A rare earth long afterglow light-controlled luminescent material and its preparation method

Abstract

The present application provides a rare earth long afterglow photoconductive luminescent material and a preparation method thereof, belonging to the technical field of luminescent materials containing rare earth metals. It is denoted as SrTiO3:Eu 3+ / SrAl2O4:Eu 2+ , and satisfies Ti:Sr:Al:Eu:Dy = x:1:2:y:0.03, where x = 0.1 - 1 and y = 0.02 - 0.08. It continuously emits various colored lights under dark conditions, with an afterglow emission time ≥ 1000 seconds and an afterglow intensity ≥ 0.217 cd / m 2 . The present application can achieve a "red shift" effect in the luminescent material, thereby forming various colored lights. At the same time, the product has excellent luminescence intensity, obvious "red shift" effect, long-lasting luminescence time, and excellent emission light and excitation light absorption effects. It is suitable for fields such as lighting, anti-counterfeiting, and clothing, and has broad application prospects.

Description

Technical Field

[0001] The present application relates to a rare earth long afterglow light-controlled luminescent material and a preparation method thereof, belonging to the technical field of luminescent materials containing rare earth metals. Background Art

[0002] In recent years, in the fields of daily clothing, plush toys, stage performances, traffic safety, etc., luminescent materials have begun to be widely used, and various clothing items made of luminescent materials have also attracted much attention. SrTiO 3 :Eu 3+ / SrAl 2 O 4 :Eu 2+ As a kind of rare earth long afterglow luminescent material, the composite luminescent material shows great potential in the fields of anti-counterfeiting, clothing and lighting, etc. It can absorb and store energy under visible light and emit visible light of various different colors in the dark state, with warning, lighting or anti-counterfeiting functions.

[0003] At present, the preparation and application of rare earth long afterglow luminescent materials are very extensive. For example, CN1221631C discloses a preparation method of a rare earth green long afterglow luminescent material. By mixing and sintering CaCO 3 , MgO, SiO 2 , CaCl 2 and a cosolvent B 2 O 3 a rare earth luminescent material that can emit green long afterglow light is prepared, which has good afterglow brightness and slow afterglow decay. CN102493017A discloses a preparation method of rare earth silicate blue long afterglow polyester fiber. By mixing, drying and special spinning processes of polyester spinning, rare earth strontium magnesium silicate and nano-functional additives, a fiber material that can emit blue long afterglow is prepared, which has excellent blue light long afterglow performance. CN101139743A discloses a special anti-counterfeiting rare earth luminescent fiber, which uses a rare earth luminous material as the matrix, polyester, polypropylene or polyamide as the carrier, and is prepared by a special spinning process. The produced rare earth luminous fiber has different emission spectra, similar to fingerprints, with uniqueness, and can be applied to anti-counterfeiting technology.

[0004] The rare earth long afterglow luminescent materials prepared and applied by the above-mentioned schemes have excellent luminous intensity and persistent luminous decay performance, but they can only emit one color of light, which limits their application in scenarios that require a variety of different complex color changes such as luminescence, lighting and clothing colors. Summary of the Invention

[0005] In view of this, the present application first provides a rare earth long afterglow light-controlled luminescent material, which has a "red shift" effect, shifting the original multiple different light colors to the red wavelength band, and then emitting multiple different light colors that are more biased towards red, solving the problem of the lack of long afterglow luminescent materials that emit multiple different light colors in the prior art.

[0006] Specifically, the present application is achieved through the following solutions:

[0007] A rare earth long afterglow light-controlled luminescent material, which is denoted as SrTiO 3 :Eu 3+ / SrAl 2 O 4 :Eu 2+ And in terms of molar ratio, it satisfies Ti:Sr:Al:Eu:Dy = x:1:2:y:0.03, where x = 0.1 - 1 and y = 0.02 - 0.08. It continuously emits light of multiple colors under dark conditions, with an afterglow emission time ≥ 1000 seconds and an afterglow intensity ≥ 0.217 cd / m 2 .

[0008] The above rare earth long afterglow light-controlled luminescent material can absorb light energy under visible light or ultraviolet light irradiation in a short time. After the light source disappears, it gradually releases the stored light energy in the form of visible light of different colors and can exhibit a luminescence phenomenon for a certain period of time.

[0009] Furthermore, as a preference:

[0010] The rare earth long afterglow luminescent material absorbs visible light or ultraviolet light and emits light of multiple colors, including blue-violet, orange, light orange, pink, green, bright green, gray, and light pink.

[0011] The applicant's second aspect objective is to provide a preparation method of a rare earth long afterglow light-controlled luminescent material, which is characterized in that: using TiO 2 , SrCO 3 , Al 2 O 3 , Eu 2 O 3 , Dy 2 O 3 as raw materials. After adding the co-solvent H 3 BO 3 and fully grinding, adding the reducing agent carbon powder, placing it in a high-temperature calcination furnace for calcination, naturally cooling and annealing, and then grinding it into a powder again, which is the rare earth long afterglow light-controlled luminescent material SrTiO 3 :Eu 3+ / SrAl 2 O 4 :Eu2+ , TiO 2 , SrCO 3 , Al 2 O 3 , Eu 2 O 3 , Dy 2 O 3 The molar ratio of to is 0.1~1:1:1:0.01~0.04:0.015.

[0012] The molar ratio of each material of the above raw materials satisfies the performance of endowing the material with different luminescent colors and luminescent intensities under dark conditions.

[0013] The reaction temperature of the calcination is 1100~1500 °C, and the calcination duration is 3~8 h. More preferably, the calcination temperature is raised from room temperature to the reaction temperature at a heating rate of 5 °C / min.

[0014] The molar ratio of the carbon powder to Eu 2 O 3 is 0~2:1, preferably 1~2:1, that is, ensuring sufficient excess is better.

[0015] Through the above preparation method, the rare earth long afterglow luminescent material shows a "red shift" situation, shifting from the original non-luminescence, blue light emission, and green light emission to the red wavelength band, emitting a more red-shifted light color, and then generating lights of different colors.

[0016] The above rare earth long afterglow light-controlled luminescent material has excellent luminescence brightness and luminescence time, can emit lights of various colors under dark conditions, and makes the main wavelength of the existing rare earth long afterglow luminescent material shift to the red wavelength band, generating a "red shift", and emitting a more red-shifted light color under dark conditions. Therefore, it can be used in the fields of anti-counterfeiting, clothing, and lighting, etc.

[0017] Before use, the light-controlled luminescent material in this case needs to be placed under light or visible light for a period of time to absorb and store energy, and then release energy in the form of visible light after the light source is withdrawn, showing visible blue-green, orange-yellow, purple, red and other visible lights.

[0018] This application can achieve a shift of the main wavelength of the luminescent material to the red wavelength band, generating a "red shift", endowing the existing rare earth long afterglow luminescent material with a luminescence state shift from the original non-luminescence, blue light emission, and green light emission to the red wavelength band under dark conditions, and then emitting a more red-shifted light color, such as blue-violet light changing to orange light, pink light changing to red light, and then generating lights of various different colors.

[0019] The beneficial effects of the present invention are:

[0020] (1) Excellent luminescence intensity: By controlling the use of reducing agents such as carbon powder, the present invention enables part of Eu3+ is reduced to Eu 2+ , and then SrAl 2 O 4 :Eu 2+ and SrTiO 3 :Eu 3+ are synthesized, enabling the material to exhibit a distinct red light emission phenomenon at night. The composite luminescent material SrTiO 3 :Eu 3+ / SrAl 2 O 4 :Eu 2+ synthesized in this invention has excellent luminescence intensity, significantly enhancing the lighting effect of the product in the dark state and broadening its application scope in fields such as night lighting and luminous clothing.

[0021] (2) Obvious "red shift" effect: By controlling the usage of TiO 2 concentration and changing the ratio of Ti:Sr in the raw materials, the main wavelength of the product shifts towards the red band, resulting in a "red shift" phenomenon. Specifically, the matrix SrAl 2 O 4 :Eu 2+ ,Dy 3+ emits visible light in the green color. Through the preparation process of this invention, the product can be made to emit visible light in the red color; it can also cause a material that originally emits blue-violet light to shift towards the red light band and emit orange light; a material that originally emits pink light to shift towards the red light band and emit red light. The obvious "red shift" effect can assist the material to shift towards the red light during preparation, meeting the preparation requirements for rare earth long afterglow photoluminescent materials.

[0022] (3) Long-lasting luminescence time: In this invention, when the luminescent material receives light, the outer electrons of Eu 2＋ ions undergo a 4f 6 5d 1 →4f 7 transition, storing the absorbed light energy into the unique defect energy levels of the material through relaxation. When the material is removed from the light source, the electrons captured by the defect energy levels are slowly released, endowing the material with long afterglow characteristics; TiO 2 acts as a photocatalyst, greatly enhancing the absorption and conversion of light energy by the material. The material can absorb the energy of visible light and ultraviolet light and emit bright visible light of various different colors in the dark state, with a duration of more than 1000 seconds.

[0023] (4) Excellent emission light and excitation light absorption effects: By controlling the usage of the reducing agent carbon powder and TiO 2 concentration, sufficient Eu 2+, when receiving visible light or ultraviolet light, the material undergoes an energy level transition, and TiO 2 As a photocatalyst, it prompts the material to greatly enhance the light absorption effect. Furthermore, it enhances the absorption effect of the material on emitted light and excitation light.

[0024] By optimizing the preparation process of the rare earth long afterglow material, this application has successfully solved the problems of the lack of long afterglow luminescent materials with multiple different light colors, short luminescence time, and low luminescence intensity in previous products. It can produce a "red shift" effect with existing rare earth long afterglow luminescent materials of different light colors, and thus form any light color. At the same time, the product has excellent luminescence intensity, obvious "red shift" effect, long-lasting luminescence time, and excellent performance such as the absorption effect of emitted light and excitation light, and is applicable to fields such as lighting, anti-counterfeiting, and clothing, with broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of this application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 SEM photos of the luminescent materials prepared in Examples 1 to 4,

[0027] (a) is the SEM photo of Example 1, (b) is the SEM photo of Example 2,

[0028] (c) is the SEM photo of Example 3, (d) is the SEM photo of Example 4;

[0029] Figure 2 EDS Mapping pictures of the luminescent materials prepared in Example 5;

[0030] Figure 3 EDS Mapping photos of the luminescent materials prepared in Example 6;

[0031] Figure 4 EDS Mapping photos of the luminescent materials prepared in Example 7;

[0032] Figure 5 EDS Mapping photos of the luminescent materials prepared in Example 8;

[0033] Figure 6 XRD patterns of the luminescent materials prepared in each example;

[0034] Figure 7Emission spectra of the luminescent materials prepared in each example;

[0035] Figure 8 Excitation spectra of the luminescent materials prepared in each example;

[0036] Figure 9 Afterglow decay curves of the luminescent materials prepared in each example;

[0037] Figure 10 Initial brightness and steady-state brightness diagrams of the dilute luminescent materials prepared in each example;

[0038] Figure 11 Emission chromaticity diagrams of the luminescent materials prepared in each example;

[0039] Figure 12 Comparison diagrams of the luminescent materials prepared in each example before and after being irradiated by light. Specific embodiments

[0040] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application clearer, the technical solutions in the embodiments of this application will be further described in detail below with reference to the accompanying drawings in the embodiments of this application. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit the technical solutions of this application. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of this application.

[0041] As used herein, "one embodiment" or "embodiment" refers to a specific feature, structure or characteristic that may be included in at least one implementation manner of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it an embodiment that is separate from or mutually exclusive of other embodiments. Unless otherwise specified, the raw materials used in the present invention are all commonly commercially available.

[0042] The micro-morphology of the material was tested by a scanning electron microscope (Su1510) to obtain the SEM photos of the material; the phase composition of the sample was tested by an X-ray diffractometer (ARL XTRA type); the emission spectrum and excitation spectrum of the material were tested by an FS5 fluorescence spectrometer (SC-10) to obtain the emission spectrum diagrams and excitation spectrum diagrams under different conditions; the afterglow brightness and afterglow time of the material were tested by a fluorescence afterglow brightness tester (PR-305) to obtain the afterglow curve diagrams, initial brightness and steady-state brightness diagrams.

[0043] Example 1

[0044] The preparation process of the rare-earth long-afterglow light-controlled luminescent material in this example is as follows:

[0045] Step 1: Take materials of SrCO3, Al2O3, TiO2, Eu2O3, Dy2O3 and carbon powder according to the molar ratio of Ti:Sr:Al:Eu:Dy:carbon powder = 1:1:2:0.05:0.03:0.025 (i.e., the molar ratio of TiO2, SrCO3, Al2O3, Eu2O3, Dy2O3, carbon powder is 1:1:1:0.025:0.015:0.025), and then weigh the cosolvent H 3 BO 3 , and mix the raw materials SrCO3, Al2O3, TiO2, Eu2O3, Dy2O3 with the cosolvent H 3 BO 3 and put them into a mortar for thorough grinding for 1 h, where H 3 BO 3 takes 3% of the total molar amount of the raw materials.

[0046] Step 2: Put the ground powder into a crucible, place it in a high-temperature calcination furnace, add the carbon powder taken according to the above ratio, and increase the temperature in the high-temperature calcination furnace from room temperature to 1200 °C at a heating rate of 5 °C / min. After calcining at 1200 °C for 4 h, conduct an annealing treatment with an annealing duration of 4 h;

[0047] Step 3: After the material after the annealing treatment is naturally cooled and the temperature drops, take out the crucible and grind it thoroughly again for 1 h to obtain the rare-earth long-afterglow light-controlled luminescent material.

[0048] Example 2

[0049] This example is the same as that of Example 1, except that in Step 1, Ti:Sr:Al:Eu:Dy:carbon powder = 1:1:2:0.08:0.03:0.025.

[0050] Example 3

[0051] This example is the same as that of Example 1, except that in Step 1, Ti:Sr:Al:Eu:Dy:carbon powder = 1:1:2:0.02:0.03:0.025.

[0052] Example 4

[0053] This example is the same as that of Example 1, except that in Step 1, Ti:Sr:Al:Eu:Dy:carbon powder = 1:1:2:0.03:0.03:0.025.

[0054] Example 5

[0055] This example is the same as that of Example 1, except that in Step 1, Ti:Sr:Al:Eu:Dy:carbon powder = 0.1:1:2:0.05:0.03:0.025.

[0056] Example 6

[0057] This example is the same as that of Example 1, except that in Step 1, Ti:Sr:Al:Eu:Dy:toner = 0.1:1:2:0.08:0.03:0.025.

[0058] Example 7

[0059] This example is the same as that of Example 1, except that in Step 1, Ti:Sr:Al:Eu:Dy:toner = 0.1:1:2:0.05:0.03:0.0125.

[0060] Example 8

[0061] This example is the same as that of Example 1, except that in Step 1, Ti:Sr:Al:Eu:Dy:toner = 0.1:1:2:0.08:0.03:0.0125.

[0062] The performance test results of the products obtained in the above examples are as Figures 1 to 12 shown.

[0063] Figure 1 SEM photographs of the rare earth long afterglow photoconductive luminescent materials prepared in Examples 1 to 4. a corresponds to Example 1: The surface of the material is uneven, the particle distribution is relatively scattered and uneven, there is agglomeration phenomenon, and there is a dispersion phenomenon of small particles around the large particles. The diameter of the small particles is about 10 μm, and the diameter of the large particles is about 50 μm. The same phenomenon is also shown in b corresponding to Example 2, c corresponding to Example 3, and d corresponding to Example 4.

[0064] Figures 2 to 5 EDS Mapping diagrams of the luminescent materials prepared in Examples 5 to 8 in sequence: The material is mainly composed of Sr, Eu, O, Al and Ti elements. The Si element in the EDS result comes from the silicon wafer substrate.

[0065] Figure 6 XRD patterns of the rare earth long afterglow photoconductive luminescent materials prepared in Examples 1 to 4, showing the main components of the materials. It can be known from the XRD pattern analysis that the main component of the material is SrTiO 3 :Eu 3+ / SrAl 2 O 4 :Eu 2+ .

[0066] Figure 7The emission spectra of the luminescent materials prepared in the above embodiments are shown, presenting the emission intensities of the materials under emission lights of different wavelengths (400 - 680 nm). Through comparison, it can be observed that: the emission spectra of the prepared luminescent materials are broadband spectra ranging from 420 nm to 680 nm. There are three emission peaks in Embodiments 1 - 4, which are 592 nm, 618 nm, and 640 nm respectively; there are three emission peaks in Embodiments 5 and 6, which are 518 nm, 618 nm, and 640 nm respectively; Embodiments 7 and 8 show the same performance, with one emission peak at 640 nm.

[0067] Figure 8 The excitation spectra of the luminescent materials prepared in the above embodiments are shown, presenting the excitation intensities of the materials under excitation lights of different wavelengths (300 - 500 nm). Through comparison, it can be observed that: the excitation spectra of the rare-earth red long-afterglow luminescent materials in Embodiments 1 - 4 and Embodiments 7 and 8 are relatively narrow, with only one excitation peak located at 415 nm. While the excitation spectra of Embodiments 5 and 6 are relatively wide, ranging from 350 nm to 450 nm, and there are two excitation peaks located at 374 nm and 415 nm respectively. This indicates that the excitation intensity of this material is strong and its absorption effect on the excitation light is good.

[0068] Figure 9 The afterglow decay curves of the luminescent materials prepared in the above embodiments are as follows: it can be seen that the afterglow decay of the materials prepared in each case has experienced two processes of fast decay and slow decay. The initial brightnesses of the materials prepared in Embodiments 1 - 4 and Embodiment 5 are relatively high. Within the subsequent 100 s, the afterglow brightness decays rapidly; at around 500 s, the brightness decay reaches a steady state. The afterglow luminescence time of this material can reach 1000 s, indicating that the material has a long luminescence time. The initial brightness of Embodiment 1 is only 2.7% of that of Embodiment 5, and the initial brightness of Embodiment 2 is only 7.8% of that of Embodiment 6. Even in the case of insufficient carbon, the initial brightnesses of Embodiments 7 and 8 are higher than those of Embodiments 3 and 4. The initial brightness of Embodiment 3 is only 69.2% of that of Embodiment 7, and the initial brightness of Embodiment 4 is only 78.3% of that of Embodiment 8. However, all can achieve an afterglow luminescence time of 1000 s. Luminescence is mainly generated by Eu 3+ and Eu 2+ absorbing light energy. The above embodiments also indirectly confirm that in this aspect, TiO 2 significantly affects the ability of the prepared luminescent materials to absorb light energy.

[0069] Figure 10 The initial brightness and steady-state brightness diagrams of the luminescent materials prepared in the above embodiments are as follows: The initial brightness of Embodiment 5 is the highest, which is 0.217 cd / m 2, significantly higher than the other cases; the steady-state brightness of Example 5 is also higher than that of the other examples. It shows that the material has high luminous brightness and excellent luminous performance.

[0070] In contrast, Examples 1 to 4 have poor absorption of the emitted light and the excitation light, low afterglow brightness, and short luminescence time, which greatly affects their luminous effect at night.

[0071] Figure 11 It is the emission chromaticity diagram of the luminescent materials prepared in the above examples. The material of Example 1 can emit more reddish visible light. By comparing all cases and the matrix SrAl 2 O 4 :Eu 2+ ,Dy 3+ in the chromaticity region where they are located, it can be seen that the dominant wavelength of all cases shifts towards the red light wavelength band. Among them, the emitted light of Example 1 is in the blue-violet light region, the emitted light of Example 2 is in the orange light region. The afterglow brightness of Example 3 is slightly lower than that of Example 1, and its emitted light is in the light orange light region. The afterglow brightness of Example 4 is slightly lower than that of Example 1 but higher than that of Example 3, and its emitted light is in the pink light region. By comparing the chromaticity region of the matrix SrAl 2 O 4 :Eu 2+ ,Dy 3+ where they are located, "red shift" phenomena occur in Examples 2, 3, and 4. The emitted lights of Examples 5 and 6 are both in the green light region and both emit green light; the emitted light of Example 7 is in the gray light region and emits gray light; the emitted light of Example 8 is in the light pink light region and emits light pink light, with a "red shift" phenomenon.

[0072] Figure 12 It is the comparison diagram of the above-mentioned luminescent materials before and after absorbing light. After being irradiated with visible light or ultraviolet light, each luminescent material emits visible lights of various different light colors. It shows that the material can produce long-afterglow visible lights of various different light colors and has many types of luminescence.

[0073] As can be seen from the above examples, the luminescent materials in this application show excellent performance in many aspects, especially in the absorption effects of the emitted light and the excitation light, the afterglow brightness, the luminescence time, and the "red shift" situation, which are better than the other methods.

[0074] In addition, the applicant also conducted experiments on the influence of the addition amount of the reducing agent carbon powder, and the results are shown in Table 1.

[0075] Example 9

[0076] This example is the same as the setting of Example 1, except that the addition amount of carbon powder is as shown in Table 1.

[0077] Table 1: Influence of Different Carbon Powder Additions (Molar Ratio Relative to Eu) on Product Performance

[0078] Toner addition amount Peak change Initial afterglow brightness and luminescence duration Color light 0 There are 3 emission peaks, which are 592 nm, 618 nm, and 640 nm; there is 1 excitation peak, which is 415 nm. <![CDATA[The initial brightness of the afterglow is 0.01069 cd / m 2 , and the afterglow emission time ≥ 1000 seconds.]]> Compared with Example 1, a "red shift" occurs, and the emission light region is located in the light red light region. 0.0125 There are 2 emission peaks, which are 592 nm and 618 nm; there is 1 excitation peak, which is 415 nm. <![CDATA[The initial luminance of the afterglow is 0.0072 cd / m 2 , and the afterglow emission time ≥ 1000 seconds.]]> Compared with Example 1, a "red shift" occurs, and the emission light region is the red light region.

[0079] Comparing Example 1 and Example 9 shows that: the introduction of carbon powder reduces some Eu 3+ to Eu 2+ , and then SrAl 2 O 4 :Eu 2+ and SrTiO 3 :Eu 3+ are synthesized, enabling the material to exhibit an obvious night-time red light emission phenomenon. When added in insufficient quantity in Example 9, the light emitted by the prepared luminescent material is different from that in Example 1.

[0080] The above-described embodiments merely represent several feasible implementation manners of the present invention. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention patent. The embodiments are not intended to limit the scope of protection in the claims of the present invention. For those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made. Any equivalent implementation or change made without departing from the present invention should be included in the technology of the present invention.

Claims

1. A rare earth long afterglow light-controlled luminescent material, characterized in that: The molar ratio of the rare earth long afterglow light-controlled luminescent material satisfies Ti:Sr:Al:Eu:Dy=0.1:1:2:0.05-0.08:0.03; The preparation method of the above-mentioned rare earth long afterglow light-controlled luminescent material is as follows: TiO2, SrCO3, Al2O3, Eu2O3, and Dy2O3 are used as raw materials, H3BO3 is added to the raw materials and fully ground, carbon powder is added, and the raw materials are placed in a high-temperature calcining furnace for calcination, and then naturally cooled and annealed, and ground into powder again, that is, the rare earth long afterglow light-controlled luminescent material TiO2, SrCO3, Al2O3, Eu2O3, Dy2O3, and carbon powder have a molar ratio of 0.1:1:1:0.025~0.04:0.015:0.025, and the amount of H3BO3 added is 3% of the total molar amount of the raw materials. The reaction temperature of the calcination is 1100-1500° C., the calcination time is 3-8 hours, and the calcination temperature is increased from room temperature to the reaction temperature at a heating rate of 5° C. / min.

2. The method for preparing a rare earth long afterglow light-controlled luminescent material according to claim 1, characterized in that: The cooling annealing time is 4 to 6 hours.

3. An application of the rare earth long afterglow light-controlled luminescent material according to claim 1, characterized in that: The rare earth long afterglow light-controlled luminescent material is used for anti-counterfeiting materials, warning clothing or lighting materials.

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