A high-toughness, high-entropy zirconate material and its preparation method

Abstract

This invention belongs to the field of high-entropy ceramic materials technology, specifically relating to a high-toughness high-entropy zirconate material and its preparation method. Using trivalent rare earth oxides and tetravalent zirconium oxide as raw materials, heterovalent doping is performed using niobium pentoxide. High-entropy ceramic powder is prepared using a mechanical activation and segmented sintering reaction method; then, the high-entropy ceramic powder is pressed into discs, and the ceramic blanks are calcined in a muffle furnace. After calcination, the blanks are cooled with the furnace. The prepared high-entropy ceramic material is entirely composed of the pyrochlore phase, exhibiting better fracture toughness.

Description

Technical Field

[0001] This invention belongs to the field of high-entropy ceramic materials, specifically relating to a high-toughness high-entropy zirconate material and its preparation method. Background Technology

[0002] Thermal barrier coatings (TBCs) are coatings that provide thermal insulation for hot-end components in aerospace and gas turbine industries. Their function is to enable materials like gas turbines to operate under high-temperature conditions for extended periods, increasing the corrosion resistance and thermal insulation of hot-end components to extend their service life. TBC materials generally need to possess the following properties: low thermal conductivity, a coefficient of thermal expansion lower than zirconium, and high-temperature phase stability. Currently, there are many new types of TBCs, such as rare-earth cerates, rare-earth silicates, rare-earth zirconates with fluorite and pyrochlore lattice structures, and rare-earth tantalates. However, these materials all have certain inherent performance defects, particularly their fracture toughness, which is lower than that of widely used yttrium-stabilized zirconia ceramic coatings. Fracture toughness represents a material's ability to prevent crack propagation. Failure of TBCs is usually due to crack initiation and propagation caused by thermal stress mismatch within the coating, leading to catastrophic failure. Higher fracture toughness ensures good performance against CMAS erosion and foreign object damage, preventing material failure. Therefore, it is necessary to research new TBC materials with higher toughness.

[0003] In recent years, materials ceramics have incorporated the high-entropy concept from high-entropy alloys to increase the entropy of ceramic materials. High entropy alters the chemical bonding and band structure of materials, thus regulating their properties. High-entropy rare-earth zirconates possess better thermal properties than YSZ (yttrium-stabilized zirconium oxide) and are considered candidate materials for thermal barrier coatings on engine hot-end components. They exhibit lower thermal conductivity and good high-temperature phase stability; however, their fracture toughness is lower than that of widely used yttrium-stabilized zirconium oxide ceramic coatings. Past studies have attempted to modify the fracture toughness by selecting different elements at the A-site in pyrochlore and fluorite structures, but the results have been unsatisfactory. Addressing the issue of low fracture toughness in high-entropy zirconates, providing a high-entropy rare-earth zirconate ceramic material with high toughness and its preparation method is of great significance for promoting the development and application of advanced ceramic materials. Summary of the Invention

[0004] The purpose of this invention is to solve the problem of toughness in high-entropy zirconate materials, and to provide a high-entropy ceramic material with high toughness and its preparation method.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a high-toughness high-entropy zirconate material with the chemical formula A2B2O7, wherein the A site is composed of five rare earth elements La, Sm, Eu, Yb, Y, Gd and Nd in equal molar ratios, and the B site is composed of at least one rare earth element Nb and Zr, wherein the molar ratio of Zr and Nb is X:1-X, and X = 0.5 to 1.

[0006] Preferably, the rare earth element A is La, Sm, Eu, Yb, Y or Yb, Sm, Eu, Gd, Nd, and the molar ratio of the elements is equal.

[0007] Preferably, the B-site is composed of rare earth elements Nb and Zr, with the molar ratio of Zr to Nb being X:1-X, where X = 0.5 to 0.6.

[0008] Preferably, the chemical formula of the high-entropy ceramic material with high toughness is: (La 0.2 Sm 0.2 Eu 0.2 Yb 0.2 Y 0.2 )2Zr2O7、(La 0.2 Sm 0.2 Eu 0.2 Yb 0.2 Y 0.2 )2(Zr 0.9 Nb 0.1 )2O7、(La 0.2 Sm 0.2 Eu 0.2 Yb 0.2 Y 0.2 )2(Zr 0.8 Nb 0.2 )2O7、(La 0.2 Sm 0.2 Eu 0.2 Yb 0.2 Y 0.2 )2(Zr 0.7 Nb 0.3 )2O7、(La 0.2 Sm 0.2 Eu 0.2 Yb 0.2 Y 0.2 )2(Zr 0.6 Nb 0.4 )2O7、(La 0.2 Sm 0.2 Eu 0.2 Yb 0.2 Y 0.2 )2(Zr 0.5 Nb 0.5 )2O7.

[0009] Furthermore, the high-toughness, high-entropy zirconate material is prepared by the following steps:

[0010] Step 1: Mixing of Oxide Raw Materials: Measure the metal oxides according to the specified proportions, mix them with the solvent, and ball mill to achieve mechanical mixing, thereby obtaining a slurry with the appropriate ratio. Pour out the mixed slurry and dry it in an oven to obtain the mixed raw material. The powder is then collected after sieving.

[0011] The solvent included anhydrous ethanol, with a solvent-to-metal oxide mass ratio of 1.5:1. The ball milling speed was set to 380 rpm, and the milling time was 12 hours. The grinding balls used had diameters of 10 mm, 7 mm, and 5 mm, corresponding to large, medium, and small balls, respectively. These three sizes of grinding balls were mixed in a 2:3:1 ratio to ensure thorough powder mixing. The drying oven temperature was set to 80℃~100℃, the drying time was 12 hours, and a 200-mesh sieve was used, with a sieve aperture size of 0.0750 mm.

[0012] Step 2: The collected powder is sintered in multiple stages. After each stage of sintering is completed, it is mechanically activated by ball milling to obtain high-entropy ceramic powder.

[0013] The sintering temperature was set at 1300–1500℃, with each sintering session lasting 2–4 hours. After each sintering, the powder was mixed with anhydrous ethanol solvent and ball-milled. Repeated ball milling achieved mechanical activation, enhancing powder activity and thus lowering the sintering temperature, which facilitated better sample synthesis. The ball mill speed was set at 320–400 rpm, and the milling time was 8–12 hours. The grinding balls used had diameters of 10 mm, 7 mm, and 5 mm, corresponding to large, medium, and small balls, respectively. These three sizes of grinding balls were mixed in a 2:3:1 ratio. The drying temperature in the oven was controlled at 80℃–100℃, and the drying time was 8–12 hours.

[0014] Step 3: Preparation of high-toughness ceramic bulk: Grind the high-entropy ceramic powder obtained in Step 2, sieve it, and place it in a powder press to obtain a round ceramic blank; after pressing, embed the ceramic blank with high-entropy ceramic powder or zirconium oxide powder and place it in a muffle furnace for segmented sintering. After sintering, allow it to cool naturally to obtain high-toughness high-entropy ceramic material.

[0015] The sintered high-entropy ceramic powder was crushed and ground in a mortar and sieved through a 200-mesh sieve. When pressing the ceramic block with a benchtop press, the pressure was set to 10-15 MPa, and the holding time was controlled to be 1.5-3 min. The powder used for embedding was the high-entropy ceramic powder or zirconium oxide powder obtained earlier. The sintering temperature was set to 1300-1500℃, and the sintering time at each temperature point was 2 hours, for a total sintering time of 6 hours.

[0016] The beneficial effects of this invention are as follows:

[0017] This invention employs heterovalent doping, using Nb with a smaller radius. 5+ Zr doped at B sites 4+ The doped materials are all in the same pyrochlore structure. Five elements were selected at the A site for high entropy enhancement. These five elements can stabilize the pyrochlore structure. The ionic radius and atomic mass of the high-entropy elements will increase the overall lattice distortion of the material, making the thermal properties of the material better.

[0018] It is difficult for ceramic blocks prepared by ordinary sintering to achieve complete density, and some pores will remain. The ratio of the volume of pores to the volume of ceramic is called porosity. An increase in porosity has an adverse effect on the performance of ceramics.

[0019] Based on the selection at position A, heterovalent doping is performed using Nb. 5+ Zr doping substitution 4+ Nb was discovered 5+ Doping with Nb can alter the structure of materials, and with the addition of Nb 5+ The doping of this material produces columnar crystals and alters the porosity of the ceramic bulk, resulting in a smaller porosity, which improves the mechanical properties of the material and enhances the toughness and hardness of zirconate high-entropy ceramics. Attached image description:

[0020] Figure 1 The images show the XRD patterns of the high-entropy ceramic materials prepared in Examples 1-6.

[0021] Figure 2 SEM images of the high-entropy ceramic blocks prepared in Examples 1(a) and 4(b);

[0022] Figure 3 Fracture toughness diagrams of the high-entropy zirconate ceramic materials prepared in Examples 1, 2, 4, 6 and Comparative Examples 1-4;

[0023] Figure 4 The XRD patterns of the high-entropy zirconate ceramic bulk prepared in Example 2.4.6, sintered at 1500℃ for 10 h, are compared with those of the unsintered bulk. Detailed Implementation

[0024] The present invention will now be described in detail with reference to specific embodiments.

[0025] The fracture toughness and strength measurement method is as follows: The Vickers hardness and fracture toughness of the ceramic sample are tested using a Vickers microhardness tester. The testing method is the indentation method, and the ceramic sample surface needs to be polished before testing. A pyramidal Vickers indenter is used to press an indentation on the sample surface, and the fracture toughness is calculated by the indentation and crack length.

[0026] Example 1

[0027] Step 1: Mixing of Oxide Raw Materials: Six oxides—La₂O₃, Sm₂O₃, Eu₂O₃, Yb₂O₃, Y₂O₃, and ZrO₂—were weighed in a molar ratio of 1:1:1:1:1:5. They were dispersed in anhydrous ethanol at a mass ratio of 1.5:1 to the total mass of the oxides. The mixture was then ball-milled using grinding balls with diameters of 10mm, 7mm, and 5mm, corresponding to large, medium, and small balls, respectively. These three sizes of grinding balls were mixed in a 2:3:1 ratio. The milling speed was 380 rpm, and the milling time was set to 12 hours. The resulting slurry was then passed through a 200-mesh sieve and placed in an oven at 100℃ for 12 hours. After drying, the slurry was passed through a 200-mesh standard sieve again to obtain the mixed powder.

[0028] Step 2: The mixed powder was sintered in a muffle furnace at 1300℃ for 2 hours, then naturally cooled to room temperature. The cooled powder was mixed with anhydrous ethanol at a mass ratio of 1:1.5 and mechanically activated in a ball mill. The grinding balls used had diameters of 10mm, 7mm, and 5mm, corresponding to large, medium, and small balls, respectively. The grinding balls were mixed in a ratio of large, medium, and small balls of 2:3:1. The milling speed was set at 380 rpm for 12 hours. After activation, the powder was dried in an oven at 100℃ for 12 hours. Subsequently, it was sintered at 1400℃ for 2 hours. The powder was then mixed with anhydrous ethanol at a mass ratio of 1:1.5 and mechanically activated (as above). Finally, the activated powder was sintered at 1500℃ for 2 hours to obtain high-entropy ceramic powder.

[0029] Step 3: Preparation of high-toughness ceramic blocks: The high-entropy ceramic powder obtained from the final activation and sintering is ground, passed through a 200-mesh sieve, and 1.5g of powder is weighed and placed into a powder press. The pressure of the press is set to 10MPa and the holding time is 2min. The ceramic blanks are pressed into round ceramic blanks. The ceramic blanks are coated with zirconium oxide powder and then placed in a muffle furnace for segmental sintering. The temperature points of 1300, 1400 and 1500℃ are held for two hours respectively. After the sintering is completed, the temperature is naturally cooled to obtain high-toughness high-entropy ceramic material blocks.

[0030] Figure 1 The XRD diffraction pattern of the ceramic material prepared in this embodiment shows the characteristic peaks (311), (331), and (511) of the pyrochlore structure. Therefore, the high-entropy ceramic material is a pyrochlore phase.

[0031] Figure 2 The image shows a SEM image of the high-entropy ceramic bulk material prepared in this embodiment. As can be seen from the image, the high-entropy ceramic bulk material has obvious grain boundaries.

[0032] from Figure 3 As can be seen from the data, the fracture toughness of the ceramic block synthesized in this embodiment is 1.65 MPa·m. 1 / 2 A comparison with the comparative example shows that the fracture toughness of the material is not significantly different from that of the comparative example.

[0033] Example 2:

[0034] The difference between Example 2 and Example 1 is that in step one, seven oxides, namely La2O3, Sm2O3, Eu2O3, Yb2O3, Y2O3, ZrO2 and Nb2O5, are weighed in a molar ratio of 1:1:1:1:1:4.5:0.5 and dispersed in anhydrous ethanol. The remaining steps are the same as in Example 1.

[0035] Figure 1 The XRD diffraction pattern of the ceramic material prepared in this embodiment shows the characteristic peaks (311), (331), and (511) of the pyrochlore structure, indicating that the high-entropy ceramic material is a pyrochlore phase.

[0036] from Figure 3 As can be seen from the data, the fracture toughness of the ceramic block synthesized in this embodiment is 1.75 MPa·m. 1 / 2 By comparing with Example 1 and the comparative example, it can be seen that the fracture toughness of the material is better than the strength when no heterovalent doping was performed.

[0037] Figure 4 The image shows a comparison of the XRD patterns of the prepared high-entropy zirconate ceramic bulk after sintering at 1500℃ for 10 hours with the unsintered material. The ceramic material prepared in this example can still maintain its original structure after sintering at 1500℃ for 10 hours, and has excellent high-temperature stability.

[0038] Example 3:

[0039] The difference between Example 3 and Example 1 is that in step one, seven oxides, namely La2O3, Sm2O3, Eu2O3, Yb2O3, Y2O3, ZrO2 and Nb2O5, are weighed in a molar ratio of 1:1:1:1:1:4:1 and dispersed in anhydrous ethanol. The remaining steps are the same as in Example 1.

[0040] Figure 1 The XRD diffraction pattern of the ceramic material prepared in this embodiment shows the characteristic peaks (311), (331), and (511) of the pyrochlore structure. Therefore, the high-entropy ceramic material is a pyrochlore phase.

[0041] from Figure 3 As can be seen from the data, the fracture toughness of the ceramic block synthesized in this embodiment is 1.92 MPa·m. 1 / 2 By comparing with the previous examples and comparative examples, it can be seen that the fracture toughness of the material is improved when heterovalent doping is performed.

[0042] Example 4:

[0043] The difference between Example 4 and Example 1 is that in step one, seven oxides, namely La2O3, Sm2O3, Eu2O3, Yb2O3, Y2O3, ZrO2 and Nb2O5, are weighed in a molar ratio of 1:1:1:1:1:3.5:1.5 and dispersed in anhydrous ethanol. The remaining steps are the same as in Example 1.

[0044] Figure 1 The XRD diffraction pattern of the ceramic material prepared in this embodiment shows the characteristic peaks (311), (331), and (511) of the pyrochlore structure. Therefore, the high-entropy ceramic material is a pyrochlore phase.

[0045] Figure 2 The image shows a SEM image of the high-entropy ceramic bulk material prepared in this embodiment. As can be seen from the image, many fine columnar crystals are generated at the grain boundaries of the high-entropy ceramic bulk material.

[0046] from Figure 3 As can be seen from the data, the fracture toughness of the ceramic block synthesized in this embodiment is 2.12 MPa·m. 1 / 2 By comparing with the previous examples and comparative examples, it can be seen that the fracture toughness of the material is improved when heterovalent doping is performed.

[0047] Figure 4The image shows a comparison of the XRD patterns of the prepared high-entropy zirconate ceramic bulk after sintering at 1500℃ for 10 hours with the unsintered material. The ceramic material prepared in this example can still maintain its original structure after sintering at 1500℃ for 10 hours, and has excellent high-temperature stability.

[0048] Example 5:

[0049] The difference between Example 5 and Example 1 is that in step one, seven oxides, namely La2O3, Sm2O3, Eu2O3, Yb2O3, Y2O3, ZrO2 and Nb2O5, are weighed in a molar ratio of 1:1:1:1:1:3:2 and dispersed in anhydrous ethanol. The remaining steps are the same as in Example 1.

[0050] Figure 1 The XRD diffraction pattern of the ceramic material prepared in this embodiment shows the characteristic peaks (311), (331), and (511) of the pyrochlore structure. Therefore, the high-entropy ceramic material is a pyrochlore phase.

[0051] from Figure 3 As can be seen from the data, the fracture toughness of the ceramic block synthesized in this embodiment is 2.46 MPa·m. 1 / 2 By comparing with the previous examples and comparative examples, it can be seen that the fracture toughness of the material is improved when heterovalent doping is performed.

[0052] Example 6:

[0053] The difference between Example 6 and Example 1 is that in step one, the seven oxides La2O3, Sm2O3, Eu2O3, Yb2O3, Y2O3, ZrO2 and Nb2O5 are weighed in a molar ratio of 1:1:1:1:1:2.5:2.5 and dispersed in anhydrous ethanol. The remaining steps are the same as in Example 1.

[0054] Figure 1 The XRD diffraction pattern of the ceramic material prepared in this embodiment shows the characteristic peaks (311), (331), and (511) of the pyrochlore structure. Therefore, the high-entropy ceramic material is a pyrochlore phase.

[0055] from Figure 3 As can be seen from the data, the fracture toughness of the ceramic block synthesized in this embodiment is 2.96 MPa·m. 1 / 2 By comparing with the previous examples and comparative examples, it can be seen that the fracture toughness of the material is improved when heterovalent doping is performed.

[0056] Figure 4To prepare a comparison of the XRD patterns of high-entropy zirconate ceramic blocks sintered at 1500℃ for 10h and unsintered, the ceramic material prepared in this example can still maintain its original structure after sintering at 1500℃ for 10h, and has excellent high-temperature stability.

[0057] Comparative Example 1:

[0058] The difference between Comparative Example 1 and Example 1 is that in Comparative Example 1, La2O3 and ZrO2 are weighed in a molar ratio of 1:2, dissolved in anhydrous ethanol, and the mass ratio of ethanol to powder is 1.5:1, followed by ball milling. The remaining steps are the same as in Example 1.

[0059] Depend on Figure 3 The fracture toughness spectrum corresponding to Comparative Example 1 shows that the fracture toughness of the ceramic prepared in this comparative example is 1.39 MPa·m. 1 / 2 Compared with other embodiments and comparative examples, the bulk mechanical properties prepared in Comparative Example 1 are poor.

[0060] Comparative Example 2:

[0061] The difference between Comparative Example 2 and Example 1 is that in step one, La2O3, Sm2O3, Eu2O3, Gd2O3, Nd2O3 and ZrO2 are weighed in a molar ratio of 1:1:1:1:1:5, dissolved in anhydrous ethanol, with an ethanol-to-powder mass ratio of 1.5:1, and then ball-milled. The remaining steps are the same as in Example 1.

[0062] Depend on Figure 3 The fracture toughness spectrum corresponding to Comparative Example 2 shows that the fracture toughness of the ceramic prepared in this comparative example is 1.33 MPa·m. 1 / 2 Compared with other embodiments and comparative examples, the bulk mechanical properties prepared in Comparative Example 2 are also poor.

[0063] Comparative Example 3:

[0064] The difference between Comparative Example 3 and Example 1 is that in step one, Yb₂O₃, Sm₂O₃, Eu₂O₃, Gd₂O₃, Nd₂O₃ and ZrO₂ are weighed in a molar ratio of 1:1:1:1:1:5, dissolved in anhydrous ethanol, with an ethanol-to-powder mass ratio of 1.5:1, and then ball-milled. The remaining steps are the same as in Example 1.

[0065] Depend on Figure 3 The fracture toughness spectrum corresponding to Comparative Example 3 shows that the fracture toughness of the ceramic prepared in this comparative example is 1.78 MPa·m. 1 / 2 .

[0066] Comparative Example 4:

[0067] The difference between Comparative Example 4 and Example 1 is that in step one, La2O3, Nd2O3, Eu2O3, Gd2O3, ZrO2, and HfO2 were weighed in a molar ratio of 1:1:1:1:2:2, dissolved in anhydrous ethanol, with an ethanol-to-powder mass ratio of 1.5:1, and then ball-milled. The remaining steps are the same as in Example 1.

[0068] Depend on Figure 3 The fracture toughness spectrum corresponding to Comparative Example 4 shows that the fracture toughness of the ceramic prepared in this comparative example is 1.63 MPa·m. 1 / 2 Compared with other embodiments and comparative examples, the mechanical properties of the block prepared in Comparative Example 4 are improved compared with the comparative examples, but they are still worse than those of the embodiments.

[0069] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A high-toughness, high-entropy zirconate material, characterized in that, The chemical formula of the high-entropy zirconate material is A2B2O7, where A is the rare earth element La, Sm, Eu, Yb, and Y, and the molar ratio of the elements is equal. B is Nb and Zr, and the molar ratio of Zr and Nb is X:1-X, where X = 0.5~0.

7.

2. A method for preparing a high-toughness, high-entropy zirconate material according to claim 1, characterized in that, The preparation method steps are as follows: Step 1: Measure the metal oxide according to the ratio, mix it with the solvent, ball mill the mixture, dry it, and collect it after sieving. Step 2: The collected powder is sintered in multiple stages. After each stage of sintering is completed, it is mechanically activated by ball milling to obtain high-entropy ceramic powder. Step 3: Grind and sieve the high-entropy ceramic powder obtained in Step 2, then press it into tablets, embed it, and sinter it in segments to prepare high-entropy ceramic blocks.

3. The method for preparing the high-toughness, high-entropy zirconate material according to claim 2, characterized in that, The solvent mentioned in step one is anhydrous ethanol; the mass ratio of the solvent to the total mass of the metal oxide is 1.5:

1.

4. The method for preparing the high-toughness, high-entropy zirconate material according to claim 2, characterized in that, The ball milling speed mentioned in step one is 320-400 revolutions per minute, and the time is 12 hours.

5. The method for preparing the high-toughness, high-entropy zirconate material according to claim 2, characterized in that, The multi-segment sintering temperature in step two is 1300~1500℃, and the sintering time for each segment is 2-4 hours; the ball milling speed in step two is set to 320-400 rpm, and the ball milling time is 8-12 hours.

6. The method for preparing the high-toughness, high-entropy zirconate material according to claim 2, characterized in that, The tableting process described in step three uses a powder tableting machine with a pressure of 10~15MPa and a holding time of 1.5~3min.

7. The method for preparing the high-toughness, high-entropy zirconate material according to claim 2, characterized in that, The embedding process in step three uses the high-entropy ceramic powder or zirconia powder obtained in step two.

8. The method for preparing the high-toughness, high-entropy zirconate material according to claim 2, characterized in that, The sintering temperature in step three is 1300℃~1500℃, the sintering time for each segment is set to 2 hours, and the total sintering time is 6 hours.

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