Near-infrared luminescent glass ceramic material and preparation method thereof

Abstract

The invention discloses a near-infrared luminescent glass ceramic material and a preparation method thereof. The crystal phase of the glass ceramic material is Li2Mg2A4O11: xCr < 3 + >, yNi < 2 + >, and the element A is selected from one or more of Si, Ge, Ti and Zr; x is more than or equal to 0% and less than or equal to 15%, y is more than or equal to 0% and less than or equal to 15%, and x and y are not 0 at the same time. The glass ceramic is prepared by high-temperature melting and amorphous crystallization treatment. The obtained near-infrared luminescent glass ceramic can be efficiently excited by blue light and red light, the emission peak wavelength covers 650-1500nm, and the prepared near-infrared LED light source can be applied to the fields of food detection, security and protection, biological imaging, illumination and sensing.

Description

Technical Field

[0001] This invention belongs to the field of luminescent materials technology, specifically relating to a near-infrared luminescent glass-ceramic material and its preparation method. Background Technology

[0002] Near-infrared light holds significant value in numerous fields, including plant growth, non-destructive testing in food analysis, night vision illumination, and bioimaging. However, existing near-infrared light sources still fall short of practical requirements in terms of luminous efficiency and emission bandwidth. Therefore, developing novel broadband near-infrared light sources has become a research focus for scholars both domestically and internationally. Among various design schemes, near-infrared phosphor-converted LEDs exhibit superior characteristics, including tunable emission bands, spectral width, luminous efficiency, and thermal stability. Furthermore, this approach offers advantages such as simple structure, tunable spectrum, green and safe fabrication methods, low cost, and ease of miniaturization. Therefore, near-infrared phosphor-converted LEDs are considered one of the most reliable broadband near-infrared light source solutions and hold promise for use in portable devices such as mobile phones.

[0003] The types of luminescent center ions capable of near-infrared emission are diverse, including transition metal ions (such as Mn). 2+ Ni 2+ Fe 3+ Cr 4+ ) and rare earth ions (such as Pr) 3+ 、Nd 3+ Tm 3+ Er 3+ and Yb 3+ However, most of these ions are inefficient, have weak absorption, narrow emission spectra, and cannot be excited by blue light. Among the numerous studies on near-infrared luminescent materials, Cr... 3+ Ions have unique 3d 3 The electronic configuration, which allows its outermost electrons to be in an unfilled state, not only enables spin forbidden ( 2 E→ 4 A2 (695nm) exhibits narrowband emission while also enabling spin-allowed emission. 4 T2→ 4 A2 (700-1100nm) transition enables broadband transmission. Furthermore, Cr... 3+ Excitation band of ions ( 4 A2→ 4 T2 (400-500nm) has a good match with the emission wavelength of low-cost commercial blue LED chips, making Cr 3+ Ions can be efficiently excited by blue light and have great application prospects.

[0004] Currently, Cr 3+The quantum efficiency of ion-doped near-infrared phosphors is close to 100%, but due to Cr 3+ The parity-forbidden dd-transitions of ions generally result in absorption efficiencies below 50%. To address this issue, an effective method is to fabricate the material as a glass-ceramic or transparent ceramic. This reduces the scattering of blue light in the phosphor, thereby enhancing the absorption efficiency of Cr. 3+ The absorption efficiency of ion-doped near-infrared phosphors in blue light. Meanwhile, traditional phosphor-converted LEDs (pc-LEDs) require encapsulation using a mixture of phosphor and curing colloid. Due to the low thermal conductivity of this mixture, prolonged operation not only degrades the device's luminous performance but also reduces the LED's lifespan. Therefore, directly encapsulating blue LEDs with glass-ceramic or transparent ceramics can not only improve the absorption efficiency of Cr... 3+ The absorption efficiency of ions in blue light can also improve their heat dissipation performance and lifespan. However, the existing conditions and methods for preparing glass-ceramics or transparent ceramics are demanding, and their luminescent performance is insufficient for large-scale applications. Therefore, the development of high-performance chromium-doped glass-ceramics or transparent ceramics is of great significance for near-infrared light source equipment and applications. Summary of the Invention

[0005] This invention overcomes the shortcomings of existing technologies and provides a simple and widely applicable method for preparing glass ceramics. Compared to powders and glass, glass ceramics exhibit significantly improved blue light absorption efficiency. When excited by a blue light chip, the emitted wavelength is between 650-1400 nm, making it suitable for applications such as bioimaging and disease diagnosis, product defect and non-destructive testing, and agricultural product quality analysis.

[0006] The objective of this invention is achieved through at least one of the following technical solutions.

[0007] A near-infrared luminescent glass-ceramic material comprising an inorganic compound with the chemical formula Li₂Mg₂A₄O. 11 :xCr 3+ :yNi 2+ Wherein, element A is selected from one or more of Si, Ge, Ti, and Zr; Cr 3+ and Ni 2+ The ions are luminescent ions, 0%≤x≤15%, 0%≤y≤15%, where x and y are not both 0.

[0008] Preferably, the luminescent glass-ceramic material emits light in the range of 650-1400nm under blue light excitation at 430-470nm, with a peak value at 800-900nm and a full width at half maximum (FWHM) of approximately 150-200nm.

[0009] The method for preparing the near-infrared glass ceramic includes the following steps:

[0010] 1) Weigh the raw materials according to the molar ratio of aLi2O-bMgO-cAO2-xCr2O3-yNiO (20≤a≤25, 28≤b≤40, c=40;), grind and mix them to obtain a mixture;

[0011] 2) The mixture obtained in step 1) is melted at high temperature, removed and shaped, cooled and annealed to obtain a glass precursor;

[0012] 3) The glass precursor obtained in step 2) is subjected to amorphous crystallization in air at a temperature of 600-900℃ for 8-12 hours. After crystallization, the crystallized material is post-processed (grinding, polishing, cleaning, cutting, etc.) to obtain the near-infrared glass ceramic.

[0013] Preferably, in step 1), the grinding time is 30-60 minutes.

[0014] Preferably, in step 2), the melting temperature is 1200-1600℃ and the melting time is 0.2-4h.

[0015] Preferably, in step 2), the annealing temperature is 650-950℃ and the annealing time is 0.5-48h.

[0016] The present invention has the following beneficial effects:

[0017] Compared to phosphors, glass ceramics significantly improve the absorption efficiency of blue light, thereby increasing the emission efficiency of near-infrared light.

[0018] Resin encapsulation was avoided when packaging the device, thus changing the LED packaging method and preventing excessive heat buildup that could lead to a decrease in luminous performance.

[0019] The method for producing fluorescent glass ceramics is simple, highly repeatable, and suitable for large-scale, batch industrial production, with luminous efficiency superior to traditional phosphors. Attached Figure Description

[0020] Figure 1 This is the XRD pattern of the near-infrared glass-ceramic prepared in Example 1;

[0021] Figure 2 The excitation and emission spectra of the near-infrared glass ceramic of Example 1 are shown.

[0022] Figure 3 This is a comparison of the emission spectra of Example 1 and Comparative Example 1;

[0023] Figure 4 This is the emission spectrum of the near-infrared glass-ceramic of Example 2;

[0024] Figure 5 The excitation and emission spectra of the near-infrared glass ceramic of Example 9 are shown.

[0025] Figure 6 This is the electroluminescence spectrum of Example 10. Detailed Implementation Plan

[0026] The present invention will be further described below with reference to specific embodiments and accompanying drawings to help understand the content of the present invention.

[0027] Example 1

[0028] The raw materials were prepared according to the composition of Li2O-MgO-SiO2-Cr2O3, with Li2O content of 20% mol, MgO content of 39.6% mol, SiO2 content of 40% mol, and Cr2O3 content of 0.4% mol. High-purity powder raw materials of Li2O, MgO, SiO2, and Cr2O3 were accurately weighed and ground in an agate mortar for about 30 minutes to ensure thorough mixing. The mixture was then transferred to an alumina crucible and melted in an air-atmosphere high-temperature reactor at 1400℃ for 30 minutes. The melt was quickly removed at high temperature and poured onto a graphite mold preheated to 600℃. It was then pressed into shape using a steel plate and rapidly transferred to an annealing furnace at 600℃ for about 6 hours. After natural cooling, a high-transparency glass material was obtained. After grinding, polishing, cleaning, and cutting, it underwent analysis, testing, and further processing. A portion of the obtained glass material was annealed and crystallized in an 800℃ high-temperature reactor for 10 hours, followed by natural cooling to obtain a glass-ceramic material with reduced transparency. This material was then polished, cleaned, and cut before analysis and testing. The XRD and fluorescence spectra of the glass-ceramic and glass are shown below. Figure 1 and Figure 2 As shown. From Figure 1 It can be seen that the XRD diffraction peaks of this glass-ceramic are similar to those of Li2Mg2Si4O. 11 The standard card matched perfectly, with almost no excess crystalline phase. Li₂Mg₂Si₄O was obtained. 11 0.01Cr 3+ Glass and ceramics. From Figure 2 It can be seen that the excitation and emission spectra of glass ceramics are basically the same as those of glass, and the luminescence intensity of glass ceramics is 7 times that of glass.

[0029] Example 2

[0030] The raw materials were prepared according to the composition of Li₂O-MgO-GeO₂-Cr₂O₃, with Li₂O content of 20% mol, MgO content of 39.6% mol, GeO₂ content of 40% mol, and Cr₂O₃ content of 0.4% mol. High-purity powder raw materials of Li₂O, MgO, GeO₂, and Cr₂O₃ were accurately weighed and ground in an agate mortar for about 20 minutes to ensure thorough mixing. The mixture was then transferred to an alumina crucible and melted at 1500℃ for 30 minutes in an air-atmosphere high-temperature reactor. The melt was quickly removed at high temperature and poured onto a graphite mold preheated to 650℃. It was then pressed into shape using a steel plate and rapidly transferred to an annealing furnace at 600℃ for about 6 hours. After natural cooling, the resulting glass was annealed and crystallized in an 850℃ high-temperature reactor for 10 hours, then allowed to cool naturally. After grinding, polishing, cleaning, and cutting, it was analyzed and tested to obtain Li₂Mg₂Ge₄O₃. 11 0.01Cr 3+ Glass ceramics. The emission spectrum of glass ceramics is as follows: Figure 4 As shown.

[0031] Example 3

[0032] The raw materials were prepared according to the composition of Li2O-MgO-TiO2-Cr2O3, with Li2O content of 20% mol, MgO content of 39.6% mol, TiO2 content of 40% mol, and Cr2O3 content of 0.4% mol. High-purity powder raw materials of Li2O, MgO, TiO2, and Cr2O3 were accurately weighed and ground in an agate mortar for about 30 minutes to ensure thorough mixing. The mixture was then transferred to an alumina crucible and melted in an air-atmosphere high-temperature reactor at 1550℃ for 30 minutes. The melt was quickly removed at high temperature and poured onto a graphite mold preheated to 650℃. It was then pressed into shape using a steel plate and rapidly transferred to an annealing furnace at 650℃ for about 6 hours. After natural cooling, the resulting glass was annealed and crystallized in an 870℃ high-temperature reactor for 10 hours. After natural cooling, it was polished, cleaned, cut, and analyzed to obtain Li2Mg2Ti4O. 11 0.01Cr 3+ Glass and ceramics.

[0033] Example 4

[0034] The raw materials were prepared according to the composition of Li₂O-MgO-ZrO₂-Cr₂O₃, with Li₂O content of 20% mol, MgO content of 39.6% mol, ZrO₂ content of 40% mol, and Cr₂O₃ content of 0.4% mol. High-purity powder raw materials of Li₂O, MgO, ZrO₂, and Cr₂O₃ were accurately weighed and ground in an agate mortar for about 30 minutes to ensure thorough mixing. The mixture was then transferred to an alumina crucible and melted at 1600℃ for 30 minutes in an air-atmosphere high-temperature reactor. The melt was quickly removed at high temperature and poured onto a graphite mold preheated to 650℃. It was then pressed into shape using a steel plate and rapidly transferred to an annealing furnace at 650℃ for about 6 hours. After natural cooling, the resulting glass was annealed and crystallized in a 900℃ high-temperature reactor for 10 hours. After natural cooling, it was polished, cleaned, cut, and analyzed to obtain Li₂Mg₂Zr₄O. 11 0.01Cr 3+ Glass and ceramics.

[0035] Example 5

[0036] The raw materials were prepared according to the composition of Li2O-MgO-SiO2-Cr2O3-NiO, with Li2O content of 20% mol, MgO content of 38.8% mol, SiO2 content of 40% mol, Cr2O3 content of 0.4% mol, and NiO content of 0.8% mol. High-purity powder raw materials of Li2O, MgO, SiO2, Cr2O3, and NiO were accurately weighed and ground in an agate mortar for about 30 minutes to ensure thorough and uniform mixing. The mixture was then transferred to an alumina crucible and melted in an air-atmosphere high-temperature reactor at 1300℃ for 30 minutes. The melt was quickly removed at high temperature and poured onto a graphite mold preheated to 600℃. It was then pressed into shape using a steel plate and rapidly transferred to an annealing furnace at 600℃ for approximately 6 hours. After natural cooling, the glass was annealed and crystallized in an 800℃ high-temperature reactor for 10 hours, then naturally cooled, polished, cleaned, cut, and analyzed to obtain Li2Mg2Si4O. 11 0.01Cr 3+ 0.02Ni 2+ Glass and ceramics.

[0037] Example 6

[0038] The raw materials were prepared according to the composition of Li2O-MgO-GeO2-Cr2O3-NiO, with Li2O content of 20% mol, MgO content of 38.8% mol, GeO2 content of 40% mol, Cr2O3 content of 0.4% mol, and NiO content of 0.8% mol. High-purity powder raw materials of Li2O, MgO, GeO2, Cr2O3, and NiO were accurately weighed and ground in an agate mortar for about 30 minutes to ensure thorough and uniform mixing. The mixture was then transferred to an alumina crucible and melted in an air-atmosphere high-temperature reactor at 1460℃ for 30 minutes. The melt was quickly removed at high temperature and poured onto a graphite mold preheated to 600℃. It was then pressed into shape using a steel plate and subsequently quickly transferred to an annealing furnace at 600℃ for about 8 hours. After natural cooling, the glass was annealed and crystallized in a high-temperature reactor at 850℃ for 10 hours, then naturally cooled, polished, cleaned, cut, and analyzed to obtain Li2Mg2Ge4O. 11 0.01Cr 3+ 0.02Ni 2+ Glass and ceramics.

[0039] Example 7

[0040] The raw materials were prepared according to the composition of Li2O-MgO-TiO2-Cr2O3-NiO, with Li2O content of 20% mol, MgO content of 38.8% mol, TiO2 content of 40% mol, Cr2O3 content of 0.4% mol, and NiO content of 0.8% mol. High-purity powder raw materials of Li2O, MgO, TiO2, Cr2O3, and NiO were accurately weighed and ground in an agate mortar for about 30 minutes to ensure thorough and uniform mixing. The mixture was then transferred to an alumina crucible and melted in an air-atmosphere high-temperature reactor at 1500℃ for 30 minutes. The melt was quickly removed at high temperature and poured onto a graphite mold preheated to 600℃. It was then pressed into shape using a steel plate and rapidly transferred to an annealing furnace at 600℃ for approximately 8 hours. After natural cooling, the glass was annealed and crystallized in a 900℃ high-temperature reactor for 10 hours, then naturally cooled, polished, cleaned, cut, and analyzed to obtain Li2Mg2Ge4O. 11 0.01Cr 3+ 0.02Ni 2+ Glass and ceramics.

[0041] Example 8

[0042] The raw materials were prepared according to the composition of Li2O-MgO-ZrO2-Cr2O3-NiO, wherein the content of Li2O was 20% mol, the content of MgO was 38.8% mol, the content of ZrO2 was 40% mol, the content of Cr2O3 was 0.4% mol, and the content of NiO was 0.8% mol. High-purity powder raw materials of Li2O, MgO, ZrO2, Cr2O3, and NiO were accurately weighed and ground in an agate mortar for about 30 minutes to ensure thorough and uniform mixing. The mixture was then transferred to an alumina crucible and melted in an air-atmosphere high-temperature reactor at 1650℃ for 30 minutes. The melt was then quickly removed at high temperature and poured onto a graphite mold preheated to 600℃. It was pressed into shape using a steel plate and then rapidly transferred to an annealing furnace at 600℃ for about 8 hours. After natural cooling, the glass was annealed and crystallized in a 900℃ high-temperature reactor for 10 hours, then naturally cooled, polished, cleaned, cut, and analyzed to obtain Li2Mg2Zr4O. 11 0.01Cr 3+ 0.02Ni 2+ Glass and ceramics.

[0043] Example 9

[0044] The raw materials were prepared according to the composition of Li₂O-MgO-SiO₂-NiO, with Li₂O content of 20% mol, MgO content of 39.2% mol, SiO₂ content of 40% mol, and NiO content of 0.8% mol. High-purity powder raw materials of Li₂O, MgO, SiO₂, and NiO were accurately weighed and ground in an agate mortar for about 30 minutes to ensure thorough and uniform mixing. The mixture was then transferred to an alumina crucible and melted at 1200℃ for 30 minutes in an air-atmosphere high-temperature reactor. The melt was quickly removed at high temperature and poured onto a graphite mold preheated to 600℃, pressed into shape with a steel plate, and then rapidly transferred to an annealing furnace at 600℃ for about 8 hours. After natural cooling, the resulting glass was annealed and crystallized in a high-temperature reactor at 750℃ for 10 hours, then allowed to cool naturally. After grinding, polishing, cleaning, and cutting, analysis and testing were performed to obtain Li₂Mg₂Si₄O. 11 0.02Ni 2+ Glass ceramics. The excitation and emission spectra of glass ceramics are as follows: Figure 5 As shown.

[0045] Example 10: LED Light Source

[0046] The glass-ceramic block obtained in Example 1 was cut into 1cm*1cm*1mm square slices, and both sides of the slices were polished before being packaged with a 460nm InGaN blue LED chip. This yielded a fluorescence-converting LED light source. The electroluminescence spectrum of the LED light source is as follows: Figure 6 As shown.

[0047] Comparative Example 1

[0048] The chemical formula of the near-infrared phosphor in this comparative example is Li₂Mg₂Si₄O₂ 11 0.01Cr 3+ According to the stoichiometric ratio of each element in the chemical formula, high-purity powder raw materials of Li₂O, MgO, SiO₂, and Cr₂O₃ were accurately weighed and ground in an agate mortar for about 30 minutes to ensure thorough and uniform mixing. The mixture was then transferred to an alumina crucible and reacted in a high-temperature furnace in an air atmosphere at 910℃ for 6 hours. After natural cooling, near-infrared phosphor Li₂Mg₂Si₄O₃ was obtained. 11 0.01Cr 3+ .

[0049] The phase composition of the samples in the examples and comparative examples was analyzed using X-ray powder diffraction (D8 advanced, Germany).

[0050] The sample synthesized by solid-state reaction method showed a homogeneous phase according to XRD analysis. The fluorescent glass-ceramic obtained after high-temperature melting and crystallization treatment contained some impurities, but these did not affect its luminescence properties. For example, the XRD diffraction pattern of the near-infrared fluorescent glass-ceramic prepared in Example 1 is shown below. Figure 1 As shown.

[0051] The excitation and emission spectra of the samples were measured using an OmniFluo960SP (Beijing Zhuolihan Optical Analytical Instruments Co., Ltd.) steady-state / transient fluorescence spectrometer. The excitation and emission spectra of the luminescent material in Example 1 are as follows: Figure 2 As shown, the excitation spectrum of this luminescent material contains three effective excitation bands, namely 400-500nm, 550-650nm and 650-750nm; it can be seen that the emission spectrum of this luminescent material covers 650-880nm, that is, it has near-infrared broadband emission performance. Figure 3 The emission spectra of Example 1 and Comparative Example 1 of this invention show that the luminescence intensity of the glass-ceramic material is significantly stronger than that of the powder material.

[0052] It should be understood that the above detailed description of the technical solutions of the present invention with reference to optimized embodiments is illustrative and not restrictive. It should not be considered that the specific implementation of the present invention is limited to this. For those skilled in the art, any modifications to the technical solutions described in the embodiments or equivalent substitutions of some technical features without departing from the concept of the present invention should be considered as falling within the scope of patent protection defined by the claims submitted by the present invention.

[0053] The above embodiments of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the implementation of the present invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A near-infrared luminescent glass-ceramic material, characterized in that, The crystal phase of the glass-ceramic material is Li2Mg2A4O. 11 :xCr 3+ ,yNi 2+ Wherein, element A is selected from one or more of Si, Ge, Ti, and Zr; Cr 3+ The sum is Ni 2+ The luminescent ions are 0% ≤ x ≤ 15% and 0% ≤ y ≤ 15%, where x and y are not both 0.

2. The method for preparing near-infrared luminescent glass-ceramic materials according to claim 1, characterized in that, The preparation method includes the following steps: 1) Prepare the raw materials according to the composition aLi2O-bMgO-cAO2-xCr2O3-yNiO, where 20≤a≤25, 28≤b≤40, c=40, 0%≤x≤15%, 0%≤y≤15%, where the contents of x and y are not both 0. Mix the raw materials and grind them evenly to obtain a raw material mixture. 2) The mixture obtained in step 1 is melted at high temperature, removed and shaped, cooled and annealed to obtain a glass precursor; 3) The glass precursor obtained in step 2 is subjected to crystallization and ceramicization in air atmosphere using an amorphous crystallization method. The crystallized sample is then post-processed to obtain the near-infrared glass ceramic.

3. The preparation method according to claim 2, characterized in that, In step 1), the grinding time is 5-60 minutes.

4. The preparation method according to claim 2, characterized in that, In step 2), the high-temperature melting is carried out in air or an inert atmosphere at a temperature of 1200-1500℃ for 0.2-8h; the cooling is carried out naturally in air; the annealing temperature is 650-850℃ and the annealing time is 0.5-48h.

5. The preparation method according to claim 2, characterized in that, In step 3), the amorphous crystallization method is as follows: the crystallization temperature is 650-1000℃ and the crystallization time is 1-24h; the post-treatment includes polishing with 320-grit, 600-grit, 1000-grit and 2000-grit sandpaper respectively, followed by polishing, cutting, washing and drying with polishing powder.

6. An LED light source, characterized in that, The LED light source includes a fluorescence conversion layer and an LED semiconductor chip or a laser light source, and the fluorescence conversion layer is placed on the LED semiconductor chip or the laser light source; wherein, the fluorescence conversion layer includes at least one near-infrared fluorescent glass-ceramic material as described in any one of claims 1 or 2; the LED semiconductor chip is selected from at least one of blue LED chips and red LED chips, and the laser light source is at least one of blue lasers or red lasers.

7. The LED light source according to claim 6, characterized in that, This light source can be used in biometrics, sensing, food inspection, medical testing, agricultural production, or bioimaging.

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