Fluorescent ceramic, method for preparing the same, and light emitting device

Abstract

The application discloses a fluorescent ceramic and a preparation method thereof and a light-emitting device, and belongs to the technical field of luminescent materials. Specifically, the fluorescent ceramic comprises a fluorescent ceramic substrate, the fluorescent ceramic substrate comprises a light-incident surface, a light-emitting surface and a side surface connecting the light-incident surface and the light-emitting surface, and the light-incident surface and the light-emitting surface are oppositely arranged; the side surface comprises a first region close to the light-emitting surface, the surface roughness of the first region is Ra1, and 100 nm <= Ra1 <= 500 nm is satisfied; the side surface further comprises a second region close to the light-incident surface, the surface roughness of the second region is Ra2, and 20 nm <= Ra2 <= 100 nm is satisfied; and the ratio of Ra1 / Ra2 satisfies 2 <= Ra1 / Ra2 <= 25. The application cooperatively controls the luminescent efficiency, the color temperature and the spatial light distribution of the high-performance fluorescent ceramic by designing the specific differential roughness of the light-incident surface, the light-emitting surface and the side surface of the fluorescent ceramic and the application of the fluorescent ceramic in solid-state lighting.

Description

Technical Field

[0001] This application belongs to the field of luminescent materials technology, specifically relating to a fluorescent ceramic, its preparation method, and a luminescent device. Background Technology

[0002] Fluorescent ceramics, as functional materials capable of light-to-light conversion under the excitation of blue light diodes or laser diodes, have become core light conversion components for high-power LED and laser lighting due to their excellent thermal stability, high luminous efficiency, and good mechanical properties. Their luminescent performance is influenced by various factors, including material composition, microstructure, ceramic thickness, and surface condition. Summary of the Invention

[0003] In view of this, this application provides a fluorescent ceramic, its preparation method and light-emitting device, which achieves high-performance fluorescent ceramics and their application in solid-state lighting by designing specific differentiated roughness on the light-incident surface, light-emitting surface and side surface of the fluorescent ceramic to synergistically control luminous efficiency, color temperature and spatial light distribution.

[0004] In a first aspect, this application provides a fluorescent ceramic, including a fluorescent ceramic substrate. The fluorescent ceramic substrate includes an incident surface, an emitting surface, and a side surface connecting the incident surface and the emitting surface, with the incident surface and the emitting surface disposed opposite to each other. The side surface includes a first region near the emitting surface, the surface of which has a surface roughness of Ra1, satisfying 100 nm ≤ Ra1 ≤ 500 nm. The side surface also includes a second region near the incident surface, the surface of which has a surface roughness of Ra2, satisfying 20 nm ≤ Ra2 ≤ 100 nm. The ratio of Ra1 / Ra2 satisfies 2 ≤ Ra1 / Ra2 ≤ 25.

[0005] This application modifies the surface roughness of the side surfaces. The second region near the incident light surface has a lower surface roughness, and the light is mainly incident blue light, which can form specular reflection or low-loss reflection of the light source, concentrating the light source inside the fluorescent ceramic and transmitting it towards the light emitting surface, reducing the side leakage loss of the excitation light source. The first region near the light emitting surface has a higher surface roughness, and the light is mainly converted yellow light with strong waveguide propagation. The high surface roughness can convert a large number of fluorescent photons that are reflected back to the side due to total internal reflection of the light emitting surface into diffuse reflection, repositioning the light direction so that it returns to the light emitting surface with a smaller incident angle and successfully escapes, reducing light leakage and suppressing the side yellow light effect. Furthermore, by limiting the ratio of the two regions to the above range, the light source is absorbed to the maximum extent, reducing light source loss and light leakage, and improving the light extraction efficiency and luminous efficiency of the fluorescent ceramic.

[0006] In some embodiments, the surface roughness of the side surface and the thickness of the fluorescent ceramic substrate satisfy a linear or stepwise increasing relationship, and the surface roughness change rate is controlled within 5 nm / mm to 50 nm / mm.

[0007] This application further limits the surface roughness variation on the side of the fluorescent ceramic, making the light source propagate smoothly on the side, reducing local hot spots or dark areas caused by abrupt changes in side roughness, which is conducive to forming gradual optical boundary conditions. This allows the reflection characteristics of the side to smoothly transition from "waveguide constraint" to "diffuse reflection extraction", reducing light loss and improving the light extraction efficiency and luminous efficiency of the fluorescent ceramic.

[0008] In some embodiments, the surface roughness of the light-incident surface is Ra3, satisfying 1 nm ≤ Ra3 ≤ 20 nm, preferably 1 nm ≤ Ra3 ≤ 10 nm; the surface roughness of the light-exiting surface is Ra4, satisfying 200 nm ≤ Ra4 ≤ 800 nm, preferably 300 nm ≤ Ra4 ≤ 600 nm; and the ratio of Ra4 / Ra3 satisfies 10 ≤ Ra4 / Ra3 ≤ 800, preferably 30 ≤ Ra4 / Ra3 ≤ 600.

[0009] This invention sets the roughness of the incident and emitting surfaces of the fluorescent ceramic within the aforementioned range. The highly smooth incident surface minimizes reflection and scattering losses of the blue light excitation source at the incident interface, ensuring efficient coupling of the excitation source into the ceramic in a collimated or focused state, while avoiding heat generation caused by incident light scattering due to surface unevenness. The highly rough emitting surface design maximizes light extraction by utilizing surface microstructure, while effectively breaking the total internal reflection critical angle limitation between the fluorescent ceramic and air interface. By controlling the ratio of the emitting to the incident surface within the aforementioned range, light loss is further reduced, improving the light extraction and luminous efficiency of the fluorescent ceramic.

[0010] In some embodiments, the material of the fluorescent ceramic substrate includes one or more of Ce:YAG transparent ceramic, Ce:YAG-Al2O3 composite phase fluorescent ceramic, or Ce:YAG fluorescent ceramic.

[0011] Secondly, this application also provides a method for preparing the above-mentioned fluorescent ceramic, comprising the following steps: (1) Provide fluorescent ceramic blanks or pre-sintered ceramic sheets, and vacuum sinter them to obtain dense fluorescent ceramic substrates; (2) The light-incident surface of the fluorescent ceramic substrate obtained in step (1) is precisely polished so that its surface roughness Ra3 is controlled at 1 nm~20 nm. (3) The light-emitting surface of the fluorescent ceramic substrate after step (2) is subjected to a first roughening treatment so that its surface roughness Ra4 reaches 200 nm~800 nm; (4) The side surface of the fluorescent ceramic substrate after step (3) is subjected to gradient roughening treatment so that the side surface forms a roughness gradient structure along the thickness direction of the fluorescent ceramic substrate. The surface roughness Ra1 of the first side surface is controlled at 100 nm to 500 nm, and the surface roughness Ra2 of the second side surface is controlled at 20 nm to 100 nm.

[0012] In some embodiments, the vacuum sintering process in step (1) is carried out at a sintering temperature of 1600℃~1800℃, a holding time of 4 hours~20 hours, and a vacuum degree ≤10. -3 Pa.

[0013] In some embodiments, the precision polishing process in step (2) uses diamond polishing paste or cerium oxide polishing liquid, and uses polishing powder of different particle sizes to perform multi-stage polishing in sequence, so that the surface roughness Ra3 of the light-receiving surface is controlled at 1 nm to 20 nm.

[0014] In some embodiments, the first roughening process in step (3) is selected from one or more of mechanical grinding, chemical etching, laser etching or plasma etching.

[0015] In some embodiments, when chemical etching is used, the etching solution is phosphoric acid or a mixture of phosphoric acid and sulfuric acid, the etching temperature is 100°C to 300°C, and the etching time is 1 min to 60 min.

[0016] In some implementations, the gradient roughening process in step (4) employs either a partitioned stepwise etching method or a dynamic immersion etching method.

[0017] In some implementations, the partitioned step-by-step etching method includes dividing the side of the fluorescent ceramic substrate into 2 to 5 regions, and performing multi-step etching from the second region to the first region by increasing the etching time or increasing the etching solution concentration.

[0018] In some embodiments, the dynamic immersion etching method includes gradually immersing a fluorescent ceramic substrate in an etching solution at a speed of 0.5 mm / min to 5 mm / min, with the immersion direction from the light-emitting surface to the light-receiving surface. As the immersion depth increases, different regions on the side have different residence times in the etching solution: the first region (closest to the light-emitting surface) has the longest residence time, and the second region (closest to the light-receiving surface) has the shortest residence time. By controlling the immersion speed and depth, a gradient change in side roughness is achieved from the first region to the second region. This method can achieve a continuous gradient change, resulting in a more uniform roughness transition.

[0019] In some embodiments, steps (2) and (3) further include a step of shielding and protecting the side surface, that is, during the roughening process of the light-emitting surface, a corrosion-resistant mask is used to protect the side surface. After the roughening of the light-emitting surface is completed, the mask is removed and the gradient roughening process of the side surface is carried out.

[0020] In some embodiments, step (4) further includes a step of shielding and protecting the light-incident surface and the light-exit surface, that is, during the gradient roughening process on the side, a corrosion-resistant mask is used to protect the light-incident surface and the light-exit surface, and the mask is removed after the gradient roughening on the side is completed.

[0021] In some embodiments, the preparation method further includes step (5) annealing: the fluorescent ceramic substrate after step (4) is annealed in air or oxygen atmosphere at a temperature of 800°C to 1400°C for 2 to 10 hours.

[0022] By adding annealing treatment, residual surface stress introduced during machining or etching can be eliminated, and surface lattice defects caused by etching can be repaired, thereby improving the luminescence efficiency of the fluorescent ceramic surface layer.

[0023] Thirdly, this application also provides a light-emitting device, including a blue light excitation source and the above-described fluorescent ceramic or the fluorescent ceramic prepared by the above-described preparation method, wherein the light incident surface of the fluorescent ceramic is disposed facing the blue light excitation source.

[0024] In some embodiments, an optical coupling layer or antireflection film is also provided between the light incident surface and the blue light excitation source. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the cross-sectional structure of the fluorescent ceramic provided in Embodiment 1 of this application; wherein, 100 is the fluorescent ceramic substrate, 101 is the light-emitting surface, 102 is the light-incident surface, 103 is the side surface, and the arrow direction indicates the light propagation path; Figure 2 This is a partially enlarged schematic diagram of the side gradient roughness structure of the fluorescent ceramic provided in Embodiment 1 of this application; The surface roughness shows a gradient along the thickness direction (Z direction), with the top roughness being greater than the bottom roughness.

[0027] Figure 3This is a schematic diagram of the light-emitting surface roughening treatment in the fluorescent ceramic preparation method provided in Example 1 of this application; Figure 4 This is a schematic diagram of the side gradient roughening treatment in the fluorescent ceramic preparation method provided in Example 1 of this application; Figure 5 This is a schematic diagram of the structure of the fluorescent ceramic with an asymmetric partitioned gradient roughness structure provided in Embodiment 1 of this application; Figure 6 This is a comparison curve of the luminous efficiency of Example 1, Comparative Example 1 (fully polished), and Comparative Example 2 (only the light-emitting surface is roughened) of this application; where the horizontal axis is the excitation current (mA) and the vertical axis is the luminous efficiency (lm / W). Figure 7 Different angular color coordinate offsets for Embodiment 1 of this application; Figure 8 The color coordinate offsets at different angles are shown in Comparative Example 1 of this application. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0029] In this application, the "light-incident surface" of fluorescent ceramics refers to the optical incident end face of the fluorescent ceramic substrate used to receive external excitation light source (such as blue laser or LED light) and allow the excitation light to enter the ceramic body.

[0030] In this application, the "light-emitting surface" of fluorescent ceramic refers to the optical emitting end face of the fluorescent ceramic substrate that is disposed opposite to the incident surface and is used to export the fluorescence generated inside the ceramic after wavelength conversion and the unabsorbed residual excitation light to form an illumination beam.

[0031] In this application, the "side surface" of a fluorescent ceramic refers to the circumferential surface that connects the incident and emitted light surfaces and surrounds the periphery of the fluorescent ceramic substrate in a direction other than the principal optical axis. In typical sheet-like or bulk fluorescent converters, the side surface is the boundary of thickness.

[0032] The inventors discovered that existing research primarily focuses on the impact of roughness on a single surface of the light-emitting or light-receiving surface of fluorescent ceramics. While some studies mention differentiated designs for the light-receiving and light-receiving surfaces, they do not consider the synergistic effect of roughness on the three surfaces (light-receiving, light-receiving, and side surfaces). Although existing patents involve side corrosion, they only perform overall uniform roughening on the side surfaces. In reality, when light propagates within the ceramic, the light field distribution varies significantly at different heights along the thickness direction: the area near the light-receiving surface is dominated by blue light, while the area near the light-receiving surface is dominated by converted yellow light. Therefore, uniform roughening of the side surfaces cannot specifically control the scattering behavior of different wavelengths of light. Furthermore, while existing technologies pursue high light extraction efficiency, they often struggle to precisely control color temperature and spatial light distribution. Excessive roughness, while improving light extraction efficiency, may lead to increased blue light backscattering and color temperature drift, limiting the application of fluorescent ceramics in high-quality lighting applications.

[0033] To overcome the problems existing in the prior art, this application provides a fluorescent ceramic, including a fluorescent ceramic substrate. The fluorescent ceramic substrate includes an incident surface, an emitting surface, and a side surface connecting the incident surface and the emitting surface, with the incident surface and the emitting surface disposed opposite to each other. The side surface includes a first region near the emitting surface, with a surface roughness of Ra1, satisfying 100 nm ≤ Ra1 ≤ 500 nm. The side surface also includes a second region near the incident surface, with a surface roughness of Ra2, satisfying 20 nm ≤ Ra2 ≤ 100 nm. The ratio of Ra1 / Ra2 satisfies 2 ≤ Ra1 / Ra2 ≤ 25.

[0034] For example, Ra1 is a range of 100 nm, 123 nm, 149 nm, 178 nm, 220 nm, 250 nm, 260 nm, 297 nm, 316 nm, 359 nm, 379 nm, 422 nm, 441 nm, 481 nm, 500 nm or any two of the above values; Ra2 is a range of 20 nm, 27 nm, 35 nm, 39 nm, 50 nm, 51 nm, 60 nm, 67 nm, 73 nm, 76 nm, 85 nm, 92 nm, 97 nm, 100 nm or any two of the above values; Ra1 / Ra2 is a range of 2, 3.3, 3.8, 7.3, 7.5, 10.2, 11.0, 13.7, 15.3, 17.5, 18.7, 20.0, 22.8, 23.5, 25 or any two of the above values.

[0035] This application modifies the roughness of the side surfaces. The second region near the incident light surface has a lower roughness, and the light is mainly incident blue light, which can form specular reflection or low-loss reflection of the light source, concentrating the light source inside the fluorescent ceramic and transmitting it towards the light emitting surface, reducing the side leakage loss of the excitation light source. The first region near the light emitting surface has a higher roughness, and the light is mainly converted into yellow light with strong waveguide propagation. The high roughness can convert a large number of fluorescent photons reflected back to the side due to total internal reflection of the light emitting surface into diffuse reflection, repositioning the light direction so that it returns to the light emitting surface with a smaller incident angle and successfully escapes, reducing light leakage and suppressing the side yellow light effect. Furthermore, by limiting the ratio of the two regions to the above range, the light source is absorbed to the maximum extent, reducing light source loss and light leakage, and improving the light extraction efficiency and luminous efficiency of the fluorescent ceramic.

[0036] In some embodiments, the surface roughness of the side surface and the thickness of the fluorescent ceramic substrate satisfy a linear or stepwise increasing relationship, and the surface roughness change rate is controlled within 5 nm / mm to 50 nm / mm.

[0037] For example, the surface roughness variation rate is a range of 5 nm / mm, 8 nm / mm, 11 nm / mm, 15 nm / mm, 16 nm / mm, 21 nm / mm, 25 nm / mm, 28 nm / mm, 30 nm / mm, 36 nm / mm, 37 nm / mm, 40 nm / mm, 43 nm / mm, 49 nm / mm, 50 nm / mm, or any two of the above values.

[0038] This application further limits the surface roughness variation on the side of the fluorescent ceramic, making the light source propagate smoothly on the side, reducing local hot spots or dark areas caused by abrupt changes in surface roughness, which is conducive to forming gradual optical boundary conditions. This allows the reflection characteristics of the side to smoothly transition from "waveguide constraint" to "diffuse reflection extraction", reducing light loss and improving the light extraction efficiency and luminous efficiency of the fluorescent ceramic.

[0039] In some embodiments, the surface roughness of the light-incident surface is Ra3, satisfying 1 nm ≤ Ra3 ≤ 20 nm, preferably 1 nm ≤ Ra3 ≤ 10 nm; the surface roughness of the light-exiting surface is Ra4, satisfying 200 nm ≤ Ra4 ≤ 800 nm, preferably 300 nm ≤ Ra4 ≤ 600 nm; and the ratio of Ra4 / Ra3 satisfies 10 ≤ Ra4 / Ra3 ≤ 800, preferably 30 ≤ Ra4 / Ra3 ≤ 600.

[0040] For example, Ra3 is a range of 1 nm, 3 nm, 5 nm, 6 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 15 nm, 17 nm, 18 nm, 19 nm, 20 nm or any two of the above values; Ra4 is a range of 200 nm, 209 nm, 284 nm, 300 nm, 320 nm, 340 nm, 404 nm, 464 nm, 482 nm, 567 nm, 589 nm, 600 nm, 651 nm, 679 nm, 734 nm, 794 nm, 800 nm or any two of the above values; Ra4 / Ra3 is a range of 10, 30, 59, 84, 145, 211, 282, 327, 406, 486, 547, 583, 600, 657, 726, 758, 800 or any two of the above values.

[0041] This invention sets the surface roughness of the incident and emitting surfaces of the fluorescent ceramic within the aforementioned range. The high-smoothness incident surface minimizes reflection and scattering losses of the blue light excitation source at the incident interface, ensuring efficient coupling of the excitation source into the ceramic in a collimated or focused state, while avoiding heat generation caused by incident light scattering due to surface unevenness. The high-surface-roughness emitting surface design maximizes light extraction by utilizing surface microstructure, while effectively breaking the total internal reflection critical angle limitation between the fluorescent ceramic and air interface. By controlling the ratio of the emitting surface to the incident surface within the aforementioned range, light loss is further reduced, improving the light extraction efficiency and luminous efficiency of the fluorescent ceramic.

[0042] In some embodiments, the material of the fluorescent ceramic substrate includes one or more of Ce:YAG transparent ceramic, Ce:YAG-Al2O3 composite phase fluorescent ceramic, or Ce:YAG fluorescent ceramic.

[0043] It should be noted that, in this application, fluorescent ceramics refer to a class of materials that are doped with rare-earth luminescent ions (especially Ce). 3 + yttrium aluminum garnet (Y3Al5O) 12 Ce:YAG (Ce:YAG for short) crystalline phase is a polycrystalline or transparent inorganic non-metallic luminescent material prepared through ceramic processes such as high-temperature solid-state reaction and vacuum sintering, using Ce:YAG as the main matrix. In this application, the material of the fluorescent ceramic substrate includes one or more of Ce:YAG transparent ceramic, Ce:YAG-Al2O3 composite phase fluorescent ceramic, or Ce:YAG fluorescent ceramic. Specifically, Ce:YAG transparent ceramic refers to a material with Ce:YAG as the main matrix. 3+Ions are doped into the YAG lattice as activators, and after densification sintering and subsequent treatment, a transparent polycrystalline ceramic with extremely high theoretical density, extremely low internal porosity, and high transmittance in the visible light band is achieved. Ce:YAG-Al2O3 composite fluorescent ceramics refer to composite ceramic materials formed by introducing a second phase Al2O3 (alumina) grains into the Ce:YAG matrix. The Al2O3 phase is dispersed as a scattering medium with high thermal conductivity and low refractive index to regulate the light transmission path and improve the thermomechanical properties of the ceramic body. Ce:YAG fluorescent ceramics refer to fluorescent ceramic materials with Ce:YAG as the main crystalline phase, covering Ce:YAG ceramic bodies that have not specifically introduced second phase scattering particles or have not fully achieved optical transparency.

[0044] Secondly, this application also provides a method for preparing the above-mentioned fluorescent ceramic, comprising the following steps: (1) Provide fluorescent ceramic blanks or pre-sintered ceramic sheets, and perform vacuum sintering treatment on them to obtain dense fluorescent ceramic substrates; (2) The light-incident surface of the fluorescent ceramic substrate obtained in step (1) is precisely polished so that its surface roughness Ra3 is controlled at 1 nm~20 nm. (3) The light-emitting surface of the fluorescent ceramic substrate after step (2) is subjected to a first roughening treatment so that its surface roughness Ra4 reaches 200 nm~800 nm; (4) The side surface of the fluorescent ceramic substrate after step (3) is subjected to gradient roughening treatment so that the side surface forms a surface roughness gradient structure along the thickness direction of the fluorescent ceramic substrate, wherein the surface roughness Ra1 of the first region is controlled at 100 nm to 500 nm, and the surface roughness Ra2 of the second region is controlled at 20 nm to 100 nm.

[0045] In some embodiments, the vacuum sintering process in step (1) is carried out at a sintering temperature of 1600℃~1800℃, a holding time of 4 hours~20 hours, and a vacuum degree ≤10. -3 Pa.

[0046] For example, the sintering temperature is 1600℃, 1603℃, 1621℃, 1636℃, 1653℃, 1668℃, 1687℃, 1700℃, 1719℃, 1728℃, 1744℃, 1754℃, 1778℃, 1800℃ or any two of the above values; the holding time is 4 hours, 5 hours, 6 hours, 8 hours, 9 hours, 11 hours, 12 hours, 13 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours or any two of the above values.

[0047] In some embodiments, the precision polishing process in step (2) uses diamond polishing paste or cerium oxide polishing liquid, and uses polishing powder of different particle sizes to perform multi-stage polishing in sequence, so that the surface roughness Ra3 of the light-receiving surface is finally controlled at 1 nm to 20 nm.

[0048] In some embodiments, the first roughening process in step (3) is selected from one or more of mechanical grinding, chemical etching, laser etching or plasma etching.

[0049] In some embodiments, when chemical etching is used, the etching solution is phosphoric acid or a mixture of phosphoric acid and sulfuric acid, the etching temperature is 100°C to 300°C, and the etching time is 1 min to 60 min.

[0050] For example, the corrosion temperature is 100℃, 101℃, 117℃, 137℃, 151℃, 173℃, 178℃, 193℃, 211℃, 238℃, 240℃, 263℃, 275℃, 287℃, 300℃ or any two of the above values; the corrosion time is 1 min, 5 min, 6 min, 11 min, 15 min, 23 min, 28 min, 32 min, 37 min, 40 min, 46 min, 47 min, 52 min, 59 min, 60 min or any two of the above values.

[0051] In some embodiments, the gradient coarsening process in step (4) employs either a partitioned stepwise corrosion method or a dynamic immersion corrosion method.

[0052] In some embodiments, the partitioned step-by-step etching method includes: dividing the side of the fluorescent ceramic substrate into 2 to 5 regions, and performing multi-step etching from the second region to the first region by increasing the etching time or increasing the etching solution concentration.

[0053] For example, the side of the fluorescent ceramic substrate is divided into a bottom region T1 (near the light-incident surface), a middle region T2, and a top region T3 (near the light-emitting surface). Etching is performed at etching times t1, t2, and t3, respectively, with t1 < t2 < t3. The gradient change of surface roughness is achieved by controlling the etching degree of each region.

[0054] In some embodiments, the dynamic immersion etching method includes: gradually immersing a fluorescent ceramic substrate into an etching solution at a speed of 0.5 mm / min to 5 mm / min, with the immersion direction from the light-emitting surface to the light-receiving surface. As the immersion depth increases, different regions on the side surface have different residence times in the etching solution: the first region near the light-emitting surface has the longest residence time, and the second region near the light-receiving surface has the shortest residence time. By controlling the immersion speed and immersion depth, a gradient change in the surface roughness of the side surface is achieved from the first region to the second region. This method can achieve a continuous gradient change, resulting in a more uniform transition of surface roughness.

[0055] For example, the immersion rate in the corrosive solution is 0.5 mm / min, 0.7 mm / min, 1.1 mm / min, 1.3 mm / min, 1.6 mm / min, 2.0 mm / min, 2.3 mm / min, 2.8 mm / min, 3.1 mm / min, 3.4 mm / min, 3.6 mm / min, 4.0 mm / min, 4.5 mm / min, 4.8 mm / min, 5 mm / min, or a range of any two of the above values.

[0056] In some embodiments, steps (2) and (3) further include a step of shielding and protecting the side surface, that is, during the roughening process of the light-emitting surface, a corrosion-resistant mask is used to protect the side surface, and after the roughening of the light-emitting surface is completed, the mask is removed, and then the gradient roughening process of the side surface is performed.

[0057] In some embodiments, step (4) further includes a step of shielding and protecting the light-incident surface and the light-exit surface, that is, during the gradient roughening process on the side, a corrosion-resistant mask is used to protect the light-incident surface and the light-exit surface, and the mask is removed after the gradient roughening on the side is completed.

[0058] In some embodiments, the corrosion-resistant mask includes photoresist or polytetrafluoroethylene film.

[0059] In some embodiments, the preparation method further includes step (5) annealing: the fluorescent ceramic substrate after step (4) is annealed in air or oxygen atmosphere at a temperature of 800°C to 1400°C for 2 to 10 hours.

[0060] For example, the annealing temperature is 800℃, 825℃, 884℃, 919℃, 983℃, 987℃, 1033℃, 1079℃, 1144℃, 1203℃, 1229℃, 1275℃, 1325℃, 1377℃, 1400℃ or any two of the above values; the annealing time is 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours or any two of the above values.

[0061] By adding annealing treatment, residual surface stress introduced during machining or etching can be eliminated, and surface lattice defects caused by etching can be repaired, thereby improving the luminescence efficiency of the fluorescent ceramic surface layer.

[0062] Thirdly, this application also provides a light-emitting device, including a blue light excitation source and the above-described fluorescent ceramic or the fluorescent ceramic prepared by the above-described preparation method, wherein the light incident surface of the fluorescent ceramic is disposed facing the blue light excitation source.

[0063] In some embodiments, an optical coupling layer or antireflection film is further disposed between the light incident surface and the blue light excitation source.

[0064] Measurement methods The physical properties mentioned in this application can be measured using the following methods, and the physical properties in the following embodiments and comparative examples are measured using the following methods.

[0065] Surface roughness testing: Non-contact three-dimensional optical profilometer (or contact surface roughness profilometer) was used for testing, and the arithmetic mean deviation Ra of the profile was used as the evaluation parameter in accordance with GB / T 1031-2009. At least three different locations were selected for measurement for each sample, and the arithmetic mean was taken as the final result.

[0066] Color temperature (correlated color temperature) test: The colorimeter method or integrating sphere spectroscopy method is used for determination. The fluorescent ceramic sample is placed under a standard excitation light source (blue LD or LED), and the emission spectrum of the sample is collected using a spectroradiometer or colorimeter. The chromaticity coordinates (x, y) are calculated, and the correlated color temperature (CCT) value is calculated using the blackbody locus interpolation method according to the CIE 1931 colorimetric system. The color temperature measurement method is performed according to the specifications in GB / T 7922-2008 "Methods for Measurement of Color of Lighting Sources" or GB / T 4070-1996 "Test Methods for Performance of Phosphors".

[0067] Light intensity distribution uniformity test: The measurement is performed using an imaging luminance meter method or a multi-point illuminance scanning method. The fluorescent ceramic sample is placed under a standard excitation light source. A two-dimensional luminance distribution image of the sample's emitting surface is acquired using an imaging luminance meter, or the illuminance distribution of the sample's emitting surface is scanned point-by-point using a two-dimensional scanning platform equipped with an illuminance probe. The uniformity of light intensity distribution is evaluated by calculating the deviation between each measurement point and the average value. For fluorescent ceramics used in laser lighting, the illuminance instability index is evaluated according to T / CI 073-2022 "Test Methods for Optical Properties of Rare Earth Fluorescent Ceramics for Laser Lighting". For fluorescent ceramics used in LED lighting, the spatial light intensity distribution test geometry conditions specified in GB / T 26184-2010 "Measurement Method for Absolute Luminous Intensity Distribution" or ISO / CIE19476:2014 can be used for measurement.

[0068] Light extraction efficiency test: The internal quantum efficiency (IQE) and external quantum efficiency (EQE) of the fluorescent ceramic were measured using an integrating sphere and a fluorescence spectrometer. The light extraction efficiency was characterized by the ratio of external quantum efficiency to internal quantum efficiency.

[0069] Light emission performance testing: Excitation and emission spectra were measured using a fluorescence spectrometer; luminous flux and luminous efficiency were measured using integrating sphere spectroscopy; for fluorescent ceramics used in laser lighting, parameters such as saturation threshold, chromaticity coordinates, and illuminance instability were measured according to the laser diode (LD) excitation-integrating sphere system and in accordance with the T / CI 073-2022 standard.

[0070] The solution of this application will be described below with reference to the following specific embodiments. Unless otherwise specified, the raw materials used in the following embodiments and comparative examples are all from commercially available products, and the devices or equipment used are all purchased from conventional market sales channels.

[0071] Example 1 This embodiment 1 provides a fluorescent ceramic. Its preparation method is as follows: (1) According to the chemical formula (Y0). 998 Ce0. 002 )3Al5O 12 According to the stoichiometric ratio, high-purity Y2O3, Al2O3 and CeO2 powders were accurately weighed, mixed by planetary ball milling, dried and sieved, and then dry-pressed and cold isostatically pressed to obtain fluorescent ceramic green bodies. The fluorescent ceramic green bodies were then held at 1750℃ for 10 hours in a vacuum sintering furnace to obtain dense Ce:YAG transparent fluorescent ceramic substrates with dimensions of 10 mm × 10 mm × 0.5 mm. (2) The light-incident surface of the fluorescent ceramic substrate was precisely polished with diamond polishing paste, and then polished in multiple stages with polishing pastes of W14, W7, W3.5 and W1.5 in sequence. Finally, it was finely polished with cerium oxide polishing liquid. According to AFM test, the surface roughness of the light-incident surface Ra3=8 nm. (3) The light-emitting surface of the fluorescent ceramic substrate was chemically etched with phosphoric acid etching solution at a temperature of 200℃ for 15 minutes. The surface roughness of the light-emitting surface after etching was Ra4=420 nm. During the etching process, a polytetrafluoroethylene mask was used to protect the side surface. (4) Remove the side mask and perform gradient roughening treatment on the side using dynamic immersion etching method; gradually immerse the fluorescent ceramic substrate in phosphoric acid etching solution at 200℃ at a speed of 2 mm / min, with the immersion direction from the bottom (incident surface) to the top (exit surface), and the immersion depth is the ceramic thickness (0.5 mm). After etching, the surface roughness of the top side (the first area near the light-exit surface) is Ra1=380 nm, the surface roughness of the bottom side (the second area near the incident surface) is Ra2=45 nm, and Ra1 / Ra2=8.4.

[0072] (5) Anneal the fluorescent ceramic substrate after step four in air at 1200°C for 4 hours to eliminate surface defects and residual stress.

[0073] Performance testing: The fluorescent ceramic prepared in this embodiment was encapsulated on a blue LED chip (455 nm) and tested under a 350 mA current drive. The luminous efficacy was 205 lm / W, the color temperature was 5450 K, and the color temperature deviation ΔCCT = 180 K. The light extraction efficiency was tested using an integrating sphere, showing a 38% improvement compared to Comparative Example 1 (fully polished) and a 16% improvement compared to Comparative Example 2 (only the light-emitting surface was roughened). Spatial light distribution testing showed that the uniformity of light intensity distribution on the light-emitting surface reached 92%, while the side light intensity decreased by 65%.

[0074] Example 2 This embodiment 2 provides a fluorescent ceramic. The difference between its preparation method and that of embodiment 1 is that: in step (2), the light-incident surface is polished to a surface roughness Ra3 = 3 nm; in step (3), the etching time of the light-exiting surface is extended to 25 minutes, so that the surface roughness of the light-exiting surface is Ra4 = 650 nm and Ra4 / Ra3 = 216.7; in step (4), the dynamic immersion etching method is adjusted to a partitioned step-by-step etching method, and the side of the fluorescent ceramic substrate is divided into three regions: the second region, the third region, and the first region, which are etched for 5 min, 15 min, and 25 min respectively, so that the surface roughness of the first region is Ra1 = 480 nm and the surface roughness of the second region is Ra2 = 35 nm.

[0075] Performance testing: The fluorescent ceramic prepared in this embodiment was encapsulated on a blue LED chip (455 nm) and tested under a 350 mA current drive. The luminous efficacy was 212 lm / W, the color temperature was 4850 K, and the color temperature deviation ΔCCT = 165 K. The light extraction efficiency was tested using an integrating sphere, showing a 43% improvement compared to Comparative Example 1 (fully polished) and a 19.8% improvement compared to Comparative Example 2 (only the light-emitting surface was roughened). Due to the higher surface roughness of the light-emitting surface, the light extraction efficiency was further improved, but the color temperature decreased slightly. Spatial light distribution testing showed that the uniformity of light intensity distribution on the light-emitting surface reached 94%, while the intensity of light emitted from the side decreased by 19%.

[0076] Example 3 This embodiment 3 provides a fluorescent ceramic. The difference between its preparation method and that of embodiment 1 is that the surface roughness of the first region in step (4) is adjusted to Ra1=100 nm.

[0077] Performance testing: The fluorescent ceramic prepared in this embodiment was encapsulated on a blue LED chip (455 nm) and tested under a 350 mA current drive. The luminous efficacy was 196 lm / W, the color temperature was 5050 K, and the color temperature deviation ΔCCT = 150 K. The light extraction efficiency was tested using an integrating sphere, showing a 32% improvement compared to Comparative Example 1 (fully polished) and a 10.7% improvement compared to Comparative Example 2 (only the light-emitting surface was roughened). Spatial light distribution testing showed that the uniformity of light intensity distribution on the light-emitting surface reached 88%, while the side light intensity decreased by 13%.

[0078] Example 4 This embodiment 4 provides a fluorescent ceramic. The difference between its preparation method and that of embodiment 1 is that the surface roughness of the first region in step (4) is adjusted to Ra1=500 nm.

[0079] Performance testing: The fluorescent ceramic prepared in this embodiment was encapsulated on a blue LED chip (455 nm) and tested under a 350 mA current drive. The luminous efficacy was 210 lm / W, the color temperature was 4830 K, and the color temperature deviation ΔCCT = 148 K. The light extraction efficiency was tested using an integrating sphere, showing a 42% improvement compared to Comparative Example 1 (fully polished) and an 18.6% improvement compared to Comparative Example 2 (only the light-emitting surface was roughened). Spatial light distribution testing showed that the uniformity of light intensity distribution on the light-emitting surface reached 94%, while the side light intensity decreased by 19%.

[0080] Example 5 This embodiment 5 provides a fluorescent ceramic. The difference between its preparation method and that of embodiment 1 is that the surface roughness of the second region in step (4) is adjusted to Ra2=20 nm.

[0081] Performance testing: The fluorescent ceramic prepared in this embodiment was encapsulated on a blue LED chip (455 nm) and tested under a 350 mA current drive. The luminous efficacy was 202 lm / W, the color temperature was 4900 K, and the color temperature deviation ΔCCT = 153 K. The light extraction efficiency was tested using an integrating sphere, showing a 36% improvement compared to Comparative Example 1 (fully polished) and a 14% improvement compared to Comparative Example 2 (only the light-emitting surface was roughened). Spatial light distribution testing showed that the uniformity of light intensity distribution on the light-emitting surface reached 90%, while the side light intensity decreased by 15%.

[0082] Example 6 This embodiment 6 provides a fluorescent ceramic. The difference between its preparation method and that of embodiment 1 is that the surface roughness of the second region in step (4) is adjusted to Ra2=100 nm.

[0083] Performance testing: The fluorescent ceramic prepared in this embodiment was encapsulated on a blue LED chip (455 nm) and tested under a 350 mA current drive. The luminous efficacy was 210 lm / W, the color temperature was 4940 K, and the color temperature deviation ΔCCT = 155 K. The light extraction efficiency was tested using an integrating sphere, showing a 42% improvement compared to Comparative Example 1 (fully polished) and an 18.6% improvement compared to Comparative Example 2 (only the light-emitting surface was roughened). Spatial light distribution testing showed that the uniformity of light intensity distribution on the light-emitting surface reached 93%, while the light intensity emitted from the side decreased by 18%.

[0084] Example 7 This embodiment 7 provides a fluorescent ceramic. The difference between its preparation method and that of embodiment 1 is that the surface roughness of the incident surface in step (2) is adjusted to Ra3=5 nm.

[0085] Performance testing: The fluorescent ceramic prepared in this embodiment was encapsulated on a blue LED chip (455 nm) and tested under a 350 mA current drive. The luminous efficacy was 211 lm / W, the color temperature was 4880 K, and the color temperature deviation ΔCCT = 148 K. The light extraction efficiency was tested using an integrating sphere, showing a 42% improvement compared to Comparative Example 1 (fully polished) and a 19% improvement compared to Comparative Example 2 (only the light-emitting surface was roughened). Spatial light distribution testing showed that the uniformity of light intensity distribution on the light-emitting surface reached 92%, while the light intensity emitted from the sides decreased by 17%.

[0086] Example 8 This embodiment 8 provides a fluorescent ceramic. The difference between its preparation method and that of embodiment 1 is that the surface roughness of the incident surface in step (2) is adjusted to Ra3=10 nm.

[0087] Performance testing: The fluorescent ceramic prepared in this embodiment was encapsulated on a blue LED chip (455 nm) and tested under a 350 mA current drive. The luminous efficacy was 209 lm / W, the color temperature was 4850 K, and the color temperature deviation ΔCCT = 149 K. The light extraction efficiency was tested using an integrating sphere, showing a 41% improvement compared to Comparative Example 1 (fully polished) and an 18% improvement compared to Comparative Example 2 (only the light-emitting surface was roughened). Spatial light distribution testing showed that the uniformity of light intensity distribution on the light-emitting surface reached 91%, while the side light intensity decreased by 16%.

[0088] Example 9 This embodiment 9 provides a fluorescent ceramic. The difference between its preparation method and that of embodiment 1 is that the surface roughness of the incident surface in step (2) is adjusted to Ra3=20 nm.

[0089] Performance testing: The fluorescent ceramic prepared in this embodiment was encapsulated on a blue LED chip (455 nm) and tested under a 350 mA current drive. The luminous efficacy was 204 lm / W, the color temperature was 4910 K, and the color temperature deviation ΔCCT = 150 K. The light extraction efficiency was tested using an integrating sphere, showing a 37% improvement compared to Comparative Example 1 (fully polished) and a 15% improvement compared to Comparative Example 2 (only the light-emitting surface was roughened). Spatial light distribution testing showed that the uniformity of light intensity distribution on the light-emitting surface reached 93%, while the light intensity emitted from the sides decreased by 18%.

[0090] Example 10 This embodiment 10 provides a fluorescent ceramic. The difference between its preparation method and that of embodiment 1 is that the surface roughness of the light-emitting surface in step (3) is adjusted to Ra4=200 nm.

[0091] Performance testing: The fluorescent ceramic prepared in this embodiment was encapsulated on a blue LED chip (455 nm) and tested under a 350 mA current drive. The luminous efficacy was 202 lm / W, the color temperature was 4880 K, and the color temperature deviation ΔCCT = 149 K. The light extraction efficiency was tested using an integrating sphere, showing a 36% improvement compared to Comparative Example 1 (fully polished) and a 14% improvement compared to Comparative Example 2 (only the light-emitting surface was roughened). Spatial light distribution testing showed that the uniformity of light intensity distribution on the light-emitting surface reached 90%, while the light intensity emitted from the sides decreased by 15%.

[0092] Example 11 This embodiment 11 provides a fluorescent ceramic. The difference between its preparation method and that of embodiment 1 is that the surface roughness of the light-emitting surface in step (3) is adjusted to Ra4=300 nm.

[0093] Performance testing: The fluorescent ceramic prepared in this embodiment was encapsulated on a blue LED chip (455 nm) and tested under a 350 mA current drive. The luminous efficacy was 204 lm / W, the color temperature was 4860 K, and the color temperature deviation ΔCCT = 147 K. The light extraction efficiency was tested using an integrating sphere, showing a 37.8% improvement compared to Comparative Example 1 (fully polished) and a 15% improvement compared to Comparative Example 2 (only the light-emitting surface was roughened). Spatial light distribution testing showed that the uniformity of light intensity distribution on the light-emitting surface reached 94%, while the side light intensity decreased by 19%.

[0094] Example 12 This embodiment 12 provides a fluorescent ceramic. The difference between its preparation method and that of embodiment 1 is that the surface roughness of the light-emitting surface in step (3) is adjusted to Ra4=600 nm.

[0095] Performance testing: The fluorescent ceramic prepared in this embodiment was encapsulated on a blue LED chip (455 nm) and tested under a 350 mA current drive. The luminous efficacy was 206 lm / W, the color temperature was 4870 K, and the color temperature deviation ΔCCT = 150 K. The light extraction efficiency was tested using an integrating sphere, showing a 39% improvement compared to Comparative Example 1 (fully polished) and a 16% improvement compared to Comparative Example 2 (only the light-emitting surface was roughened). Spatial light distribution testing showed that the uniformity of light intensity distribution on the light-emitting surface reached 94%, while the light intensity emitted from the sides decreased by 19%.

[0096] Example 13 This embodiment 13 provides a fluorescent ceramic. The difference between its preparation method and that of embodiment 1 is that the surface roughness of the light-emitting surface in step (3) is adjusted to Ra4=800 nm.

[0097] Performance testing: The fluorescent ceramic prepared in this embodiment was encapsulated on a blue LED chip (455 nm) and tested under a 350 mA current drive. The luminous efficacy was 205 lm / W, the color temperature was 4850 K, and the color temperature deviation ΔCCT = 148 K. The light extraction efficiency was tested using an integrating sphere, showing a 38% improvement compared to Comparative Example 1 (fully polished) and a 15% improvement compared to Comparative Example 2 (only the light-emitting surface was roughened). Spatial light distribution testing showed that the uniformity of light intensity distribution on the light-emitting surface reached 94%, while the side light intensity decreased by 19%.

[0098] Example 14 This embodiment 14 provides a fluorescent ceramic. The difference between its preparation method and that of embodiment 1 is that: in step (1), the fluorescent ceramic substrate material is a Ce:YAG-Al2O3 composite phase fluorescent ceramic (Ce doping 0.2 at.%); in step (2), the incident light surface Ra3 = 8 nm; in step (3), the emitted light surface Ra4 = 420 nm; in step (4), a dynamic impregnation etching method is used to make Ra1 = 380 nm and Ra2 = 45 nm.

[0099] Performance testing: The Ce:YAG-Al2O3 composite fluorescent ceramic prepared in this embodiment was encapsulated on a blue LED chip (455 nm) and tested under a 350 mA current drive. The luminous efficiency was 188 lm / W. The color temperature was 6080 K, and the color temperature deviation ΔCCT = 160 K. The light extraction efficiency was tested using an integrating sphere, showing a 27% improvement compared to Comparative Example 1 (fully polished) and a 6% improvement compared to Comparative Example 2 (only the light-emitting surface was roughened). Spatial light distribution testing showed that the uniformity of light intensity distribution on the light-emitting surface reached 80%, while the light intensity emitted from the side decreased by 5%. Due to the presence of the Al2O3 second phase, the ceramic has higher thermal conductivity and a weaker thermal quenching effect under high-power excitation.

[0100] Example 15 This embodiment 15 provides a fluorescent ceramic. The difference between its preparation method and that of embodiment 1 is that: in step (1), the fluorescent ceramic substrate material is Ce:YAG fluorescent ceramic; in step (2), the incident light surface Ra3=8 nm; in step (3), the light emitting surface Ra4=420 nm; in step (4), the dynamic impregnation etching method is used to make Ra1=380 nm and Ra2=45 nm.

[0101] Performance testing: The Ce:YAG fluorescent ceramic prepared in this embodiment was encapsulated on a blue LED chip (455 nm) and tested under a 350 mA current drive. The luminous efficacy was 168 lm / W. The color temperature was 6050 K, and the color temperature deviation ΔCCT = 156 K. The light extraction efficiency was tested using an integrating sphere, showing a 13.5% improvement compared to Comparative Example 1 (fully polished) and a 2% improvement compared to Comparative Example 2 (only the light-emitting surface was roughened). Spatial light distribution testing showed that the uniformity of light intensity distribution on the light-emitting surface reached 78%, while the side light intensity decreased by 3%.

[0102] Comparative Example 1 Comparative Example 1 provides a fluorescent ceramic. Its preparation method differs from that of Example 1 in that steps (3) and (4) are not performed, and steps (2) and (3) are both precision polished. The surface roughness Ra of the light-incident surface and the light-exit surface is 8 nm, and the side surface is not roughened.

[0103] Performance testing: The fluorescent ceramic prepared in this comparative example was encapsulated on a blue LED chip (455 nm) and tested under a 350 mA current drive. The luminous efficacy was 148 lm / W. The color temperature was 6200 K. Spatial light distribution testing showed that the uniformity of light intensity distribution on the emitting surface reached 75%, with obvious side emitting and a significant yellow edge effect.

[0104] Comparative Example 2 Comparative Example 2 provides a fluorescent ceramic. Its preparation method differs from that of Example 1 in that step (4) is omitted, and the surface roughness of the light-emitting surface in step (3) is Ra4=420 nm, and the side surface is not roughened.

[0105] Performance testing: The fluorescent ceramic prepared in this comparative example was encapsulated on a blue LED chip (455 nm) and tested under a 350 mA current drive. The luminous efficacy was 177 lm / W. The color temperature was 6030 K. Spatial light distribution testing showed that the uniformity of light intensity distribution on the emitting surface reached 82%, but a certain degree of side yellowing effect still existed.

[0106] Comparative Example 3 Comparative Example 3 provides a fluorescent ceramic. Its preparation method differs from that of Example 1 in that: in step (4), the entire side surface is immersed in the etching solution for 15 minutes, so that the surface roughness of the entire side surface is uniform at 350 nm and no gradient structure is formed.

[0107] Performance testing: The fluorescent ceramic prepared in this comparative example was encapsulated on a blue LED chip (455 nm) and tested under a 350 mA current drive. The luminous efficacy was 182 lm / W. The color temperature was 5980 K. Spatial light distribution testing showed that the uniformity of light intensity distribution on the emitting surface reached 86%. However, due to the excessively high surface roughness of the second region, some incident blue light leaked from the bottom side, reducing the actual blue light used for excitation.

[0108] Table 1

[0109] Note: " / " in Table 1 indicates that the corresponding parameter or substance does not exist.

[0110] As shown in Table 1, by introducing an asymmetric partitioned gradient roughness structure, the luminous efficiency, color temperature controllability, and uniformity of light intensity distribution on the light-emitting surface of the fluorescent ceramic are significantly improved.

[0111] Combining Example 1 with Comparative Example 1 (fully polished) and Comparative Example 2 (roughening only the light-emitting surface), the luminous efficiency of Example 1 is 205 lm / W, which is about 38.5% higher than 148 lm / W of Comparative Example 1 and about 15.8% higher than 177 lm / W of Comparative Example 2. The uniformity of light intensity distribution on the light-emitting surface also increased from 75% and 82% to 92%, indicating that the synergistic design of the roughness of the incident surface, the light-emitting surface, and the side surface can effectively suppress side light leakage and yellow edge effect, and enhance light extraction capability. Compared with Comparative Example 3 (uniformly roughened side surface), Example 1, with the same light-emitting surface Ra4, uses a gradient roughness structure on the side surface, which increases the luminous efficiency from 182 lm / W to 205 lm / W, and the color temperature is closer to the target value. This shows that the gradient change side surface can balance the constraint of blue light by the low roughness at the bottom and the diffuse reflection extraction of converted yellow light by the high roughness at the top, avoiding the blue light leakage problem caused by uniform roughening.

[0112] As can be seen from Examples 1 to 6, when the Ra1 / Ra2 ratio is in the range of 2 to 25, the luminous efficiency remains at a relatively high level of 196 to 212 lm / W, and the uniformity of the light-emitting surface is between 88% and 94%. Among them, Example 2 achieved the highest luminous efficiency of 212 lm / W and the best uniformity of 94% when Ra1 = 480 nm and Ra2 = 35 nm (Ra1 / Ra2 = 13.71), indicating that appropriately increasing the roughness of the first region and decreasing the roughness of the second region can further optimize the luminous efficiency. Examples 7 to 13 demonstrate the effect of different combinations of Ra3 and Ra4 on performance. In the ranges of Ra3 = 1 nm to 20 nm, Ra4 = 200 nm to 800 nm, and Ra4 / Ra3 = 10 to 800, the luminous efficiency is better than that of the comparative example, and the uniformity of light intensity distribution on the light-emitting surface is generally above 90%, verifying the promoting effect of the differentiated design of high smoothness of the light-incident surface and high roughness of the light-emitting surface on coupling efficiency and light extraction. Examples 14 and 15 used Ce:YAG-Al2O3 composite phase and ordinary Ce:YAG fluorescent ceramic, respectively. Under the same roughness design, the luminous efficiencies were 188 lm / W and 168 lm / W, respectively, which were significantly better than the corresponding unoptimized surface samples, indicating that the surface roughness design scheme of this application has universality for different material systems.

[0113] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the principles of this application should be included within the protection scope of this application.

Claims

1. A fluorescent ceramic, characterized in that, The invention includes a fluorescent ceramic substrate, which includes a light-incident surface, a light-emitting surface, and a side surface connecting the light-incident surface and the light-emitting surface, wherein the light-incident surface and the light-emitting surface are disposed opposite to each other. The side surface includes a first region near the light-emitting surface, with a surface roughness of Ra1, satisfying 100 nm ≤ Ra1 ≤ 500 nm; the side surface also includes a second region near the light-incident surface, with a surface roughness of Ra2, satisfying 20 nm ≤ Ra2 ≤ 100 nm; and the ratio of Ra1 / Ra2 satisfies 2 ≤ Ra1 / Ra2 ≤ 25.

2. The fluorescent ceramic according to claim 1, characterized in that, The surface roughness of the side surface and the thickness of the fluorescent ceramic substrate satisfy a linear or stepwise increasing relationship, and the surface roughness change rate is controlled within 5 nm / mm to 50 nm / mm.

3. The fluorescent ceramic according to claim 1, characterized in that, The surface roughness of the light-incident surface is Ra3, satisfying 1 nm ≤ Ra3 ≤ 20 nm; the surface roughness of the light-exiting surface is Ra4, satisfying 200 nm ≤ Ra4 ≤ 800 nm; and the ratio of Ra4 / Ra3 satisfies 10 ≤ Ra4 / Ra3 ≤ 800.

4. The fluorescent ceramic according to claim 1, characterized in that, The fluorescent ceramic satisfies at least one of the following conditions: (1) 1 nm ≤ Ra3 ≤ 10 nm; (2)300 nm≤Ra4≤600 nm; (3) 30≤Ra4 / Ra3≤600; (4) The material of the fluorescent ceramic substrate includes one or more of Ce:YAG transparent ceramic, Ce:YAG-Al2O3 composite phase fluorescent ceramic or Ce:YAG fluorescent ceramic.

5. A method for preparing fluorescent ceramics as described in any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Provide fluorescent ceramic blanks or pre-sintered ceramic sheets, and vacuum sinter them to obtain dense fluorescent ceramic substrates; (2) The light-incident surface of the fluorescent ceramic substrate obtained in step (1) is precisely polished so that its surface roughness Ra3 is controlled at 1 nm~20 nm. (3) The light-emitting surface of the fluorescent ceramic substrate after step (2) is subjected to a first roughening treatment so that its surface roughness Ra4 reaches 200 nm~800 nm; (4) The side surface of the fluorescent ceramic substrate after step (3) is subjected to gradient roughening treatment so that the side surface forms a surface roughness gradient structure along the thickness direction of the fluorescent ceramic substrate, wherein the surface roughness Ra1 of the first region is controlled at 100 nm to 500 nm, and the surface roughness Ra2 of the second region is controlled at 20 nm to 100 nm.

6. The preparation method according to claim 5, characterized in that, In step (3), the first roughening treatment is selected from one or more of mechanical grinding, chemical etching, laser etching, or plasma etching; When chemical corrosion is used, the corrosion solution is phosphoric acid or a mixture of phosphoric acid and sulfuric acid, the corrosion temperature is 100℃~300℃, and the corrosion time is 1 min~60 min.

7. The preparation method according to claim 5, characterized in that, The gradient coarsening process described in step (4) employs either a partitioned step-by-step etching method or a dynamic immersion etching method. The partitioned step-by-step etching method includes: dividing the side of the fluorescent ceramic substrate into 2 to 5 regions, and performing multi-step etching from the second region to the first region by increasing the etching time or increasing the etching solution concentration. The dynamic immersion etching method includes: gradually immersing the fluorescent ceramic substrate into the etching solution at a speed of 0.5 mm / min to 5 mm / min, with the immersion direction being from the light-emitting side to the light-incoming side.

8. The preparation method according to claim 5, characterized in that, Steps (2) and (3) also include a step of shielding and protecting the side surface, that is, during the roughening process of the light-incident surface and the light-exit surface, a corrosion-resistant mask is used to protect the side surface. After the light-incident surface and the light-exit surface are roughened, the mask is removed and then the gradient roughening process of the side surface is performed.

9. The preparation method according to claim 5, characterized in that, The preparation method further includes step (5) annealing: the fluorescent ceramic substrate after step (4) is annealed in air or oxygen atmosphere at a temperature of 800℃~1400℃ for 2 hours to 10 hours.

10. A light-emitting device, characterized in that, It includes a blue light excitation source and a fluorescent ceramic as described in any one of claims 1 to 4 or a fluorescent ceramic prepared by the preparation method described in any one of claims 5 to 9, wherein the light incident surface of the fluorescent ceramic is disposed facing the blue light excitation source.

11. The light-emitting device according to claim 10, characterized in that, An optical coupling layer or antireflective film is also provided between the light incident surface and the blue light excitation source.

Images