A double perovskite-based phosphor material and its preparation method and application

Abstract

The present invention is applicable to the field of inorganic luminescent material technology and provides a phosphor material based on a double perovskite structure and its preparation method and application. The chemical formula of the phosphor is Ca2AlNbO6:xEu 3+ , where x is a molar fraction of 0.06 to 0.30; the excitation spectrum of the phosphor under the monitoring of 615nm emission wavelength covers a range of 260-500nm, and the main emission peak is located at 615nm; when x=0.18, the quantum efficiency under 396nm ultraviolet light excitation is ≥91%, and the red light emission accounts for ≥85%. The present invention uses Ca2AlNbO6 double perovskite as the matrix and uses Eu 3+ Through high-concentration doping and local symmetry control design engineering, a red phosphor material with both broad-spectrum excitation and high quantum efficiency was designed, achieving high quantum efficiency, efficient red light emission, broad-spectrum excitation and excellent resistance to concentration quenching.

Description

Technical Field

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

[0002] White light-emitting diodes (LEDs), one of the most revolutionary lighting technologies of the 21st century, rely heavily on the light conversion efficiency and spectral control capabilities of their phosphor materials for their core performance. In white LEDs, which strive for high color rendering index (Ra>90) and low color temperature (CCT<4500K), red phosphor plays a crucial role. It not only fills the gap in the red light spectrum between the blue chip and yellow phosphor combination but also precisely controls color coordinates by adjusting the ratio of red, green, and blue light, thereby meeting diverse lighting needs from cool white to warm white. However, current commercial red phosphors still face bottlenecks in material design, luminous efficiency, and environmental stability, severely hindering the development of high-end lighting and display technologies.

[0003] Double perovskite structure (A 2 BB'O6) has been regarded as a potential candidate material for solving the above problems in recent years due to its tunable crystal field environment and excellent chemical stability. 2 In the BB'O6 structure, the larger cation A is coordinated with 12 oxygen ions, while the smaller cation B is coordinated with a total of 6 oxygen ions. The lattice symmetry and electronic structure can also be flexibly adjusted by ion doping at the A / B position. To this end, the present invention proposes a rare earth doped phosphor material based on a double perovskite structure (chemical formula: Ca 2-x AlNbO6:xEu 3+ , 0.06 ≤ x ≤ 0.30) and its preparation method and application. 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 and application thereof, aiming to solve the problems raised in the above background technology, such as low absorption efficiency of existing red phosphor materials in the ultraviolet excitation band, easy concentration quenching caused by high concentration doping, and insufficient proportion of red light emission.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A rare earth Eu based on double perovskite structure 3+ Doped phosphor material, the chemical formula of the phosphor is Ca2AlNbO6:xEu 3+ , where x is a mole fraction ranging from 0.06 to 0.30, Ca 2+ As an A-site ion, its larger ionic radius (1.12 Å) is similar to that of Eu3+ (1.07Å) is a good match, making Eu 3+ Able to stably occupy Ca 2+ The 8-coordinate lattice site of the phosphor covers an excitation spectrum range of 260-500nm under the monitoring of the emission wavelength of 615nm, and the main emission peak is at 615nm; when x=0.18, the quantum efficiency under 396nm ultraviolet light excitation is ≥91%, and the red light emission accounts for ≥85%. At this time, the luminous intensity reaches the peak, breaking through the traditional Eu 3+ Concentration limit of the doping system (usually x ≤ 0.10).

[0007] Furthermore, the crystal structure of the phosphor is a monoclinic double perovskite type (space group P21 / n); Eu 3+ Replace Ca 2 + Afterwards, its local coordination environment changes from the original high symmetry to low symmetry.

[0008] A method for preparing the phosphor material according to the above-mentioned method comprises the following steps:

[0009] (1) Weigh CaCO3, Al2O3, Nb2O5 and Eu2O3 with a purity of ≥99.9% according to the stoichiometric ratio, add Li2CO3 as a flux, and finally synthesize Ca2AlNbO6:xEu 3+ 5g phosphor; Li2CO3 is used to compensate for Eu 3+ Replace Ca 2+ The charge imbalance and promote crystallization;

[0010] (2) The raw materials were mixed with zirconia balls at a ball-to-material mass ratio of 10:1, and 15% anhydrous ethanol was added for wet ball milling at a ball milling speed of 300 rpm for 8 h.

[0011] (3) The milled slurry is dried and sieved, and then heated to 1250-1350°C at 5°C / min in an air atmosphere and sintered for 8 hours; the air atmosphere ensures that Eu 3+ The stable valence state of Nb2O5 is achieved by precise temperature control, and the excessive volatilization of Nb2O5 is avoided;

[0012] (4) Grind the solid obtained after cooling in the furnace. The white powder obtained after grinding is Ca2AlNbO6:xEu 3 + Phosphor.

[0013] Furthermore, the mass fraction of Li2CO3 is 4 wt %, which can eliminate the impurity phase and form a pure phase double perovskite structure.

[0014] A white light LED device comprises the phosphor material mentioned above and an InGaN-based semiconductor chip with an excitation wavelength of 300-460 nm.

[0015] Furthermore, the phosphor material is mixed with β-sialon green powder with an emission peak of 530nm and BaMgAl with an emission peak of 450nm. 10 O 17 :Eu 2+ The blue phosphor is combined in a mass ratio of (0.1-0.3):(0.4-0.6):(0.2-0.4), and by adjusting the ratio, white light with a color temperature of 2500-6500K can be output. By adjusting the mass ratio of phosphor, blue powder, and green powder, high-performance white light LED devices can be constructed after silicone encapsulation.

[0016] Furthermore, 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.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention designs Ca2AlNbO6 double perovskite as the matrix and Eu 3+ The high concentration doping strategy realizes the wide spectrum excitation characteristics of the phosphor in the 260-500nm ultraviolet-blue light band, which is perfectly adapted to a variety of LED chips (such as 365nm, 395nm and 465nm). At the same time, it is achieved through the local symmetry control design. 5 D0→ 7 The F2 electric dipole transition accounts for more than 85%, and the main emission peak is located at 615nm, which significantly improves the red light intensity; further, it effectively suppresses the Eu 3+ Energy migration between ions enables the material to achieve optimal luminescence performance at a high doping concentration of x=0.18, and can still maintain optical emission at a high concentration of x=0.30, breaking through the traditional Eu 3+ The system's concentration quenching bottleneck. Combined with an air atmosphere solid-phase preparation process (sintering at 1300°C, using a 4wt% Li2CO3 flux), this not only reduces production costs but also avoids the environmental pollution issues associated with sulfide or lead-containing raw materials. Combining these advantages, this phosphor, when co-packaged with UV / blue light chips and commercial blue-green powders, can be used to construct high-performance white light LEDs, achieving an efficient, stable, and low-cost lighting solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Ca2AlNbO6:xEu 3+ XRD pattern of phosphor and comparison with standard card.

[0020] Figure 2 Ca2AlNbO6:xEu 3+ Excitation spectrum (λem=615nm).

[0021] Figure 3 Ca2AlNbO6:xEu 3+ Emission spectrum (λex=396nm).

[0022] Figure 4 Ca2AlNbO6:0.18Eu 3+ The quantum efficiency test results.

[0023] Figure 5 Ca2AlNbO6:xEu 3+ XRD patterns of phosphors with 1-5wt% Li2CO3 added as flux. DETAILED DESCRIPTION

[0024] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be understood as limiting the scope of implementation of the present invention.

[0025] The specific implementation of the present invention is described in detail below with reference to specific embodiments.

[0026] Example 1: This example provides a rare earth Eu based on a double perovskite structure 3+ Doped phosphor material (Ca2AlNbO6:0.06Eu 3+ ), which specifically comprises the following steps:

[0027] (1) Raw materials (including CaCO3, Al2O3, Nb2O5 and Eu2O3) were weighed according to the stoichiometric ratio, and 4wt% Li2CO3 was added as flux (the final synthesis was Ca2AlNbO6:0.06Eu 3+ Phosphor 5g);

[0028] (2) The raw materials were mixed with zirconia balls at a ball-to-material mass ratio of 10:1, and 15% anhydrous ethanol was added for wet ball milling at a ball milling speed of 300 rpm for 8 h.

[0029] (3) The milled slurry was dried and sieved, and then heated to 1300°C at a rate of 5°C / min in air and sintered for 8 h;

[0030] (4) Grind the solid obtained after cooling in the furnace. The white powder obtained after grinding is Ca2AlNbO6:0.06Eu 3+ Phosphor.

[0031] Example 2: This example provides a rare earth Eu based on a double perovskite structure 3+ Doped phosphor material (Ca2AlNbO6:0.12Eu 3+ ) preparation method, the difference from Example 1 is that the weighing of Eu2O3 in this example is twice that of Example 1, and the rest is the same as Example 1, and finally Ca2AlNbO6:0.12Eu 3+ Phosphor.

[0032] Example 3: This example provides a rare earth Eu based on a double perovskite structure 3+ Doped phosphor material (Ca2AlNbO6:0.18Eu 3+ ) preparation method, the difference from Example 1 is that the weighing of Eu2O3 in this example is 3 times that of Example 1, and the rest is the same as Example 1, and finally Ca2AlNbO6:0.18Eu 3+ Phosphor.

[0033] Example 4: This example provides a rare earth Eu based on a double perovskite structure 3+ Doped phosphor material (Ca2AlNbO6:0.24Eu 3+ ) preparation method, the difference from Example 1 is that the weighing of Eu2O3 in this example is 4 times that of Example 1, and the rest is the same as Example 1, and finally Ca2AlNbO6:0.24Eu 3+ Phosphor.

[0034] Example 5: This example provides a rare earth Eu based on a double perovskite structure 3+ Doped phosphor material (Ca2AlNbO6:0.30Eu 3+ ) preparation method, the difference from Example 1 is that the weighing of Eu2O3 in this example is 5 times that of Example 1, and the rest is the same as Example 1, and finally Ca2AlNbO6:0.30Eu 3+ Phosphor.

[0035] Figure 1 The present invention shows Ca2AlNbO6:xEu 3+ (Abbreviated as CANO:xEu in the figure 3+ ) XRD patterns of the phosphors are compared with those of the standard card PDF#53-1283 (Ca2AlNbO6). 3+ Ca2AlNbO6:xEu with doping amount (x ranges from 0.06 to 0.30) 3+ The XRD pattern of the sample is completely consistent with the standard card, and all diffraction peaks are free of impurity phases, which indicates that Ca2AlNbO6:xEu 3+The sample is pure phase. Ca2AlNbO6:xEu 3+ The sample has a double perovskite structure with a space group of P21 / n. Moreover, as the x value gradually increases, the main diffraction peak shifts slightly toward the high angle direction, which means that the unit cell volume shrinks. This is because Eu 3+ (1.07 Å) substituted Ca 2+ (1.12Å), the lattice distortion is caused by the difference in ionic radius.

[0036] Compared with traditional double perovskite phosphors, the Eu 3+ When the doping concentration reaches x=0.30, the sample still maintains a single-phase structure without the formation of impurities, which confirms the rigid framework of double perovskite for Eu 3+ High concentration doping has good compatibility.

[0037] Figure 2 The present invention shows Ca2AlNbO6:xEu 3+ (Abbreviated as CANO:xEu in the figure 3+ ) excitation spectrum (λem=615nm). As can be seen from the figure, under the condition of monitoring the emission wavelength of 615nm, the excitation spectrum of the material covers the range of 260-500nm. Among them, the charge transfer band (CTB) is located at 300-350nm (broad peak), which is caused by O 2- →Eu 3+ The charge transfer contribution of Eu is strong, and its strong absorption ability enables the material to efficiently capture ultraviolet light energy. 3+ The ff transition peak is 362nm ( 7 F0→ 5 D4), 396nm ( 7 F0→ 5 L6) and 465nm ( 7 F0→ 5 D2), covering the near-ultraviolet to blue light region. These spectral characteristics indicate that the material is suitable for excitation of chips from ultraviolet to blue light.

[0038] Figure 3 The present invention shows Ca2AlNbO6:xEu 3+ (Abbreviated as CANO:xEu in the figure 3+ ) emission spectrum (λex=396nm). As can be seen from the figure, under the excitation of 396nm, the emission spectra of samples with different x values ​​are all centered at 615nm (corresponding to 5 D0→ 7 The main peak is the F2 electric dipole transition, with red light accounting for ≥85%. The emission intensity shows a trend as the x value increases from 0.06 to 0.30, reaching a peak at x = 0.18, indicating that the material can achieve high-concentration doping characteristics.

[0039] Figure 4 The present invention Ca2AlNbO6:0.18Eu 3+ The quantum efficiency test results. As can be seen from the figure, when x=0.18, the quantum efficiency reaches 91.38%, which is higher than that of commercial Y2O3:Eu 3+ (quantum efficiency is 85%) increased by 6.38%, and the red light ratio (615nm / 593nm intensity ratio) reached 8.5:1, which is significantly better than commercial Y2O3:Eu 3+ The 3.2:1 ratio of the phosphor shows the advantages of the material in luminescence performance.

[0040] Example 6: This example provides a rare earth Eu based on a double perovskite structure 3+ The preparation method of the doped phosphor material specifically comprises the following steps:

[0041] (1) According to Ca2AlNbO6:0.18Eu 3+ CaCO3, Al2O3, Nb2O5 and Eu2O3 were weighed in stoichiometric ratio, and 1wt% Li2CO3 was added as flux (the final synthesis was Ca2AlNbO6:018Eu 3+ Phosphor 5g);

[0042] (2) The raw materials were mixed with zirconia balls at a ball-to-material mass ratio of 10:1, and 15% anhydrous ethanol was added for wet ball milling at a ball milling speed of 300 rpm for 8 h.

[0043] (3) The milled slurry was dried and sieved, and then heated to 1300°C at a rate of 5°C / min in air and sintered for 8 h;

[0044] (4) Grind the solid obtained after cooling in the furnace. The white powder obtained after grinding is Ca2AlNbO6:0.18Eu 3+ Phosphor.

[0045] Example 7: This example provides a rare earth Eu based on a double perovskite structure 3+ The method for preparing the doped phosphor material is different from that in Example 1 in that 2 wt % Li 2 CO 3 is added as a flux, and the rest is the same as in Example 1.

[0046] Example 8: This example provides a rare earth Eu based on a double perovskite structure 3+ The method for preparing the doped phosphor material is different from that in Example 1 in that 3 wt % Li 2 CO 3 is added as a flux, and the rest is the same as in Example 1.

[0047] Example 9: This example provides a rare earth Eu based on a double perovskite structure3+ The method for preparing the doped phosphor material is different from that in Example 1 in that 4 wt % Li 2 CO 3 is added as a flux, and the rest is the same as in Example 1.

[0048] Example 10: This example provides a rare earth Eu based on a double perovskite structure 3+ The method for preparing the doped phosphor material is different from that in Example 1 in that 5 wt % Li 2 CO 3 is added as a flux, and the rest is the same as in Example 1.

[0049] Figure 5 The present invention shows Ca2AlNbO6:xEu 3+ XRD patterns of phosphors with 1-5wt% Li2CO3 added as flux. As can be seen from the figure, Ca2AlNbO6:xEu with different Li2CO3 addition amounts (1-5wt%) 3+ The sample's XRD pattern shows major diffraction peaks that generally match those of standard card PDF#53-1283 (Ca2AlNbO6). When 1 wt% Li2CO3 flux is added, three minor peaks appear in the spectrum. These peaks gradually disappear as the Li2CO3 concentration increases, reaching a pure phase at 4 wt%. However, when the Li2CO3 flux concentration is increased to 5 wt%, the impurities reappear, indicating that a 4 wt% flux concentration provides optimal results.

[0050] The above are only preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, several variations and improvements can be made without departing from the concept of the present invention. These should also be regarded as the scope of protection of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A rare earth Eu based on double perovskite structure 3+ Doped phosphor material, characterized in that The chemical formula of the phosphor is Ca2AlNbO6:0.18Eu 3+ The quantum efficiency under 396nm ultraviolet light excitation is ≥91%, and the red light emission accounts for ≥85%.

2. The phosphor material according to claim 1, characterized in that: The crystal structure of the phosphor is monoclinic double perovskite type, Eu 3+ Occupancy of Ca 2+ Location.

3. A method for preparing the phosphor material according to claim 1 or 2, characterized in that: The following steps are involved: (1) Weigh CaCO3, Al2O3, Nb2O5 and Eu2O3 in stoichiometric ratio, add Li2CO3 as flux, and finally synthesize Ca2AlNbO6:xEu 3+ 5g of phosphor; the mass fraction of Li2CO3 is 4wt%; (2) The raw materials were mixed with zirconia balls at a ball-to-material mass ratio of 10:1, and 15% anhydrous ethanol was added for wet ball milling at a ball milling speed of 300 rpm for 8 h. (3) The milled slurry was dried and sieved, and then heated to 1250-1350°C at 5°C / min in air atmosphere and sintered for 8 h; (4) Grind the solid obtained after cooling in the furnace. The white powder obtained after grinding is Ca2AlNbO6:0.18Eu 3+ Phosphor.

4. A white light LED device, characterized in that: The invention comprises the phosphor material according to claim 1 or 2 and an InGaN-based semiconductor chip with an excitation wavelength of 300-460 nm.

5. The white light LED device according to claim 4, characterized in that: The phosphor material is combined with β-sialon green powder with an emission peak of 530nm and BaMgAl with an emission peak of 450nm. 10 O 17 :Eu 2+ The blue powder is combined in a mass ratio of (0.1-0.3):(0.4-0.6):(0.2-0.4), and the white light with a color temperature of 2500-6500K is output by adjusting the ratio.

6. The white light LED device according to claim 4, characterized in that: 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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