High-entropy rare earth tantalate ceramic with ultralow transmittance / broadband high emissivity and preparation method of high-entropy rare earth tantalate ceramic

Abstract

The invention discloses a high-entropy rare earth tantalate ceramic with ultralow transmittance / broadband high emissivity and a preparation method of the high-entropy rare earth tantalate ceramic, and belongs to the technical field of thermal barrier coating materials. The invention aims to solve the problems that the existing rare earth tantalate ceramic material is insufficient in thermal radiation penetration resistance and poor in infrared radiation performance, and the thermal conductivity is too high due to doping of transition group ions and a second phase. The phase composition of the high-entropy rare earth tantalate ceramic with ultralow transmittance / broadband high emissivity is (4RE < 0.2 > Gd < 0.2 >) 3TaO7, RE is a combination of any four elements of Pr, Nd, Sm, Eu, Tb, Dy and Y, and the molar ratio of the four elements to Gd is 1: 1: 1: 1: 1. According to the prepared high-entropy rare earth tantalate ceramic, the near-infrared band transmittance is smaller than 3%, the emissivity is larger than 0.9, the high-temperature emissivity is larger than 0.75, and the heat conductivity at the high temperature is smaller than 1.3 W.m <-1 >. K <-1 >.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal barrier coating materials, and specifically relates to a high-entropy rare earth tantalate ceramic with ultra-low transmittance / wide-band high emissivity and a preparation method thereof. Background Art

[0002] Thermal barrier coatings (TBCs) are key materials for protecting hot-end components working in high-temperature environments (such as the outer skin of hypersonic vehicles, aircraft engines, and large gas turbine blades, etc.), and can significantly improve the stability and working efficiency of engineering systems in high-temperature environments. Rare earth tantalates are considered to be highly promising thermal barrier coating materials due to their excellent comprehensive properties, including low thermal conductivity, good phase stability, corrosion resistance, suitable thermal expansion coefficient, and mechanical properties. However, similar to conventional TBC materials, rare earth tantalates exhibit semi-transparent properties to short-wave infrared radiation, which allows the thermal radiation generated by the external high-temperature heat flow to penetrate the coating, causing thermal damage to the substrate material. Studies have shown that under a high-temperature heat flow environment of 2000K, the internal conduction-radiation coupled heat flux of TBCs is about 30% higher than the pure conduction heat flux. This problem of reduced thermal insulation performance caused by infrared radiation heat transfer needs to be solved urgently. At present, improving the radiation penetration resistance of TBC materials has become an urgent need for the development of a new generation of ultra-high temperature gas turbine systems. However, the research on the regulation of the radiation penetration resistance of thermal barrier coating material systems is still in its infancy, and related results are relatively scarce. In the past five years, only Chinese patents CN 115233069A and CN 115010492A have reported composite materials and preparation methods of platinum micron sheets and precious metal nanoparticles dispersed in a ceramic matrix to improve the infrared radiation shielding performance of ceramics. However, the introduction of the second phase has defects such as poor thermal expansion matching with the ceramic matrix and increased high-temperature thermal conductivity. Therefore, the development of infrared radiation shielding thermal barrier coating ceramic materials and preparation methods with integrated characteristics of low cost, low infrared transmittance, high emissivity and low thermal conductivity is still the focus of current research. Summary of the invention

[0003] The purpose of the present invention is to solve the problems of insufficient thermal radiation penetration resistance (high transmittance), poor infrared radiation performance (low emissivity) of existing rare earth tantalate ceramic materials, and excessively high thermal conductivity caused by doping with transition group ions and second phases, and to provide a high-entropy rare earth tantalate ceramic with ultra-low transmittance / wide-band high emissivity and a preparation method thereof.

[0004] A high entropy rare earth tantalate ceramic with ultra-low transmittance / wide-band high emissivity, the phase composition is (4RE 0.2 G 0.2 ) 3 TaO 7, wherein RE is a combination of any four elements among Pr, Nd, Sm, Eu, Tb, Dy and Y, and the molar ratio of the four elements and Gd is 1:1:1:1:1; the selected rare earth elements must satisfy at least three RE 3+ The ions undergo multiple electronic transitions that can be excited in the blackbody radiation region (1000℃-1700℃, 0.5-2.5μm), among which Pr 3+ The electron transition band of Nd 3+ The electronic transition bands of Sm 3+ The electron transition band of Eu 3+ The electron transition band of Tb is concentrated in 1750-2500nm. 3+ The electronic transition band of Dy is concentrated in 1600-2500nm. 3+ The electron transition band is concentrated in 1500-2500nm; the high-entropy rare earth tantalate ceramic with ultra-low transmittance / wide-band high emissivity has ultra-low infrared transmittance (<3%) in the near-infrared band (780-2500nm), achieving resistance to thermal radiation penetration.

[0005] A high-entropy rare earth tantalate ceramic with ultra-low transmittance and wide-band high emissivity 3+ The ionic radius is between 101.3pm and 90pm, which satisfies the requirements of the five rare earth oxide RE 2 O 3 With Ta 2 O 5 Solid solution forms a single-phase solid solution with a Weber structure, and the five rare earth elements are dispersed in the lattice without element segregation; the rare earth tantalate with Weber structure has the characteristics of low thermal conductivity, high thermal expansion coefficient and high fracture toughness; RE is any combination of four elements among Pr, Nd, Sm, Eu, Tb, Dy and Y, and at least three RE 3+ Ions have multiple electronic transition phenomena between 0.5-2.5μm, and the atomic configuration entropy S≥1.62R; five rare earth elements are dispersed in the lattice, which is a single-phase solid solution with a Weber structure, and the ceramic grain size is 1000-3000nm, so as to meet the size close to the wavelength of the radiation band at 1273K-1873K, ensuring that high-temperature thermal radiation is scattered in large quantities at its internal grain boundaries; this high-entropy rare earth tantalate ceramic material with both high infrared emissivity and low transmittance has an infrared transmittance of less than 3% in the near-infrared band; the average emissivity at room temperature in the infrared band (2.5-14μm) is greater than 0.9, and the average emissivity at high temperature (1200℃) is greater than 0.75; in an air atmosphere, there is no phase change after 200h of heat preservation at 1500℃; the high-temperature thermal conductivity is less than 1.3W·m-1 ·K -1 ~1000℃.

[0006] A high entropy rare earth tantalate ceramic with ultra-low transmittance / wide-band high emissivity, characterized in that the phase composition of the high entropy rare earth tantalate ceramic (4RE 0.2 G 0.2 ) 3 TaO 7 , where RE is a combination of any four elements from Pr, Nd, Sm, Eu, Tb, Dy and Y, and the near-infrared high absorption contribution band of the selected rare earth elements is: Pr 3+ The high absorption contribution band of Nd is 1000-2500nm. 3+ The high absorption contribution bands are 400-1000nm and 1750-2500nm, Sm 3+ The high absorption contribution band of Eu is 1000-2000nm. 3+ The high absorption contribution band of Tb is 1750-2500nm. 3+ The high absorption contribution band of Dy is 1600-2500nm. 3+ The high absorption contribution band is 1500-2500nm; the near-infrared high absorption contribution of the selected rare earth elements: Dy 3+ >Nd 3+ ≈Pr 3+ >Sm 3+ Tb 3+ >Eu 3+ .

[0007] A method for preparing a high-entropy rare earth tantalate ceramic with ultra-low transmittance / wide-band high emissivity is specifically completed in the following steps:

[0008] 1. According to the phase composition of the high entropy rare earth tantalate ceramic, four RE 2 O 3 , Gd 2 O 3 and Ta 2 O 5 ; Remove four REs 2 O 3 , Gd 2 O 3 and Ta 2 O 5 The impurities and bound water in the raw material are removed, and then the raw material powder is mixed uniformly by wet ball milling, evaporated and dried, ground and sieved to obtain a uniformly mixed raw material powder; the uniformly mixed raw material powder is calcined to obtain a high entropy rare earth tantalate ceramic raw material powder;

[0009] RE described in step 1 2O 3 Pr 2 O 3 、Nd 2 O 3 、Sm 2 O 3 、Eu 2 O 3 , Tb 2 O 3 、Dy 2 O 3 and Y 2 O 3 Any 4 rare earth oxides; 4 rare earth oxides, Gd 2 O 3 And 2 O 5 The molar ratio is 0.6:0.6:0.6:0.6:0.6:1;

[0010] 2. Pre-pressing the raw material powder of high-entropy rare earth tantalate ceramics, cold isostatic pressing, and high-temperature pressureless sintering to obtain high-entropy rare earth tantalate ceramics with ultra-low transmittance / wide-band high emissivity.

[0011] Principle of the present invention:

[0012] The present invention adopts a two-step solid phase reaction calcination technology, based on the different difficulty of electronic transition of different rare earth ions in the near infrared band, to design and prepare a high entropy rare earth tantalate ceramic containing five kinds of rare earth ions, and utilizes a variety of RE inside the high entropy rare earth tantalate ceramic. 3+ The narrow bandgap characteristics caused by a large number of electron transitions realize the "sub-band high absorption" of rare earth ions, as well as high oxygen vacancy concentration and a large number of lattice vibrations, coupled with grain boundary photon scattering, making the near-infrared band transmittance (780-2500nm) less than 3%; through a variety of RE inside the high-entropy rare earth tantalate ceramics 3+ The narrow bandgap characteristics caused by a large number of electron transitions, the strong lattice distortion caused by the high entropy effect, the additional multi-mode vibration and the high oxygen vacancy concentration make the average emissivity in the infrared band (2.5-14μm) greater than 0.9 at room temperature and the average emissivity at high temperature (1200℃) greater than 0.75, which improves the radiation heat dissipation capacity and infrared radiation shielding of pure phase rare earth tantalate ceramics; and the large lattice disorder inside the high entropy ceramic ensures that there is no phase change after 200h of heat preservation at 1500℃ in air atmosphere; the large amount of phonon scattering behavior inside the lattice combined with the low photon thermal conductivity caused by the low infrared transmittance makes the high temperature thermal conductivity less than 1.3W·m -1 ·K -1 ~1000℃, much lower than 8YSZ (8mol%Y 2 O 3 Stable ZrO 2 ), ensuring its service feasibility.

[0013] Advantages of the present invention

[0014] 1. The present invention provides a high-entropy rare earth tantalate ceramic with ultra-low transmittance / wide-band high emissivity and a preparation method thereof. Compared with the existing transition metal ion doping and precious metal composite second phase system, the present invention provides a new design concept, adopts a low-cost process, and obtains excellent radiation heat dissipation and thermal radiation shielding performance. At the same time, the high-entropy rare earth tantalate ceramic has both low thermal conductivity and high-temperature stability, ensuring its feasibility of application in the field of new generation TBC materials, and has great reference significance for the development of TBCs that resist radiation penetration;

[0015] 2. The high entropy rare earth tantalate ceramics with ultra-low transmittance and wide-band high emissivity prepared by the present invention have a grain size of 1000-3000nm, an average emissivity of >0.9 at room temperature in the 2.5-14μm infrared band, and an average emissivity of >0.75 at 1200℃; there is no phase change after being kept at 1500℃ for 200h in an air atmosphere; the high-temperature thermal conductivity is <1.3W·m -1 ·K -1 ~1000℃, much lower than 8YSZ. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 X-ray diffraction patterns of high entropy rare earth tantalate ceramics and pure phase gadolinium tantalate ceramic blocks prepared in Examples 1 and 2 of the present invention and Comparative Examples 1, 2, and 3;

[0017] Figure 2 The scanning electron microscope (SEM) morphology and corresponding macroscopic morphology of the high entropy rare earth tantalate ceramics and pure phase gadolinium tantalate ceramic blocks prepared in Examples 1 and 2 of the present invention and Comparative Examples 1, 2, and 3;

[0018] Figure 3 The spectral emissivity from 2.5 μm to 14 μm of the high entropy rare earth tantalate ceramics and pure phase gadolinium tantalate ceramic blocks prepared in Examples 1 and 2 of the present invention and Comparative Examples 1, 2 and 3;

[0019] Figure 4 The linear-hemispherical transmittance of the high-entropy rare earth tantalate ceramics and pure-phase gadolinium tantalate ceramic blocks prepared in Examples 1 and 2 of the present invention and Comparative Examples 1, 2, and 3 from 400 nm to 2500 nm;

[0020] Figure 5 Thermal conductivity of the high entropy rare earth tantalate ceramics and pure phase gadolinium tantalate ceramic blocks prepared in Examples 1 and 2 of the present invention and Comparative Examples 1, 2, and 3 at 50°C, 200°C, 400°C, 600°C, 800°C, 1000°C, and 1200°C. DETAILED DESCRIPTION

[0021] The following examples further illustrate the content of the present invention, but should not be construed as limiting the present invention. Without departing from the essence of the present invention, modifications and substitutions made to the methods, steps or conditions of the present invention all fall within the scope of the present invention.

[0022] Specific implementation method 1: This implementation method is a high entropy rare earth tantalate ceramic with ultra-low transmittance / wide-band high emissivity, and the phase composition is (4RE 0.2 G 0.2 ) 3 TaO 7 , wherein RE is a combination of any four elements among Pr, Nd, Sm, Eu, Tb, Dy and Y, and the molar ratio of the four elements and Gd is 1:1:1:1:1.

[0023] Different rare earth ions have different difficulties in electronic transition in the near-infrared band. Through high entropy design, the "high absorption in different bands" of rare earth ions, high oxygen vacancy concentration and a large number of lattice vibrations can be achieved. Combined with grain boundary photon scattering, high entropy rare earth tantalate ceramics can have the characteristics of high emissivity, low transmittance, low thermal conductivity and high temperature stability. To this end, the present invention provides a high entropy rare earth tantalate ceramic with ultra-low transmittance / wide-band high emissivity and a preparation method thereof, which greatly improves the radiation heat dissipation and radiation penetration resistance of pure phase rare earth tantalate ceramics.

[0024] The high entropy rare earth tantalate ceramic with high infrared emissivity and low transmittance described in the present invention has a phase composition of (4RE 0.2 G 0.2 ) 3 TaO 7 , where RE 3+ The ionic radius is between 101.3pm and 90pm, wherein RE is a combination of any four elements among Pr, Nd, Sm, Eu, Tb, Dy, and Y, and the molar ratio of the four elements and Gd is 1:1:1:1:1, and at least three RE 3+ Ions undergo a variety of electronic transitions between 0.5-2.5μm, and the atomic configuration entropy S≥1.62R; five rare earth elements are dispersed in the lattice, forming a single-phase solid solution with a Weber structure, and the ceramic grain size is between 1000 and 3000nm.

[0025] Specific implementation method 2: This implementation method is different from specific implementation method 1 in that the grain size of the high entropy rare earth tantalate ceramic is 1000-3000 nm. The other steps are the same as those of specific implementation method 1.

[0026] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that the atomic configuration entropy S of the high entropy rare earth tantalate ceramic is ≥ 1.62R (R represents the atomic configuration entropy unit). The other steps are the same as those of specific implementation method 1 or 2.

[0027] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the infrared transmittance of the high entropy rare earth tantalate ceramic in the near-infrared band of 780nm to 2500nm is less than 3%, the average emissivity at room temperature in the infrared band of 2.5 to 14μm is greater than 0.9, and the average emissivity at high temperature of 1200℃ is greater than 0.75. The other steps are the same as those in specific embodiments 1 to 3.

[0028] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that: the high entropy rare earth tantalate ceramic has no phase change after being kept at 1500°C for 200h in air atmosphere; the thermal conductivity at high temperature of 1000°C is less than 1.3W·m -1 ·K -1 , which is much lower than 8YSZ. The other steps are the same as those in the first to fourth embodiments.

[0029] Specific implementation method 6: This implementation method is a method for preparing a high-entropy rare earth tantalate ceramic with ultra-low transmittance / wide-band high emissivity, which is specifically completed in the following steps:

[0030] 1. According to the phase composition of the high entropy rare earth tantalate ceramic, four RE 2 O 3 , Gd 2 O 3 and Ta 2 O 5 ; Remove four REs 2 O 3 , Gd 2 O 3 and Ta 2 O 5 The impurities and bound water in the raw material are removed, and then the raw material powder is mixed uniformly by wet ball milling, evaporated and dried, ground and sieved to obtain a uniformly mixed raw material powder; the uniformly mixed raw material powder is calcined to obtain a high entropy rare earth tantalate ceramic raw material powder;

[0031] RE described in step 1 2 O 3 Pr 2 O 3 、Nd 2 O 3 、Sm 2 O 3 、Eu 2 O 3 , Tb2 O 3 、Dy 2 O 3 and Y 2 O 3 Any 4 rare earth oxides; 4 rare earth oxides, Gd 2 O 3 And 2 O 5 The molar ratio is 0.6:0.6:0.6:0.6:0.6:1;

[0032] 2. Pre-pressing the raw material powder of high-entropy rare earth tantalate ceramics, cold isostatic pressing, and high-temperature pressureless sintering to obtain high-entropy rare earth tantalate ceramics with ultra-low transmittance / wide-band high emissivity.

[0033] Specific embodiment 7: The difference between this embodiment and specific embodiments 1 to 6 is that the particle size of the raw material powder described in step 1 is 1 to 3 μm, and the purity is ≥ 99.9%; the four RE are removed in step 1 2 O 3 , Gd 2 O 3 and Ta 2 O 5 The method for determining the impurities and bound water in the mixture is as follows: weigh the four RE 2 O 3 , Gd 2 O 3 and Ta 2 O 5 The four REs were calcined at 600℃~900℃ for 3h~6h and cooled to room temperature to obtain the four REs with impurities and bound water removed. 2 O 3 , Gd 2 O 3 and Ta 2 O 5 The other steps are the same as those in Specific Embodiments 1 to 6.

[0034] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that the wet ball milling method described in step 1 is to remove impurities and bound water from the four RE 2 O 3 , Gd 2 O 3 、 2 O 5 , anhydrous ethanol and zirconium oxide grinding balls are placed in a ball mill, and then ball milled at a speed of 500r / min to 600r / min for 10h to 15h; the four REs for removing impurities and bound water are 2 O 3 , Gd 2O 3 and Ta 2 O 5 The total mass of the anhydrous ethanol and the mass ratio of the zirconium oxide microspheres is 1:(0.15-0.25):(4-6); the diameter of the zirconium oxide microspheres is 1 mm to 5 mm. The other steps are the same as those of the first to seventh embodiments.

[0035] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that: the evaporation drying method described in step 1 is: drying at 90°C to 110°C for 10h to 15h; the sieving described in step 1 is sieving through a 400-600 mesh sieve; the calcination process described in step 1 is: heating from room temperature to 1450°C at a heating rate of 1°C / min to 3°C / min, calcining at 1450°C for 6-8h, and then cooling to room temperature with the furnace. The other steps are the same as those of specific embodiments 1 to 8.

[0036] Specific embodiment 10: The difference between this embodiment and specific embodiments 1 to 9 is that: the method of high-temperature pressureless sintering described in step 2 is: heating from room temperature to 1700°C at a heating rate of 1°C / min to 3°C / min, calcining at 1700°C for 8 to 10 hours, and then cooling to room temperature with the furnace; the method of pre-pressing molding described in step 2 is: using a press to pre-press the high-entropy rare earth tantalate ceramic raw material powder into a columnar block, the pressure is 8 to 10MPa, and the holding time is 4min to 6min; the pressure of cold isostatic pressing described in step 2 is 180MPa to 220MPa, and the holding time is 4min to 6min. The other steps are the same as specific embodiments 1 to 9.

[0037] The following examples are used to verify the beneficial effects of the present invention:

[0038] Example 1: A high entropy rare earth tantalate ceramic (Nd 0.2 Sm 0.2 G 0.2 Dy 0.2 Y 0.2 ) 3 TaO 7 , denoted as NSGDYTO), which is specifically completed by the following steps:

[0039] 1. According to the phase composition of the high entropy rare earth tantalate ceramic, Nd 2 O 3 、Sm 2 O 3 , Gd 2 O 3 、Dy 2 O 3 , Y2 O 3 and Ta 2 O 5 ; Remove Nd 2 O 3 、Sm 2 O 3 , Gd 2 O 3 、Dy 2 O 3 , Y 2 O 3 and Ta 2 O 5 The impurities and bound water in the raw material are removed, and then the raw material powder is mixed uniformly by wet ball milling, evaporated and dried, ground for 4 hours, and sieved to obtain a uniformly mixed raw material powder; the uniformly mixed raw material powder is calcined to obtain a high entropy rare earth tantalate ceramic raw material powder;

[0040] Nd as described in step 1 2 O 3 、Sm 2 O 3 , Gd 2 O 3 、Dy 2 O 3 , Y 2 O 3 and Ta 2 O 5 The molar ratio is 0.6:0.6:0.6:0.6:0.6:1;

[0041] The particle size of the raw material powder in step 1 is 1 to 3 μm, and the purity is ≥ 99.9%;

[0042] Removal of Nd in step 1 2 O 3 、Sm 2 O 3 , Gd 2 O 3 、Dy 2 O 3 , Y 2 O 3 and Ta 2 O 5 The method of combining impurities and water in the mixture is as follows: weigh Nd 2 O 3 、Sm 2 O 3 , Gd 2 O 3 、Dy 2 O 3 , Y 2 O 3 and Ta 2 O5 They were calcined at 700℃ for 6h and cooled to room temperature to obtain four types of Nd 2 O 3 、Sm 2 O 3 , Gd 2 O 3 、Dy 2 O 3 , Y 2 O 3 and Ta 2 O 5 ;

[0043] The wet ball milling method described in step 1 is: remove impurities and bound water from the Nd 2 O 3 、Sm 2 O 3 , Gd 2 O 3 、Dy 2 O 3 , Y 2 O 3 and Ta 2 O 5 , anhydrous ethanol and zirconium oxide grinding balls are placed in a ball mill, and then ball milled at a speed of 600r / min for 12h; the Nd 2 O 3 、Sm 2 O 3 , Gd 2 O 3 、Dy 2 O 3 , Y 2 O 3 and Ta 2 O 5 The total mass of the zirconia microspheres is in a mass ratio of 1:0.25:4 to anhydrous ethanol; the diameters of the zirconia microspheres are 1 mm, 3 mm and 5 mm, and the mass ratio of the three is 1:1:1;

[0044] The evaporation drying method described in step 1 is: drying at 110° C. for 10 h;

[0045] The sieving described in step 1 is through a 600 mesh sieve;

[0046] The calcination process described in step 1 is: heating from room temperature to 1450° C. at a heating rate of 3° C. / min, calcining at 1450° C. for 8 h, and then cooling to room temperature in the furnace;

[0047] Second, the raw material powder of high entropy rare earth tantalate ceramic is pre-pressed, cold isostatically pressed, and sintered at high temperature without pressure to obtain high entropy rare earth tantalate ceramic ((Nd 0.2 Sm 0.2 G 0.2 Dy 0.2 Y 0.2 ) 3 TaO 7 , denoted as NSGDYTO);

[0048] The high temperature pressureless sintering method described in step 2 is: heating from room temperature to 1700°C at a heating rate of 2°C / min, calcining at 1700°C for 10 hours, and then cooling to room temperature with the furnace;

[0049] The pre-pressing method described in step 2 is: using a press to pre-press the high entropy rare earth tantalate ceramic raw material powder into a columnar block, the pressure is 10MPa, and the pressure holding time is 4min;

[0050] The cold isostatic pressing pressure in step 2 is 180 MPa, and the holding time is 6 min.

[0051] Example 2: The difference between this example and Example 1 is that in step 1, Eu is weighed in a stoichiometric ratio according to the phase composition of the high entropy rare earth tantalate ceramic. 2 O 3 、Sm 2 O 3 , Gd 2 O 3 、Dy 2 O 3 , Y 2 O 3 and Ta 2 O 5 ; Remove Eu 2 O 3 、Sm 2 O 3 , Gd 2 O 3 、Dy 2 O 3 , Y 2 O 3 and Ta 2 O 5 The impurities and bound water in the raw material are removed, and then the raw material powder is mixed uniformly by wet ball milling, evaporated and dried, ground for 4 hours, and sieved to obtain a uniformly mixed raw material powder; the uniformly mixed raw material powder is calcined to obtain a high entropy rare earth tantalate ceramic raw material powder;

[0052] Eu as described in step 1 2 O 3 、Sm2 O 3 , Gd 2 O 3 、Dy 2 O 3 , Y 2 O 3 and Ta 2 O 5 The molar ratio is 0.6:0.6:0.6:0.6:0.6:1; the phase of the high entropy rare earth tantalate ceramic with ultra-low transmittance / wide-band high emissivity obtained in step 2 is: (Eu 0.2 Smd 0.2 G 0.2 Dy 0.2 Y 0.2 ) 3 TaO 7 , denoted as ESGDYTO. Other steps and parameters are the same as those in Example 1.

[0053] Comparative Example 1: Pure phase rare earth tantalate (Gd 3 TaO 7 The preparation method of the ceramic block is specifically completed by the following steps:

[0054] 1. Weigh Gd 2 O 3 and Ta 2 O 5 , the Gd 2 O 3 and Ta 2 O 5 The mixed powder is calcined to obtain a pure phase rare earth tantalate ceramic powder (Gd 3 TaO 7 );

[0055] Gd as described in step 1 2 O 3 and Ta 2 O 5 The molar ratio is 3:1;

[0056] The mixing method described in step 1 is: weigh the Gd 2 O 3 、 2 O 5 The samples were calcined at 900 °C for 6 h and cooled to room temperature to obtain Gd 2 O 3 , Ta2O5; Gd 2 O 3 and Ta 2 O 5, anhydrous ethanol and zirconium oxide grinding balls were put into a ball mill, and then ball milled at a speed of 450 r / min for 12 h, dried at 100 ° C for 10 h, ground for 2 h, and passed through a 200-mesh sieve to obtain a mixed powder; the Gd 2 O 3 and Ta 2 O 5 The mass ratio of the total mass to anhydrous ethanol and zirconium oxide microspheres is 1:0.2:4; the diameters of the zirconium oxide microspheres are 1 mm and 3 mm, and the mass ratio of the zirconium oxide microspheres with diameters of 1 mm and 3 mm is 1:1;

[0057] The calcination process described in step 1 is: heating to 1450° C. at a heating rate of 5° C. / min, calcining at 1450° C. for 6 hours, and then cooling to room temperature in the furnace;

[0058] 2. Pure phase rare earth tantalate ceramic powder (Gd 3 TaO 7 ) pre-pressed, cold isostatically pressed, and calcined to obtain pure phase rare earth tantalate (Gd 3 TaO 7 , denoted as GTO) ceramic block;

[0059] The pre-pressing molding in step 2 is as follows: using a press to press the pure phase rare earth tantalate ceramic powder (Gd 3 TaO 7 ) is pre-pressed into a columnar block at a pressure of 12 MPa and a holding time of 5 min;

[0060] The cold isostatic pressing pressure in step 2 is 250 MPa, and the holding time is 5 min;

[0061] The calcination process described in step 2 is: heating to 1650° C. at a heating rate of 5° C. / min, calcining at 1650° C. for 10 hours, and then cooling to room temperature in the furnace.

[0062] Comparative Example 2: Medium Entropy Rare Earth Tantalate (Gd 1 / 3 Dy 1 / 3 Y 1 / 3 ) 3 TaO 7 The preparation method of the ceramic block is specifically completed by the following steps:

[0063] 1. Weigh Gd 2 O 3 、Dy 2 O 3 , Y 2 O 3 and Ta 2 O 5 , the Gd2 O 3 、Dy 2 O 3 , Y 2 O 3 and Ta 2 O 5 The mixed powder I is calcined to obtain rare earth tantalate-based ceramic powder (Gd 1 / 3 Dy 1 / 3 Y 1 / 3 ) 3 TaO 7 );

[0064] Gd as described in step 1 2 O 3 、Dy 2 O 3 , Y 2 O 3 and Ta 2 O 5 The molar ratio is 1:1:1:1;

[0065] The mixing method described in step 1 is: weigh the Gd 2 O 3 、Dy 2 O 3 , Y 2 O 3 and Ta 2 O 5 , calcined at 700℃ for 6h, and cooled to room temperature to obtain Gd 2 O 3 、Dy 2 O 3 , Y 2 O 3 and Ta 2 O 5 ; Gd that removes impurities and bound water 2 O 3 、Dy 2 O 3 , Y 2 O 3 、 2 O 5 , anhydrous ethanol and zirconium oxide grinding balls were put into a ball mill, and then ball milled at a speed of 600 r / min for 12 h, dried at 110 ° C for 10 h, ground for 4 h, and passed through a 600-mesh sieve to obtain a mixed powder I; the Gd 2 O 3 、Dy 2 O 3 , Y 2 O3 and Ta 2 O 5 The mass ratio of the total mass of the anhydrous ethanol and the zirconium oxide microspheres is 1:0.25:4; the diameter sizes of the zirconium oxide microspheres are 1mm, 3mm and 5mm, and the mass ratio of the zirconium oxide microspheres with diameters of 1mm, 3mm and 5mm is 1:1:1 for mixing;

[0066] The calcination process described in step 1 is: heating to 1450° C. at a heating rate of 3° C. / min, calcining at 1450° C. for 8 h, and then cooling to room temperature in the furnace;

[0067] 2. Rare earth tantalate-based ceramic powder (Gd 1 / 3 Dy 1 / 3 Y 1 / 3 ) 3 TaO 7 ) pre-pressing, cold isostatic pressing, high temperature pressureless sintering, synthesis of medium entropy rare earth tantalate ((Gd 1 / 3 Dy 1 / 3 Y 1 / 3 ) 3 TaO 7 , denoted as GDYTO) ceramic block.

[0068] The pre-pressing molding in step 2 is as follows: using a press to press the rare earth tantalate-based ceramic powder ((Gd 1 / 3 Dy 1 / 3 Y 1 / 3 ) 3 TaO 7 ) is pre-pressed into a columnar block at a pressure of 10 MPa and a holding time of 4 minutes; the pressure of the cold isostatic pressing described in step 2 is 180 MPa and the holding time is 6 minutes; the process of high-temperature pressureless sintering described in step 2 is: heating to 1700°C at a heating rate of 2°C / min, calcining at 1700°C for 10 hours, and then cooling to room temperature with the furnace.

[0069] Comparative Example 3: Medium Entropy Rare Earth Tantalate (Sm 0.25 G 0.25 Dy 0.25 Y 0.25 ) 3 TaO 7 The preparation method of the ceramic block is specifically completed by the following steps:

[0070] 1. Weigh Sm 2 O 3 , Gd 2 O 3 、Dy 2 O 3 , Y2 O 3 and Ta 2 O 5 , the weighed Sm 2 O 3 , Gd 2 O 3 、Dy 2 O 3 , Y 2 O 3 and Ta 2 O 5 The mixed powder I is calcined to obtain rare earth tantalate-based ceramic powder (Sm 0.25 G 0.25 Dy 0.25 Y 0.25 ) 3 TaO 7 );

[0071] Sm described in step 1 2 O 3 , Gd 2 O 3 、Dy 2 O 3 , Y 2 O 3 and Ta 2 O 5 The molar ratio is 0.75:0.75:0.75:0.75:1;

[0072] The mixing method described in step 1 is: weigh the Sm 2 O 3 , Gd 2 O 3 、Dy 2 O 3 , Y 2 O 3 and Ta 2 O 5 , calcined at 700℃ for 6h, and cooled to room temperature to obtain Sm 2 O 3 , Gd 2 O 3 、Dy 2 O 3 , Y 2 O 3 and Ta 2 O 5 ; Remove impurities and bound water from Sm 2 O 3 , Gd 2 O 3 、Dy2 O 3 , Y 2 O 3 、 2 O 5 , anhydrous ethanol and zirconium oxide grinding balls were put into a ball mill, and then ball milled at a speed of 600 r / min for 12 h, dried at 110 ° C for 10 h, ground for 4 h, and passed through a 600-mesh sieve to obtain a mixed powder I; the Sm 2 O 3 , Gd 2 O 3 、Dy 2 O 3 , Y 2 O 3 and Ta 2 O 5 The mass ratio of the total mass of the zirconia microspheres to anhydrous ethanol and zirconium oxide microspheres is 1:0.25:4; the diameters of the zirconium oxide microspheres are 1mm, 3mm and 5mm, and the mass ratio of the zirconium oxide microspheres with diameters of 1mm, 3mm and 5mm is 1:1:1;

[0073] The calcination process described in step 1 is: heating to 1450° C. at a heating rate of 3° C. / min, calcining at 1450° C. for 8 h, and then cooling to room temperature in the furnace;

[0074] Second, the ceramic powder is pre-pressed, cold isostatically pressed, and sintered at high temperature without pressure to obtain medium entropy rare earth tantalate (Sm 0.25 G 0.25 Dy 0.25 Y 0.25 ) 3 TaO 7 , denoted as SGDYTO) ceramic block;

[0075] The pre-pressing molding described in step 2 is: use a press to pre-press the ceramic powder into a columnar block, the pressure is 10MPa, and the holding time is 4min; the pressure of the cold isostatic pressing described in step 2 is 180MPa, and the holding time is 6min; the high-temperature pressureless sintering process described in step 2 is: heat up to 1700℃ at a heating rate of 2℃ / min, calcine at 1700℃ for 10h, and then cool to room temperature with the furnace.

[0076] Test: The ceramic samples prepared in Examples 1, 2 and Comparative Examples 1, 2 and 3 were cut into the required sizes according to the test requirements. The phases of the samples were analyzed by X-ray diffractometer (XRD), and the 2θ range was 10° to 90°. The test results are as follows: Figure 1 The surface morphology of the sample was observed by scanning electron microscopy (SEM), and the test results are shown in Figure 2The linear-hemispherical transmittance of the sample at 400nm to 2500nm was measured using a UV-Vis-NIR spectrometer. The test results are shown in Figure 3 As shown. Using the spectral integrating sphere reflection method, with gold as the reference sample and the light incident angle of 0°, the sample spectral emissivity is measured. The test results are shown in Figure 4 The thermal conductivity of the sample was measured using an LFA457 laser thermal conductivity meter at 20°C to 1200°C, where the interval from room temperature to 1200°C was 200°C. The test results are shown in Figure 5 shown.

[0077] from Figure 1 It can be seen from the XRD diffraction patterns that the NSGDYTO, ESGDYTO, GDYTO and SGDYTO materials prepared in Examples 1 and 2 and Comparative Examples 2 and 3 respectively have no obvious impurity peaks and are all Weber structure. Compared with the standard card of GTO, the XRD peaks all show a certain degree of deviation, which indicates a high degree of lattice distortion inside the lattice. Compared with the standard card of GTO prepared in Comparative Example 1, the GTO material prepared in Comparative Example 1 shows that the Weber structure Gd 3 TaO 7 composition.

[0078] from Figure 2 The SEM spectra show that Examples 1 and 2 have the smallest grain size, specifically between 1000-3000 nm, while Comparative Examples 1, 2, and 3 have larger grain sizes. The porosity of all samples is <1%, and it can be considered that the difference in porosity between the samples has negligible effect on their performance.

[0079] from Figure 3 It can be seen from the infrared transmittance test chart that the high entropy materials prepared in Examples 1 and 2 respectively have extremely low transmittance, and the transmittance is <1.5% in the wavelength range of 400-2500nm. This verifies the excellent infrared radiation shielding performance of the high entropy rare earth tantalate ceramics with ultra-low transmittance / wide-band high emissivity proposed in the present invention. The GTO material prepared in Comparative Example 1 has a significant increase in infrared transmittance with increasing wavelength, and the transmittance is as high as 60% in the wavelength range of 400nm-2500nm; the medium entropy rare earth tantalate ceramics prepared in Comparative Examples 2 and 3 have a transmittance of up to 8% in the wavelength range of 400nm-2500nm. This proves the importance of the basis for selecting rare earth elements.

[0080] from Figure 4 It can be seen from the infrared emissivity test graph that the high entropy ceramic materials prepared in Examples 1 and 2 respectively have a higher infrared emissivity, while the tantalate materials prepared in Comparative Examples 1, 2, and 3 have a lower emissivity in the 2.5μm-14μm band, especially in the low infrared band of 2.5μm-6μm, reflecting its low infrared absorption characteristics.

[0081] from Figure 5 The thermal conductivity test graph shows that the high entropy ceramic materials prepared in Examples 1 and 2 have the lowest thermal conductivity, and their thermal conductivity at 1000°C is lower than 1.3 W·m -1 ·K -1 More importantly, its thermal conductivity curve after high temperature (over 600°C) shows a downward trend, which proves the fact that its high-temperature transmittance is the lowest. The thermal conductivity of the tantalate materials prepared in Comparative Examples 1, 2, and 3 is higher than that of the high-entropy sample, which confirms the feasibility of reducing thermal conductivity by introducing a high-entropy design strategy in the present invention.

Claims

1. A high entropy rare earth tantalate ceramic with ultra-low transmittance / wide-band high emissivity, characterized in that The phase composition of the high entropy rare earth tantalate ceramic is (4RE 0.2 G 0.2 )3TaO7, wherein RE is a combination of any 4 elements among Pr, Nd, Sm, Eu, Tb, Dy and Y, and the molar ratio of the 4 elements and Gd is 1:1:1:1:

1.

2. A high entropy rare earth tantalate ceramic with ultra-low transmittance / wide-band high emissivity according to claim 1, characterized in that The grain size of the high-entropy rare earth tantalate ceramic is 1000-3000nm.

3. The high entropy rare earth tantalate ceramic with ultra-low transmittance / wide-band high emissivity according to claim 1, characterized in that The atomic configuration entropy S of the high-entropy rare earth tantalate ceramic is ≥1.62R.

4. The high entropy rare earth tantalate ceramic with ultra-low transmittance / wide-band high emissivity according to claim 1, characterized in that The high entropy rare earth tantalate ceramic has an infrared transmittance of less than 3% in the near infrared band of 780nm to 2500nm, an average emissivity of more than 0.9 at room temperature in the infrared band of 2.5 to 14μm, and an average emissivity of more than 0.75 at a high temperature of 1200°C.

5. The high entropy rare earth tantalate ceramic with ultra-low transmittance / wide-band high emissivity according to claim 1, characterized in that The high entropy rare earth tantalate ceramic has no phase change after being kept at 1500°C for 200 hours in an air atmosphere; the thermal conductivity at 1000°C is less than 1.3 W·m -1 ·K -1 , much lower than 8YSZ.

6. The method for preparing a high entropy rare earth tantalate ceramic having both ultra-low transmittance and wide-band high emissivity as claimed in claim 1, characterized in that The preparation method is specifically completed according to the following steps:

1. According to the phase composition of the high-entropy rare earth tantalate ceramic, four kinds of RE2O3, Gd2O3 and Ta2O5 are weighed in a stoichiometric ratio; impurities and bound water in the four kinds of RE2O3, Gd2O3 and Ta2O5 are removed, and then wet ball milling is used to mix them uniformly, evaporate and dry, grind and sieve to obtain a uniformly mixed raw material powder; the uniformly mixed raw material powder is calcined to obtain a high-entropy rare earth tantalate ceramic raw material powder; The RE2O3 described in step 1 is any four rare earth oxides of Pr2O3, Nd2O3, Sm2O3, Eu2O3, Tb2O3, Dy2O3 and Y2O3; the molar ratio of the four rare earth oxides, Gd2O3 and Ta2O5 is 0.6:0.6:0.6:0.6:0.6:1; 2. Pre-pressing the raw material powder of high-entropy rare earth tantalate ceramics, cold isostatic pressing, and high-temperature pressureless sintering to obtain high-entropy rare earth tantalate ceramics with ultra-low transmittance / wide-band high emissivity.

7. The method for preparing a high entropy rare earth tantalate ceramic having both ultra-low transmittance and wide-band high emissivity according to claim 6, characterized in that The particle size of the raw material powder described in step one is 1 to 3 μm, and the purity is ≥ 99.9%; the method for removing impurities and bound water in the four RE2O3, Gd2O3 and Ta2O5 in step one is: the four weighed RE2O3, Gd2O3 and Ta2O5 are calcined at 600°C to 900°C for 3h to 6h respectively, and cooled to room temperature with the furnace to obtain the four RE2O3, Gd2O3 and Ta2O5 with impurities and bound water removed.

8. The method for preparing a high entropy rare earth tantalate ceramic having both ultra-low transmittance and wide-band high emissivity according to claim 6, characterized in that The wet ball milling method described in step one is: put the four RE2O3, Gd2O3, Ta2O5 from which impurities and bound water are removed, anhydrous ethanol and zirconia grinding balls into a ball mill, and then ball mill at a speed of 500r / min~600r / min for 10h~15h; the total mass of the four RE2O3, Gd2O3 and Ta2O5 from which impurities and bound water are removed, the mass ratio of anhydrous ethanol and zirconia microspheres is 1:(0.15~0.25):(4~6); the diameter of the zirconia microspheres is 1mm~5mm.

9. The method for preparing a high entropy rare earth tantalate ceramic having both ultra-low transmittance and wide-band high emissivity according to claim 6, characterized in that The evaporation drying method described in step one is: drying at 90°C to 110°C for 10h to 15h; the screening described in step one is through a 400-600 mesh sieve; the calcination process described in step one is: heating from room temperature to 1450°C at a heating rate of 1°C / min to 3°C / min, calcining at 1450°C for 6-8h, and then cooling to room temperature with the furnace.

10. The method for preparing a high entropy rare earth tantalate ceramic with ultra-low transmittance / wide-band high emissivity according to claim 6, characterized in that The high-temperature pressureless sintering method described in step 2 is: heating from room temperature to 1700°C at a heating rate of 1°C / min to 3°C / min, calcining at 1700°C for 8 to 10 hours, and then cooling to room temperature with the furnace; the pre-pressing method described in step 2 is: using a press to pre-press the high-entropy rare earth tantalate ceramic raw material powder into a columnar block, the pressure is 8 to 10MPa, and the holding time is 4min to 6min; the cold isostatic pressing pressure described in step 2 is 180MPa to 220MPa, and the holding time is 4min to 6min.

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