sr, and Ba. The weighed raw materials are placed in an agate mortar and ground until evenly mixed to obtain a preliminary mixed powder; The pre-mixed powder was loaded into a corundum crucible, and the crucible was placed in a muffle furnace and pre-fired at 1000°C for 6 hours. Take out the pre-fired sample and grind it again in an agate mortar until it is evenly ground. The sample, which was ground evenly again, was put back into the corundum crucible, and the crucible was placed in a muffle furnace and calcined at 1400℃ for 10 hours. The calcined sample is taken out and ground in an agate mortar to obtain the final product.

[0014] Preferably, the compound containing A is a carbonate, and the compound containing Sn is SnO2.

[0015] Preferably, the grinding process continues until the powder is evenly mixed and there is no obvious particle feel.

[0016] Preferably, the heating rate of the muffle furnace is 5℃ / min to 10℃ / min, and the cooling process is natural cooling along with the furnace.

[0017] This invention provides a rare-earth-doped layered stannate-based white phosphor material and its preparation method. It has the following beneficial effects: 1. This invention utilizes Eu 3+ With Dy 3+ Synergistic doping and ratio control, combined with Y 3+ By optimizing charge compensation and lattice occupancy, precise matching of the emission intensity of red and blue-yellow phosphors is achieved, thereby obtaining white light emission with excellent color rendering and stable hue, effectively overcoming the problem of luminous efficiency decay caused by the lack of red light or the mixing of multi-color phosphors in traditional white LED phosphors.

[0018] 2. This invention uses stannate with a Ruddlesden-Popper phase layered perovskite structure as the matrix material. By leveraging its stable physicochemical properties and good optical inertness, combined with a simple process design using a high-temperature solid-state method, it achieves low-cost and green preparation of phosphor materials. At the same time, it endows the materials with good thermal stability and long-term storage performance, thus broadening the practical application scenarios of the materials.

[0019] 3. This invention utilizes Eu 3+ With Dy 3+ The wavelength corresponding to the intersection of the excitation spectra is used as the excitation wavelength to achieve simultaneous and efficient excitation of two rare earth ions, avoiding the defect of uneven luminescence intensity under a single excitation wavelength. Meanwhile, Y... 3+ The introduction of rare earth ions can prevent Sn from being occupied. 4+The interference of lattice sites on luminescence performance significantly improves the luminescence intensity and overall optical performance of phosphors, providing a new technical path for the research and development of high-quality white phosphors. Attached Figure Description

[0020] Figure 1 This is a process flow diagram of the method of the present invention.

[0021] Figure 2 The XRD patterns of the luminescent material and the Ca2SnO4 standard card of this invention are shown.

[0022] Figure 3 This is the excitation spectrum of the luminescent material of the present invention.

[0023] Figure 4 This is the emission spectrum of the luminescent material of the present invention.

[0024] Figure 5 This is a chromaticity diagram of the emission spectrum of the luminescent material of this invention, corresponding to the color coordinates. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Please see the appendix Figure 1 -Appendix Figure 5 This invention provides a rare earth-doped layered stannate-based white phosphor material and its preparation method.

[0027] The process steps are as follows: Raw materials such as CaCO3, SnO2, Eu2O3, and Dy2O3 were weighed according to the stoichiometric ratio of the chemical formula Ca1.97Eu0.003Dy0.027Y0.03Sn0.97O4. The above raw materials are ground in an agate mortar and mixed evenly to obtain a preliminary mixed powder. The pre-mixed powder was loaded into a corundum crucible and placed in a muffle furnace for pre-firing at 1000°C for 6 hours. The sample in the corundum crucible was ground again with an agate mortar until uniform; The sample, which has been ground evenly again, is placed in a corundum crucible and then calcined in a muffle furnace at 1400°C for 10 hours. The calcined sample was ground into a fine powder using an agate mortar and pestle to obtain the final sample.

[0028] Preliminary characterization and testing of the samples: X-ray diffraction (XRD) was performed on the sample, and the XRD pattern of the sample was obtained. After comparison with the Ca2SnO4 standard card, no impurity peaks were found, indicating that we have obtained a pure phase sample. The sample XRD pattern is shown in Figure (2).

[0029] The excitation spectrum of the test sample was measured using the standard emission peak wavelengths of Eu3+ and Dy3+ as the receiving wavelengths. The two excitation spectra were then combined to find the intersection point of the two spectral lines, and the x-coordinate of the intersection point was determined to be 320 nm. The sample excitation spectrum is shown in Figure (3).

[0030] The sample was excited at a wavelength of 320 nm to obtain its emission spectrum. It can be seen that the characteristic emission peaks of Eu3+ and Dy3+ were excited and their intensities were similar. The emission spectrum of the sample is shown in Figure (4).

[0031] The color coordinates were calculated using the measured emission spectrum. The color coordinates (0.326, 0.322) corresponding to the emission spectrum of the sample were found in the colorimetric diagram. These coordinates fall within the range of the white light we wanted to obtain and are very close to the standard white light (0.33, 0.33). The color coordinate diagram of the sample is shown in Figure (5).

[0032] Example 1 According to the chemical formula Ca1. 99 (Eu 3+ 0. 005 (Dy 3+ 0. 005 Y0. 01 Sn0. 99 Based on the stoichiometric ratio of O4, weigh out the raw materials CaCO3, SnO2, Eu2O3, Dy2O3, and Y2O3 respectively; The above raw materials are placed in an agate mortar and ground thoroughly to obtain a preliminary mixed powder; The pre-mixed powder was loaded into a corundum crucible, which was then placed in a muffle furnace and heated to 1000°C at a heating rate of 8°C / min for 6 hours. After the muffle furnace has cooled down naturally, take out the sample and grind it again in an agate mortar until it is evenly ground. The sample, which has been ground uniformly again, is put back into the corundum crucible and placed in a muffle furnace. The temperature is increased to 1400℃ at a heating rate of 8℃ / min and calcined for 10 hours. After calcination, the furnace body is allowed to cool down naturally. The sample is then removed and ground to obtain the final product.

[0033] Example 2 According to the chemical formula Sr1. 97 (Eu 3+ 0. 01 (Dy 3+ 0.02 Y0. 03 Sn0. 97 Based on the stoichiometric ratio of O4, weigh out the raw materials SrCO3, SnO2, Eu2O3, Dy2O3, and Y2O3 respectively; The above raw materials are placed in an agate mortar and ground thoroughly to obtain a preliminary mixed powder; The pre-mixed powder was loaded into a corundum crucible, which was then placed in a muffle furnace and heated to 1000°C at a heating rate of 7°C / min for 6 hours. After the muffle furnace has cooled down naturally, take out the sample and grind it again in an agate mortar until it is evenly ground. The sample, which has been ground uniformly again, is put back into the corundum crucible and placed in a muffle furnace. The temperature is increased to 1400℃ at a heating rate of 7℃ / min and calcined for 10 hours. After calcination, the furnace body is allowed to cool down naturally. The sample is then removed and ground to obtain the final product.

[0034] Example 3 According to the chemical formula Ba1. 95 (Eu 3+ 0. 015 (Dy 3+ 0. 035 Y0. 05 Sn0. 95 The stoichiometric ratio of O4 was determined by weighing out the raw materials BaCO3, SnO2, Eu2O3, Dy2O3, and Y2O3 respectively. The above raw materials are placed in an agate mortar and ground thoroughly to obtain a preliminary mixed powder; The pre-mixed powder was loaded into a corundum crucible, which was then placed in a muffle furnace and heated to 1000°C at a heating rate of 9°C / min for 6 hours. After the muffle furnace has cooled down naturally, take out the sample and grind it again in an agate mortar until it is evenly ground. The sample, which has been ground uniformly again, is put back into the corundum crucible and placed in a muffle furnace. The temperature is increased to 1400℃ at a heating rate of 9℃ / min and calcined for 10 hours. After calcination, the furnace body is allowed to cool down naturally. The sample is then removed and ground to obtain the final product.

[0035] Example 4 According to the chemical formula Ca1. 96 Sr0. 01 (Eu 3+ 0. 01 (Dy 3+ 0. 02 Y0. 03 Sn0. 97Based on the stoichiometric ratio of O4, weigh out the raw materials CaCO3, SrCO3, SnO2, Eu2O3, Dy2O3, and Y2O3 respectively; The above raw materials are placed in an agate mortar and ground thoroughly to obtain a preliminary mixed powder; The pre-mixed powder was loaded into a corundum crucible, which was then placed in a muffle furnace and heated to 1000°C at a heating rate of 6°C / min for 6 hours. After the muffle furnace has cooled down naturally, take out the sample and grind it again in an agate mortar until it is evenly ground. The sample, which has been ground uniformly again, is put back into the corundum crucible and placed in a muffle furnace. The temperature is increased to 1400℃ at a heating rate of 6℃ / min and calcined for 10 hours. After calcination, the furnace body is allowed to cool down naturally. The sample is then removed and ground to obtain the final product.

[0036] Example 5 According to the chemical formula Ca1. 90 Ba0. 02 (Eu 3+ 0. 02 (Dy 3+ 0. 03 Y0. 05 Sn0. 95 The stoichiometric ratio of O4 was determined by weighing out CaCO3, BaCO3, SnO2, Eu2O3, Dy2O3, and Y2O3 raw materials respectively. The above raw materials are placed in an agate mortar and ground thoroughly to obtain a preliminary mixed powder; The pre-mixed powder was loaded into a corundum crucible, which was then placed in a muffle furnace and heated to 1000°C at a heating rate of 10°C / min for 6 hours. After the muffle furnace has cooled down naturally, take out the sample and grind it again in an agate mortar until it is evenly ground. The sample, which has been ground uniformly again, is put back into the corundum crucible and placed in a muffle furnace. The temperature is increased to 1400℃ at a heating rate of 10℃ / min and calcined for 10 hours. After calcination, the furnace body is allowed to cool down naturally. The sample is then removed and ground to obtain the final product.

[0037] To verify the beneficial effects of the present invention, five sets of comparative samples were set up, corresponding to Examples 1-5 above, respectively. Comparative samples 1-5 did not contain added Y. 3+ Furthermore, a single excitation wavelength (Eu) is used. 3+(Specific excitation wavelength), and other preparation conditions are consistent with the corresponding examples. Performance tests were conducted on the products of Examples 1-5 and Comparative Samples 1-5. Test indicators included color rendering index (Ra), luminescence intensity (relative value), thermal stability (luminescence intensity retention rate after 100 hours of heat treatment at 200℃), and color coordinates (x, y). The test results are shown in Table 1 below: ; Table 1 As can be seen from the data in Table 1 above: Regarding the color development index (CRI), the CRIs of Examples 1-5 were all above 88.7, with the highest reaching 91.3, while the CRIs of Comparative Samples 1-5 were all below 74.2, significantly lower than the products of the Examples. This indicates that the present invention utilizes Y... 3+ Charge compensation effect and Eu 3+ Dy 3+ The synergistic doping and exclusive excitation wavelength selection effectively improve the color development performance of phosphors, solving the problem of poor color development in traditional phosphors.

[0038] Regarding luminous intensity, the relative values ​​of the luminous intensity of the products in the examples were all above 97.8, while the relative values ​​of the luminous intensity of the control samples were all below 77.2, showing a significant difference. (Note: Y) 3+ The addition of rare earth ions prevents them from occupying Sn. 4+ The interference of lattice sites on luminescence performance, and the selection of the wavelength at the intersection of the two excitation spectra, achieve Eu 3+ and Dy 3+ The synchronous and efficient excitation significantly improves the luminescence intensity.

[0039] Regarding thermal stability, after being kept at 200°C for 100 hours, the luminescence intensity retention rate of the products in the examples was all above 94.8%, while the retention rate of the control samples was all below 84.0%. This is due to Y... 3+ The repair effect on lattice defects and the stable structure of the stannate matrix itself give the product of this invention superior thermal stability, meeting the requirements for long-term use.

[0040] Regarding color coordinates, the color coordinates of the products in the examples are all close to standard white light (0.33, 0.33), while the color coordinates of the comparison samples deviate significantly from the standard white light range. This demonstrates that the present invention achieves this by adjusting Eu... 3+ With Dy 3+ The doping ratio can precisely match the emission intensity of red and blue-yellow light to achieve high-quality white light emission.

Claims

1. A rare-earth-doped layered stannate-based white phosphor material, characterized in that, The chemical formula is A 2- x(Eu 3+ / Dy 3+ )xYxSn 1- xO4, where 0 < x ≤ 0.05, A is one or more divalent alkaline earth metal ions selected from Ca, Sr, and Ba, and Eu 3+ and Dy 3+ Doping was carried out in different proportions.

2. The rare earth-doped layered stannate-based white phosphor material according to claim 1, characterized in that, The Eu 3 + Provides red light emitting components, Dy 3+ Provides blue and yellow light emission components, by modulating Eu 3+ and Dy 3+ The doping ratio can be adjusted to control the emission intensity of red and blue-yellow light.

3. The rare-earth-doped layered stannate-based white phosphor material according to claim 1, characterized in that, The Y 3+ The ionic radius of Sn 4+ The ionic radii are similar, Y 3+ Replace Sn 4+ The lattice position.

4. The rare earth-doped layered stannate-based white phosphor material according to claim 1, characterized in that, The Y 3+ It is used to compensate for the valence imbalance caused by trivalent rare earth ions replacing divalent alkaline earth metal ions at the A site, and to ensure the conservation of molecular formula and valence in the material.

5. The rare-earth-doped layered stannate-based white phosphor material according to claim 1, characterized in that, Excitation wavelength is Eu 3+ The corresponding excitation spectrum and Dy 3+ The wavelength at the intersection of the corresponding excitation spectra can simultaneously excite high-intensity Eu. 3+ Feature emission and Dy 3+ Feature emission.

6. The rare-earth-doped layered stannate-based white phosphor material according to claim 1, characterized in that, The material has a layered perovskite phase structure.

7. A method for preparing a rare-earth-doped layered stannate-based white phosphor material, characterized in that, Includes the following steps: According to the chemical formula A 2- x(Eu 3+ / Dy 3+ )xYxSn 1- The raw materials for xO4 are weighed according to their stoichiometric ratio. The raw materials include compounds containing A, compounds containing Sn, Eu2O3, Dy2O3, and Y2O3, where 0 < x ≤ 0.05, and A is one or more divalent alkaline earth metal ions selected from Ca, Sr, and Ba. The weighed raw materials are placed in an agate mortar and ground until evenly mixed to obtain a preliminary mixed powder; The pre-mixed powder was loaded into a corundum crucible, and the crucible was placed in a muffle furnace and pre-fired at 1000°C for 6 hours. Take out the pre-fired sample and grind it again in an agate mortar until it is evenly ground. The sample, which was ground evenly again, was put back into the corundum crucible, and the crucible was placed in a muffle furnace and calcined at 1400℃ for 10 hours. The calcined sample is taken out and ground in an agate mortar to obtain the final product.

8. The method for preparing rare earth-doped layered stannate-based white phosphor material according to claim 7, characterized in that, The compound containing A is a carbonate, and the compound containing Sn is SnO2.

9. The method for preparing rare earth-doped layered stannate-based white phosphor material according to claim 7, characterized in that, The grinding process continues until the powder is evenly mixed and there is no obvious particle feel.

10. The method for preparing rare earth-doped layered stannate-based white phosphor material according to claim 7, characterized in that, The heating rate of the muffle furnace is 5℃ / min to 10℃ / min, and the cooling process is natural cooling along with the furnace.

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