Fluorescent powder material based on double perovskite structure and preparation method and application thereof

Abstract

The invention is suitable for the technical field of inorganic luminescent materials, and provides a fluorescent powder material based on a double-perovskite structure and a preparation method and application thereof. The general chemical formula of the fluorescent powder is Ca2AlNbO6: xEu < 3 + >, wherein x is a molar fraction of 0.06 to 0.30; the excitation spectrum coverage range of the fluorescent powder under the condition of monitoring the emission wavelength of 615 nm is 260-500 nm, and the emission main peak is located at 615 nm; when x is equal to 0.18, the quantum efficiency under the excitation of 396nm ultraviolet light is greater than or equal to 91%, and the red light emission ratio is greater than or equal to 85%. According to the invention, Ca2AlNbO6 double perovskite is taken as a substrate, and a red fluorescent powder material with wide-spectrum excitation and high quantum efficiency is designed through Eu < 3 + > high-concentration doping and local symmetry regulation and control design engineering, so that the characteristics of high quantum efficiency, efficient red light emission, wide-spectrum excitation and excellent concentration quenching resistance are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic luminescent materials, and particularly relates to a phosphor material based on a double perovskite structure, a preparation method thereof, and an application thereof. Background Art

[0002] As one of the most revolutionary lighting technologies in the 21st century, the core performance of white light-emitting diodes (LEDs) highly depends on the light conversion efficiency and spectral regulation ability of phosphor materials. In white LED devices pursuing a high color rendering index (Ra>90) and a low color temperature (CCT<4500K), red phosphors play a decisive role. It can not only fill the gap in the red light spectrum in the combination of blue chips and yellow phosphors, but also precisely control the color coordinates by adjusting the ratio of red, green, and blue lights, so as to meet the diverse lighting requirements from cold white light to warm white light. However, current commercial red phosphors still have bottlenecks in material design, luminescence efficiency, and environmental stability, seriously restricting the development of high-end lighting and display technologies.

[0003] The double perovskite structure (A 2 BB’O6) has been regarded as a potential candidate material to solve the above problems in recent years due to its adjustable crystal field environment and excellent chemical stability. In the A 2 BB’O6 structure, the larger-sized cation A coordinates with 12 oxygen ions, while the smaller-sized cation B coordinates with a total of 6 oxygen ions, and the lattice symmetry and electronic structure can be flexibly adjusted by ion doping at the A / B sites. Therefore, the present invention proposes a rare-earth doped phosphor material based on a double perovskite structure (chemical general formula: Ca 2-x AlNbO6:xEu 3+ , 0.06 ≤ x ≤ 0.30), a preparation method thereof, and an application thereof. Summary of the Invention

[0004] The purpose of the present invention is to provide a phosphor material based on a double perovskite structure, a preparation method thereof, and an application thereof, aiming to solve the problems of low absorption efficiency in the ultraviolet excitation band, easy occurrence of concentration quenching in high-concentration doping, and insufficient proportion of red light emission in the existing red phosphor materials as mentioned in the above background art.

[0005] The purpose of the present invention is achieved through the following technical solutions: A rare-earth Eu 3+ -doped phosphor material based on a double perovskite structure, the chemical general formula of the phosphor being Ca2AlNbO6:xEu 3+ , where x is a molar fraction from 0.06 to 0.30, and Ca 2+ acts as the A-site ion, and its relatively large ionic radius (1.12 Å) and Eu 3+The high matching degree (1.07 Å) enables Eu 3+ to stably occupy the 8 - coordinate lattice sites of Ca 2+ ; the excitation spectrum coverage range of the phosphor at the monitored emission wavelength of 615 nm is 260 - 500 nm, and the emission peak is located at 615 nm; when x = 0.18, the quantum efficiency under 396 nm ultraviolet light excitation is ≥91%, and the proportion of red light emission is ≥85%. At this time, the luminous intensity reaches the peak, breaking through the concentration limit of the traditional Eu 3+ doping system (usually x ≤ 0.10).

[0006] Furthermore, the crystal structure of the phosphor is monoclinic double perovskite type (space group P21 / n); after Eu 3+ replaces Ca 2 + , its local coordination environment changes from the original high symmetry to low symmetry.

[0007] A preparation method of the phosphor material according to the above - mentioned, comprising the following steps: (1) Weigh CaCO3, Al2O3, Nb2O5 and Eu2O3 with a purity of ≥99.9% according to the stoichiometric ratio, and add Li2CO3 as a flux to finally synthesize 5 g of Ca2AlNbO6:xEu 3+ phosphor; where Li2CO3 is used to compensate for the charge imbalance caused by Eu 3+ replacing Ca 2+ and promote crystallization; (2) Mix the raw materials with zirconia balls at a ball - to - material mass ratio of 10:1, add 15% anhydrous ethanol for wet ball milling, with a ball - milling speed of 300 r / min and a time of 8 h; (3) Dry and screen the ball - milled slurry, and sinter it at 1250 - 1350 °C for 8 h with a heating rate of 5 °C / min in an air atmosphere; the air atmosphere ensures the stable valence state of Eu 3+ , and precise temperature control avoids excessive volatilization of Nb2O5; (4) Grind the solid obtained after furnace cooling, and the obtained white powder is Ca2AlNbO6:xEu 3 + phosphor.

[0008] Furthermore, the mass fraction of Li2CO3 is 4 wt%, and this ratio can eliminate the impurity phase and form a pure - phase double perovskite structure.

[0009] A white - light LED device comprises the above - mentioned phosphor material and an InGaN - based semiconductor chip with an excitation wavelength of 300 - 460 nm.

[0010] Further, the phosphor material, β-sialon green phosphor with an emission peak at 530 nm, and BaMgAl 10 O 17 :Eu 2+ blue phosphor are combined in a mass ratio of (0.1 - 0.3):(0.4 - 0.6):(0.2 - 0.4), and white light with a color temperature of 2500 - 6500 K is output by adjusting the ratio. By controlling the mass ratio of the phosphor to the blue and green phosphors, a high-performance white LED device can be constructed after encapsulation with silica gel.

[0011] Further, the InGaN-based semiconductor chip is selected from at least one of an ultraviolet chip and a blue light chip. The excitation wavelength of the ultraviolet chip is 300 - 400 nm, and the excitation wavelength of the blue light chip is 450 - 460 nm.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: By designing Ca2AlNbO6 double perovskite as the matrix and Eu 3+ high-concentration doping strategy, the phosphor achieves broadband excitation characteristics in the 260 - 500 nm ultraviolet-blue light band, perfectly adapting to a variety of LED chips (such as 365 nm, 395 nm, and 465 nm). At the same time, through the design of local symmetry regulation, the proportion of 5 D0→ 7 F2 electric dipole transition accounts for more than 85%, and the emission main peak is located at 615 nm, significantly improving the red light intensity. Further, the energy migration between Eu 3+ ions is effectively suppressed, enabling the material to achieve the best luminescence performance at a high doping concentration of x = 0.18, and still maintaining optical emission at a high concentration of x = 0.30, breaking through the concentration quenching bottleneck of the traditional Eu 3+ system. Combining the air atmosphere solid-phase preparation process (sintering at 1300 °C, 4 wt% Li2CO3 flux) not only reduces the production cost but also avoids the environmental pollution problems of sulfide or lead-containing raw materials. Combining the above advantages, after the phosphor is co-encapsulated with ultraviolet / blue light chips and commercial blue-green phosphors, a high-performance white LED can be constructed to achieve an efficient, stable, and low-cost lighting solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 XRD pattern of the Ca2AlNbO6:xEu 3+ phosphor and the comparison with the standard card.

[0014] Figure 2 Excitation spectrum of Ca2AlNbO6:xEu 3+ (λem = 615 nm).

[0015] Figure 3 is Ca2AlNbO6:xEu 3+ emission spectrum (λex = 396 nm).

[0016] Figure 4 is the quantum efficiency test result of Ca2AlNbO6:0.18Eu 3+

[0017] Figure 5 is the XRD pattern of the phosphor Ca2AlNbO6:xEu 3+ added with 1 - 5 wt% Li2CO3 as a flux. Detailed implementation mode

[0018] For a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the technical solution of the present invention will be described in detail below, but it should not be construed as a limitation on the implementable scope of the present invention.

[0019] The following describes the specific implementation of the present invention in detail with reference to specific embodiments.

[0020] Example 1: This example provides a preparation method of a rare earth Eu 3+ doped phosphor material (Ca2AlNbO6:0.06Eu 3+ ), which specifically includes the following steps: (1) Weigh the raw materials (including CaCO3, Al2O3, Nb2O5, and Eu2O3) according to the stoichiometric ratio, and add 4 wt% Li2CO3 as a flux (finally synthesize 5 g of Ca2AlNbO6:0.06Eu 3+ phosphor); (2) Mix the raw materials with zirconia balls at a ball - to - material mass ratio of 10:1, add 15% anhydrous ethanol for wet ball milling, with a ball milling speed of 300 revolutions per minute and a time of 8 h; (3) Dry and screen the ball - milled slurry, and sinter it in an air atmosphere at a heating rate of 5 °C / min to 1300 °C for 8 h; (4) Grind the solid obtained after furnace cooling, and the obtained white powder is Ca2AlNbO6:0.06Eu 3+ phosphor.

[0021] Example 2: This example provides a preparation method of a rare earth Eu 3+ doped phosphor material (Ca2AlNbO6:0.12Eu 3+ ). Different from Example 1, in this example, the weighing of Eu2O3 is twice that of Example 1, and the rest is the same as Example 1. Finally, Ca2AlNbO6:0.12Eu​3+ Phosphor

[0022] Example 3: This example provides a rare earth Eu-doped phosphor material (Ca2AlNbO6:0.18Eu 3+ ), and the preparation method is different from that of Example 1 in that the weighing of Eu2O3 in this example is 3 times that of Example 1, and the rest is the same as that of Example 1. Finally, Ca2AlNbO6:0.18Eu 3+ phosphor is obtained. 3+ Phosphor

[0023] Example 4: This example provides a rare earth Eu-doped phosphor material (Ca2AlNbO6:0.24Eu 3+ ), and the preparation method is different from that of Example 1 in that the weighing of Eu2O3 in this example is 4 times that of Example 1, and the rest is the same as that of Example 1. Finally, Ca2AlNbO6:0.24Eu 3+ phosphor is obtained. 3+ Phosphor

[0024] Example 5: This example provides a rare earth Eu-doped phosphor material (Ca2AlNbO6:0.30Eu 3+ ), and the preparation method is different from that of Example 1 in that the weighing of Eu2O3 in this example is 5 times that of Example 1, and the rest is the same as that of Example 1. Finally, Ca2AlNbO6:0.30Eu 3+ phosphor is obtained. 3+ Phosphor

[0025] Figure 1 shows the XRD pattern of the Ca2AlNbO6:xEu 3+ phosphor of the present invention (abbreviated as CANO:xEu in the figure 3+ ), and is compared with the standard card PDF#53-1283 (Ca2AlNbO6). It can be seen from the figure that for Ca2AlNbO6:xEu 3+ samples with different Eu doping amounts (x ranges from 0.06 to 0.30), their XRD patterns are completely matched with the standard card, and no impurity phase appears in all diffraction peaks, indicating that the Ca2AlNbO6:xEu 3+ samples are pure phases. The Ca2AlNbO6:xEu 3+ samples have a double perovskite structure with a space group of P21 / n. Moreover, as the x value gradually increases, the main diffraction peak shifts slightly towards the high angle direction, which means that the unit cell volume shrinks. This is because Eu 3+ (1.07 Å) replaces Ca 3+ (1.07 Å) replacing Ca 2+After (1.12 Å), lattice distortion was induced due to the difference in ionic radii.

[0026] Compared with traditional double perovskite phosphors, Eu in the present invention 3+ When the doping concentration reaches x = 0.30, the sample still maintains a single-phase structure without the formation of impurity phases, confirming the good compatibility of the double perovskite rigid framework with high-concentration Eu doping. 3+ has good compatibility with high-concentration doping.

[0027] Figure 2 shows the excitation spectrum (λem = 615 nm) of Ca2AlNbO6:xEu of the present invention 3+ (abbreviated as CANO:xEu in the figure 3+ ). As can be seen from the figure, under the condition of monitoring the emission wavelength of 615 nm, the excitation spectrum of the material covers the range of 260 - 500 nm. Among them, the charge transfer band (CTB) is located at 300 - 350 nm (broad peak), which is contributed by the charge transfer of O 2- →Eu 3+ . Its strong absorption ability enables the material to efficiently capture ultraviolet light energy. In addition, the f-f transition peaks of Eu 3+ are at 362 nm ( 7 F0→ 5 D4), 396 nm ( 7 F0→ 5 L6), and 465 nm ( 7 F0→ 5 D2), covering the near-ultraviolet to blue light region. These spectral characteristics indicate that the material can be adapted to the excitation from ultraviolet to blue light chips.

[0028] Figure 3 shows the emission spectrum (λex = 396 nm) of Ca2AlNbO6:xEu of the present invention 3+ (abbreviated as CANO:xEu in the figure 3+ ). As can be seen from the figure, under the excitation of 396 nm, the emission spectra of samples with different x values are all dominated by 615 nm (corresponding to 5 D0→ 7 F2 electric dipole transition), and the proportion of red light is ≥ 85%. As the x value gradually increases from 0.06 to 0.30, the emission intensity shows a changing trend and reaches a peak at x = 0.18, indicating that the material can achieve high-concentration doping characteristics.

[0029] Figure 4 shows the quantum efficiency test results of Ca2AlNbO6:0.18Eu of the present invention 3+ . As can be seen from the figure, when x = 0.18, the quantum efficiency reaches 91.38%, compared with commercial Y2O3:Eu 3+(The quantum efficiency is 85%) has increased by 6.38%, and the proportion of red light (the intensity ratio of 615nm / 593nm) reaches 8.5:1, which is significantly better than that of commercial Y2O3:Eu 3+ phosphor of 3.2:1, demonstrating the advantages of this material in luminescence performance.

[0030] Example 6: This example provides a preparation method of a rare earth Eu 3+ doped phosphor material based on a double perovskite structure, which specifically includes the following steps: (1) Weigh CaCO3, Al2O3, Nb2O5 and Eu2O3 according to the stoichiometric ratio of Ca2AlNbO6:0.18Eu 3+ and add 1wt% Li2CO3 as a flux (finally synthesize 5g of Ca2AlNbO6:018Eu 3+ phosphor); (2) Mix the raw materials with zirconia balls at a ball-to-material mass ratio of 10:1, add 15% anhydrous ethanol for wet ball milling, with a ball milling speed of 300 revolutions per minute and a time of 8 hours; (3) Dry and screen the ball-milled slurry, and sinter it at 1300°C for 8 hours with a heating rate of 5°C / min in an air atmosphere; (4) Grind the solid obtained after furnace cooling, and the obtained white powder is Ca2AlNbO6:0.18Eu 3+ phosphor.

[0031] Example 7: This example provides a preparation method of a rare earth Eu 3+ doped phosphor material based on a double perovskite structure. Different from Example 1, this example adds 2wt% Li2CO3 as a flux, and the rest is the same as Example 1.

[0032] Example 8: This example provides a preparation method of a rare earth Eu 3+ doped phosphor material based on a double perovskite structure. Different from Example 1, this example adds 3wt% Li2CO3 as a flux, and the rest is the same as Example 1.

[0033] Example 9: This example provides a preparation method of a rare earth Eu 3+ doped phosphor material based on a double perovskite structure. Different from Example 1, this example adds 4wt% Li2CO3 as a flux, and the rest is the same as Example 1.

[0034] Example 10: This example provides a preparation method of a rare earth Eu 3+Preparation method of doped phosphor material. Different from Example 1, 5 wt% Li2CO3 is added as a flux in this example, and the rest is the same as in Example 1.

[0035] Figure 5 Shows the XRD patterns of Ca2AlNbO6:xEu 3+ phosphor with 1-5 wt% Li2CO3 added as a flux. It can be seen from the figure that for Ca2AlNbO6:xEu 3+ samples with different Li2CO3 addition amounts (1-5 wt%), the main diffraction peaks of their XRD patterns are basically consistent with the standard card PDF#53-1283 (Ca2AlNbO6). When 1 wt% Li2CO3 flux is added, 3 small impurity peaks appear in the pattern. As the Li2CO3 addition concentration increases, the impurity peaks gradually disappear. When the addition amount reaches 4 wt%, the impurity peaks all disappear and the material presents a pure phase. When the Li2CO3 addition amount continues to increase to 5 wt%, the impurity phase appears again, indicating that the best effect is achieved when the flux addition amount is 4 wt%.

[0036] The above is only the preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, without departing from the concept of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent.

Claims

1. A rare earth Eu-doped phosphor material based on a double perovskite structure, characterized in that, 3+ The chemical general formula of the phosphor is Ca2AlNbO6:xEu 3+ , where x is a molar fraction of 0.06 to 0.30; the excitation spectrum coverage range of the phosphor at a monitored emission wavelength of 615 nm is 260 - 500 nm, and the emission main peak is located at 615 nm; when x = 0.18, the quantum efficiency under 396 nm ultraviolet light excitation is ≥91%, and the proportion of red light emission is ≥85%. ​ 2. The phosphor material according to claim 1, wherein The crystal structure of the phosphor is monoclinic double perovskite type, and Eu 3+ occupies the Ca 2+ site.

3. A method for preparing the phosphor material according to claim 1 or 2, characterized in that, It includes the following steps: (1)Weigh CaCO3, Al2O3, Nb2O5 and Eu2O3 according to the stoichiometric ratio, and add Li2CO3 as a flux to finally synthesize 5 g of Ca2AlNbO6:xEu phosphor; 3+ phosphor; (2) Mix the raw materials with zirconia balls at a ball-to-material mass ratio of 10:1, add 15% absolute ethanol for wet ball milling, with a ball milling speed of 300 revolutions / min and a time of 8 h; (3) Dry and screen the ball-milled slurry, and sinter it at 1250 - 1350 °C for 8 h in an air atmosphere with a heating rate of 5 °C / min; (4)The solid obtained after furnace cooling is milled, and the white powder obtained after milling is Ca2AlNbO6:xEu 3+ phosphor.

4. The preparation method according to claim 3, wherein The mass fraction of the Li2CO3 is 4 wt%.

5. A white light LED device, characterized in that, It includes the phosphor material described in claim 1 or 2 and an InGaN-based semiconductor chip with an excitation wavelength of 300 - 460 nm.

6. The white light LED device according to claim 5, characterized in that, The phosphor material, β-sialon green phosphor with an emission peak at 530 nm, and BaMgAl 10 O 17 :Eu 2+ blue phosphor are combined in a mass ratio of (0.1 - 0.3):(0.4 - 0.6):(0.2 - 0.4), and white light with a color temperature of 2500 - 6500 K is output by adjusting the ratio.

7. The white light LED device according to claim 5, wherein, The InGaN-based semiconductor chip is selected from at least one of an ultraviolet chip and a blue light chip. The excitation wavelength of the ultraviolet chip is 300 - 400 nm, and the excitation wavelength of the blue light chip is 450 - 460 nm.

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