Lanthanum-based perovskite gradient composite ceramic light absorber and preparation method thereof

Abstract

The invention discloses a lanthanum-based perovskite gradient composite ceramic light absorber and a preparation method thereof, and belongs to the technical field of high-power laser measurement and optical protection materials. The preparation method comprises the following steps: (1) preparing La2-xCaxABO6 (x is more than or equal to 0.6 and less than or equal to 1.2, and A / B is Cr, Mn, Fe or Ni) double perovskite and LaAlO3 ceramic powder by adopting a solid-phase reaction method; (2) constructing an integrated gradient ceramic composed of a light absorption layer, a heat transfer layer and an insulating layer through hot pressed sintering; and (3) depositing a ZrO2 / HfO2 / Al2O3 multi-layer refractive index gradient anti-reflection film on the surface of the compact ceramic. The integrated gradient ceramic heat transfer layer is composed of nine transition layers with continuous components, interface stress caused by difference of thermal expansion coefficients can be effectively relieved, and the structural stability at high temperature is improved. The surface multi-layer refractive index gradient film realizes smooth transition of the refractive index and reduces reflection loss. The obtained light absorber has the advantages of wide spectrum, high absorption, excellent thermal stability and electrical insulating property, and is suitable for a laser power meter, a thermopile probe and a high-energy light protection element.

Description

TECHNICAL FIELD

[0001] The present application relates to a lanthanum-based perovskite gradient composite ceramic light absorber and a preparation method thereof, and belongs to the technical field of high-temperature optical functional ceramics and optical protection materials, and can be applied to the field of optical detection such as laser detectors, solar devices and infrared sensors. BACKGROUND

[0002] Laser technology plays an important role in the fields of industrial manufacturing, national defense and optical detection. With the continuous improvement of the energy density of lasers, the detection accuracy and stability of existing thermoelectric type laser power meters are greatly limited under high-power laser conditions, which is difficult to meet the wide-spectrum detection needs of high-power lasers. This not only restricts the further application of laser technology, but also affects the realization process of national strategic goals.

[0003] Currently, the core component of the thermoelectric type laser power meter, the light absorber, still has obvious technical bottlenecks under high-power laser irradiation. The existing laser power meter light absorber mostly adopts a metal, carbon-based or oxide thin film structure, and its typical configuration is a metal heat transfer substrate surface deposited with an absorption layer and an insulating layer. Although the metal substrate (such as copper, aluminum, etc.) has good thermal conductivity, it is easy to produce local overheating and thermal fatigue failure under high-energy laser irradiation; the carbon-based and blackened metal coating has a relatively high light absorption rate, but it is easy to cause ablation, peeling and micro-crack propagation under strong laser action due to its large thermal expansion coefficient and weak film / substrate interfacial bonding force. In comparison, oxide ceramics and semiconductor light absorbers are concerned due to their excellent thermal stability and chemical inertness, but their light absorption spectrum width is limited, and they usually only perform well in specific visible or near-infrared bands, and their absorption capacity decreases significantly in a wider wavelength range, making it difficult to balance wide-spectrum absorption and laser damage resistance. On the other hand, although bulk absorption materials can alleviate the damage caused by surface overheating to some extent, the internal structure of the bulk absorption materials is not uniform, which easily causes light scattering and thus reduces the stability and accuracy of the measurement signal. At the same time, the existing research on the anti-reflection film or high-transparency film on the surface of the light absorber mostly focuses on narrow-spectrum optimization, and it is difficult to achieve wide-spectrum high absorption and high laser damage resistance; and there is a lack of systematic study on the thermal-mechanical coupling response law of the film / substrate system under laser action, which greatly restricts the design and performance improvement of the composite structure light absorber.

[0004] Therefore, it is a key technical problem to improve the performance of the thermoelectric type laser power meter to achieve wide-spectrum high absorption and low reflection of the light absorber, significantly improve its laser damage threshold, and maintain thermal stability and structural integrity at high temperatures. SUMMARY

[0005] The present application aims to overcome the deficiencies of the prior art, and provides a lanthanum-based perovskite gradient composite ceramic light absorber and a preparation method thereof, the light absorber having high absorption and low reflectivity in a wide spectral range of 200-1400 nm, and being able to maintain excellent thermal conductivity and structural stability at 0-1200°C. By introducing a refractive index gradient antireflection film on the surface layer La 2-x Ca x ABO6 (light absorption layer) and the bottom layer LaAlO3 (insulating layer), a 9-layer gradient transition layer is constructed between the two layers, effectively relieving the interface stress and failure problems caused by the difference in thermal expansion coefficient; and a refractive index gradient antireflection film is introduced on the surface, realizing the synergistic optimization from light absorption, heat transfer to reflection inhibition, and significantly improving the wide-spectrum absorption capacity and laser damage resistance of the material.

[0006] The present application adopts the following technical scheme: a lanthanum-based perovskite gradient composite ceramic light absorber, from outside to inside, composed of a gradient antireflection film, a light absorption layer, a heat transfer transition layer, and an insulating layer, the light absorption layer is La 2-x Ca x ABO6, the insulating layer is LaAlO3 ceramic, the heat transfer transition layer is composed of La 2-x Ca x ABO6 and LaAlO3, and the gradient antireflection film is composed of ZrO2 / HfO2 / Al2O3 in three layers, and the refractive index increases from outside to inside.

[0007] Further, the light absorption layer is La 2-x Ca x ABO6, A and B are any one or a combination of Cr, Mn, Fe or Ni, and the doping ratio x of Ca is 0.6-1.2.

[0008] Further, the heat transfer transition layer is provided with nine sub-layers from the surface to the base in turn, and the mass ratio of the sub-layers is 9:1, 8:2, 7:3, 6:4, 1:1, 4:6, 3:7, 2:8 and 1:9 respectively, the total thickness of the heat transfer transition layer is 2mm, and a gradient distribution of gradually decreasing absorption phase content from the surface to the base is formed.

[0009] The present application also adopts the following technical scheme:

[0010] A preparation method of a lanthanum-based perovskite gradient composite ceramic light absorber, the steps are as follows:

[0011] (1) high-purity La2O3, CaCO3 and doping source oxides Cr2O3, MnO2, Fe2O3 or Ni2O3 are selected as raw materials, and are weighed, mixed uniformly and synthesized into La 2-x Ca xABO6 and LaAlO3 ceramic bulk, the ceramic bulk is placed in a ball mill tank, dried after ball milling, to obtain La 2-x Ca x ABO6 and LaAlO3 powder;

[0012] (2) The two kinds of powders are mixed according to the design proportion of the heat transfer transition layer to form nine gradient sub-layers with mass ratios of 9:1, 8:2, 7:3, 6:4, 1:1, 4:6, 3:7, 2:8 and 1:9 respectively, the powders in each layer are ball milled to obtain granulated powders, the granulated powders are dried in vacuum, then cold isostatic pressing is adopted for forming, and then hot-pressing sintering is carried out in an air atmosphere to obtain dense gradient ceramics.

[0013] (3) A ZrO2 / HfO2 / Al2O3 multilayer refractive index gradient antireflection film is deposited on the surface of the sintered ceramic at different temperatures in sequence by using an atomic layer deposition method to construct a multilayer interference antireflection film.

[0014] Further, the sintering reaction in step (1) is specifically that the mixture is heated to 1400-1700°C at a heating rate of 5°C / min in a high-temperature muffle furnace in an air atmosphere, and is kept for 6h.

[0015] Further, the ball milling process in step (1) is specifically that wet ball milling is carried out with ethanol as a dispersion medium, the ball-to-material ratio is 15:1, the rotation speed is 500rpm, and the ball milling time is 24h.

[0016] Further, the high-energy ball milling in step (2) is specifically that the mixed powders are prepared into 30-50wt% slurry with ethanol as a medium, spray granulation is carried out, the atomization gas pressure is 0.2-0.5MPa, the out-mist temperature is 120-180°C, the granulated powder with a particle size of 10-50μm is obtained, and the granulated powder is dried in vacuum at 80°C for 12h.

[0017] Further, the deposition temperature of the ZrO2 / HfO2 / Al2O3 three-layer film in step (3) is 180-200°C, 170-200°C and 150-200°C respectively, wherein the thickness of the ZrO2 film is 60-70nm, the thickness of the HfO2 film is 60-70nm, and the thickness of the Al2O3 film is 75-85nm.

[0018] Further, in step (3), a mixed transition layer with a thickness of 5-10nm is formed through short-time retention between the film layers by the atomic layer deposition process, and after the deposition is completed, annealing is carried out at 450-550°C in an air atmosphere for 30-60min.

[0019] The present application has the following beneficial effects:

[0020] (1) The surface layer of the light absorber in the present application is La 2-x Cax ABO6 ceramic, by A / B site doping to regulate the band structure and crystal structure, the absorption spectrum domain of visible light to near infrared band is widened and the absorption efficiency is improved; meanwhile, a multilayer refractive index gradient film is deposited on the surface, a smooth refractive index transition interface is formed, the surface and interface reflection loss is effectively reduced, and the synergistic optimization of wide spectrum high absorption and low reflection is realized;

[0021] (2) The present application constructs a 9-layer gradient transition layer with continuous composition between the light absorption layer and the insulating layer, which can effectively alleviate the interface thermal stress concentration caused by the difference in thermal expansion coefficient, prevent interlayer cracking, peeling or failure behavior under high-energy laser impact and high-temperature cycle, and significantly improve the structural stability and laser damage resistance of the composite ceramic under strong light and high thermal load. At the same time, the gradient structure can also realize smooth heat flow transmission between the absorption layer and the insulating layer, reduce the interface thermal resistance, and thus balance the structural integrity and thermal response characteristics; the bottom LaAlO3 insulating layer has excellent electrical insulation performance, which can effectively prevent electrical interference and ensure the accuracy of thermocouple temperature measurement, thereby balancing the thermal conductivity performance and electrical isolation function.

[0022] (3) The ceramic substrate and the high-melting-point oxide film layer on the surface thereof together form a dense film / base structure, which can effectively inhibit local ablation and thermal crack propagation under laser irradiation; the film layer realizes high density and interface bonding strength through an atomic layer deposition process, significantly improves the laser damage threshold, and maintains the optical performance and structural stability under high-temperature environment. BRIEF DESCRIPTION OF DRAWINGS

[0023] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification. The illustrations are shown to explain the present application and are not intended to limit the present application in any way.

[0024] Figure 1 A cross-sectional schematic diagram of the lanthanum-based perovskite gradient composite ceramic light absorber described in the present application.

[0025] Figure 2 The optical absorption rate of La1.4Ca0.6CrMnO6, LaCaCrFeO6, LaCaFeNiO6 and La0.8Ca1.2MnFeO6 samples described in the present application in the range of 200-1400 nm.

[0026] Figure 3 A scanning electron microscope photo of the La1.4Ca0.6CrMnO6 ceramic sample described in the present application.

[0027] Figure 4 A scanning electron microscope photo of the LaCaCrFeO6 ceramic sample described in the present application.

[0028] Figure 5A scanning electron microscope photo of a LaCaFeNiO6 ceramic sample according to the present application.

[0029] Figure 6 A scanning electron microscope photo of a La0.8Ca1.2MnFeO6 ceramic sample according to the present application. DETAILED DESCRIPTION

[0030] The present application will be further described below with reference to the accompanying drawings.

[0031] The present application is a lanthanum-based perovskite gradient composite ceramic light absorber, which comprises, from the outside in, a gradient antireflection film, a light absorption layer, a heat transfer transition layer, and an insulating layer, wherein the light absorption layer is La 2-x Ca x ABO6 (0.6≤x≤1.2) ceramic powder, wherein A and B are any one or combination of Cr, Mn, Fe, or Ni; the insulating layer is LaAlO3 ceramic; the heat transfer transition layer is La 2-x Ca x ABO6 and LaAlO3, and nine sub-layers are arranged in the direction from the surface to the base, with mass ratios of 9:1, 8:2, 7:3, 6:4, 1:1, 4:6, 3:7, 2:8, and 1:9, respectively, to form a gradient structure with gradually decreasing absorption phase content, and the total thickness is about 2 mm, to form a gradient distribution with gradually decreasing absorption phase content in the direction from the surface to the base; the gradient antireflection film is composed of three layers of ZrO2, HfO2, and Al2O3 in sequence, and the refractive index increases from the outside to the inside to realize the multi-layer interference antireflection effect.

[0032] The present application is a lanthanum-based perovskite gradient composite ceramic light absorber, which comprises, from the outside in, a gradient antireflection film, a light absorption layer, a heat transfer transition layer, and an insulating layer, wherein the light absorption layer is La 2- x Ca x ABO6 and LaAlO3 ceramic powder, to obtain high-purity and refined base materials; secondly, a gradient composite design and hot-pressing sintering process are used to prepare a dense and element-distribution-uniform gradient ceramic, to realize the organic integration of the light absorption layer, the heat transfer transition layer, and the insulating layer; finally, a multi-layer refractive index gradient antireflection film is constructed on the surface of the ceramic by using atomic layer deposition technology, to realize wide-spectrum low reflection and high laser damage resistance.

[0033] The present application is a lanthanum-based perovskite gradient composite ceramic light absorber, which comprises, from the outside in, a gradient antireflection film, a light absorption layer, a heat transfer transition layer, and an insulating layer, wherein the light absorption layer is La

[0034] (1) high-purity (≥99.9%) La2O3, CaCO3, and doped source oxides (Cr2O3, MnO2, Fe2O3, or Ni2O3) are selected as raw materials, and are weighed and mixed uniformly according to the stoichiometric ratio; the mixture is heated to 1400-1700°C at a heating rate of 5°C / min under air atmosphere in a high-temperature muffle furnace, and is kept for 6h, to synthesize La2-x Ca x ABO6 (0.6≤x≤1.2) and LaAlO3 ceramic bulk. The ceramic bulk was placed in a ball milling jar and wet ball-milled with ethanol as the dispersion medium, with a ball-to-powder ratio of 15:1 and a rotation speed of 500 rpm for 24 h. After ball milling, the ceramic bulk was dried to obtain La 2-x Ca x ABO6 and LaAlO3 powders.

[0035] (2) The two powders were mixed according to the design ratio of the heat transfer transition layer to form nine gradient sub-layers with mass ratios of 9:1, 8:2, 7:3, 6:4, 1:1, 4:6, 3:7, 2:8, and 1:9, respectively. After high-energy ball milling (rotation speed of 500 rpm, ball-to-powder ratio of 15:1, and ball milling time of 24 h), the powders in each layer were prepared into a slurry with a concentration of 30-50 wt% using ethanol as the medium, and spray granulation was performed (atomization gas pressure of 0.2-0.5 MPa, and out-mist temperature of 120-180 °C) to obtain granulated powders with a particle size of 10-50 μm. After vacuum drying at 80 °C for 12 h, about 0.3 g of the granulated powders was weighed layer by layer in gradient order, cold isostatic pressing was performed (pressure of 300 MPa and pressure holding time of 10 min), and then hot-press sintering was performed in an air atmosphere (pressure of 30-50 MPa, heating rate of 5 °C / min, sintering temperature of 1400-1700 °C, and holding time of 1-4 h) to obtain dense gradient ceramics. A composition transition zone of about 10 μm was formed between the gradient layers, the interface between the layers was dense, and the elements were uniformly distributed.

[0036] (3) A multilayer refractive index gradient antireflection film of ZrO2 / HfO2 / Al2O3 was deposited on the surface of the sintered ceramic at different temperatures by atomic layer deposition to construct a multilayer interference antireflection film. The specific deposition conditions were as follows: ZrO2 layer thickness of 60-70 nm (180-200 °C), HfO2 layer thickness of 60-70 nm (170-200 °C), and Al2O3 layer thickness of 75-85 nm (150-200 °C). A mixed transition layer with a thickness of 5-10 nm was formed between the film layers by short-time retention deposition (1-3 s) to achieve nanoscale interface smoothing and refractive index transition. After deposition, the film was annealed in an air atmosphere at 450-550 °C for 30-60 min to improve the film density and interface bonding strength and significantly enhance the laser damage resistance.

[0037] The ceramic material can be used for high-temperature light absorption coating, infrared detection devices, wide-spectrum photoelectric conversion, or laser protection elements, can achieve low reflection and high absorption in the wavelength range of 200-1400 nm, and can maintain excellent thermal conductivity and structural stability at 0-1200 °C.

[0038] The following will be described in detail with reference to the accompanying drawings. Figures 1-6The present invention will be described in detail with reference to typical embodiments. It is worth noting that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0039] Example 1:

[0040] (1) First, La2O3, CaCO3, and dopant source oxides (Cr2O3, MnO2) were used as raw materials and mixed uniformly according to stoichiometric ratio. The mixture was heated to 1400°C at a heating rate of 5°C / min under air atmosphere and held for 6 hours to synthesize La2O3. 1.4 Ca 0.6 CrMnO6 and LaAlO3 ceramic blocks were prepared. The resulting blocks were then wet-milled at a ball-to-material ratio of 15:1, a rotation speed of 500 rpm, and a milling time of 24 hours to obtain high-purity, refined La. 1.4 Ca 0.6 CrMnO6 and LaAlO3 powders.

[0041] (2) Then, the two powders were mixed according to the design ratio of the heat transfer transition layer to form nine gradient sublayers with mass ratios of 9:1, 8:2, 7:3, 6:4, 1:1, 4:6, 3:7, 2:8, and 1:9. Each layer of powder was ball-milled at 500 rpm (ball ratio 15:1, ball-milling time 24 h) and a 30 wt% slurry was prepared using ethanol as the medium. The slurry was then spray-granulated (atomizing pressure 0.5 MPa, mist outlet temperature 130°C) to obtain granulated powder with a particle size of 20 μm. After the granulated powder was vacuum dried at 80°C for 12 hours, about 0.3 g of powder was weighed layer by layer in gradient order and cold isostatic pressing was used for molding (pressure 300 MPa, holding pressure for 10 min). Then, hot pressing sintering was carried out in air atmosphere (pressure 30 MPa, heating rate 5°C / min, sintering temperature 1400°C, holding temperature for 4 h) to obtain dense gradient perovskite ceramic. A compositional transition zone of about 10 μm was formed between each gradient layer. The interlayer interface was dense and the element distribution was uniform. Figure 1 This is a cross-sectional schematic diagram of a gradient composite ceramic light absorber. The heat insulation pad and thermocouple shown in the diagram are only auxiliary temperature measurement and fixing devices and are not part of the light absorber of this invention. 1.4 Ca 0.6 The absorption rate curves of CrMnO6 dense ceramics in the spectral range of 200–1400 nm are shown below. Figure 2 As shown, the average light absorption rate is 87.7%; Figure 3 This is a scanning electron microscope image of the ceramic surface.

[0042] (3) Finally, a multilayer antireflective coating of ZrO2 / HfO2 / Al2O3 refractive index gradient was sequentially deposited on the ceramic surface using atomic layer deposition to construct a multilayer interference antireflective coating. The specific deposition conditions were: ZrO2 layer thickness 60 nm (200°C), HfO2 layer thickness 70 nm (170°C), and Al2O3 layer thickness 80 nm (150°C). An 8 nm thick mixed transition layer was formed between the film layers by short-time deposition for 2 s to achieve nanoscale interface smoothness and refractive index transition. After deposition, the coating was annealed at 450°C for 60 min in air atmosphere to improve the film density and interfacial bonding strength, and significantly enhance the resistance to laser damage.

[0043] Example 2:

[0044] (1) First, La2O3, CaCO3, and doped source oxides (Cr2O3, Fe2O3) were used as raw materials and mixed uniformly according to stoichiometric ratio. The mixture was heated to 1500°C at a heating rate of 5°C / min under air atmosphere and held for 6 hours to synthesize LaCaCrFeO6 and LaAlO3 ceramic blocks. The obtained blocks were then wet-milled at a ball-to-material ratio of 15:1, a rotation speed of 500 rpm, and a milling time of 24 hours to obtain high-purity and refined LaCaCrFeO6 and LaAlO3 powders.

[0045] (2) Then, the two powders were mixed according to the design ratio of the heat transfer transition layer to form nine gradient sublayers with mass ratios of 9:1, 8:2, 7:3, 6:4, 1:1, 4:6, 3:7, 2:8, and 1:9. Each layer of powder was ball-milled at 500 rpm (ball ratio 15:1, ball-milling time 24 h) and a 40 wt% slurry was prepared using ethanol as the medium. The slurry was then spray-granulated (atomizing pressure 0.4 MPa, mist outlet temperature 150°C) to obtain granulated powder with a particle size of 35 μm. After the granulated powder was vacuum dried at 80°C for 12 hours, approximately 0.3 g of powder was weighed layer by layer in a gradient sequence and cold isostatically pressed (pressure 300 MPa, holding pressure for 10 min). Then, it was hot-pressed and sintered in air (pressure 40 MPa, heating rate 5°C / min, sintering temperature 1500°C, holding temperature for 3 hours) to obtain a dense gradient perovskite ceramic. A compositional transition zone of approximately 10 μm was formed between each gradient layer, with dense interlayer bonding and uniform elemental distribution. Figure 1 This is a cross-sectional schematic diagram of a gradient composite ceramic light absorber. The heat insulation pad and thermocouple shown in the diagram are only auxiliary temperature measurement and fixing devices and are not part of the light absorber of this invention. The absorption rate curve of LaCaCrFeO6 dense ceramic in the 200–1400 nm spectral range is shown below. Figure 2 As shown, the average light absorption rate is 84.7%; Figure 4 This is a scanning electron microscope image of the ceramic surface.

[0046] (3) Finally, a multilayer antireflective coating of ZrO2 / HfO2 / Al2O3 refractive index gradient was sequentially deposited on the ceramic surface using atomic layer deposition to construct a multilayer interference antireflective coating. The specific deposition conditions were: ZrO2 layer thickness 65 nm (190°C), HfO2 layer thickness 65 nm (190°C), and Al2O3 layer thickness 75 nm (180°C). A 5 nm thick mixed transition layer was formed between the film layers by short-time deposition of 1 s to achieve nanoscale interface smoothness and refractive index transition. After deposition, the coating was annealed at 500°C for 45 min in air atmosphere to improve the film density and interfacial bonding strength, and significantly enhance the resistance to laser damage.

[0047] Example 3:

[0048] (1) First, La2O3, CaCO3, and doped source oxides (Fe2O3, Ni2O3) were used as raw materials and mixed uniformly according to stoichiometric ratio. The mixture was heated to 1600°C at a heating rate of 5°C / min under air atmosphere and held for 6 hours to synthesize LaCaFeNiO6 and LaAlO3 ceramic blocks. The obtained blocks were then wet-milled at a ball-to-material ratio of 15:1, a rotation speed of 500 rpm, and a milling time of 24 hours to obtain high-purity and refined LaCaFeNiO6 and LaAlO3 powders.

[0049] (2) Then, the two powders were mixed according to the design ratio of the heat transfer transition layer to form nine gradient sublayers with mass ratios of 9:1, 8:2, 7:3, 6:4, 1:1, 4:6, 3:7, 2:8, and 1:9. Each layer of powder was ball-milled at 500 rpm (ball ratio 15:1, ball-milling time 24 h), and a 50 wt% slurry was prepared using ethanol as the medium. The slurry was then spray-granulated (atomizing pressure 0.3 MPa, mist outlet temperature 180°C) to obtain granulated powder with a particle size of 50 μm. After the granulated powder was vacuum dried at 80°C for 12 hours, approximately 0.3 g of powder was weighed layer by layer in a gradient sequence and cold isostatically pressed (pressure 300 MPa, holding pressure for 10 min). Then, it was hot-pressed and sintered in air (pressure 50 MPa, heating rate 5°C / min, sintering temperature 1600°C, holding temperature for 2 hours) to obtain a dense gradient perovskite ceramic. A compositional transition zone of approximately 10 μm was formed between each gradient layer, with dense interlayer bonding and uniform elemental distribution. Figure 1 This is a cross-sectional schematic diagram of a gradient composite ceramic light absorber. The heat insulation pad and thermocouple shown in the diagram are only auxiliary temperature measurement and fixing devices and are not part of the light absorber of this invention. The absorption rate curve of LaCaFeNiO6 dense ceramic in the 200-1400nm spectral range is shown below. Figure 2 As shown, the average light absorption rate is 84.5%; Figure 5 This is a scanning electron microscope image of the ceramic surface.

[0050] (3) Finally, the Zr02 / Hf02 / Al203 multilayer refractive index gradient antireflection film is deposited on the ceramic surface by atomic layer deposition method. The specific deposition conditions are as follows: the thickness of Zr02 layer is 70 nm (180°C), the thickness of Hf02 layer is 60 nm (180°C), and the thickness of Al203 layer is 85 nm (170°C); a 10 nm thick mixed transition layer is formed between the film layers by short-time retention deposition for 3 s to realize the interface smoothing and refractive index transition in nanoscale. After the deposition is completed, the film layer is annealed at 520°C for 40 min in air atmosphere to improve the film layer density and interface bonding strength, and significantly enhance the laser damage resistance.

[0051] Example 4:

[0052] (1) First, La203, CaCO3 and doped source oxides (MnO2, Fe203) are mixed uniformly according to the stoichiometric ratio. The mixture is heated to 1700°C at a heating rate of 5°C / min in air atmosphere, and kept for 6 h to synthesize La 0.8 Ca 1.2 MnFeO6 and LaAlO3 ceramic bulk. The obtained bulk is wet ball milled at a ball-to-material ratio of 15:1 and a rotation speed of 500 rpm for 24 h to obtain high-purity and refined La 0.8 Ca 1.2 MnFeO6 and LaAlO3 powders.

[0053] (2) Then, the two kinds of powders are mixed according to the design ratio of the heat transfer transition layer to form nine gradient sub-layers with mass ratios of 9:1, 8:2, 7:3, 6:4, 1:1, 4:6, 3:7, 2:8 and 1:9. After high-energy ball milling (rotation speed of 500 rpm, ball-to-material ratio of 15:1, and ball milling time of 24 h), the powders of each layer are prepared into a slurry with a concentration of 45 wt% using ethanol as the medium, and spray granulation is performed (atomization gas pressure of 0.2 MPa, and out-mist temperature of 120°C) to obtain granulated powders with a particle size of 10 μm. After vacuum drying at 80°C for 12 h, about 0.3 g of the granulated powders of each layer are weighed and sequentially cold isostatic pressed (pressure of 300 MPa, and pressure maintaining time of 10 min), and then hot-pressed sintered (pressure of 40 MPa, heating rate of 5°C / min, sintering temperature of 1700°C, and holding time of 1 h) in air atmosphere to obtain the dense gradient perovskite ceramic. A composition transition zone with a thickness of about 10 μm is formed between the gradient layers, the interface between the layers is combined densely, and the elements are uniformly distributed. Figure 1 FIG. 1 is a cross-sectional schematic view of a gradient composite ceramic light absorber, wherein the heat insulation pad and thermocouple shown in the figure are only auxiliary temperature measuring and fixing devices, and do not belong to the composition of the light absorber of the present application. La 0.8 Ca 1.2The absorption rate curve of the MnFeO6 dense ceramic in the 200-1400 nm spectral range is shown in Figure 2 The average light absorption rate is 81.7%; Figure 6 The scanning electron microscope image of the ceramic surface is shown.

[0054] (3) Finally, the ZrO2 / HfO2 / Al2O3 multilayer refractive index gradient antireflection film is deposited on the ceramic surface by atomic layer deposition method, and the multilayer interference antireflection film is constructed. The specific deposition conditions are: the thickness of ZrO2 layer is 62 nm (185°C), the thickness of HfO2 layer is 68 nm (200°C), and the thickness of Al2O3 layer is 82 nm (200°C); the mixed transition layer with a thickness of 5 nm is formed by short-time retention deposition for 1s between the film layers, so as to realize the interface smoothing and refractive index transition in nanoscale. After the deposition is completed, the film layer is annealed at 550°C for 30 min in air atmosphere, so as to improve the compactness and interface bonding strength of the film layer, and the laser damage resistance is significantly enhanced.

[0055] The present application can effectively relieve the interface stress caused by the difference of thermal expansion coefficient, improve the heat conduction efficiency, optimize the light absorption and reflection characteristics, realize the synergistic enhancement of light absorption, heat transfer and laser damage resistance, and provide reliable material technical support for high-power laser measurement and wide-spectrum optical detection.

[0056] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled in the art, some improvements can be made without departing from the principles of the present application, and these improvements should also be considered as the protection scope of the present application.

Claims

1. A lanthanum-based perovskite gradient composite ceramic light absorber, characterized in that: From the outside in, it consists of a gradient antireflection film, a light absorption layer, a heat transfer transition layer, and an insulating layer. The light absorption layer is La. 2-x Ca x ABO6, the insulating layer is LaAlO3 ceramic, and the heat transfer transition layer is made of La... 2-x Ca x The gradient antireflection film is composed of three layers: ZrO2, HfO2, and Al2O3, with the refractive index increasing from the outside to the inside.

2. The lanthanum-based perovskite gradient composite ceramic light absorber as described in claim 1, characterized in that: The light-absorbing layer is La. 2-x Ca x In ABO6, A and B are any one or a combination of Cr, Mn, Fe, or Ni, and the doping ratio x of Ca is 0.6–1.

2.

3. The lanthanum-based perovskite gradient composite ceramic light absorber as described in claim 2, characterized in that: The heat transfer transition layer consists of nine sublayers arranged sequentially from the surface to the substrate, with mass ratios of 9:1, 8:2, 7:3, 6:4, 1:1, 4:6, 3:7, 2:8, and 1:9, respectively. The total thickness of the heat transfer transition layer is 2 mm, forming a gradient distribution in which the content of the absorbing phase gradually decreases from the surface to the substrate.

4. A method for preparing a lanthanum-based perovskite gradient composite ceramic light absorber, characterized in that: The steps are as follows: (1) High-purity La2O3, CaCO3 and doped source oxides Cr2O3, MnO2, Fe2O3 or Ni2O3 are selected as raw materials, weighed and mixed evenly according to stoichiometric ratio, and La is synthesized through sintering reaction. 2-x Ca x ABO6 and LaAlO3 ceramic blocks were placed in a ball mill jar, ball-milled, and then dried to obtain La. 2-x Ca x ABO6 and LaAlO3 powders; (2) The two powders are mixed according to the design ratio of the heat transfer transition layer to form nine gradient sub-layers with mass ratios of 9:1, 8:2, 7:3, 6:4, 1:1, 4:6, 3:7, 2:8 and 1:9 respectively. Each layer of powder is ball-milled to obtain granulated powder. After vacuum drying, the granulated powder is cold isostatically pressed and then hot-pressed and sintered in air atmosphere to obtain dense gradient ceramics. (3) A multilayer antireflection film of ZrO2 / HfO2 / Al2O3 was sequentially deposited on the surface of the sintered ceramic at different temperatures using atomic layer deposition method to construct a multilayer interference antireflection film.

5. The method for preparing the lanthanum-based perovskite gradient composite ceramic light absorber as described in claim 4, characterized in that: In step (1), the sintering reaction specifically involves placing the mixture in a high-temperature muffle furnace under an air atmosphere and heating it to 1400–1700°C at a heating rate of 5°C / min, and holding it at that temperature for 6 hours.

6. The method for preparing the lanthanum-based perovskite gradient composite ceramic light absorber as described in claim 5, characterized in that: The ball milling process in step (1) is as follows: wet ball milling is carried out with ethanol as the dispersion medium, the ball-to-material ratio is 15:1, the rotation speed is 500 rpm, and the ball milling time is 24 h.

7. The method for preparing the lanthanum-based perovskite gradient composite ceramic light absorber as described in claim 6, characterized in that: In step (2), the high-energy ball milling is specifically as follows: the mixed powder is prepared into a slurry of 30–50 wt% using ethanol as the medium, spray granulation is performed, the atomizing gas pressure is 0.2–0.5 MPa, the mist outlet temperature is 120–180°C, and granulated powder with a particle size of 10–50 μm is obtained. The granulated powder is then vacuum dried at 80°C for 12 h.

8. The method for preparing the lanthanum-based perovskite gradient composite ceramic light absorber as described in claim 7, characterized in that: In step (3), the deposition temperatures of the three-layer films ZrO2, HfO2 and Al2O3 are 180–200°C, 170–200°C and 150–200°C, respectively, with ZrO2 film thickness of 60–70 nm, HfO2 film thickness of 60–70 nm and Al2O3 film thickness of 75–85 nm.

9. The method for preparing the lanthanum-based perovskite gradient composite ceramic light absorber as described in claim 8, characterized in that: In step (3), a 5–10 nm thick mixed transition layer is formed between the film layers by short-term retention of the atomic layer deposition process. After deposition, the layer is annealed at 450–550°C for 30–60 min in an air atmosphere.

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