A non-stoichiometric long afterglow transparent ceramic and its preparation method

Abstract

This invention discloses a non-stoichiometric long afterglow transparent ceramic and its preparation method. The general chemical formula of the ceramic is: (RE 1‑x Ce x )3(Al 1‑y Cr y )2Ga 3+z O 12 RE is selected from Lu, Y, and Gd, and the values ​​of x, y, and z are in the range of: 0.001≤x≤0.005, 0.0005≤y≤0.02, and 0.01≤z≤0.15. This ceramic is prepared by vacuum sintering combined with hot isostatic pressing (HIP). Using garnet as the matrix, this invention employs matrix control methods and ion co-doping techniques to prepare a ceramic with a transmittance of 78–85%. The afterglow time is increased by 720–1080 minutes compared to Ce-doped long-afterglow transparent ceramics, by 180–300 minutes compared to ceramics without HIP sintering, and by 180–480 minutes compared to stoichiometric ceramics.

Description

Technical Field

[0001] This invention relates to the field of transparent ceramic preparation technology, specifically to a non-stoichiometric long afterglow transparent ceramic and its preparation method. Background Technology

[0002] The phenomenon where a material continues to emit light after it has stopped absorbing external excitation energy is called long-afterglow luminescence, and materials that can achieve long-afterglow luminescence are called long-afterglow materials. Visible light long-afterglow materials have been widely used as emergency indicator lights in public places, highways, airports, and dangerous areas. Especially during the 9 / 11 attacks, long-afterglow materials played a crucial role in emergency evacuation. SrAl2O4:Eu, with its excellent afterglow properties... 2+ ,Dy 3+ Long-afterglow powders have been commercialized, but their water resistance is poor, and their afterglow duration and brightness are prone to significant decay under high-temperature conditions, which limits their practical application.

[0003] Long-afterglow transparent ceramics possess advantages such as good water resistance, high and low temperature resistance, corrosion resistance, and excellent mechanical properties. Their high light transmittance allows for effective excitation throughout the bulk space, significantly enhancing the ceramic's carrier capture ability and luminescence uniformity. Furthermore, thanks to their unique "volume effect," the afterglow performance can be flexibly controlled by altering the ceramic thickness. Yttrium aluminum gallium garnet (Y3Al) 5-x Ga x O 12 (x=0,1,2,3,4) transparent ceramics are among the transparent ceramics with the greatest potential for long-afterglow luminescence. In the research of yttrium aluminum gallium garnet long-afterglow transparent ceramics, the Ueda research group at Kyoto University, Japan (XU J, UEDA J, KUROISHI K, et al. Fabrication of Ce...) 3+ -Cr 3+ Co-doped yttrium aluminum gallium garnet transparent ceramic phosphors with super long persistent luminescence[J].Scripta Mater,2015,102:47-50.) Y3Al2Ga3O was prepared by solid-state reaction combined with vacuum sintering. 12Ce,Cr, and a 2.1 mm thick ceramic exhibited an afterglow time of 846 min after 5 min of 460 nm blue light excitation. A 1.4 mm thick ceramic showed a transmittance of 72% at 800 nm. The raw material powders used in this process are of high purity and quality, but are difficult to source and expensive. Furthermore, there is no reliable solution to the volatilization problem of Ga under vacuum and high temperature, thus the preparation of this ceramic lacks reproducibility. (Liu Q, WANG WL, DAI ZF, et al. Fabrication and long persistent luminescence of Ce,Cr) 3+ -Cr 3+ Co-doped yttrium aluminum gallium garnet transparent ceramics[J]. J Rare Earth, 2022, 40(11): 1699-1705.) Different Ce materials were prepared using HIP sintering technology. 3+ Y3Al2Ga3O ion doping concentration 12 :Ce 3+ ,Cr 3+ Long afterglow transparent ceramics, of which Ce 3+ The initial afterglow brightness of a ceramic with a doping concentration of 0.2% after being excited by 365nm violet light for 5 minutes can reach 3614 mcd / m. 2 Under the same excitation conditions, the initial afterglow brightness of the ceramic annealed in air atmosphere is 4424 mcd / m². 2 The afterglow duration can reach 865 minutes. Air sintering effectively mitigates Ga volatilization, but the ceramic's transmittance at 800 nm is only 28%, resulting in poor performance. High-quality long-afterglow transparent ceramics, facing harsh environments, can maintain stable afterglow performance and extend their service life due to their excellent mechanical properties, corrosion resistance, and high-temperature resistance. Therefore, there is an urgent need in this field for a long-afterglow transparent ceramic with high transmittance and a long afterglow time. Summary of the Invention

[0004] The purpose of this invention is to provide a non-stoichiometric long-afterglow transparent ceramic with good light transmittance and long afterglow time.

[0005] Another objective of this invention is to provide a method for preparing the above-mentioned non-stoichiometric long afterglow transparent ceramic, which is easy to operate and can be industrialized.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] On one hand, the present invention provides a non-stoichiometric long afterglow transparent ceramic, the general chemical formula of which is:

[0008] (RE 1-x Ce x )3(Al 1-y Cr y )2Ga 3+z O 12 ,

[0009] RE is selected from Lu, Y, and Gd, and the values ​​of x, y, and z are: 0.001≤x≤0.005, 0.0005≤y≤0.02, and 0.01≤z≤0.15.

[0010] The transmittance of the ceramic can reach 78-85% at 800nm, the emission wavelength is 480-600nm, and the afterglow time is 15-30 hours.

[0011] On the other hand, the present invention also provides a method for preparing the above-mentioned non-stoichiometric long afterglow transparent ceramic, which employs vacuum sintering combined with hot isostatic pressing, specifically including the following steps:

[0012] (1) According to the chemical formula (RE) 1-x Ce x )3(Al 1-y Cr y )2Ga 3+z O 12 The stoichiometric ratio of each element is determined by weighing RE2O3, Al2O3, Ga2O3, CeO2, and Cr2O3 with a purity greater than 99.99% as raw material powders. The raw material powders, sintering aids, and ball milling media are mixed and ball-milled in a certain proportion to obtain a mixed slurry. Among them, RE is selected from Lu, Y, and Gd, with 0.001≤x≤0.005, 0.0005≤y≤0.02, and 0.01≤z≤0.15.

[0013] (2) The mixed slurry obtained in step (1) is placed in a drying oven to dry, and then the dried mixed powder is sieved and calcined in an air atmosphere in a muffle furnace.

[0014] (3) Place the calcined powder from step (2) into a mold and dry press it into shape, then perform cold isostatic pressing.

[0015] (4) Place the green blank obtained in step (3) into a vacuum furnace for sintering;

[0016] (5) The ceramic obtained in step (4) is subjected to hot isostatic pressing sintering, cooled to room temperature and then subjected to double-sided polishing to obtain the long afterglow transparent ceramic.

[0017] Preferably, in step (1), the ball milling speed is 170-250 r / min and the ball milling time is 10-16 h.

[0018] Preferably, in step (1), the sintering aid is composed of 0.5-1.2 wt.% tetraethyl orthosilicate or 0.03-0.1 wt.% magnesium oxide, the amount of sintering aid added is 0.1-1% of the total mass of the raw material powder, the ball milling medium is anhydrous ethanol, and the mass-volume ratio of the raw material powder to the ball milling medium is 1 g: (2-4) mL.

[0019] Preferably, in step (2), the drying time is 15 to 30 hours and the drying temperature is 80 to 90 degrees Celsius.

[0020] Preferably, in step (2), the mesh size of the sieve is 60 to 200 mesh.

[0021] Preferably, in step (2), the calcination temperature is 600-900℃ and the calcination time is 5-8h.

[0022] Preferably, in step (3), the cold isostatic pressing pressure is 150-200 MPa and the holding time is 200-400 s.

[0023] Preferably, in step (4), the sintering temperature is 1520–1750℃, the holding time is 8–24 h, and the sintering vacuum degree is not less than 10. -3 Pa.

[0024] Preferably, in step (5), the pressure of hot isostatic pressing sintering is 120-200 MPa, the sintering temperature is 1550-1780℃, the holding time is 2-4 h, and the heating rate is 1.5-3.0℃ / min.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The present invention uses garnet as matrix, adopts matrix control method, and combines ion co-doping method to prepare ceramics with a transmittance of 78-85% and an afterglow time of 720-1080 minutes compared with Ce ion single doping long afterglow transparent ceramics.

[0027] (2) The sintering method used in this invention is vacuum sintering combined with hot isostatic pressing. The inert gas in hot isostatic pressing is conducive to the generation of oxygen vacancies, which can improve the afterglow performance of the transparent ceramic. The afterglow time is increased by 180 to 300 minutes compared with ceramics that do not use HIP sintering.

[0028] (3) The present invention adopts a non-stoichiometric method. The appropriate increase of Ga effectively alleviates the volatilization under vacuum and high temperature, and improves the optical quality and afterglow time of the ceramic. The transmittance of the prepared ceramic is increased by 5-15% compared with the stoichiometric ceramic, and the afterglow time is increased by 180-480 minutes compared with the stoichiometric ceramic.

[0029] (4) The sintering aid used in this invention is tetraethyl orthosilicate. The appropriate amount of tetraethyl orthosilicate can effectively improve the densification of ceramics and play a role in regulating the valence state of transition metal ions Cr, thereby improving the afterglow performance of ceramics. The afterglow time of the prepared ceramics is 600 to 900 minutes longer than that of ceramics without tetraethyl orthosilicate. Attached Figure Description

[0030] Figure 1 The XRD pattern of the long afterglow transparent ceramic prepared in Example 4 of this invention.

[0031] Figure 2 The transmittance curves are for the long afterglow transparent ceramics prepared in Example 4 and Comparative Example 4 of this invention.

[0032] Figure 3 The afterglow emission spectrum of the long afterglow transparent ceramic prepared in Example 4 of this invention.

[0033] Figure 4 The afterglow decay curves are for the long afterglow transparent ceramics prepared in Example 4, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 of this invention. Detailed Implementation

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0035] Unless otherwise stated, all raw materials used in the following examples are commercially available products.

[0036] Example 1

[0037] (1) According to the chemical formula (Lu 0.999 Ce 0.001 )3(Al 0.9995 Cr 0.0005 )2Ga 3.05 O 12 100 grams of raw material powder were weighed according to the stoichiometric ratio of each element. Using 200 mL of anhydrous ethanol as the ball milling medium and 600 μL of tetraethyl orthosilicate as the sintering aid, the accurately weighed raw material powder was placed in a ball mill jar and ball milled at 170 r / min for 15 h to obtain a uniformly mixed slurry. The ball-milled slurry was placed in an oven at 80 °C and dried for 15 h. After passing through an 80-mesh sieve, it was placed in a muffle furnace and calcined at 800 °C for 8 h.

[0038] (2) The calcined powder was dry-pressed at 10MPa for 180s and then cold isostatically pressed at 150MPa for 360s to obtain a ceramic blank.

[0039] (3) The ceramic blank was placed in a vacuum furnace for sintering at a temperature of 1520℃ for 8 hours, with a vacuum degree of 10. -3 Pa;

[0040] (4) The ceramic obtained by vacuum sintering is placed in a hot isostatic pressing furnace for HIP sintering, wherein the argon pressure is 120MPa, the sintering temperature is 1550℃, the holding time is 120min, the heating rate is 1.5℃ / min, the cooling rate is 1.5℃ / min, and the ceramic is polished to 2mm on both sides to obtain the desired ceramic.

[0041] The resulting transparent ceramic has a transmittance of 78% at 800 nm and an afterglow time of up to 1080 minutes at 495 nm.

[0042] Example 2

[0043] (1) According to the chemical formula (Y 0.997 Ce 0.003 )3(Al 0.999 Cr 0.001 )2Ga 3.05 O 12 100 grams of raw material powder were weighed according to the stoichiometric ratio of each element. Using 220 mL of anhydrous ethanol as the ball milling medium and 650 μL of tetraethyl orthosilicate as the sintering aid, the accurately weighed raw material powder was placed in a ball mill jar and ball milled at 180 r / min for 12 h to obtain a uniformly mixed slurry. The ball-milled slurry was placed in an oven at 82 °C and dried for 16 h. After passing through an 80-mesh sieve, it was placed in a muffle furnace and calcined at 800 °C for 8 h.

[0044] (2) The calcined powder was dry-pressed at 20MPa for 90s and then cold isostatically pressed at 150MPa for 360s to obtain a ceramic blank.

[0045] (3) The ceramic blank was placed in a vacuum furnace for sintering at a temperature of 1560℃ for 10 hours, with a vacuum degree of 10. -3 Pa;

[0046] (4) The ceramic obtained by vacuum sintering is placed in a hot isostatic pressing furnace for HIP sintering, wherein the argon pressure is 140MPa, the sintering temperature is 1580℃, the holding time is 120min, the heating rate is 1.5℃ / min, the cooling rate is 1.5℃ / min, and the ceramic is polished to 2mm on both sides to obtain the desired ceramic.

[0047] The resulting transparent ceramic has a transmittance of 80% at 800 nm and an afterglow time of up to 1250 minutes at 515 nm.

[0048] Example 3

[0049] (1) According to the chemical formula (Gd 0.995 Ce 0.005 )3(Al 0.995 Cr 0.005 )2Ga 3.1 O 12 100 grams of raw material powder were weighed according to the stoichiometric ratio of each element. Using 200 mL of anhydrous ethanol as the ball milling medium and 700 μL of tetraethyl orthosilicate as the sintering aid, the accurately weighed raw material powder was placed in a ball mill jar and ball milled at 200 r / min for 10 h to obtain a uniformly mixed slurry. The ball-milled slurry was placed in an oven at 85 °C and dried for 17 h. After passing through an 80-mesh sieve, it was placed in a muffle furnace and calcined at 800 °C for 8 h.

[0050] (2) The calcined powder was dry-pressed at 20MPa for 90s and then cold isostatically pressed at 150MPa for 360s to obtain a ceramic blank.

[0051] (3) The ceramic blank was placed in a vacuum furnace for sintering at a temperature of 1580℃ for 10 hours, with a vacuum degree of 10. -3 Pa;

[0052] (4) The ceramic obtained by vacuum sintering is placed in a hot isostatic pressing furnace for HIP sintering, wherein the argon pressure is 150MPa, the sintering temperature is 1600℃, the holding time is 180min, the heating rate is 2.0℃ / min, the cooling rate is 2.0℃ / min, and the ceramic is polished to 2mm on both sides to obtain the desired ceramic.

[0053] The resulting transparent ceramic has a transmittance of 82% at 800 nm and an afterglow time of up to 1440 minutes at 550 nm.

[0054] Example 4

[0055] (1) According to the chemical formula (Y 0.995 Ce 0.005 )3(Al 0.995 Cr 0.005 )2Ga 3.15 O 12100 grams of raw material powder were weighed according to the stoichiometric ratio of each element. Using 200 mL of anhydrous ethanol as the ball milling medium and 720 μL of tetraethyl orthosilicate as the sintering aid, the accurately weighed raw material powder was placed in a ball mill jar and ball milled at 220 r / min for 12 h to obtain a uniformly mixed slurry. The ball-milled slurry was placed in an oven at 88 °C and dried for 18 h. After passing through an 80-mesh sieve, it was placed in a muffle furnace and calcined at 800 °C for 8 h.

[0056] (2) The calcined powder was dry-pressed at 20MPa for 90s and then cold isostatically pressed at 160MPa for 360s to obtain a ceramic blank.

[0057] (3) The ceramic blank was placed in a vacuum furnace for sintering at a temperature of 1600℃ for 10 hours, with a vacuum degree of 10. -3 Pa;

[0058] (4) The ceramic obtained by vacuum sintering is placed in a hot isostatic pressing furnace for HIP sintering, wherein the argon pressure is 150MPa, the sintering temperature is 1620℃, the holding time is 180min, the heating rate is 3℃ / min, the cooling rate is 3℃ / min, and the ceramic is polished to 2mm on both sides to obtain the desired ceramic.

[0059] Comparative Example 1

[0060] The preparation method of the ceramic is basically the same as that in Example 4, except that it is doped with Ce. 3+ The chemical formula is (Y 0.995 Ce 0.005 )3Al2Ga 3.15 O 12 .

[0061] Comparative Example 2

[0062] The preparation method of the ceramic is basically the same as that in Example 4, except that HIP sintering was not used.

[0063] Comparative Example 3

[0064] The preparation method of the ceramic is basically the same as that in Example 4, except that the sintering aid TEOS was not added.

[0065] Comparative Example 4

[0066] The preparation method of the ceramic is basically the same as that in Example 4, except that it is prepared according to the chemical formula (Y). 0.995 Ce 0.005 )3(Al 0.995 Cr 0.005 )2Ga3O 12 Weigh the raw material powder according to the stoichiometric ratio of each element.

[0067] Figure 1 The (Y) prepared in Example 4 of this invention 0.995 Ce 0.005 )3(Al 0.995 Cr 0.005 )2Ga 3.15 O 12 XRD pattern of long-afterglow transparent ceramic. The diffraction peaks of the prepared ceramic sample are consistent with the standard YAGG card PDF.

[0068] Figure 2 Prepared for Example 4 (Y) 0.995 Ce 0.005 )3(Al 0.995 Cr 0.005 )2Ga 3.15 O 12 Long-afterglow transparent ceramics and Comparative Example 4 (Y 0.995 Ce 0.005 )3(Al 0.995 Cr 0.005 )2Ga3O 12 The transmittance curves of long-afterglow transparent ceramics show that the former has a transmittance of 85% at 800nm, while the latter has a transmittance of only 70% at 800nm.

[0069] Figure 3 Prepared for Example 4 (Y) 0.995 Ce 0.005 )3(Al 0.995 Cr 0.005 )2Ga 3.15 O 12 The emission spectrum of long-afterglow transparent ceramics shows strong luminescence in the range of 480–600 nm, with a peak emission value around 515 nm.

[0070] Figure 4 To measure the afterglow decay curves of the long-afterglow transparent ceramics prepared in Example 4, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 using an afterglow meter, after stopping the excitation of the irradiation source (blue light 460nm), the (Y) ceramic prepared in Example 4 was... 0.995 Ce 0.005 )3(Al 0.995 Cr 0.005 )2Ga 3.15 O 12 Long-afterglow transparent ceramics have an afterglow time of up to 1900 minutes and an initial luminance of 6235 mcd / m². 2 Comparative Example 1 prepared (Y) 0.995 Ce 0.005 )3Al2Ga 3.15 O 12 The long-afterglow transparent ceramic has an afterglow time of 610 minutes and an initial luminance of 3820 mcd / m².2 Comparative Example 2 prepared (Y) 0.995 Ce 0.005 )3(Al 0.995 Cr 0.005 )2Ga 3.15 O 12 The long-afterglow transparent ceramic (without HIP sintering) has an afterglow time of 1650 minutes and an initial luminance of 5980 mcd / m². 2 Comparative Example 3 prepared (Y) 0.995 Ce 0.005 )3(Al 0.995 Cr 0.005 )2Ga 3.15 O 12 The long-afterglow transparent ceramic (without the sintering aid TEOS) has an afterglow time of 780 minutes and an initial luminance of 4386 mcd / m². 2 Comparative Example 4 prepared (Y) 0.995 Ce 0.005 )3(Al 0.995 Cr 0.005 )2Ga3O 12 The long-afterglow transparent ceramic has an afterglow time of 1580 minutes and an initial luminance of 5380 mcd / m². 2 .

[0071] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a non-stoichiometric long afterglow transparent ceramic, characterized in that, The general chemical formula of the ceramic is: (RE 1-x Ce x )3(Al 1-y Cr y )2Ga 3+z O 12 , wherein RE is selected from one of Lu, Y, Gd, x 、 y and z the value range of is: 0.001≤ x ≤0.005, 0.0005≤ y ≤0.02, 0.01≤ z ≤0.15; The vacuum sintering method combined with hot isostatic pressing comprises the following steps: (1) According to the chemical formula (RE) 1-x Ce x )3(Al 1-y Cr y )2Ga 3+z O 12 The stoichiometric ratio of each element in the mixture is determined by weighing RE2O3, Al2O3, Ga2O3, CeO2, and Cr2O3 with a purity greater than 99.99% as raw material powders. The raw material powders, sintering aids, and ball milling media are mixed in proportion and ball milled to obtain a mixed slurry. (2) drying the mixed slurry obtained in step (1) in a drying box, sieving the dried mixed powder, and calcining the sieved powder in a muffle furnace under air atmosphere; (3) dry-pressing the calcined powder obtained in step (2) into a mold, and then cold isostatic pressing; (4) sintering the green body obtained in step (3) in a vacuum furnace, the sintering temperature being 1520-1750°C, the holding time being 8-24 h, and the sintering vacuum degree being not less than 10 -3 Pa; (5) performing hot isostatic pressing sintering on the ceramic obtained in step (4), and then performing double-side polishing treatment after cooling to room temperature, to obtain the long-afterglow transparent ceramic, wherein the pressure of the hot isostatic pressing sintering is 120-200 MPa, the sintering temperature is 1550-1780℃, the holding time is 2-4 h, and the heating rate is 1.5-3.0℃ / min.

2. The method for preparing non-stoichiometric long afterglow transparent ceramic according to claim 1, characterized in that, In step (1), the ball milling speed is 170-250 r / min, and the ball milling time is 10-16 h.

3. The method for preparing non-stoichiometric long afterglow transparent ceramic according to claim 1, characterized in that, In step (1), the sintering aid is 0.5-1.2 wt.% of tetraethyl orthosilicate or 0.03-0.1 wt.% of magnesium oxide, the addition amount of the sintering aid is 0.1-1% of the total mass of the raw material powder, the ball milling medium is anhydrous ethanol, and the mass-volume ratio of the raw material powder to the ball milling medium is 1 g:(2-4) mL.

4. The method for preparing non-stoichiometric long afterglow transparent ceramic according to claim 1, characterized in that, In step (2), the drying time is 15-30 h, and the drying temperature is 80-90℃.

5. The method for preparing non-stoichiometric long afterglow transparent ceramic according to claim 1, characterized in that, In step (2), the mesh number of the sieve is 60-200.

6. The method of claim 1, wherein the non-stoichiometric long afterglow transparent ceramic is prepared by the steps of: In step (2), the calcining temperature is 600-900℃, and the calcining time is 5-8 h.

7. The method for preparing non-stoichiometric long afterglow transparent ceramic according to claim 1, characterized in that, In step (3), the holding pressure of the cold isostatic pressing is 150-200 MPa, and the holding time is 200-400 s.

Images