A red europium-doped tungstate fluorescent material, preparation and application thereof

Abstract

This invention belongs to the field of luminescent materials technology, and discloses a europium-doped tungstate red fluorescent material, its preparation, and its application. The chemical formula of the fluorescent material is: Ca2La 18‑x W8O 53 :xEu 3+ 0.10≤x≤0.50. The preparation method includes the following steps: Raw materials are weighed according to their chemical formulas and stoichiometric ratios: calcium-containing compounds, lanthanum-containing compounds, tungsten-containing compounds, and europium-containing compounds; the weighed raw materials are thoroughly ground and then placed in a muffle furnace for high-temperature calcination in air to obtain the desired red fluorescent material. Under ultraviolet or blue light excitation, the phosphor emits bright red light. This fluorescent material has high chromatic purity, low correlated color temperature, and high emission intensity. The preparation process is a one-step synthesis method, which is simple, pollution-free, energy-saving, and environmentally friendly, enabling large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of luminescent materials technology, and specifically relates to a europium-doped tungstate red fluorescent material and its preparation and application. Background Technology

[0002] White light-emitting diodes (W-LEDs), as a new generation of solid-state lighting light sources, have attracted the interest of scholars both domestically and internationally due to their advantages such as high efficiency, energy saving, and environmental friendliness. Currently, the most common method for achieving white light is to combine a blue-light-emitting InGaN LED chip with a yellow fluorescent material (YAG:Ce) that can be effectively excited by blue light. 3+ This method combines various techniques. However, it lacks red light components, has a high correlated color temperature, and a low color rendering index. Fluorescent conversion W-LEDs, on the other hand, use direct current to excite a chip that emits near-ultraviolet light. Three phosphors (red, green, and blue) that can be excited by near-ultraviolet light are coated onto the chip. Under the chip's excitation, the proportions of the three phosphors are adjusted to achieve white light emission. In this method of achieving white light emission, the traditional matrix materials for red phosphors, a crucial component of W-LEDs, are sulfides, nitrides, sulfur oxides, and silicates, with few tungstate-based red phosphor materials. Therefore, there is a need to further enrich the types of red phosphors, especially those that can be excited by near-ultraviolet light.

[0003] It is worth noting that rare earth ions Eu 3+ It possesses abundant energy levels and can be effectively excited by near-ultraviolet light to produce red light. Furthermore, while previous reports have discussed tungstate systems extensively, they have primarily focused on [WO4]-containing compounds. 2- Tetrahedral fluorescent materials, while those containing multiple cations (e.g., Ca) 2+ ,La 2+ W 6+ There is relatively little research on this topic.

[0004] Currently, the most common red phosphors have unstable physicochemical properties, their preparation processes are not environmentally friendly, and their luminous efficiency is low under 300-500nm excitation light, failing to meet the requirements. Furthermore, the phosphors' low luminous stability and efficiency, poor color rendering of LEDs, and high color temperature are also problems and shortcomings that urgently need to be addressed. Summary of the Invention

[0005] To overcome the shortcomings and deficiencies of the prior art, the primary objective of this invention is to provide a novel red fluorescent material doped with europium tungstate. This phosphor exhibits high luminescence intensity and a high color rendering index.

[0006] Another objective of this invention is to provide a method for preparing the novel red fluorescent material of europium-doped tungstate. This method is a one-step synthesis method, with a simple synthesis process, no pollution at any stage, energy saving and environmental protection, and can be used for large-scale industrial production.

[0007] Another object of the present invention is to provide the application of the novel europium-doped tungstate red fluorescent material in white light-emitting diodes.

[0008] The objective of this invention is achieved through the following solution:

[0009] A novel europium-doped tungstate red fluorescent material has the following chemical formula: Ca2La 18-x W8O 53 :xEu 3+ , 0.10≤x≤0.50.

[0010] A method for preparing the above-mentioned novel europium-doped tungstate red fluorescent material includes the following steps:

[0011] (1) According to Ca2La 18-x W8O 53 :xEu 3+ The raw materials were weighed according to the stoichiometric ratios: calcium-containing compounds, lanthanum-containing compounds, tungsten-containing compounds, and europium-containing compounds.

[0012] (2) After thoroughly grinding the raw materials weighed in step (1) into a uniform powder, place them in a muffle furnace and calcine them at high temperature in an air atmosphere to obtain the desired Ca2La. 18-x W8O 53 :xEu 3+ sample.

[0013] The calcium-containing compound shown in step (1) is preferably CaCO3 or CaO; the lanthanum-containing compound is preferably La2O3; the tungsten-containing compound is preferably WO3; and the europium-containing compound is preferably Eu2O3.

[0014] In step (2), it is preferable to add ethanol as a co-solvent to ensure better grinding and mixing. After the ethanol has completely evaporated, the mixture is transferred to a muffle furnace for high-temperature calcination.

[0015] The high-temperature calcination mentioned in step (2) refers to heating to 1250-1350℃ and holding at that temperature for 5-8 hours in an air atmosphere at a heating rate of 5℃ / min.

[0016] After high-temperature calcination in step (2), the sample is removed and ground evenly after the muffle furnace cools to room temperature to obtain the desired Ca2La. 18-x W8O 53 :xEu 3+ sample.

[0017] Application of the above-mentioned europium-doped tungstate novel red fluorescent material in white light-emitting diodes.

[0018] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0019] The present invention can be ultraviolet excited Eu 3+ The doped tungstate red fluorescent material can effectively absorb ultraviolet light and can be excited by ultraviolet LED chips to produce bright red light. The preparation process is a one-step synthesis method, which is simple, pollution-free, energy-saving and environmentally friendly, and can realize large-scale industrial production. Attached Figure Description

[0020] Figure 1 The fluorescent material Ca2La prepared in Example 3 17.5 W8O 53 0.5Eu 3+ XRD patterns.

[0021] Figure 2 The fluorescent material Ca2La prepared in Example 3 17.5 W8O 53 0.5Eu 3+ The excitation spectrum.

[0022] Figure 3 The fluorescent material Ca2La prepared in Example 3 17.5 W8O 53 0.5Eu 3+ The emission spectrum.

[0023] Figure 4 The fluorescent material Ca2La prepared in Example 3 17.5 W8O 53 0.5Eu 3+ CIE map. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0025] In this embodiment, an Edinburgh FLS1000 spectrometer equipped with a PMT-900 photomultiplier tube with a cooled housing was used to record the UV-Vis excitation and emission spectra of the samples. A 450W xenon lamp was used as the excitation source for steady-state excitation and emission spectra.

[0026] Example 1

[0027] This embodiment provides a europium-doped tungstate red fluorescent material and its preparation method. The chemical structural formula of the red fluorescent material is Ca2La. 17.9 W8O 53 0.1Eu 3+ ;

[0028] The main methods for preparing europium-doped tungstate red fluorescent materials include:

[0029] Step 1, according to the chemical formula Ca2La 17.9 W8O 53 0.1Eu 3+ The raw materials were weighed according to the stoichiometric ratios as follows: CaCO3 (99.99%), La2O3 (99.99%), WO3 (99.99%), and Eu2O3 (99.99%).

[0030] Step 2: Place the weighed raw materials into an agate mortar, add anhydrous ethanol, and grind and mix evenly. After the ethanol has completely evaporated, transfer the ground mixture into an alumina crucible.

[0031] Step 3: Place the alumina crucible in a muffle furnace for high-temperature sintering, then wait for the muffle furnace to cool to room temperature before removing it. Grind the obtained product into powder again to obtain europium-doped tungstate red fluorescent material.

[0032] The high-temperature sintering atmosphere is air sintering. The high-temperature sintering conditions are: heating to 1350°C at a heating rate of 5°C / min and holding at that temperature for 5 hours in an air atmosphere.

[0033] Example 2

[0034] This embodiment provides a europium-doped tungstate red fluorescent material and its preparation method. The chemical structural formula of the red fluorescent material is Ca2La. 17.7 W8O 53 0.3Eu 3+ ;

[0035] The main methods for preparing europium-doped tungstate red fluorescent materials include:

[0036] Step 1, according to the chemical formula Ca2La 17.7 W8O 53 0.3Eu 3+ The raw materials were weighed according to the stoichiometric ratios as follows: CaCO3 (99.99%), La2O3 (99.99%), WO3 (99.99%), and Eu2O3 (99.99%).

[0037] Step 2: Place the weighed raw materials into an agate mortar, add anhydrous ethanol, and grind and mix evenly. After the ethanol has completely evaporated, transfer the ground mixture into an alumina crucible.

[0038] Step 3: Place the alumina crucible in a muffle furnace for high-temperature sintering, then wait for the muffle furnace to cool to room temperature before removing it. Grind the obtained product into powder again to obtain europium-doped tungstate red fluorescent material.

[0039] The high-temperature sintering atmosphere is air sintering. The high-temperature sintering conditions are: heating to 1350°C at a heating rate of 5°C / min and holding at that temperature for 5 hours in an air atmosphere.

[0040] Example 3:

[0041] This embodiment provides a europium-doped tungstate red fluorescent material and its preparation method. The chemical structural formula of the red fluorescent material is Ca2La. 17.5 W8O 53 0.5Eu 3+ ;

[0042] The main methods for preparing europium-doped tungstate red fluorescent materials include:

[0043] Step 1, according to the chemical formula Ca2La 17.7 W8O 53 0.3Eu 3+ The raw materials were weighed according to the stoichiometric ratios as follows: calcium oxide (99.99%), lanthanum oxide (99.99%), tungsten oxide (99.99%), and europium oxide (99.99%).

[0044] Step 2: Place the weighed raw materials into an agate mortar, add anhydrous ethanol, and grind and mix evenly. After the ethanol has completely evaporated, transfer the ground mixture into an alumina crucible.

[0045] Step 3: Place the alumina crucible in a muffle furnace for high-temperature sintering, then wait for the muffle furnace to cool to room temperature before removing it. Grind the obtained product into powder again to obtain europium-doped tungstate red fluorescent material.

[0046] The high-temperature sintering atmosphere is air sintering, and the high-temperature sintering conditions are: heating to 1350°C at a heating rate of 5°C / min and holding at that temperature for 5 hours in an air atmosphere.

[0047] Figure 1 This is the XRD pattern of the red fluorescent material prepared in Example 3. The figure shows that the sample diffraction peaks are similar to those of Ca2La. 18 W8O 53The standard card PDF#00-049-0966 is a perfect match, indicating that Eu has replaced part of La and completely entered the lattice, and there are no obvious impurity peaks, indicating that the phase purity of the prepared sample is high.

[0048] like Figure 2 The image shows the fluorescent material Ca2La prepared in Example 3. 17.5 W8O 53 0.5Eu 3+ Its excitation spectrum can be effectively excited by ultraviolet light.

[0049] like Figure 3 The image shows the fluorescent material Ca2La prepared in Example 3. 17.5 W8O 53 0.5Eu 3+ The emission spectrum at an excitation wavelength of 394 nm exhibits high luminescence intensity, with the main peak at 614 nm primarily originating from europium ions. 5 D0→ 7 F2 jump.

[0050] Figure 4 The CIE spectrum of this invention shows that the color coordinates of the fluorescent material are (0.6496, 0.3475), which are located in the red region and are close to the standard red coordinates (0.666, 0.333), indicating high color purity and low correlated color temperature.

[0051] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A europium-doped tungstate red fluorescent material, characterized in that... The chemical formula of the fluorescent material is: Ca2La 18-x W8O 53 :xEu 3+ , 0.10≤x≤0.

50.

2. A method for preparing a europium-doped tungstate red fluorescent material according to claim 1, characterized in that... Includes the following steps: (1) According to Ca2La 18-x W8O 53 xEu 3+ The raw materials were weighed according to the stoichiometric ratios: calcium-containing compounds, lanthanum-containing compounds, tungsten-containing compounds, and europium-containing compounds. (2) After thoroughly grinding the raw materials weighed in step (1) and placing them in a muffle furnace, calcine them at high temperature in an air atmosphere to obtain the desired Ca2La. 18-x W8O 53 xEu 3+ sample.

3. The method for preparing the europium-doped tungstate red fluorescent material according to claim 2, characterized in that: The calcium-containing compound mentioned in step (1) is CaCO3 or CaO.

4. The method for preparing the europium-doped tungstate red fluorescent material according to claim 2, characterized in that: The lanthanum-containing compound mentioned in step (1) is La2O3.

5. The method for preparing the europium-doped tungstate red fluorescent material according to claim 2, characterized in that: The tungsten-containing compound mentioned in step (1) is WO3.

6. The method for preparing the europium-doped tungstate red fluorescent material according to claim 2, characterized in that: The europium-containing compound mentioned in step (1) is Eu2O3.

7. The method for preparing the europium-doped tungstate red fluorescent material according to claim 2, characterized in that: The grinding process described in step (2) involves adding ethanol to ensure better grinding and mixing. After the ethanol has completely evaporated, the mixture is transferred to a muffle furnace for high-temperature calcination.

8. The method for preparing the europium-doped tungstate red fluorescent material according to claim 2, characterized in that: The high-temperature calcination mentioned in step (2) refers to calcining at 1250-1350℃ in an air atmosphere for 5-8 hours.

9. The application of the europium-doped tungstate red fluorescent material of claim 1 in white light-emitting diodes.

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