Fluorite-hooperite dual-phase high-entropy oxide ceramic powder and preparation method thereof

Abstract

This invention discloses a fluorite-pyrochlore dual-phase high-entropy oxide ceramic powder and its preparation method, relating to the field of high-performance ceramic technology. The preparation process is as follows: (1) Weigh out ZrO2, HfO2, and Pr6O in equal atomic percentages. 11 (1) Place the La2O3 and Sm2O3 powders in a crucible and calcine them in a muffle furnace to remove moisture and impurities; (2) Calcine the ZrO2, HfO2, and Pr6O3 powders after calcination. 11 (2) Powders of La2O3 and Sm2O3 were ball-milled and mixed. After ball milling, the powders were dried and ground in a drying oven to obtain high-entropy ceramic oxide precursor powder. (3) The high-entropy ceramic oxide precursor powder was placed in a muffle furnace and heat-treated in an air atmosphere. After cooling and grinding, high-entropy oxide ceramic powder with a fluorite-pyrochlore dual-phase structure was obtained. The chemical formula of the dual-phase high-entropy ceramic powder material prepared by this invention is (Zr,Hf,Pr,La,Sm)O 2‑δ It has a fluorite-pyrochlore two-phase structure, with low thermal conductivity and high coefficient of thermal expansion, and good thermal conductivity.

Description

Technical Field

[0001] This invention relates to the field of high-performance ceramics technology, specifically to a fluorite-pyrochlore dual-phase high-entropy oxide ceramic powder and its preparation method. Background Technology

[0002] High-entropy ceramics, also known as high-entropy compounds, are solid solutions of a class of inorganic compounds. The concept of high-entropy materials primarily originates from high-entropy alloys, aiming to maximize the entropy of the material system's configuration by mixing multiple different elements, thereby stabilizing multiple phases and ultimately forming a solid solution that maintains a stable single-phase structure at room temperature. Compared to traditional ceramic powders, high-entropy ceramics have a more complex chemical composition and structure, typically composed of multiple elements distributed more uniformly within the material. They lack a distinct lattice structure, instead exhibiting a relatively disordered amorphous structure.

[0003] High-entropy oxide ceramics, as a type of high-entropy ceramics, have shown great potential in applications such as radiation resistance, thermoelectricity, catalysis, coating, and energy storage. Currently, fluorite-type and pyrochlore-type high-entropy oxides have attracted widespread attention due to their superior performance in coating applications. However, existing research on materials with high hardness, low conductivity, and high melting points mainly focuses on single-phase fluorite-type and pyrochlore-type high-entropy oxides, which suffer from low thermal conductivity. Currently, the latest synthesis strategy for fluorite-pyrochlore dual-phase high-entropy ceramics uses the chemical formula A2B2O7, while there are no reports on AO-type fluorite-pyrochlore dual-phase high-entropy ceramics. This limits the diversity of high-entropy fluorite-pyrochlore dual-phase ceramics and the possibility of breakthroughs in their performance. Therefore, this invention provides a fluorite-pyrochlore dual-phase high-entropy oxide ceramic powder and its preparation method. Summary of the Invention

[0004] The purpose of this invention is to provide a fluorite-pyrochlore dual-phase high-entropy oxide ceramic powder and its preparation method, thereby improving the thermal conductivity of high-entropy ceramic powder materials.

[0005] To achieve the above objectives, the present invention provides a fluorite-pyrochlore dual-phase high-entropy oxide ceramic powder, wherein the chemical formula of the dual-phase high-entropy ceramic powder material is (Zr,Hf,Pr,La,Sm)O. 2-δ It has a fluorite-pyrochlore two-phase structure, in which the molar ratio of Zr:Hf:Pr:La:Sm is 1:1:1:1:1.

[0006] This invention also provides a method for preparing the above-mentioned fluorite-pyrochlore dual-phase high-entropy oxide ceramic powder, comprising the following steps:

[0007] (1) Weigh out ZrO2, HfO2, and Pr6O in equal atomic percentages. 11La2O3 and Sm2O3 powders were placed in a crucible and calcined in a muffle furnace to remove moisture and impurities;

[0008] (2) The calcined ZrO2, HfO2, Pr6O 11 La2O3 and Sm2O3 powders were ball-milled and mixed. After ball milling, the mixture was placed in a drying oven for drying and grinding to obtain high-entropy ceramic oxide precursor powder.

[0009] (3) The high-entropy ceramic oxide precursor powder is placed in a muffle furnace and heat-treated in an air atmosphere. After cooling and grinding, a high-entropy oxide ceramic powder with a fluorite-pyrochlore dual-phase structure is obtained.

[0010] Preferably, in step (1), the calcination temperature in the muffle furnace is 900°C and the calcination time is 2 hours.

[0011] Preferably, in step (2), the powder is placed in a planetary ball mill for ball milling, the ball milling medium is ethanol, the ball milling speed is 280-330 r / min, the ball milling time is 10 h, and the ball-to-material ratio is 1:10.

[0012] Preferably, in step (2), the drying temperature is 60-120°C and the drying time is 12-20h.

[0013] Preferably, in step (3), the heat treatment method is segmented calcination, first heating to 1200°C at 5°C / min, then heating to 1500°C at 2°C / min, then heating to 1600°C at 1°C / min, and then calcining at 1600°C for 5 hours.

[0014] Preferably, in step (3), the cooling method is segmented cooling. After calcination, the temperature is first reduced to 1500°C at a rate of 1°C / min, then reduced to 1200°C at a rate of 2°C / min, and then reduced to 500°C with the furnace at a rate of 5°C / min.

[0015] Therefore, the present invention provides a fluorite-pyrochlore dual-phase high-entropy oxide ceramic powder and its preparation method, with the following specific beneficial effects:

[0016] 1. The high-entropy ceramic powder obtained by this invention contains two crystal structures: fluorite and pyrochlore. The fluorite phase belongs to the Fm-3m space group and is typically characterized by interpenetrating twinning, where anions are arranged in a close-packed manner and cations occupy tetrahedral voids. The pyrochlore phase belongs to the Oh7-Fd-3m isometric crystal system and usually contains two types of cations that achieve overall valence electron balance. The larger cation and oxygen ion form an oxygen octahedral framework structure at the vertices, while the smaller cation is located in the interstices of the oxygen octahedral framework. The coexistence of these two phases within the high-entropy lattice results in high purity, stable phase structure, and uniform elemental distribution.

[0017] 2. The high-entropy ceramic powder prepared by this invention uses the cubic rare-earth multi-valence element Pr as the controlling matrix for two-phase formation. As a solid solution substrate, it more easily fosters the growth of fluorite and pyrochlore phases, both belonging to the cubic structure. Furthermore, the coexistence of multiple valence states allows the disordered electron distribution in the high-entropy system to reach equilibrium, thus making the structure more stable. (Fluorite-structured Zr) 4+ Then, as the matrix for fluorite phase formation, Hf 4+ With a similar ionic radius, La is more easily integrated into the system and maintains stability. 3+ and Sm 3+ As a large-radius ion, it increases the internal radius difference of the system, increases the degree of lattice distortion, and thus increases the defect density to achieve the effects of reducing thermal conductivity and enhancing hardness.

[0018] 3. The high-entropy ceramic powder prepared by this invention does not undergo any phase decomposition reaction after long-term calcination. It exhibits extremely low thermal conductivity (0.827 W / m·℃) at 100℃ and reaches 1.40 W / m·℃ at 1100℃. The coefficient of thermal expansion reaches 11.60 × 10⁻⁶ at 1100℃. -6 ·℃ -1 Compared to single-phase fluorite and single-phase pyrochlore high-entropy oxides, two-phase high-entropy ceramic materials have lower thermal conductivity and higher coefficient of thermal expansion.

[0019] 4. This invention uses mechanical wet grinding and solid-phase reaction preparation, which can ensure that the elements are fully and uniformly mixed. It has the advantages of simple operation, short production cycle and industrialization.

[0020] The main reasons why the dual-phase high-entropy oxide ceramic powder prepared by this invention has low thermal conductivity and high coefficient of thermal expansion are as follows:

[0021] (1) The differences in radius and mass of various elements cause an increase in internal disorder and a corresponding increase in the degree of lattice distortion, which leads to an increase in oxygen vacancy concentration, enhances the degree of phonon scattering, and thus reduces thermal conductivity.

[0022] (2) The two-phase structure is at the critical point between disorder and order, and the lattice distortion and relaxation are more obvious, which leads to a reduction in the phonon free path. Specifically, the appearance of two phases leads to more severe thermal scattering of the heat conduction process at the interface between different phases, which in turn causes a decrease in thermal conductivity.

[0023] (3) The heat transfer coefficients between different phases are different, which will also lead to an increase in the resistance to heat transfer. At the same time, the appearance of the second phase will increase the defect density inside the crystal lattice, resulting in a decrease in thermal conductivity.

[0024] (4) The lattice parameter of the calcined chlorite phase in dual-phase ceramics is relatively large. Generally speaking, substances with larger lattice parameters also experience larger size changes during heating, which leads to an increase in the coefficient of thermal expansion.

[0025] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0026] Figure 1 This is Embodiment 1 of the present invention (Zr, Hf, Pr, La, Sm)O 2-δ XRD pattern;

[0027] Figure 2 This is Embodiment 2 of the present invention (Zr, Hf, Pr, La, Sm)O 2-δ XRD pattern;

[0028] Figure 3 This is Embodiment 1 of the present invention (Zr, Hf, Pr, La, Sm)O 2-δ SEM-EDS plot;

[0029] Figure 4 This is Embodiment 1 of the present invention (Zr, Hf, Pr, La, Sm)O 2-δ Thermal conductivity as a function of temperature;

[0030] Figure 5 This is Embodiment 1 of the present invention (Zr, Hf, Pr, La, Sm)O 2-δ The graph shows the change of the coefficient of thermal expansion with temperature.

[0031] Figure 6 This is Embodiment 1 of the present invention (Zr, Hf, Pr, La, Sm)O 2-δ XRD pattern after annealing at 1600℃ for 30 hours. Detailed Implementation

[0032] This invention provides a fluorite-pyrochlore dual-phase high-entropy ceramic powder, the chemical formula of which is (Zr,Hf,Pr,La,Sm)O. 2-δIt has a fluorite-pyrochlore two-phase structure, in which each element exists in an equimolar ratio, and δ depends on the oxygen vacancy concentration in the structure.

[0033] The thermal conductivity of this high-entropy dual-phase ceramic powder material ranges from 0.827 W / m·℃ to 1.40 W / m·℃ in the temperature range of 100–1100℃, and its coefficient of thermal expansion reaches 11.60 × 10⁻⁶ at 1100℃. -6 ·℃ -1 It also exhibits good high-temperature phase stability (1600℃).

[0034] This invention also provides a method for preparing the above-mentioned fluorite-pyrochlore dual-phase high-entropy ceramic powder material, comprising the following steps:

[0035] (1) Select ZrO2, HfO2, and Pr6O with equal atomic percentages. 11 Using La2O3 and Sm2O3 powders as raw materials, each rare earth and metal element is introduced in an equimolar ratio. After weighing, the powder mixture is placed in a crucible and calcined in a muffle furnace at 900℃ for 2 hours to remove moisture and impurities.

[0036] (2) A planetary ball mill was selected for ball milling. The ball milling medium was ethanol. The ball milling speed was 280-330 r / min. The ball milling time was 10 h. The ball-to-material ratio was 1:10. Then, the ball mill was placed in a drying oven and dried at 60-120℃ for 12-20 h before grinding to obtain high-entropy ceramic oxide precursor powder.

[0037] (3) The high-entropy ceramic oxide precursor powder was placed in a muffle furnace and calcined in stages in an air atmosphere. The temperature was first increased to 1200℃ at 5℃ / min, then to 1500℃ at 2℃ / min, and then to 1600℃ at 1℃ / min. Calcination was then carried out at 1600℃ for 5 hours. After calcination, the temperature was decreased to 1500℃ at a rate of 1℃ / min, then to 1200℃ at 2℃ / min, and finally to 500℃ at 5℃ / min for furnace cooling. After grinding, sintered biphase (Zr,Hf,Pr,La,Sm)O was obtained. 2-δ High-entropy ceramic powder materials.

[0038] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the invention should be considered equivalent substitutions and are included within the scope of protection of the invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims and are all within the scope of protection of the invention.

[0039] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0040] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0041] Unless otherwise specified, the reagents, instruments, and equipment used in this invention are all commonly used by those skilled in the art.

[0042] Example 1

[0043] This embodiment provides a method for preparing fluorite-pyrochlore dual-phase high-entropy oxide ceramic powder, including the following steps:

[0044] (1) Weigh out ZrO2 (1.2322g), HfO2 (2.105g), and Pr6O in a metal atomic ratio of 1:1:1:1:1. 11 Powders of La2O3 (1.7024g), La2O3 (1.629g), and Sm2O3 (1.7436g) were placed in a crucible and calcined in a muffle furnace at 900℃ for 2 hours to remove moisture and impurities.

[0045] (2) A planetary ball mill was used for ball milling. The ball milling medium was ethanol, and the ball-to-material ratio was 1:10. The milling was first carried out for half an hour in a clockwise direction at a speed of 280 r / min, followed by a 10-minute pause. Then, the milling was carried out for half an hour in a counterclockwise direction at a speed of 280 r / min, followed by a 10-minute pause. This process constituted one cycle, with a total effective milling time of 10 hours. After drying at 100℃ for 14 hours, the product was thoroughly ground to obtain high-entropy ceramic oxide precursor powder.

[0046] (3) The high-entropy ceramic oxide precursor powder was placed in a muffle furnace and calcined in stages in an air atmosphere. The temperature was first increased to 1200℃ at 5℃ / min, then to 1500℃ at 2℃ / min, and then to 1600℃ at 1℃ / min. Calcination was then carried out at 1600℃ for 5 hours. After calcination, the temperature was decreased to 1500℃ at a rate of 1℃ / min, then to 1200℃ at 2℃ / min, and finally to 500℃ at 5℃ / min for furnace cooling. After grinding, sintered biphase (Zr,Hf,Pr,La,Sm)O was obtained. 2-δ High-entropy ceramic powder materials.

[0047] The (Zr,Hf,Pr,La,Sm)O prepared in this embodiment 2-δ X-ray diffraction testing was performed on high-entropy ceramic powder materials, and the results were... Figure 1 As shown. By Figure 1 It can be seen that the diffraction peaks correspond to the fluorite and pyrochlore dual phases, indicating that a high-entropy ceramic with a fluorite-pyrochlore dual-phase structure has been obtained.

[0048] The (Zr,Hf,Pr,La,Sm)O prepared in this embodiment 2-δ SEM-EDS images of high-entropy ceramic powder materials are shown below. Figure 3 As shown. By Figure 3 It can be seen that (Zr,Hf,Pr,La,Sm)O 2-δ High-entropy ceramic powder materials have been successfully sintered with high density, and there are no obvious pores on the surface. No obvious segregation or aggregation of other elements was observed, indicating that all five elements were successfully dissolved in the high-entropy lattice.

[0049] (Zr,Hf,Pr,La,Sm)O 2-δ The thermal conductivity of the high-entropy ceramic powder was calculated based on the thermal diffusivity measured by laser method; the coefficient of thermal expansion was measured using a high-temperature dilatometer manufactured by Netzsch DIL402SE, Germany. The test range for both thermal conductivity and coefficient of thermal expansion was 25–1100℃; the high-temperature thermal stability of the two-phase high-entropy ceramic powder was tested for 30 hours in a high-temperature box furnace.

[0050] Take 0.5g of (Zr,Hf,Pr,La,Sm)O prepared in this embodiment 2-δ High-entropy ceramic powder materials, the change of thermal conductivity with temperature is as follows: Figure 4 As shown. By Figure 4 It can be seen that its thermal conductivity ranges from 0.827 W / m·℃ to 1.40 W / m·℃ in the temperature range of 100–1100℃. The coefficient of thermal expansion changes with temperature as follows: Figure 5 As shown, by Figure 5 It can be seen that its coefficient of thermal expansion reaches 11.60 × 10⁻⁶ at a temperature of 1100℃. -6·℃ -1 .

[0051] The (Zr,Hf,Pr,La,Sm)O prepared in this embodiment 2-δ High-entropy dual-phase ceramic powder material was annealed at 1600℃ for 30 hours, and then subjected to X-ray diffraction testing. The results are as follows: Figure 6 As shown. By Figure 6 It can be seen that the powder material still maintains the fluorite-pyrochlore dual-phase structure, indicating that the high-entropy dual-phase ceramic powder material has excellent high-temperature phase stability.

[0052] Example 2

[0053] This embodiment provides a method for preparing fluorite-pyrochlore dual-phase high-entropy oxide ceramic powder, including the following steps:

[0054] (1) Weigh out ZrO2 (2.4644g), HfO2 (4.21g), and Pr6O in a metal element ratio of 1:1:1:1:1. 11 Powders of La2O3 (3.4048g), La2O3 (3.258g), and Sm2O3 (3.4872g) were placed in a crucible and calcined in a muffle furnace at 900℃ for 2 hours to remove moisture and impurities.

[0055] (2) A planetary ball mill was used for ball milling. The ball milling medium was ethanol, and the ball-to-material ratio was 1:10. The milling was first carried out for half an hour in a clockwise direction at a speed of 330 r / min, followed by a 10-minute pause. Then, the milling was carried out for half an hour in a counterclockwise direction at a speed of 330 r / min, followed by a 10-minute pause. This process constituted one cycle, with a total effective milling time of 10 hours. After drying at 120℃ for 12 hours, the product was thoroughly ground to obtain high-entropy ceramic oxide precursor powder.

[0056] (3) The high-entropy ceramic oxide precursor powder was placed in a muffle furnace and calcined in stages in an air atmosphere. The temperature was first increased to 1200℃ at 5℃ / min, then to 1500℃ at 2℃ / min, and then to 1600℃ at 1℃ / min. Calcination was then carried out at 1600℃ for 5 hours. After calcination, the temperature was decreased to 1500℃ at a rate of 1℃ / min, then to 1200℃ at 2℃ / min, and finally to 500℃ at 5℃ / min for furnace cooling. After grinding, sintered biphase (Zr,Hf,Pr,La,Sm)O was obtained. 2-δ High-entropy ceramic powder materials.

[0057] The (Zr,Hf,Pr,La,Sm)O prepared in this embodiment 2-δ X-ray diffraction testing was performed on high-entropy ceramic powder materials, and the results were... Figure 2 As shown. By Figure 2It can be seen that the diffraction peaks correspond to the fluorite and pyrochlore dual phases, indicating that a high-entropy ceramic with a fluorite-pyrochlore dual-phase structure has been obtained.

[0058] The (Zr,Hf,Pr,La,Sm)O prepared in this embodiment 2-δ The thermal conductivity, coefficient of thermal expansion, and thermal stability of the high-entropy ceramic powder material were tested as in Example 1. 0.5g of (Zr, Hf, Pr, La, Sm)O was taken. 2-δ The high-entropy ceramic powder material was found to have a thermal conductivity ranging from 0.825 W / m·℃ to 1.39 W / m·℃ in the temperature range of 100–1100℃, and a coefficient of thermal expansion reaching 11.70 × 10⁻⁶·℃ at 1100℃. -1 The high-entropy ceramic powder material retains its fluorite-pyrochlore dual-phase structure after annealing at 1600℃ for 30 hours, exhibiting excellent high-temperature phase stability.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A fluorite-microlite dual-phase high-entropy oxide ceramic powder, characterized in that, The chemical formula of the dual-phase high-entropy ceramic powder material is (Zr, Hf, Pr, La, Sm)O 2-δ is a fluorite-hollandite dual-phase structure, wherein the molar ratio of Zr:Hf:Pr:La:Sm is 1:1:1:1:

1.

2. The method for preparing fluorite-pyrochlore dual-phase high-entropy oxide ceramic powder as described in claim 1, characterized in that, Includes the following steps: (1) Take equal atomic percentage of ZrO2, HfO2, Pr6O 11 , La2O3, Sm2O3 powder in the crucible, calcination in the muffle furnace to remove moisture and impurities; (2) The calcined ZrO2, HfO2, Pr6O 11 La2O3 and Sm2O3 powders were ball-milled and mixed. After ball milling, the mixture was placed in a drying oven for drying and grinding to obtain high-entropy ceramic oxide precursor powder. (3) The high-entropy ceramic oxide precursor powder is placed in a muffle furnace and heat-treated in an air atmosphere. After cooling and grinding, a high-entropy oxide ceramic powder with a fluorite-pyrochlore dual-phase structure is obtained.

3. The method according to claim 2, wherein the method is characterized by: In step (1), the calcination temperature in the muffle furnace is 900℃ and the calcination time is 2h.

4. The method according to claim 2, wherein the method is characterized by: In step (2), the powder is placed in a planetary ball mill for ball milling. The ball milling medium is ethanol, the ball milling speed is 280-330 r / min, the ball milling time is 10 h, and the ball-to-material ratio is 1:

10.

5. The method according to claim 2, wherein the method is characterized by: In step (2), the drying temperature is 60-120℃ and the drying time is 12-20h.

6. The method according to claim 2, wherein the method is characterized by: In step (3), the heat treatment method is segmented calcination. First, the temperature is increased to 1200℃ at 5℃ / min, then increased to 1500℃ at 2℃ / min, then increased to 1600℃ at 1℃ / min, and then calcined at 1600℃ for 5 hours.

7. The method according to claim 2, wherein the method is characterized by: In step (3), the cooling method is segmented cooling. After calcination, the temperature is first reduced to 1500℃ at a rate of 1℃ / min, then reduced to 1200℃ at a rate of 2℃ / min, and then reduced to 500℃ with the furnace at a rate of 5℃ / min.

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