High-performance ultra-wideband composite fluorescent ceramic for hyperspectral imaging and preparation method thereof

Abstract

The application discloses a kind of high-performance ultra-wideband composite fluorescent ceramic for hyperspectral imaging and preparation method thereof.The composite fluorescent ceramic includes high thermal conductivity ceramic layer and fluorescent ceramic layer from bottom to top, high thermal conductivity ceramic layer is selected from one or more of Al2O3, BN, SiC, Si3N4, AlN, BeO, MgO;The chemical composition of fluorescent ceramic layer is 11MgO•22Al2O3·67SiO2-xCr2O3-yEu2O3, 0.001≤x≤0.01, 0.005≤y≤0.01.The composite fluorescent ceramic is prepared by glass melting, bonding sintering and glass crystallization steps.The fluorescent ceramic layer of the application is constructed by Eu 2+ →Cr 3+ Energy transfer transfer mechanism, efficient ET between Eu 2+ And Cr 3+ Ion can compensate Cr 3+ Emission loss at high temperature, still can maintain 86-94% fluorescent intensity at 473K.Under the excitation of 450-460nm blue light emitting diode, can emit wavelength at 500-1200nm ultra-wideband light emission.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of inorganic luminescent materials, and relates to a fluorescent ceramic, in particular to a high-performance ultra-wideband composite fluorescent ceramic for hyperspectral imaging and a preparation method thereof. BACKGROUND

[0002] As a new technology to replace traditional near-infrared light sources (such as halogen lamps), near-infrared phosphor-converted light-emitting diodes (PC-LEDs) have the advantages of low energy consumption, long service life, low heat release, etc., and show great potential in the fields of agriculture, food and biological imaging. However, the key material for near-infrared PC-LEDs, long-wave Cr 3+ activated near-infrared phosphors, are severely dependent on expensive Sc and In-based compounds. For example, LiScGeO4 is a typical long-wave near-infrared fluorescent material with a peak wavelength of 1120 nm and a half-peak width of 300 nm, and has a high penetration ability, which can realize high-sensitivity detection of opaque objects; (Li, Na)In2SbO6:Cr 3+ emits a peak wavelength of 1020 nm by replacing Li + with Na + , and the half-peak width increases from 225 nm to 285 nm, which has the advantage of avoiding "red rain". However, the low thermal stability, low thermal conductivity and high cost of LiScGeO4, (Li, Na)In2SbO6:Cr 3+ materials limit their practical application.

[0003] In addition, the characteristics of Cr 3+ doped near-infrared phosphors in the ultraviolet and visible light absorption bands make it impossible to achieve short-wavelength emission, ignoring the demand for super-wide visible-near-infrared luminescent materials for hyperspectral imaging, etc. Therefore, designing long-wave broadband Cr 3+ doped near-infrared phosphors and super-wide emission visible-near-infrared phosphors is still an important challenge. On the one hand, when designing long-wave broadband Cr 3+ doped near-infrared phosphors, the optical properties of Cr 3+ doping need to be considered, which are affected by the strength of the crystal field of the base, especially the crystal field splitting parameter Dq, which is strongly dependent on the bond length between the central ion and the ligand, the atomic number of the ligand and the coordination number. On the other hand, developing super-wide emission visible-near-infrared phosphors by co-doping rare earth and Cr 3+ ion activators in the matrix is a simple and feasible strategy, which can further realize efficient energy transfer without causing reabsorption energy loss due to mixing multiple phosphors, for example: Ca2LuZr2Al3O 12 :Ce 3+ , Cr 3+ , YAGG:Ce3+ Cr 3+ Ca2LuHf2Al3O 12 :Ce 3+ Cr 3+ and Y2BaAl4SiO 12 :Ce 3+ Cr 3+ The fluorescent materials exhibit super-wide visible-near infrared emission, which is due to the high efficiency energy transfer of Ce 3+ Cr 3+ in the garnet matrix. However, the narrow emission range and different excitation bands between the exciter and the sensitizer seriously hinder the application field of these fluorescent materials. SUMMARY

[0004] One of the purposes of the present application is to provide a high-performance super-wideband composite fluorescent ceramic for hyperspectral imaging.

[0005] To achieve the above purpose, the present application provides a high-performance super-wideband composite fluorescent ceramic for hyperspectral imaging, which comprises a high-thermal-conductivity ceramic layer and a fluorescent ceramic layer from bottom to top, the high-thermal-conductivity ceramic layer is selected from any one or more than one of Al2O3, BN, SiC, Si3N4, AlN, BeO, and MgO; the chemical composition of the fluorescent ceramic layer is 11MgO·22Al2O3·67SiO2-xCr2O3-yEu2O3, 0.001≤x≤0.01, 0.005≤y≤0.01. The high-thermal-conductivity ceramic layer serves as a substrate, has excellent anti-thermal-quenching effect, and has good ceramic heat dissipation; the coated fluorescent ceramic layer can realize visible-near infrared super-wideband luminescence.

[0006] Preferably, the thickness ratio of the fluorescent ceramic layer to the high-thermal-conductivity ceramic layer is 1:(1-2.5).

[0007] Preferably, the high-performance super-wideband composite fluorescent ceramic exhibits visible-near infrared super-wideband luminescence of 500-1200 nm under the excitation of a 450-460 nm blue light emitting diode. Its thermal conductivity is 24-28 Wm -1 K -1 and can still maintain 86-94% of the fluorescent intensity at 473 K.

[0008] The second purpose of the present application is to provide a preparation method of the above composite fluorescent ceramic, which has controllable preparation process and conditions, high repeatability, and is conducive to industrialization.

[0009] To achieve the above purpose, the present application further provides a preparation method of the above high-performance super-wideband composite fluorescent ceramic, which comprises the following steps:

[0010] (1) according to the chemical composition of the fluorescent ceramic layer 11MgO·22Al2O3·67SiO2-xCr2O3-yEu2O3, 0.001≤x≤0.01, 0.005≤y≤0.02, the raw materials of the fluorescent ceramic layer are weighed;

[0011] (2) the raw materials are placed in a ball mill tank for drum ball milling with anhydrous ethanol as a ball milling medium, and then after drying and grinding, the fluorescent layer mixed raw material powder is obtained;

[0012] (3) the ground fluorescent layer mixed raw material powder is melted at a high temperature of 1750-1840 DEG C for 10-90 min in an induction melting furnace, quenched and cooled, and ground to obtain a fluorescent layer precursor glass powder;

[0013] (4) the fluorescent layer precursor glass powder and 6-12 wt% PVB ethanol solution are mixed, ground in a mortar for 1-2 h, and then coated on the surface of the high thermal conductivity ceramic to obtain a composite fluorescent ceramic body;

[0014] (5) the composite fluorescent ceramic body is placed in a muffle furnace, after degassing, nucleated at 820-850 DEG C for 12-18 h, crystallized at 1020-1140 DEG C for 10-25 min, and naturally cooled to room temperature to obtain a composite fluorescent ceramic.

[0015] Preferably, in step (2), the drum ball milling speed is 180-240 r / min, and the ball milling time is 10-22 h.

[0016] Preferably, in step (4), the thickness ratio of the coating layer to the high thermal conductivity ceramic layer is 1:(1-10).

[0017] More preferably, in step (4), the thickness of the coating layer is 0.1-0.4 mm, and the thickness of the high thermal conductivity ceramic layer is 0.4-1 mm.

[0018] Preferably, in step (5), the degassing mechanism is degassing at 600-630 DEG C for 1-2 h.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] 1、 the present application adopts high thermal conductivity ceramic as a substrate, and the ceramic has good heat dissipation, and the thermal conductivity is maintained at 24-28 Wm -1 K -1 ;

[0021] 2、 the present application coats the fluorescent glass powder on the high thermal conductivity ceramic, and through low-temperature bonding sintering and crystallization of the glass powder, the high thermal conductivity ceramic layer and the fluorescent ceramic layer can be effectively compounded, and the process is simple, the repeatability is high, and it is beneficial to realize large-scale industrialization.

[0022] 3. The fluorescent ceramic layer of this invention is constructed by forming Eu in 11MgO·22Al2O3·67SiO2. 2+ →Cr 3+ Energy transfer mechanism (ET), Eu 2+ and Cr 3+ The efficient ET between ions can compensate for Cr 3+ Despite emission loss at high temperatures, it retains 86–94% of its fluorescence intensity at 473K. When excited by a 450–460nm blue light-emitting diode, it can emit ultra-wideband light with wavelengths in the range of 500–1200nm. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the composite fluorescent ceramic of the present invention;

[0024] Figure 2 The emission spectrum of the composite fluorescent ceramic prepared in Example 1 of this invention under 450 nm excitation;

[0025] Figure 3 The images show the temperature-dependent fluorescence spectra of the composite fluorescent ceramics prepared in Examples 1-4 of this invention. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] The structure of the composite fluorescent ceramic of this invention is as follows: Figure 1 As shown, the fluorescent ceramic consists of two parts. From bottom to top, the first layer is a high thermal conductivity ceramic layer, taking commercial Al2O3 ceramic as an example; the second layer is a fluorescent ceramic layer with the chemical composition 11MgO·22Al2O3·67SiO2-xCr2O3-yEu2O3, where 0.001≤x≤0.01 and 0.005≤y≤0.02. This composite fluorescent ceramic is prepared using sintering techniques such as glass melting, bonding sintering, and glass crystallization.

[0028] To prepare 20g of the target product, the raw material powder for the fluorescent ceramic layer was weighed, as shown in Table 1. The measurement methods used in the following examples are all conventional techniques in the art. The raw material powder and the high thermal conductivity Al2O3 ceramic are commercially available finished products, and will not be described further here.

[0029] Table 1 Ingredients list for the embodiment

[0030] MgO Al2O3 SiO2 Cr2O3 Eu2O3 Alcohol Example 1 4.08g 5.60g 10.51g 0.02g 0.10g 30ml Example 2 4.08g 5.60g 10.51g 0.08g 0.20g 35ml Example 3 4.08g 5.60g 10.51g 0.14g 0.30g 40ml Example 4 4.08g 5.60g 10.51g 0.20g 0.40g 45ml

[0031] Example 1:

[0032] A high-performance ultra-wideband composite fluorescent ceramic for hyperspectral imaging, from bottom to top, the first layer of high-thermal-conductivity ceramic layer is a commercial Al2O3 ceramic; the second layer is a fluorescent ceramic layer, and the chemical composition is 11MgO·22Al2O3·67SiO2-0.001Cr2O3-0.005Eu2O3.

[0033] The preparation method of the composite fluorescent ceramic, comprising the following steps:

[0034] (1) The raw material powders are weighed according to the stoichiometric ratio shown in Table 1, Example 1, and the raw materials are placed in a ball mill tank for drum ball milling with anhydrous ethanol as the ball milling medium, the speed is 180 r / min, the ball milling time is 10 h, and then the fluorescent layer mixed raw material powder is obtained after drying and grinding;

[0035] (2) The ground fluorescent layer mixed raw material powder is melted at a high temperature of 1750 DEG C for 90 min in an induction melting furnace, quenched and cooled, and then ground to obtain a precursor glass powder;

[0036] (3) The precursor glass powder and a 6wt% PVB ethanol solution are mixed, and the mixture is ground in a mortar for 1 h, and then coated on the surface of the high-thermal-conductivity ceramic, the thickness of the high-thermal-conductivity ceramic layer is 1 mm, and the thickness of the coating layer is 0.1 mm, to obtain a composite fluorescent ceramic body;

[0037] (4) The composite fluorescent ceramic body is placed in a muffle furnace, and the following steps are performed: 600 DEG C for 1 h for glue removal, 820 DEG C for 12 h for nucleation, and 1020 DEG C for 25 min for crystallization, and then naturally cooled to room temperature, to obtain a composite fluorescent ceramic.

[0038] The obtained composite fluorescent ceramic emits an ultra-wideband luminescence with a wavelength of 500-1200 nm after being packaged with a 450 nm blue laser, Figure 2 , and the thermal conductivity is 24 Wm -1 K -1 , and the fluorescent intensity can still maintain 86% at 473 K, Figure 3 .

[0039] Example 2:

[0040] A high-performance ultra-wideband composite fluorescent ceramic for hyperspectral imaging, from bottom to top, the first layer of high-thermal-conductivity ceramic layer is a commercial Al2O3 ceramic; the second layer is a fluorescent ceramic layer, and the chemical composition is 11MgO·22Al2O3·67SiO2-0.004Cr2O3-0.010Eu2O3.

[0041] The preparation method of the composite fluorescent ceramic, comprising the following steps:

[0042] (1) The raw material powders are weighed according to the stoichiometric ratio shown in Table 1 in Example 2, and the raw materials are placed in a ball mill tank with anhydrous ethanol as the ball milling medium, and drum-type ball milling is performed at a speed of 200 r / min for 14 h, followed by drying and grinding to obtain the fluorescent layer mixed raw material powder;

[0043] (2) The ground fluorescent layer mixed raw material powder is melted at a high temperature of 1780℃ for 60 min in an induction melting furnace, quenched and cooled, and ground to obtain a precursor glass powder;

[0044] (3) The precursor glass powder and an ethanol solution of 8wt% PVB are mixed and ground in a mortar for 1 h, and then coated on a high-thermal-conductivity ceramic surface after being fully mixed and uniformly distributed, to obtain a composite fluorescent ceramic body, wherein the thickness of the high-thermal-conductivity ceramic layer is 0.6 mm, and the thickness of the coating layer is 0.2 mm;

[0045] (4) The composite fluorescent ceramic body is placed in a muffle furnace, and the following steps are performed: degassing at 610℃ for 1 h, nucleation at 830℃ for 14 h, and crystallization at 1060℃ for 20 min, and then naturally cooling to room temperature, to obtain a composite fluorescent ceramic.

[0046] The obtained composite fluorescent ceramic emits super-wide-band luminescence with a wavelength of 500-1200 nm after being packaged with a 450 nm blue laser. The thermal conductivity of the composite fluorescent ceramic is 25.6 Wm -1 K -1 , and the fluorescent intensity can still maintain 88.6% at 473K, as shown in Figure 3 .

[0047] Example 3:

[0048] A high-performance super-wide-band composite fluorescent ceramic for hyperspectral imaging, from bottom to top, the first layer is a high-thermal-conductivity ceramic layer of commercial Al2O3 ceramic; and the second layer is a fluorescent ceramic layer with a chemical composition of 11MgO·22Al2O3·67SiO2-0.007Cr2O3-0.015Eu2O3.

[0049] The preparation method of the composite fluorescent ceramic comprises the following steps:

[0050] (1) The raw material powders are weighed according to the stoichiometric ratio shown in Table 1 in Example 3, and the raw materials are placed in a ball mill tank with anhydrous ethanol as the ball milling medium, and drum-type ball milling is performed at a speed of 220 r / min for 18 h, followed by drying and grinding to obtain the fluorescent layer mixed raw material powder;

[0051] (2) The ground fluorescent layer mixed raw material powder is melted at a high temperature of 1810℃ for 30 min in an induction melting furnace, quenched and cooled, and ground to obtain a precursor glass powder;

[0052] (3) The precursor glass powder and an ethanol solution of 10wt% PVB are mixed, and the mixture is ground in a grinding bowl for 2h to make it fully mixed and uniform, and then coated on the high-thermal-conductivity ceramic surface, with a thickness of the high-thermal-conductivity ceramic layer of 0.5mm and a thickness of the coating layer of 0.3mm, to obtain a composite fluorescent ceramic body;

[0053] (4) The composite fluorescent ceramic body is placed in a muffle furnace, and subjected to glue removal at 620℃ for 2h, nucleation at 840℃ for 16h, and crystallization at 1100℃ for 15min, and then naturally cooled to room temperature, to obtain a composite fluorescent ceramic.

[0054] The obtained composite fluorescent ceramic emits super-wide-band luminescence with a wavelength of 500-1200nm after being packaged with a blue laser with a wavelength of 450nm. The thermal conductivity of the composite fluorescent ceramic is 28Wm -1 K -1 , and the fluorescent intensity can still maintain 94% at 473K, as shown in Figure 3 .

[0055] Example 4:

[0056] A high-performance super-wide-band composite fluorescent ceramic for hyperspectral imaging, from bottom to top, the first layer is a high-thermal-conductivity ceramic layer of commercial Al2O3 ceramic; the second layer is a fluorescent ceramic layer, and the chemical composition is 11MgO·22Al2O3·67SiO2-0.01Cr2O3-0.020Eu2O3.

[0057] The preparation method of the composite fluorescent ceramic comprises the following steps:

[0058] (1) The raw material powders are weighed according to the stoichiometric ratio shown in Table 1 of Example 4, and anhydrous ethanol is used as a ball milling medium, the raw materials are placed in a ball milling tank for drum-type ball milling at a speed of 240r / min for 22h, and then dried and ground to obtain fluorescent layer mixed raw material powders;

[0059] (2) The ground fluorescent layer mixed raw material powders are melted at a high temperature of 1840℃ for 10min in an induction melting furnace, and then quenched and cooled, and ground to obtain precursor glass powders;

[0060] (3) The precursor glass powders and an ethanol solution of 12wt% PVB are mixed, and the mixture is ground in a grinding bowl for 2h to make it fully mixed and uniform, and then coated on the high-thermal-conductivity ceramic surface, with a thickness of the high-thermal-conductivity ceramic layer of 0.4mm and a thickness of the coating layer of 0.4mm, to obtain a composite fluorescent ceramic body;

[0061] (4) The composite fluorescent ceramic body is placed in a muffle furnace, and subjected to glue removal at 630℃ for 2h, nucleation at 850℃ for 18h, and crystallization at 1140℃ for 10min, and then naturally cooled to room temperature, to obtain a composite fluorescent ceramic.

[0062] The obtained composite fluorescent ceramic emits super wide band luminescence with wavelength of 500-1200 nm after being packaged with blue laser with wavelength of 450 nm. The thermal conductivity of the composite fluorescent ceramic is 26.5 Wm -1 K -1 At 473 K, the fluorescent intensity can still maintain 91%, like Figure 3 .

[0063] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited to this. Any modification, equivalent replacement and improvement within the technical range disclosed by the present application and within the spirit and principle of the present application should be covered within the protection scope of the present application.

Claims

1. A high performance ultra-wideband composite fluorescent ceramic for hyperspectral imaging, characterized in that, The composite fluorescent ceramic comprises a high-thermal-conductivity ceramic layer and a fluorescent ceramic layer from bottom to top, the high-thermal-conductivity ceramic layer is selected from any one or more than one of Al2O3, BN, SiC, Si3N4, AlN, BeO and MgO; the chemical composition of the fluorescent ceramic layer is 11MgO·22Al2O3·67SiO2-xCr2O3-yEu2O3, 0.001≤x≤0.01 and 0.005≤y≤0.01; The composite fluorescent ceramic is prepared by the following steps: (1) according to the chemical composition 11MgO·22Al2O3·67SiO2-xCr2O3-yEu2O3, 0.001≤x≤0.01 and 0.005≤y≤0.02 of the fluorescent ceramic layer, the raw materials of the fluorescent ceramic layer are weighed; (2) the raw materials are placed in a ball mill tank for drum-type ball milling with anhydrous ethanol as a ball milling medium, and then dried and ground to obtain a fluorescent layer mixed raw material powder; (3) the ground fluorescent layer mixed raw material powder is high-temperature melted at 1750-1840℃ for 10-90min in an induction melting furnace, quenched and cooled, and ground to obtain a fluorescent layer precursor glass powder; (4) the fluorescent layer precursor glass powder and an ethanol solution of 6-12wt% PVB are mixed, ground in a grinding bowl for 1-2h, and then coated on the surface of the high-thermal-conductivity ceramic to obtain a composite fluorescent ceramic body after fully mixing and uniformity; (5) the composite fluorescent ceramic body is placed in a muffle furnace, nucleated at 820-850℃ for 12-18h after degassing, crystallized at 1020-1140℃ for 10-25min, and naturally reduced to room temperature to obtain a composite fluorescent ceramic.

2. The high performance ultra-wideband composite fluorescent ceramic according to claim 1, wherein, In step (2), the drum-type ball milling speed is 180-240r / min, and the ball milling time is 10-22h.

3. The high performance ultra-wideband composite phosphor ceramic of claim 1, wherein, In step (4), the thickness ratio of the coating layer to the high-thermal-conductivity ceramic layer is 1:(1-10).

4. The high performance ultra-wideband composite phosphor ceramic of claim 3, wherein, In step (4), the thickness of the coating layer is 0.1-0.4mm, and the thickness of the high-thermal-conductivity ceramic layer is 0.4-1mm.

5. The high performance ultra-wideband composite phosphor ceramic of claim 1, wherein, In step (5), the degassing mechanism is degassing at 600-630℃ for 1-2h.

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