Preposed light performance enhanced composite fluorescent ceramic for laser illumination and preparation method of preposed light performance enhanced composite fluorescent ceramic

Abstract

The invention discloses a preposed light performance enhanced composite fluorescent ceramic for laser illumination and a preparation method thereof. The composite fluorescent ceramic comprises YAG: Ce fluorescent ceramic and ZrO2-Al2O3 ceramic, wherein a zigzag microstructure is constructed on the surface of the YAG: Ce fluorescent ceramic, and the ZrO2-Al2O3 ceramic and the YAG: Ce fluorescent ceramic are sintered into a whole. According to the zigzag microstructure YAG: Ce ceramic, the contact interface area with blue light can be increased, so that the probability of interaction between the blue light and the ceramic is improved, and the fluorescence conversion efficiency is improved; meanwhile, the sawtooth-shaped microstructure can reduce the total internal reflection effect of fluorescent light, and can regulate and control the propagation direction of emergent light, so that blue light and yellow light can be mixed more uniformly. The composite fluorescent ceramic prepared by the invention realizes high-brightness white light emission under the excitation of a blue light LD chip with the wavelength of 450-460 nm, and can bear the excitation power density of 60-75 W / mm < 2 > and the luminous efficiency of 210-260 lm / W. Compared with the traditional planar fluorescent ceramic without a microstructure, the luminous efficiency is improved by 40-60%, the divergence angle of emergent light is reduced from more than 100 degrees of a planar structure to 60-80 degrees, and the thermal conductivity at 20-30 DEG C is 20-27Wm <-1 > k <-1 >.

Description

Technical Field

[0001] This invention relates to the field of fluorescent ceramics technology, specifically to a composite fluorescent ceramic for laser illumination with enhanced pre-light performance and its preparation method. Background Technology

[0002] Fluorescent ceramics, as a light-to-light conversion functional material, exhibit excellent performance under high-power blue light-emitting diode (LED) excitation due to their unique crystal structure and doping system. When laser is used as the excitation source, fluorescent ceramic-based light source devices can efficiently convert laser energy into visible light, with single-module brightness exceeding 100,000 lumens, a range of over 1 kilometer, and a device size that is more than 60% smaller than traditional light sources. They possess advantages such as high brightness, long range, long lifespan, and small size, and are widely used in outdoor plaza lighting, sports venues, automotive headlights, and aviation and marine lighting applications.

[0003] However, in high power density lasers (power density > 10 W / mm²) 2 Under excitation conditions, fluorescent ceramics face severe heat dissipation challenges. Due to energy loss mechanisms such as Stokes shift and nonradiative transitions, approximately 30%-40% of the laser energy is released as heat during the light conversion process, leading to heat accumulation in the laser-irradiated area. The thermal conductivity of fluorescent ceramics is only 12 W·m. -1 ·K -1 Only 1 / 40 the thermal conductivity of copper, it is difficult to meet the requirements of efficient heat dissipation. To solve the above problems, existing technologies mainly focus on structural design and material composites. In terms of structural design, the literature (Heat-conducting LSN: Ce-in-glass film on AlN substrate for high-brightness laser-driven whitelighting. CERAMINT, 48(24) 2022) proposes to use a high thermal conductivity AlN ceramic substrate (thermal conductivity > 320 W·m) as the basis for heat dissipation. -1 ·K -1 A PiG glass film coated with LuAG:Ce was used to construct a "heat dissipation substrate-phosphor layer" composite structure. However, the thermal conductivity of the glass phosphor was only 1-2 W·m. -1 ·K -1 Under 5W high-power excitation, an interfacial thermal resistance as high as 20℃ / W is formed between the film layer and the substrate, resulting in limited overall heat dissipation efficiency and a final luminous efficiency of only 158lm / W. In the field of material composites, patent application CN108527960A discloses a composite scheme using fluorescent ceramics and sapphire, which utilizes the high thermal conductivity of sapphire (approximately 40W·m). -1 ·K -1While it improves heat dissipation, the glass powder and epoxy resin used in the intermediate layer have a thermal conductivity of less than 0.5 W·m. -1 ·K -1 Furthermore, the interfacial bonding strength is only 15 MPa, far lower than the ceramic's own strength (>300 MPa), severely hindering the heat conduction path and causing delamination of the composite structure under thermal stress, further deteriorating the luminescence performance. In addition, in methods that improve thermal conductivity by introducing a second phase, the high thermal conductivity second phase (such as silicon carbide particles) easily forms agglomerates or disperses within the ceramic matrix, cutting off effective heat conduction paths and failing to address the fundamental problem of heat concentration at the laser spot; its local heat dissipation improvement effect is less than 20%.

[0004] In summary, fluorescent ceramics, as high-performance light-to-light conversion materials, face significant heat dissipation challenges during high-power-density laser excitation, leading to a series of performance degradation issues. Existing solutions focusing on structural design and material composites have all failed to effectively address these problems due to their respective limitations, exhibiting shortcomings in heat dissipation or structural stability. Summary of the Invention

[0005] One of the objectives of this invention is to provide a method for preparing composite fluorescent ceramics with enhanced front-light performance for laser illumination, which is easy to industrialize.

[0006] The second objective of this invention is to provide a composite fluorescent ceramic for laser illumination with enhanced pre-light performance prepared by the above method. This ceramic, as a luminescent material, has the advantages of strong heat dissipation, high thermal conductivity, high luminous efficiency, and low incident light surface temperature.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention provides a method for preparing a pre-light performance enhancement composite fluorescent ceramic for laser illumination, specifically comprising the following steps:

[0009] Step 1: YAG:Ce precursor and ZrO2-Al2O3 precursor were prepared by high-temperature solid-state method respectively;

[0010] Step 2: Press the YAG:Ce / ZrO2-Al2O3 composite ceramic green body using dry pressing, and then perform vacuum sintering and annealing treatments in sequence;

[0011] Step 3: A serrated structure array is formed on the surface of the composite ceramic using femtosecond laser engraving, and the final thickness of the composite fluorescent ceramic is 4-5 mm.

[0012] Preferably, in step one, the Ce in the YAG:Ce precursor 3+ The doping concentration is 0.01–0.2 at%.

[0013] Preferably, in step one, the mass ratio of the second phase Al2O3 in the ZrO2-Al2O3 precursor is 80% to 90%. When the Al2O3 content is 80% to 90%, heat dissipation, light reflection, thermal matching, and cost can be balanced, which is suitable for ceramic requirements.

[0014] Preferably, in step two, the ZrO2-Al2O3 precursor is pressed first, and then the YAG:Ce precursor is pressed; wherein the mass ratio of the ZrO2-Al2O3 precursor to the YAG:Ce precursor is 2:1; at this time, heat dissipation, light effect and co-firing stability can be balanced, heat dissipation can be guaranteed, light function can be matched and cracking of green blank can be avoided.

[0015] Preferably, in step two, a single-axis press is used to pre-press YAG:Ce / ZrO2-Al2O3 under a pressure of 50MPa, and the holding time is set to 20s. Then, the pre-pressed green blank is placed in a cold isostatic press and held under a pressure of 200MPa for 200s.

[0016] Preferably, in step two, the vacuum sintering temperature is 1740–1760°C, and the holding time is 8–10 hours.

[0017] Preferably, in step two, the annealing temperature is 1350–1450°C, and the holding time is 6–10 hours.

[0018] Preferably, in step three, the longitudinal cross-section of the unit of the sawtooth structure array is a right triangle with a bottom width of 0.3mm to 0.5mm and an angle of 20° to 30° between the inclined side of the unit and the normal vector of the ceramic surface.

[0019] Secondly, this invention also provides a composite fluorescent ceramic for laser illumination with enhanced pre-light performance, prepared by the above-described method. The composite fluorescent ceramic comprises a YAG:Ce fluorescent ceramic with a serrated microstructure on its surface and a ZrO2-Al2O3 ceramic sintered integrally with the YAG:Ce fluorescent ceramic. The serrated microstructure of the YAG:Ce ceramic increases the contact area with blue light, thereby increasing the probability of interaction between blue light and the ceramic, thus improving fluorescence conversion efficiency. Simultaneously, the serrated microstructure reduces total internal reflection of fluorescence and allows for control of the propagation direction of the emitted light, resulting in a more uniform mixing of blue and yellow light. The ZrO2-Al2O3 ceramic possesses reflective properties for both blue and yellow light and also exhibits heat dissipation characteristics, effectively dissipating heat generated in relevant areas through thermal conduction.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The composite fluorescent ceramic prepared in this invention achieves high-brightness white light emission when excited by a blue LD chip with a wavelength of 450nm to 460nm, and can withstand an excitation power density of 60W / mm². 2 ~75W / mm 2 The luminous efficacy is 210–260 lm / W. Compared with traditional planar unstructured fluorescent ceramics, the luminous efficacy is improved by 40%–60%, and the emitted light divergence angle is reduced from more than 100° in planar structures to 60°–80°. Its thermal conductivity at 20–30℃ is 20–27 W / m. -1 k -1 .

[0022] (2) The composite fluorescent ceramic in this invention is composed of YAG:Ce fluorescent ceramic and ZrO2-Al2O3 ceramic with a serrated microstructure on the surface. By increasing the contact area with blue light, the fluorescence conversion efficiency is improved, allowing a unit of blue light to be converted into more yellow light. Combined with the serrated structure to optimize the uniformity of light mixing, the blue light and yellow light are efficiently fused into high-quality white light, effectively reducing total internal reflection of fluorescence, reducing the ineffective loss of light energy inside the ceramic, allowing more converted fluorescence to be emitted smoothly, improving light utilization, and enhancing the performance of the front light.

[0023] (3) The present invention uses dry pressing to prepare composite fluorescent ceramic blanks, which can effectively control the fine structure of the blanks without defects such as cracks and deformation, and at the same time realize mass production, which is conducive to the industrialization of the preparation of composite fluorescent ceramics.

[0024] (4) The present invention adopts a co-firing scheme to tightly bond YAG:Ce fluorescent ceramic and ZrO2-Al2O3 ceramic together. Since YAG:Ce, ZrO2 and Al2O3 have similar thermal expansion coefficients, they can be sintered in one step without cracking. The high thermal conductivity ZrO2-Al2O3 ceramic provides better heat dissipation, thereby improving the overall thermal conductivity of the composite ceramic, making it applicable to high-power lighting devices. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the composite fluorescent ceramic structure in this invention;

[0026] Figure 2 This is a schematic diagram of the optical path of the composite fluorescent ceramic in this invention.

[0027] Figure 3 The graph shows the luminescence efficiency of the composite fluorescent ceramics prepared in Examples 1-3 of this invention.

[0028] Figure 4 This is a schematic diagram of the composite fluorescent ceramic comparative example in this invention. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0030] The raw material powders used in the following examples are all commercially available products with a purity greater than 99.9%.

[0031] Example 1

[0032] The composite fluorescent ceramic structure prepared in this embodiment is as follows: Figure 1 As shown, it includes 0.1 at.% Ce:YAG fluorescent ceramic with a serrated microstructure on its surface and ZrO2-Al2O3 ceramic sintered integrally with the 0.1 at.% Ce:YAG fluorescent ceramic. The second phase Al2O3 accounts for 80% of the mass of the ZrO2-Al2O3 ceramic.

[0033] Step 1: YAG:Ce precursor and ZrO2-Al2O3 precursor were prepared by high-temperature solid-state method respectively;

[0034] Step 2: Dry pressing is used to press the YAG:Ce / ZrO2-Al2O3 composite ceramic green body, wherein the mass ratio of ZrO2-Al2O3 precursor to YAG:Ce precursor is 2:1. The green body is then pressed under a vacuum of not less than 10°C. -3 Heated to 1760°C in a vacuum atmosphere of Pa and held for 10 hours, then air annealed at 1450°C and held for 10 hours.

[0035] Step 3: A serrated microstructure is formed on the YAG:Ce surface of the composite ceramic using femtosecond laser engraving. The bottom width of a single serrated unit is 0.5 mm, and the angle between the inclined side of the serrated unit and the normal vector of the ceramic surface is 30°. The final thickness of the composite fluorescent ceramic is 5 mm.

[0036] When a 450nm blue laser is used to excite a composite fluorescent ceramic, its power density reaches 70.71W / mm² when the blue light output power is 5W. 2 The fluorescent ceramic device exhibits stable luminescence, operates at a temperature of 75.3℃, and has a thermal conductivity of 23.8 W / m². -1 k -1 The luminous efficacy is 233.9 lm / W. Figure 3 The luminous flux reaches 1169.5 lm, the luminous efficacy is increased by 40%, and the outgoing light divergence angle is reduced to 80°.

[0037] Example 2

[0038] The composite fluorescent ceramic structure prepared in this embodiment is as follows: Figure 1As shown, it includes 0.15 at.% Ce:YAG fluorescent ceramic with a serrated microstructure on its surface and ZrO2-Al2O3 ceramic sintered integrally with the 0.15 at.% Ce:YAG fluorescent ceramic. The second phase Al2O3 accounts for 85% of the mass of the ZrO2-Al2O3 ceramic.

[0039] Step 1: YAG:Ce precursor and ZrO2-Al2O3 precursor were prepared by high-temperature solid-state method, with the mass ratio of ZrO2-Al2O3 precursor to YAG:Ce precursor being 2:1.

[0040] Step 2: Press the YAG:Ce / ZrO2-Al2O3 composite ceramic green body using dry pressing, and then press the green body under a vacuum of not less than 10°C. -3 Heated to 1750°C in a vacuum atmosphere of Pa and held for 9 hours, then air annealed at 1400°C and held for 8 hours.

[0041] Step 3: A serrated structure is formed on the YAG:Ce part of the composite ceramic surface using femtosecond laser engraving. The bottom width of a single serrated unit is 0.4mm, and the angle between the inclined side of the serrated unit and the normal vector of the ceramic surface is 25°. The final thickness of the composite fluorescent ceramic is 5mm.

[0042] When a 455nm blue laser is used to excite a composite fluorescent ceramic, its power density reaches 70.71W / mm² when the blue light output power is 5W. 2 The fluorescent ceramic device exhibits stable luminescence, operates at a temperature of 68.8℃, and has a thermal conductivity of 25.8 W / m². -1 k -1 The luminous efficacy is 244.5 lm / W. Figure 3 The luminous flux reaches 1222.5 lm, the luminous efficacy is increased by 50%, and the outgoing light divergence angle is reduced to 70°.

[0043] Example 3

[0044] The composite fluorescent ceramic structure prepared in this embodiment is as follows: Figure 1 As shown, it includes 0.2 at.% Ce:YAG fluorescent ceramic with a serrated microstructure on its surface and ZrO2-Al2O3 ceramic sintered integrally with the 0.2 at.% Ce:YAG fluorescent ceramic. The second phase Al2O3 accounts for 90% of the mass of the ZrO2-Al2O3 ceramic.

[0045] Step 1: YAG:Ce precursor and ZrO2-Al2O3 precursor were prepared by high-temperature solid-state method, with the mass ratio of ZrO2-Al2O3 precursor to YAG:Ce precursor being 2:1.

[0046] Step 2: Press the YAG:Ce / ZrO2-Al2O3 composite ceramic green body using dry pressing, and then press the green body under a vacuum of not less than 10°C. -3 Heated to 1740°C in a vacuum atmosphere of Pa and held for 8 hours, then air annealed at 1350°C and held for 6 hours.

[0047] Step 3: A serrated structure is formed on the YAG:Ce part of the composite ceramic surface using femtosecond laser engraving. The bottom width of a single serrated unit is 0.3mm, and the angle between the inclined side of the serrated unit and the normal vector of the ceramic surface is 20°. The final thickness of the composite fluorescent ceramic is 5mm.

[0048] The composite fluorescent ceramic was excited by a 460nm blue laser, and its power density reached 71.91W / mm² when the blue light output power was 5W. 2 The fluorescent ceramic device exhibits stable luminescence, operates at a temperature of 57.2℃, and has a thermal conductivity of 25.9 W / m². -1 k -1 The luminous efficacy is 252.6 lm / W. Figure 3 The luminous flux reaches 1263.1 lm, the luminous efficacy is increased by 60%, and the divergence angle of the emitted light is reduced to 60°.

[0049] Comparative Example

[0050] The composite fluorescent ceramic structure prepared in this comparative example is as follows: Figure 4 As shown, it includes 0.1 at.% Ce:YAG fluorescent ceramic without surface microstructure and ZrO2-Al2O3 ceramic sintered integrally with the 0.1 at.% Ce:YAG fluorescent ceramic. The second phase Al2O3 accounts for 80% of the mass of the ZrO2-Al2O3 ceramic.

[0051] Step 1: YAG:Ce precursor and ZrO2-Al2O3 precursor were prepared by high-temperature solid-state method, with the mass ratio of ZrO2-Al2O3 precursor to YAG:Ce precursor being 2:1.

[0052] Step 2: Press the YAG:Ce / ZrO2-Al2O3 composite ceramic green body using dry pressing, and then press the green body under a vacuum of not less than 10°C. -3 Heated to 1760°C in a vacuum atmosphere of Pa and held for 10 hours, then air annealed at 1450°C and held for 10 hours.

[0053] Step 3: Use polishing powder of different particle sizes to perform double-sided grinding and polishing on the surface of the annealed composite ceramic, polish the sample surface to a mirror smooth surface (surface roughness Ra≤1nm), and the final thickness of the composite fluorescent ceramic is 5mm.

[0054] When a 450nm blue laser is used to excite a composite fluorescent ceramic, its power density reaches 60.31W / mm² when the blue light output power is 5W. 2 The fluorescent ceramic device exhibits stable luminescence, operates at a temperature of 85.3℃, and has a thermal conductivity of 21.8 W / m². -1 k -1 The luminous efficacy is 201.9 lm / W, and the luminous flux is 969.5 lm.

[0055] The optical path model diagram of the composite fluorescent ceramic in this invention is as follows: Figure 2 As shown, 450nm–460nm blue light is incident on a YAG:Ce fluorescent ceramic with a serrated microstructure on its surface. Some of the blue light reacts with YAG:Ce to convert into yellow light. The serrated microstructure increases the contact area and improves the conversion efficiency, while reducing total internal reflection of fluorescence. The unconverted blue light and the generated yellow light are partially reflected back to the YAG:Ce layer by the underlying ZrO2-Al2O3 ceramic for secondary interaction, and the propagation direction is adjusted under the control of the serrated structure. Finally, the blue light and yellow light are uniformly mixed and emitted at a divergence angle of 60°–80°.

[0056] 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 composite fluorescent ceramic for enhancing the performance of a front light for laser illumination, characterized by, Specifically comprising the following steps: Step one: YAG: Ce precursor and ZrO2-Al2O3 precursor are prepared by high-temperature solid phase method respectively; Step two: YAG: Ce / ZrO2-Al2O3 composite ceramic green body is pressed by dry pressing, and vacuum sintering and annealing treatment are carried out in sequence; Step three: sawtooth structure array is formed on the surface of the composite ceramic by femtosecond laser engraving, and the final thickness of the composite fluorescent ceramic is 4-5mm.

2. The preparation method of the pre-light performance enhancement composite fluorescent ceramic for laser illumination according to claim 1, characterized in that, In step one, the Ce in the YAG:Ce precursor 3+ The doping concentration is 0.01-0.2 at%.

3. The method for preparing a pre-light performance enhancement composite fluorescent ceramic for laser illumination according to claim 1, characterized in that, In step one, the mass ratio of the second phase Al2O3 in the ZrO2-Al2O3 precursor is 80%-90%.

4. The method for preparing a pre-light performance enhancement composite fluorescent ceramic for laser illumination according to claim 1, characterized in that, In step two, the ZrO2-Al2O3 precursor is pressed first, and then the YAG: Ce precursor is pressed; the mass ratio of the ZrO2-Al2O3 precursor to the YAG: Ce precursor is 2:

1.

5. The method for preparing a pre-light performance enhancement composite fluorescent ceramic for laser illumination according to claim 1, characterized in that, In step two, the YAG: Ce / ZrO2-Al2O3 is pre-pressed by a single-axis press at a pressure of 50MPa, and the pressure holding time is set to 20s, and then the pre-pressed green body is placed into a cold isostatic pressing device and pressed at a pressure of 200MPa for 200s.

6. The method of claim 1, wherein the method is characterized by the steps of: In step two, the vacuum sintering temperature is 1740-1760℃, and the holding time is 8-10h.

7. The method for preparing a pre-light performance enhancement composite fluorescent ceramic for laser illumination according to claim 1, characterized in that, In step two, the annealing temperature is 1350-1450℃, and the holding time is 6-10h.

8. The method of claim 1, wherein the method is characterized by: In step three, the unit longitudinal section of the sawtooth structure array is a right triangle, the bottom width is 0.3-0.5mm, and the included angle between the unit inclined side and the normal vector of the ceramic surface is 20-30°.

9. The pre-pumped light performance enhancing composite phosphor ceramic for laser illumination prepared by the method of any one of claims 1 to 8, characterized in that, The composite fluorescent ceramic comprises YAG: Ce fluorescent ceramic with sawtooth structure array on the surface and ZrO2-Al2O3 ceramic sintered with the YAG: Ce fluorescent ceramic; the YAG: Ce ceramic is used to increase the contact interface area with blue light, thereby improving the interaction probability of blue light and the ceramic, to improve the fluorescent conversion efficiency; at the same time, the sawtooth structure array can reduce the total internal reflection effect of fluorescent light, and can regulate the propagation direction of the outgoing light, so that the blue light and yellow light can be more uniformly mixed; the ZrO2-Al2O3 ceramic has the reflection performance of blue light and yellow light, and also has the heat dissipation characteristic, which is used to diffuse the heat generated in the related area by heat conduction, thereby realizing effective heat dissipation.

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