High-entropy rare earth phosphate nano ceramic powder and preparation method thereof

Abstract

The invention discloses high-entropy rare earth phosphate nano ceramic powder and a preparation method thereof, the high-entropy rare earth phosphate nano ceramic powder with a xenotime structure is synthesized by combining an in-situ coprecipitation method with a low-temperature calcination process, and the average grain size of the nano ceramic powder is 45-60 nm; h3PO4 is used as a phosphorus-containing raw material and a precipitant at the same time, so that the problem of excessive impurity substances in a sample caused by introduction of other precipitants such as ammonia water and the like is avoided; and precipitates are collected in a direct evaporation manner, so that the problem of loss of part of component elements in the filtering process is completely prevented, the proportion of each element in the nano powder is consistent with the expected height, and each element is uniformly distributed. According to the method, five elements with different ion radiuses and masses are added into REPO4 crystal lattices, so that the configuration entropy and the lattice distortion degree of a sample are remarkably improved, the stability and the phonon scattering intensity of xenotime type crystal lattices in the sample are improved, and the heat conductivity of the sample is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramics, and in particular to a high-entropy rare earth phosphate nano-ceramic powder and a preparation method thereof. Background Art

[0002] To date, xenotime-type rare earth phosphates (REPO4) have attracted much attention in environmental barrier coatings (EBCs) due to their excellent high-temperature stability, corrosion resistance, and low thermal expansion coefficient. However, traditional single rare earth phosphates (such as YPO4, YbPO4, etc.) still have the following limitations: 1) High thermal conductivity: The room temperature thermal conductivity of single-component REPO4 is generally 9-12 W·m -1 ·K -1 , it is difficult to meet the thermal insulation requirements of the new generation of ultra-high temperature coatings; 2) Insufficient phase stability: phase decomposition or grain boundary degradation is likely to occur in long-term high-temperature service (>1400℃) or corrosive environments (such as water, oxygen, CMAS molten salt); 3) Mechanical performance bottleneck: It is difficult for a single rare earth element to significantly improve hardness and fracture toughness through traditional solid solution strengthening.

[0003] To improve these properties, the current approach to optimizing material systems is through single or double rare earth element doping (e.g., (Y,Gd)PO4). While these methods can partially control the thermal expansion coefficient or corrosion resistance, due to the limited variety of doping elements and insufficient lattice distortion, the effects on reducing thermal conductivity and improving high-temperature stability are minimal. Furthermore, multi-element doping can easily induce the precipitation of secondary phases, leading to reduced material homogeneity and significant performance degradation under long-term high-temperature conditions.

[0004] In recent years, high-entropy ceramics have shown breakthrough potential in the field of material design due to their unique multi-principal component solid solution effect. High-entropy ceramics are usually composed of five or more elements in equal molar ratios. Their high configurational entropy (ΔSmix ≥ 1.5R) can inhibit element segregation, stabilize the single-phase structure, and enhance phonon scattering through lattice distortion, thereby significantly reducing thermal conductivity. Studies have shown that high-entropy strategies have been successfully applied in carbide, oxide and silicate systems. For example, the thermal conductivity of high-entropy rare earth zirconates is reduced by more than 40% compared with traditional YSZ, and the phase stability is extended to 1600°C. However, there are few reports on the high-entropy design of xenotime-type rare earth phosphates. The synthesizability of high-entropy phosphate nanoceramic powders with a single xenotime-type structure and the mechanism by which the synthesis process affects the grain size of high-entropy phosphate ceramic powders still need to be explored.

[0005] Therefore, in order to solve the above problems, this paper proposes a high-entropy rare earth phosphate nanoceramic powder and a preparation method thereof. Summary of the Invention

[0006] The purpose of the present invention is to provide a high-entropy rare earth phosphate nano-ceramic powder that adopts a high-entropy design strategy, constructs a multi-principal component solid solution by introducing five rare earth elements with different ionic radii and elemental masses, and combines it with nano-preparation technology.

[0007] In order to achieve the above technical effects, the present invention is implemented by the following technical solution: a high entropy rare earth phosphate nano ceramic powder, characterized in that: the chemical formula of the high entropy rare earth phosphate ceramic powder is as follows:

[0008] (Dy 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 )PO4,

[0009] (Dy 0.2 Ho 0.2 Er 0.2 Tm 0.2 Lu 0.2 )PO4,

[0010] (Dy 0.2 Ho 0.2 Er 0.2 Yb 0.2 Lu 0.2 )PO4,

[0011] (Dy 0.2 Ho 0.2 Tm 0.2 Yb 0.2 Lu 0.2 )PO4,

[0012] (Dy 0.2 Er 0.2 Tm 0.2 Yb 0.2 Lu 0.2 )PO4,

[0013] (Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 Lu 0.2 )PO4.

[0014] Furthermore, the high-entropy rare earth phosphate ceramic powder has a single xenotime-type crystal structure, each element is evenly distributed, and the powder grains are irregular spheres of 45 to 60 nm.

[0015] Another object of the present invention is to provide a method for preparing high-entropy rare earth phosphate nano-ceramic powder, characterized in that it comprises the following steps:

[0016] S1. Weighing nitrate powder and distilled water in a molar ratio of nitrate powder to distilled water = 1:5-7, and then dissolving the weighed nitrate powder in the distilled water to obtain a mixed solution;

[0017] S2. Add H3PO4 solution dropwise to the mixed solution to produce a white precipitate, stir the mixed solution with a magnetic stirrer for 2 to 4 hours, and after the mixture is fully stirred, pour the sample into an evaporating dish and place it in a drying oven at 100 to 120°C for 20 to 24 hours to obtain a white solid;

[0018] S3. Grind and sieve the white solid, place it in a muffle furnace at 900-1200° C. and calcine it for 4-10 hours to obtain high-entropy rare earth phosphate ceramic powder.

[0019] Furthermore, in S1, the nitrate powder is a mixture of Dy(NO3)3·6H2O powder, Ho(NO3)3·5H2O powder, Er(NO3)3·5H2O powder, Tm(NO3)3·nH2O powder, Yb(NO3)3·5H2O powder and Lu(NO3)3·6H2O powder in a molar ratio of 1:1:1:1:1:1.

[0020] Furthermore, in S2, the concentration of H3PO4 is 70-85 wt%.

[0021] Furthermore, in S3, the solid grinding and screening comprises the following steps:

[0022] 1) Grind the white solid in an agate mortar for 200-30 min;

[0023] 2) The powder obtained by grinding is sieved with a mesh size between 300 and 600 meshes.

[0024] The beneficial effects of the present invention are:

[0025] In the synthesis process of the present invention, H3PO4 is used as both a phosphorus-containing raw material and a precipitant, thereby avoiding the problem of excessive impurities in the sample caused by the introduction of other precipitants such as ammonia water;

[0026] The present invention also improves the precipitation collection process by using direct evaporation to collect the precipitate, completely preventing the problem of loss of some constituent elements during the filtration process, so that the ratio of each element in the nanopowder is highly consistent with the expected level and the elements are evenly distributed;

[0027] The present invention adds five elements with different ionic radii and masses into the REPO4 lattice, thereby significantly improving the configurational entropy and lattice distortion of the sample, increasing the stability and phonon scattering intensity of the xenotime-type lattice in the sample, and helping to reduce the thermal conductivity of the sample. The sample powder also has a grain size of 45 to 60 nm, with extremely high specific surface area and sintering activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 XRD patterns of high-entropy rare earth phosphate nanoceramic powders having a xenotime-type structure prepared in Examples 1 to 6 of the present invention;

[0030] Figure 2 SEM images of high-entropy rare earth phosphate nanoceramic powders having a xenotime-type structure prepared in Examples 1 to 6 of the present invention;

[0031] Figure 3 The grain size distribution and average grain size of the high entropy rare earth phosphate nano-ceramic powder having a xenotime structure prepared in Examples 1 to 6 of the present invention;

[0032] Figure 4 This is the EDS spectrum of the high-entropy rare earth phosphate nano-ceramic powder with a xenotime-type structure prepared in Examples 1 to 6 of the present invention. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0034] Example 1

[0035] A high entropy rare earth phosphate (Dy 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 ) The preparation method of PO4 nano-ceramic powder, the specific steps are as follows:

[0036] (1) According to (Dy 0.2 Ho0.2 Er 0.2 Tm 0.2 Yb 0.2 )PO4 in a stoichiometric ratio of Dy(NO3)3·6H2O powder, Ho(NO3)3·5H2O powder, Er(NO3)3·5H2O powder, Tm(NO3)3·nH2O powder, and Yb(NO3)3·5H2O powder were weighed respectively, with the molar ratio of the total amount of all nitrates to distilled water being 1:5. The solution was then placed at 25°C and stirred for 0.5h to obtain a mixed solution;

[0037] (2) adding 85 wt% H3PO4 solution dropwise to the mixed solution at a rate of 3 drops per second, stirring for 2 h, until a white precipitate is generated in the mixed solution. After the mixture is fully stirred using a magnetic stirrer, the sample is poured into an evaporating dish and placed in a drying oven at 100°C for 20 h to obtain a white solid;

[0038] (3) The white solid was ground using an agate mortar for 20 min and passed through a 400-mesh sieve. It was then calcined in a muffle furnace at 1000 °C for 4 h to obtain high-entropy rare earth phosphate ceramic powder.

[0039] Example 2

[0040] A high entropy rare earth phosphate (Dy 0.2 Ho 0.2 Er 0.2 Tm 0.2 Lu 0.2 ) The preparation method of PO4 nano-ceramic powder, the specific steps are as follows:

[0041] (1) According to (Dy 0.2 Ho 0.2 Er 0.2 Tm 0.2 Lu 0.2 )PO4 in a stoichiometric ratio of Dy(NO3)3·6H2O powder, Ho(NO3)3·5H2O powder, Er(NO3)3·5H2O powder, Tm(NO3)3·nH2O powder, and Lu(NO3)3·6H2O powder were weighed respectively, with the molar ratio of the total amount of all nitrates to distilled water being 1:6. The solution was then placed at 30°C and stirred for 1 hour to obtain a mixed solution;

[0042] (2) adding 80 wt% H3PO4 solution dropwise to the mixed solution at a rate of 2 drops per second, stirring for 3 h, until a white precipitate is generated in the mixed solution. After the mixture is fully stirred using a magnetic stirrer, the sample is poured into an evaporating dish and placed in a drying oven at 110°C for 24 h to obtain a white solid;

[0043] (3) The white solid was ground using an agate mortar for 30 min and passed through a 600-mesh sieve. It was then calcined in a muffle furnace at 1100 °C for 6 h to obtain high-entropy rare earth phosphate ceramic powder.

[0044] Example 3

[0045] A high entropy rare earth phosphate (Dy 0.2 Ho 0.2 Er 0.2 Yb 0.2 Lu 0.2 ) The preparation method of PO4 nano-ceramic powder, the specific steps are as follows:

[0046] (1) According to (Dy 0.2 Ho 0.2 Er 0.2 Tm 0.2 Lu 0.2 )PO4 in a stoichiometric ratio of Dy(NO3)3·6H2O powder, Ho(NO3)3·5H2O powder, Er(NO3)3·5H2O powder, Yb(NO3)3·5H2O powder, and Lu(NO3)3·6H2O powder were weighed respectively, with the molar ratio of the total amount of all nitrates to distilled water being 1:7. The solution was then placed at 40°C and stirred for 2 h to obtain a mixed solution;

[0047] (2) adding a 70 wt% H3PO4 solution dropwise to the mixed solution at a rate of 4 drops per second, stirring for 4 hours, until a white precipitate is generated in the mixed solution. After the mixture is fully stirred using a magnetic stirrer, the sample is poured into an evaporating dish and placed in a drying oven at 120°C for 22 hours to obtain a white solid;

[0048] (3) The white solid was ground using an agate mortar for 25 min and passed through a 500-mesh sieve. It was then calcined in a muffle furnace at 1200 °C for 10 h to obtain high-entropy rare earth phosphate ceramic powder.

[0049] Example 4

[0050] A high entropy rare earth phosphate (Dy 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 ) The preparation method of PO4 nano-ceramic powder, the specific steps are as follows:

[0051] (1) According to (Dy 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb0.2 )PO4 in a stoichiometric ratio of Dy(NO3)3·6H2O powder, Ho(NO3)3·5H2O powder, Er(NO3)3·5H2O powder, Tm(NO3)3·nH2O powder, and Yb(NO3)3·5H2O powder were weighed respectively, with the molar ratio of the total amount of all nitrates to distilled water being 1:6. The solution was then stirred at 25°C for 1.5 h to obtain a mixed solution;

[0052] (2) adding 85 wt% H3PO4 solution dropwise to the mixed solution at a rate of 4 drops per second, stirring for 3 h, until a white precipitate is generated in the mixed solution. After the mixture is fully stirred using a magnetic stirrer, the sample is poured into an evaporating dish and placed in a drying oven at 120°C for 24 h to obtain a white solid;

[0053] (3) The white solid was ground using an agate mortar for 20 min and passed through a 300-mesh sieve. It was then calcined in a muffle furnace at 900 °C for 10 h to obtain high-entropy rare earth phosphate ceramic powder.

[0054] Example 5

[0055] A high entropy rare earth phosphate (Dy 0.2 Er 0.2 Tm 0.2 Yb 0.2 Lu 0.2 ) The preparation method of PO4 nano-ceramic powder, the specific steps are as follows:

[0056] (1) According to (Dy 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 )PO4 in a stoichiometric ratio of Dy(NO3)3·6H2O powder, Er(NO3)3·5H2O powder, Tm(NO3)3·nH2O powder, Yb(NO3)3·5H2O powder, and Lu(NO3)3·6H2O powder were weighed respectively, with the molar ratio of the total amount of all nitrates to distilled water being 1:5. The solution was then placed at 40°C and stirred for 2 h to obtain a mixed solution;

[0057] (2) adding 80 wt% H3PO4 solution dropwise to the mixed solution at a rate of 2 drops per second, stirring for 4 h, until a white precipitate is generated in the mixed solution. After the mixture is fully stirred using a magnetic stirrer, the sample is poured into an evaporating dish and placed in a drying oven at 120°C for 24 h to obtain a white solid;

[0058] (3) The white solid was ground using an agate mortar for 20 min and passed through a 400-mesh sieve. It was then calcined in a muffle furnace at 1200 °C for 10 h to obtain high-entropy rare earth phosphate ceramic powder.

[0059] Example 6

[0060] A high entropy rare earth phosphate (Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 Lu 0.2 ) The preparation method of PO4 nano-ceramic powder, the specific steps are as follows:

[0061] (1) According to (Dy 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 )PO4 in a stoichiometric ratio of 1:7. Ho(NO3)3·5H2O powder, Er(NO3)3·5H2O powder, Tm(NO3)3·nH2O powder, Yb(NO3)3·5H2O powder, and Lu(NO3)3·6H2O powder were weighed respectively. The molar ratio of the total amount of all nitrates to distilled water was 1:7. The solution was then placed at 40°C and stirred for 2 h to obtain a mixed solution.

[0062] (2) adding 85 wt% H3PO4 solution dropwise to the mixed solution at a rate of 4 drops per second, stirring for 4 h, until a white precipitate is generated in the mixed solution. After the mixture is fully stirred using a magnetic stirrer, the sample is poured into an evaporating dish and placed in a drying oven at 120°C for 24 h to obtain a white solid;

[0063] (3) The white solid was ground using an agate mortar for 30 min and passed through a 600-mesh sieve. It was then calcined in a muffle furnace at 1200 °C for 10 h to obtain high-entropy rare earth phosphate ceramic powder.

[0064] Example 7

[0065] This example explores the properties of the high entropy rare earth phosphate nano-ceramic powders of Examples 1-6, as follows:

[0066] from Figure 1 It can be seen that the XRD diffraction peaks of each high entropy rare earth phosphate ceramic powder are consistent with the standard PDF card, and there is no obvious impurity peak, indicating that the high entropy rare earth phosphate ceramic powder has a single xenotime-type crystal structure;

[0067] from Figure 2 It can be seen that the grains of each high entropy rare earth phosphate ceramic powder are irregular nano-spherical;

[0068] from Figure 3 It can be seen that the grain size distribution of each high entropy rare earth phosphate ceramic powder conforms to the Gaussian distribution, and the average grain size is between 60 and 70 nm;

[0069] from Figure 4 It can be seen that the elements in each high entropy rare earth phosphate ceramic powder are evenly distributed without obvious element segregation, and the relative atomic percentage of each element is basically consistent with the experimental design ratio;

[0070] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

Claims

1. A high-entropy rare earth phosphate nano-ceramic powder, characterized by: The chemical formula of the high entropy rare earth phosphate ceramic powder is as follows: (Of 0.2 Ho 0.2 On 0.2 Tm 0.2 Yb 0.2 )PO4, (Of 0.2 Ho 0.2 On 0.2 Tm 0.2 In 0.2 )PO4, (Of 0.2 Ho 0.2 On 0.2 Yb 0.2 In 0.2 )PO4, (Dy 0.2 Yes 0.2 Tm 0.2 Yb 0.2 Lu 0.2 )PO4, (Of 0.2 On 0.2 Tm 0.2 Yb 0.2 In 0.2 )PO4, (He 0.2 Is 0.2 Tm 0.2 Yb 0.2 Lu 0.2 )PO4.

2. The high entropy rare earth phosphate nano-ceramic powder according to claim 1, characterized in that: The high-entropy rare earth phosphate ceramic powder has a single xenotime-type crystal structure, each element is evenly distributed, and the powder grains are irregular spheres with a size of 45 to 60 nm.

3. The method for preparing a high entropy rare earth phosphate nano-ceramic powder according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1. Weighing nitrate powder and distilled water in a molar ratio of nitrate powder to distilled water = 1:5-7, and then dissolving the weighed nitrate powder in the distilled water to obtain a mixed solution; S2. Add H3PO4 solution dropwise to the mixed solution to produce a white precipitate, stir the mixed solution with a magnetic stirrer for 2 to 4 hours, and after the mixture is fully stirred, pour the sample into an evaporating dish and place it in a drying oven at 100 to 120°C for 20 to 24 hours to obtain a white solid; S3. Grind and sieve the white solid, place it in a muffle furnace at 900-1200° C. and calcine it for 4-10 hours to obtain high-entropy rare earth phosphate ceramic powder.

4. The method for preparing a high entropy rare earth phosphate nano-ceramic powder according to claim 1, characterized in that: In S1, the nitrate powder is a mixture of Dy(NO3)3·6H2O powder, Ho(NO3)3·5H2O powder, Er(NO3)3·5H2O powder, Tm(NO3)3·nH2O powder, Yb(NO3)3·5H2O powder and Lu(NO3)3·6H2O powder in a molar ratio of 1:1:1:1:1:

1.

5. The method for preparing a high entropy rare earth phosphate nano-ceramic powder according to claim 1, characterized in that: In S2, the concentration of H3PO4 is 70-85wt%.

6. The method for preparing a high entropy rare earth phosphate nano-ceramic powder according to claim 1, characterized in that: In S3, the solid grinding and screening comprises the following steps: 1) Grind the white solid in an agate mortar for 200-30 min; 2) The powder obtained by grinding is sieved with a mesh size between 300 and 600 meshes.

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