CN113943162B

CN113943162B - alpha-SiAlON high-entropy transparent ceramic material and preparation method thereof

Info

Publication number: CN113943162B
Application number: CN202111223451.8A
Authority: CN
Inventors: 许杰; 郭佳; 杨润伍; 张萍; 朱嘉桐; 位明月; 高峰
Original assignee: Northwestern Polytechnical University
Current assignee: Northwestern Polytechnical University
Priority date: 2021-10-20
Filing date: 2021-10-20
Publication date: 2023-01-17
Anticipated expiration: 2041-10-20
Also published as: CN113943162A

Abstract

An alpha-SiAlON high-entropy transparent ceramic material and a preparation method thereof, wherein the chemical general formula is (RE 1) _a RE2 _b RE3 _c RE4 _d RE5 _e ) _m/ ₃ Si _12‑(m+n) Al _m+n O _n N _16‑n . The invention obtains the alpha-SiAlON with the light transmittance of 65-76 percent and the hardness of 23-25 GPa and the fracture toughness of 4-5 MPa m by the high entropy, powder nanocrystallization, component optimization and optimized sintering process of the alpha-SiAlON ceramic ^1/2 The bending strength reaches 500-650 MPa, and the optical property and the mechanical property reach higher level high-entropy transparent ceramic material.

Description

alpha-SiAlON high-entropy transparent ceramic material and preparation method thereof

Technical Field

The invention relates to the technical field of transparent ceramic preparation, in particular to an alpha-SiAlON high-entropy transparent ceramic material and a preparation method thereof.

Background

The development of aerospace and other technologies puts increasing demands on the performance of infrared transmission materials, and infrared window or protective cover materials applied to the aerospace field need to have the performances of high temperature resistance, friction resistance, high strength, chemical stability, high light transmittance and the like. Based on various advantages and excellent mechanical properties, infrared-transmitting polycrystalline ceramics have received much attention and research. Compared with other polycrystalline ceramics, the alpha-SiAlON ceramics is widely concerned due to the lower density, excellent mechanical property, chemical stability, wear resistance, thermal stability and light transmittance, and has better application prospect.

Currently, research on SiAlON ceramics is still in a development stage, and mainly focuses on selecting different sintering aids and suitable sintering processes to improve the optical properties and mechanical properties of materials.

In the DOI: in 10.1111/j.1551-2916.2004.00714.X, jones et al published a paper of "high ply transient Lu- α -SiAlON" in which a single phase Lu- α -SiAlON ceramic was prepared by sintering under a nitrogen atmosphere at a pressure of 40MPa, 1950 ℃,2h,0.9MPa using hot press sintering. Through tests, the optical performance is good, and the transmittance of a sample with the thickness of 0.5mm in a wave band above 600nm exceeds 70%; but the mechanical property is poor, and the fracture toughness and the bending strength are only respectively 2.55 MPa.m ^1/2 And 392MPa, cannot meet the application requirements.

The invention with publication number CN 105330295A discloses a preparation method of Y-alpha-SiAlON transparent ceramics, and discloses a preparation method of Y-alpha-SiAlON transparent ceramics, the invention has simple process flow, only comprises two parts of mixing and hot-pressing sintering, but the transparent ceramics prepared by the method has light transmittance of only 30-50%.

Theoretical calculation shows that the theoretical transmittance of the alpha-SiAlON transparent ceramic in a near infrared band is close to 80%, but the highest report of the alpha-SiAlON transparent ceramic can only reach 72% (2500 nm, the thickness is 1.0 mm). In the existing report, the Vickers hardness of the alpha-SiAlON is 19-24 GPa, and the fracture toughness is 3-5 MPa m ^1/2 The bending strength is 300-560 MPa, and the mechanical property needs to be further improved.

Disclosure of Invention

In order to overcome the defects of low transparency, poor mechanical property and limited application of the alpha-SiAlON ceramic in the prior art, the invention provides an alpha-SiAlON high-entropy transparent ceramic material and a preparation method thereof.

The chemical general formula of the alpha-SiAlON high-entropy transparent ceramic material provided by the invention is (RE 1) _a RE2 _b RE3 _c RE4 _d RE5 _e ) _m/3 Si _12-(m+n) Al _m+n O _n N _16-n 。

At the position ofIn the chemical general formula, m is the number of Al-N bonds substituted for Si-N bonds, N is the number of Al-O bonds substituted for Si-N bonds, m is more than or equal to 1 and less than or equal to 1.5, and N is more than or equal to 1 and less than or equal to 1.5. A, b, c, d, e each represent one of the substances (RE 1) _a RE2 _b RE3 _c RE4 _d RE5 _e ) _m/3 Si _12-(m+n) Al _m+n O _n N _16-n The medium molecule contains a RE1 atoms, b RE2 atoms, c RE3 atoms, d RE4 atoms and e RE5 atoms. Wherein a is more than or equal to 0.1 and less than or equal to 0.5, b is more than or equal to 0.1 and less than or equal to 0.5, c is more than or equal to 0.1 and less than or equal to 0.5, d is more than or equal to 0.1 and less than or equal to 0.5, and a + b + c + d + e =1, RE1, RE2, RE3, RE4 and RE5 are respectively any one element of Y, la, ce, pr, nd, sm, eu, yb, lu, dy, gd, er and Sc and are different from each other.

A =0.1 to 0.5; b =0.1 or 0.2; c =0.2 or 0.3; d =0.1 to 0.2; e =0.1 or 0.2. The raw materials adopted by the high-entropy transparent ceramic material comprise nano silicon nitride powder, nano aluminum oxide powder and rare earth oxide powder.

The rare earth oxide is composed of any 5 different rare earth oxides of yttrium oxide, lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, ytterbium oxide, lutetium oxide, dysprosium oxide, gadolinium oxide, erbium oxide and scandium oxide. The grain diameters of the nano silicon nitride powder and the nano aluminum nitride powder are both 20-30 nm, and the purity is 98%; the grain diameters of the nano alumina powder and the rare earth oxide are both 20-30 nm, and the purity is more than 99.9%;

the specific process for preparing the alpha-SiAlON high-entropy transparent ceramic material provided by the invention comprises the following steps:

step 1, batching:

weighing raw materials of nano silicon nitride powder, nano aluminum oxide powder and rare earth oxide powder according to the proportion

Step 2, primary ball milling:

putting the weighed raw materials into a polytetrafluoroethylene ball mill tank, sequentially adding silicon nitride grinding balls and absolute ethyl alcohol, and carrying out ball milling to obtain mixed slurry. And drying the mixed slurry and then grinding the dried mixed slurry for h to obtain powder.

During primary ball milling, the weight ratio of the raw materials to the absolute ethyl alcohol to the silicon nitride grinding balls is 1; the ball milling speed is 250-350 r/min, and the ball milling time is 10-36 h.

Step 3, calcining powder:

putting the obtained powder into a ceramic crucible; the ceramic crucible was placed in a nitrogen atmosphere furnace for calcination. The calcination temperature is 1500-1650 ℃, and the temperature is kept for 2-10 h; 0.1 to 1.0MPa of nitrogen is introduced into the whole calcining process. The heating rate of the calcination is 5 ℃/min. And after the calcination, stopping introducing nitrogen, naturally cooling the furnace body to room temperature, taking out the powder, and grinding for 1h to obtain the pre-sintered powder.

Step 4, secondary ball milling:

the obtained calcined powder was ground for 1 hour. And placing the ground pre-sintered powder into a polytetrafluoroethylene ball milling tank, and adding silicon nitride grinding balls and absolute ethyl alcohol into the ball milling tank in sequence to perform ball milling for 10-96 hours to obtain mixed slurry. Drying the mixed slurry in an oven and grinding for 1h to obtain the particle diameter D ₉₀ Is 100-275 nm powder.

During secondary ball milling, the weight ratio of the pre-sintered powder, the absolute ethyl alcohol and the silicon nitride grinding balls is 1; the ball milling speed is 250-350 r/min, and the ball milling time is 10-96 h.

Step 5, hot-pressing sintering:

the obtained particle diameter D ₉₀ 100-275 nm powder is put into a graphite die and hot pressed and sintered in a hot pressing furnace.

The hot-pressing sintering process comprises the following specific steps: a layer of carbon paper coated with boron nitride powder is placed in the grinding tool and between the powder to inhibit carbon pollution. Weighing 100g of the particle size D ₉₀ 100-275 nm powder is filled into a graphite mould. And (3) putting the graphite mould into a vacuum hot pressing furnace, heating to 1800-1950 ℃ at the speed of 10-20 ℃/min under the protection of nitrogen atmosphere of 0.1-1.0 MPa, preserving heat for 1-3 h, and performing hot pressing sintering. In the temperature rising process, when the temperature of the vacuum hot-pressing furnace reaches 1000 ℃, the mechanical pressure of 20-50 MPa is applied. And (4) after the heat preservation is finished, closing the heating power supply to cool along with the furnace, and taking out after cooling along with the furnace to obtain the ceramic block.

Step 6, annealing treatment:

and placing the obtained ceramic block in a box furnace for annealing and finishing. And after the annealing is finished, taking out the sample, and grinding and polishing to obtain the alpha-SiAlON high-entropy transparent ceramic.

The annealing temperature of the annealing treatment is 700-900 ℃, and the annealing time is 2-5 h; the protective atmosphere in the annealing is air.

In recent years, the "high entropy effect" is excellent in material performance regulation, and high entropy ceramics have become one of the research hotspots in the ceramic field. High-entropy ceramics generally refer to ceramic materials having a simple crystal structure composed of five or more metal elements and one non-metal element. Because the component design and regulation space is huge, the high-entropy ceramic has the properties of better stability, higher strength, ultrahigh hardness, amorphous-like thermal conductivity, huge dielectric constant and the like, and a new feasible and effective solution is provided for further improving the optical and mechanical properties of the alpha-SiAlON transparent ceramic. The high-entropy transparent ceramic is mainly different from a single transparent ceramic in that more elements are added into a system, so that a plurality of active ions can be absorbed, and a plurality of emission bands and absorption bands are presented at the same time. Therefore, it has better optical performance. In addition, the high entropy causes the crystal lattice to be distorted, thereby improving the mechanical property of the alpha-SiAlON transparent ceramic.

In order to better apply the alpha-SiAlON transparent ceramic to the aerospace field, a method for improving the optical and mechanical properties of the alpha-SiAlON transparent ceramic is sought, and the method has important significance for the development of the SiAlON ceramic and the application in the aerospace field. The alpha-SiAlON high-entropy transparent ceramic material with high infrared transmittance and high mechanical property is obtained through the alpha-SiAlON ceramic high-entropy, powder nanocrystallization, component optimization and fine design sintering process.

The alpha-SiAlON high-entropy transparent ceramic material with the light transmittance of 65-76% and the hardness of 23-25 GPa is obtained through the alpha-SiAlON ceramic high-entropy, powder nanocrystallization, component optimization and fine design sintering process. Compared with the prior art, the invention has the following beneficial technical effects:

1. by high entropy of the alpha-SiAlON component, the solid solution strengthening of rare earth elements with different ionic radii causes the strengthening of lattice distortion and the strengthening of dislocation movement blocked by nano particles, thereby greatly improving the mechanical property of the ceramic; the high-entropy ceramic can absorb various active ions, and simultaneously presents a plurality of emission bands and absorption bands, so that the optical transmittance is improved. Meanwhile, the introduction of various elements can reduce the eutectic temperature of the oxide, and can form a liquid phase at a lower temperature, thereby being beneficial to the densification of the ceramic sintering.

2. All the raw materials adopt nanoscale high-purity powder with the particle size of 20-30 nm, and the particle size D of the powder after secondary ball milling ₉₀ The nano-powder reaches 100-275 nm, and the nano-powder has the advantages of high sintering activity and easy realization of densification of ceramic, thereby effectively reducing the porosity. The presence of pores seriously affects the light transmission performance, and a porosity of more than 1% leads to devitrification. Therefore, the realization of pore-free or extremely low porosity is very beneficial to improving the optical and mechanical properties of the ceramic.

3. The design of the regulating and controlling components can effectively improve the mechanical and optical properties of the ceramic. alpha-SiAlON alpha-Si ₃ N ₄ A solid solution of (1) has a chemical general formula of RE _m/3 Si _12-(m+n) Al _m+n O _n N _16-n M is the number of (Al-N) bonds substituted for (Si-N) bonds and N is the number of (Al-O) bonds substituted for (Si-N) bonds, which may consist of a stabilizing ion M ^v+ M and n values. The designed values of m and n will affect the phase composition, the grain morphology and the densification behavior of the sintered product, and have great influence on the optical and mechanical properties of the ceramic. In the invention, the component design range of the ceramic is accurate, and the method has the beneficial effects of obtaining the single-phase alpha-SiAlON transparent ceramic, promoting the liquid phase sintering process and basically realizing the complete densification of the prepared sample. FIG. 1 shows a scanning electron micrograph of an alpha-SiAlON high-entropy transparent ceramic microstructure obtained by the process of the invention, and it can be seen from the figure that no obvious pores are observed in the microstructure of a sample, which shows that the preferred component design promotes liquid phase sintering, thereby realizing densification.

4. The links of calcination and secondary ball milling are added, so that the original powder is more uniform, the process controllability of the raw material powder with uniform particle size distribution is good, the preparation of large-size compact samples is facilitated, and the method has wide application prospect.

5. The annealing link is added, and the influence of carbon pollution on the light transmittance is reduced. During the hot-pressing sintering process, carbon pollution is inevitably introduced, and the carbon pollution can cause the absorption coefficient of a sample to be increased and the light transmittance to be reduced. The invention reduces carbon pollution by designing a reasonable annealing process, and is beneficial to improving the light transmittance.

6. The alpha-SiAlON high-entropy transparent ceramic with good optical property and mechanical property can be obtained by the preparation method. In the existing report, the highest light transmittance of the alpha-SiAlON transparent ceramic can only reach 72 percent, which has a certain difference with the theoretical light transmittance of 80 percent; the hardness is 19-24 GPa, the fracture toughness is 3-5 MPa m ^1/2 The bending strength is 300-560 MPa. In the research, the alpha-SiAlON high-entropy transparent ceramic has the light transmittance of 65-76%, the hardness of 23-25 GPa and the fracture toughness of 4-5 MPa m ^1/2 The bending strength reaches 500-650 MPa, and the optical performance and the mechanical performance both reach higher levels. Fig. 2 shows a photograph of a real object of the alpha-SiAlON high-entropy transparent ceramic prepared by the present invention, and it is apparent from the drawing that the prepared alpha-SiAlON high-entropy transparent ceramic has excellent density and light transmittance, and a pattern on the bottom paper can be clearly observed through the ceramic sheet.

Drawings

FIG. 1 is an SEM photograph of a cross section of an alpha-SiAlON high-entropy transparent ceramic prepared in example 1;

FIG. 2 is a photograph of a 1.0mm thick solid of the α -SiAlON high entropy transparent ceramic obtained in example 2;

FIG. 3 is an infrared transmittance curve of the 1.0mm thick α -SiAlON high entropy transparent ceramic prepared in example 3;

FIG. 4 is a flow chart of the present invention.

Detailed Description

The invention relates to alpha-SiAlON high-entropy transparent ceramic with 65-76% of light transmittance and 23-25 GPa of hardness, and the chemical general formula of the alpha-SiAlON high-entropy transparent ceramic is (RE 1) _a RE2 _b RE3 _c RE4 _d RE5 _e ) _m/3 Si _12-(m+n) Al _m+n O _n N _16-n 。

In the chemical formula, m is the number of (Al-N) bonds substituted for (Si-N) bonds, N is the number of (Al-O) bonds substituted for (Si-N) bonds, and m is more than or equal to 1 and less than or equal to 1.5, and N is more than or equal to 1 and less than or equal to 1.5. A, b, c, d, e each represent one of the substances (RE 1) _a RE2 _b RE3 _c RE4 _d RE5 _e ) _m/3 Si _12-(m+n) Al _m+n O _n N _16-n The medium molecule contains a RE1 atoms, b RE2 atoms, c RE3 atoms, d RE4 atoms and e RE5 atoms. Wherein a is more than or equal to 0.1 and less than or equal to 0.5, b is more than or equal to 0.1 and less than or equal to 0.5, c is more than or equal to 0.1 and less than or equal to 0.5, d is more than or equal to 0.1 and less than or equal to 0.5, and a + b + c + d + e =1, RE1, RE2, RE3, RE4 and RE5 are respectively any one element of Y, la, ce, pr, nd, sm, eu, yb, lu, dy, gd, er and Sc and are different from each other.

a＝0.2，b＝0.2，c＝0.2，d＝0.2，e＝0.2；

a＝0.1，b＝0.2，c＝0.3，d＝0.3，e＝0.1；

a＝0.5，b＝0.1，c＝0.2，d＝0.1，e＝0.1；

The raw materials comprise nano silicon nitride powder, nano aluminum oxide powder and rare earth oxide powder. The rare earth oxide is composed of any 5 different rare earth oxides of yttrium oxide, lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, ytterbium oxide, lutetium oxide, dysprosium oxide, gadolinium oxide, erbium oxide and scandium oxide.

The grain diameters of the nano silicon nitride powder and the nano aluminum nitride powder are both 20-30 nm, and the purity is 98%; the grain diameters of the nano alumina powder and the rare earth oxide are both 20-30 nm, and the purity is more than 99.9%; other reagents and materials, if not specifically stated, are commercially available; the experimental methods are all conventional methods unless otherwise specified.

TABLE 1-1 chemical composition of the examples

Examples	m	n	RE1	RE2	RE3	RE4	RE5	a	b	c	d	e
													1	1.2	1.0	Y	La	Ce	Pr	Nd	0.2	0.2	0.2	0.2	0.2
2	1.0	1.2	Sm	Eu	Yb	Lu	Dy	0.2	0.2	0.2	0.2	0.2
													3	1.2	1.0	Gd	Er	Sc	Y	Yb	0.1	0.2	0.3	0.3	0.1
4	1.2	1.5	Y	La	Yb	Lu	Dy	0.5	0.1	0.3	0.1	0.1
													5	1.5	1.0	Y	Sm	Yb	Sc	Lu	0.2	0.2	0.2	0.2	0.2

Tables 1 to 2 chemical composition formulas of respective examples

Examples	Chemical composition formula
		1	(Y _0.2 La _0.2 Ce _0.2 Pr _0.2 Nd _0.2 ) _0.4 Si _9.8 Al _2.2 O _1.0 N _15.0
2	(Sm _0.2 Eu _0.2 Yb _0.2 Lu _0.2 Dy _0.2 ) _0.33 Si _9.8 Al _2.2 O _1.2 N _14.8
		3	(Gd _0.1 Er _0.2 Sc _0.3 Y _0.3 Yb _0.1 ) _0.4 Si _9.8 Al _2.2 O _1.0 N _15.0
4	(Y _0.5 La _0.1 Yb _0.2 Lu _0.1 Dy _0.1 ) _0.4 Si _9.3 Al _2.7 O _1.5 N _14.5
		5	(Y _0.2 Sm _0.2 Yb _0.2 Sc _0.2 Lu _0.2 ) _0.5 Si _9.5 Al _2.5 O _1.0 N _15.0

The alpha-SiAlON high-entropy transparent ceramic has the light transmittance of 65-76%, the hardness of 23-25 GPa and the fracture toughness of 4-5 MPa m ^1/2 The bending strength is 500-650 MPa. The optical performance and the mechanical performance reach higher level.

step 1, batching:

in each example, the raw materials of nano silicon nitride powder, nano aluminum oxide powder and rare earth oxide powder are accurately weighed according to the stoichiometric ratio of the chemical formula. The rare earth oxide is nano yttrium oxide or nano lanthanum oxide or nano cerium oxide or nano praseodymium oxide or nano neodymium oxide or nano samarium oxide or nano europium oxide or nano ytterbium oxide or nano lutetium oxide or nano dysprosium oxide or nano gadolinium oxide or nano erbium oxide or nano scandium oxide powder. The specific amounts of the raw materials are shown in table 2.

Step 2, primary ball milling:

putting the raw materials weighed in the step 1 into a polytetrafluoroethylene ball milling tank, and sequentially adding silicon nitride grinding balls and absolute ethyl alcohol; the weight ratio of the raw material, the absolute ethyl alcohol and the silicon nitride grinding ball is 1. And (3) placing the polytetrafluoroethylene ball milling tank in a planetary ball mill, and carrying out ball milling for 10-36 h at a ball milling rotating speed of 250-350 r/min to obtain mixed slurry. The ball milling rotation speed and the ball milling time used in each example are specifically shown in table 2; drying the obtained mixed slurry in an oven at 60 ℃ for 12 hours to obtain dry powder, and grinding for 1 hour to obtain powder;

TABLE 2 technical parameters of the examples in step 1 and step 2

Step 3, calcining powder:

putting the powder prepared in the step 2 into a ceramic crucible; the ceramic crucible was placed in a nitrogen atmosphere furnace for calcination. The calcination temperature is 1500-1650 ℃, and the temperature is kept for 2-10 h; 0.1 to 1.0MPa of nitrogen is introduced into the whole calcining process. The temperature rise rate of the calcination temperature was 5 ℃/min. And after the calcination, stopping introducing nitrogen, naturally cooling the furnace body to room temperature, taking out the powder, and grinding for 1h to obtain the pre-sintered powder.

TABLE 3 Process parameters for each example in step 3

Step 4, secondary ball milling:

and (4) grinding the pre-sintered powder obtained in the step (3) for 1 hour. And placing the ground pre-sintered powder into a polytetrafluoroethylene ball milling tank, and sequentially adding silicon nitride grinding balls and absolute ethyl alcohol into the ball milling tank. The weight ratio of the pre-sintered powder to the anhydrous ethanol to the silicon nitride grinding balls is 1. And placing the ball milling tank in a planetary ball mill, and carrying out ball milling for 10-96 h at the ball milling rotating speed of 250-350 r/min to obtain mixed slurry. The milling speeds and milling times used in the examples are specified in Table 4.

Drying the obtained mixed slurry in an oven for 12 hours at 60 ℃ to obtain dry powder; grinding the dried powder for 1h to obtain a particle size D ₉₀ Is 100-275 nm powder.

Table 4 process parameters for each example in step 4

Step 5, hot-pressing sintering:

the particle diameter D obtained in the step 4 ₉₀ 100-275 nm powder is put into a graphite die and hot pressed and sintered in a hot pressing furnace.

The hot-pressing sintering process comprises the following specific steps: a layer of carbon paper coated with boron nitride powder is placed in the grinding tool and between the powder to inhibit carbon pollution. Weighing 100g of the particle size D ₉₀ 100-275 nm powder is filled into a graphite mould. Putting the graphite mould into a vacuum hot pressing furnace, heating to 1800-1950 ℃ at the speed of 10-20 ℃/min under the protection of nitrogen atmosphere of 0.1-1.0 MPa, preserving heat for 1-3 h, and carrying out hot pressing sintering. In the temperature rising process, when the temperature of the vacuum hot-pressing furnace reaches 1000 ℃, the mechanical pressure of 20-50 MPa is applied. And (4) after the heat preservation is finished, closing the heating power supply to cool along with the furnace, and taking out after cooling along with the furnace to obtain the ceramic block.

TABLE 5 Process parameters for each example in step 5

Step 6, annealing treatment

And (5) placing the ceramic block obtained in the step (5) into a box type furnace for annealing and finishing. During the annealing treatment, the annealing temperature is 700-900 ℃, and the annealing time is 2-5 h; and (3) taking the protective atmosphere in annealing as air, taking out a sample after the annealing is finished, and grinding and polishing to obtain the alpha-SiAlON high-entropy transparent ceramic.

TABLE 6 Process parameters for each example in step 6

In order to verify the effect of the invention, the performance parameters of the alpha-SiAlON high-entropy transparent ceramic obtained in each example were tested, and the results are shown in table 7:

TABLE 7 Properties of the alpha-SiAlON high entropy transparent ceramics obtained in each example

In order to further explain that the high entropy is beneficial to improving the optical performance and the mechanical performance of the alpha-SiAlON transparent ceramic, four groups of comparative examples are designed by taking comparative example 1 as a comparison group, wherein the preparation methods adopted in comparative examples 1 to 4 are the same as those in example 1, but the raw materials selected in the preparation process are different, mainly the raw materials selected according to the target product to be prepared are selected in the same manner as that in example 1. Specific variations are detailed in the following individual ratios.

Comparative example 1

The difference from the example 1 is that the raw materials are nano silicon nitride powder, nano aluminum oxide powder and nano yttrium oxide powder according to the chemical formula Y _0.4 Si _9.8 Al _2.2 O _1.0 N _15.0 Accurately weighing various raw material powders according to the stoichiometric ratio of the raw materials.

Comparative example 2

The difference from example 1 is that the raw materials are nano silicon nitride powder, nano aluminum nitride powder, nano alumina powder, nano yttrium oxide powder and nano lanthanum oxide powder according to the chemical formula (Y) _0.5 La _0.5 ) _0.4 Si _9.8 Al _2.2 O _1.0 N _15.0 Accurately weighing various raw material powder according to the stoichiometric ratio.

Comparative example 3

The difference from example 1 is that the raw materials are nano silicon nitride powder, nano aluminum nitride powder, nano alumina powder, nano yttrium oxide powder, nano lanthanum oxide powder and nano cerium oxide powder, and the chemical formula (Y) is shown _0.6 La _0.2 Ce _0.2 ) _0.4 Si _9.8 Al _2.2 O _1.0 N _15.0 Accurately weighing various raw material powder according to the stoichiometric ratio.

Comparative example 4

The difference from example 1 is that the raw materials are nano silicon nitride powder, nano aluminum nitride powder, nano alumina powder, nano yttrium oxide powder, nano lanthanum oxide powder, nano cerium oxide powder and nano praseodymium oxide powder, and are according to the chemical formula (Y) _0.4 La _0.2 Ce _0.2 Pr _0.2 ) _0.4 Si _9.8 Al _2.2 O _1.0 N _15.0 Accurately weighing various raw material powder according to the stoichiometric ratio.

The performance parameter test results of the comparative examples 1 to 4 and the example 1 are shown in table 8, and it can be seen from the table that the high entropy is beneficial to improving the optical performance and the mechanical performance of the alpha-SiAlON transparent ceramic. The method is mainly characterized in that as the number of rare earth elements is increased from one to five and the single alpha-SiAlON transparent ceramic is changed into the alpha-SiAlON high-entropy transparent ceramic, the solid solution strengthening effect among the rare earth elements in the ceramic causes the enhancement of lattice distortion and the enhancement of dislocation movement resistance of nano particles, thereby greatly improving the mechanical property of the ceramic; the high-entropy ceramic can absorb various active ions, and simultaneously presents a plurality of emission bands and absorption bands, so that the optical transmittance is improved. Meanwhile, the introduction of various elements can reduce the eutectic temperature of the oxide, and can form a liquid phase at a lower temperature, thereby being beneficial to ceramic sintering densification.

Table 8: performance parameters for comparative examples 1 to 4 and example 1

Claims

1. The alpha-SiAlON high-entropy transparent ceramic material is characterized by having a chemical general formula of (RE 1) _a RE2 _b RE3 _c RE4 _d RE5 _e ) _m/3 Si _12-(m+n) Al _m+n O _n N _16- ；

In the chemical general formula, m is the number of Al-N bonds substituted for Si-N bonds, N is the number of Al-O bonds substituted for Si-N bonds, m is more than or equal to 1 and less than or equal to 1.5, N is more than or equal to 1 and less than or equal to 1.5; a, b, c, d, e each represent one of the substances (RE 1) _a RE2 _b RE3 _c RE4 _d RE5 _e ) _m/ ₃ Si _12-(m+n) Al _m+n O _n N _16-n The middle molecule contains a RE1 atoms, b RE2 atoms, c RE3 atoms, d RE4 atoms and e RE5 atoms; wherein a is more than or equal to 0.1 and less than or equal to 0.5, b is more than or equal to 0.1 and less than or equal to 0.5, c is more than or equal to 0.1 and less than or equal to 0.5, d is more than or equal to 0.1 and less than or equal to 0.5, and a + b + c + d + e =1, RE1, RE2, RE3, RE4 and RE5 are respectively any one element of Y, la, ce, pr, nd, sm, eu, yb, lu, dy, gd, er and Sc and are different from each other.

2. An α -SiAlON high entropy transparent ceramic material according to claim 1, wherein a =0.1 to 0.5;

b =0.1 or 0.2; c =0.2 or 0.3; d =0.1 to 0.2; e =0.1 or 0.2.

3. The alpha-SiAlON high-entropy transparent ceramic material of claim 1, wherein the raw materials of the high-entropy transparent ceramic material comprise nano silicon nitride powder, nano aluminum oxide powder and rare earth oxide powder.

4. The α -SiAlON high entropy transparent ceramic material of claim 3, wherein the rare earth oxide is composed of any 5 different rare earth oxides selected from the group consisting of yttrium oxide, lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, ytterbium oxide, lutetium oxide, dysprosium oxide, gadolinium oxide, erbium oxide, and scandium oxide.

5. The alpha-SiAlON high-entropy transparent ceramic material of claim 3, wherein the grain diameters of the nano silicon nitride powder and the nano aluminum nitride powder are both 20-30 nm, and the purity is 98%; the grain diameters of the nano alumina powder and the rare earth oxide are both 20-30 nm, and the purity is more than 99.9%.

6. A method for preparing the alpha-SiAlON high-entropy transparent ceramic material as claimed in claim 1, which is characterized by comprising the following specific steps:

step 1, batching:

weighing raw materials of nano silicon nitride powder, nano aluminum oxide powder and rare earth oxide powder according to a ratio;

step 2, primary ball milling:

placing the weighed raw materials into a polytetrafluoroethylene ball milling tank, sequentially adding silicon nitride grinding balls and absolute ethyl alcohol, and carrying out ball milling to obtain mixed slurry; drying the mixed slurry and then grinding the dried mixed slurry for h to obtain powder;

step 3, calcining powder:

putting the obtained powder into a ceramic crucible; placing the ceramic crucible in a nitrogen atmosphere furnace for calcining; the calcination temperature is 1500-1650 ℃, and the temperature is kept for 2-10 h; introducing nitrogen of 0.1-1.0 MPa in the whole calcining process; the heating rate of the calcination is 5 ℃/min; after the calcination, stopping introducing nitrogen, naturally cooling the furnace body to room temperature, taking out powder, and grinding for 1h to obtain pre-sintered powder;

step 4, secondary ball milling:

grinding the obtained pre-sintering powder for 1h; placing the ground presintered powder in a polytetrafluoroethylene ball milling tank, sequentially adding silicon nitride grinding balls and absolute ethyl alcohol into the ball milling tank, and ball milling for 10-96 hours to obtain mixed slurry; drying the obtained mixed slurry in an oven and grinding for 1h to obtain the particle size D ₉₀ 100-275 nm powder;

step 5, hot-pressing sintering:

the obtained particle diameter D ₉₀ 100-275 nm powder is put into a graphite mould and hot pressed and sintered in a hot pressing furnace;

the hot-pressing sintering process comprises the following specific steps: placing a layer of carbon paper coated with boron nitride powder in the mold and between the powder to inhibit carbon pollution; weighing 100g of the particle size D ₉₀ 100-275 nm powder is filled into a graphite mould; putting the graphite mould into a vacuum hot pressing furnace, heating to 1800-1950 ℃ at the speed of 10-20 ℃/min under the protection of nitrogen atmosphere of 0.1-1.0 MPa, preserving heat for 1-3 h, and carrying out hot pressing sintering; in the temperature rising process, when the temperature of the vacuum hot-pressing furnace reaches 1000 ℃, the mechanical pressure of 20-50 MPa is applied; after the heat preservation is finished, closing a heating power supply, cooling along with the furnace, and taking out after cooling along with the furnace to obtain a ceramic block body;

step 6, annealing treatment:

placing the obtained ceramic block in a box-type furnace for annealing and finishing; and after the annealing is finished, taking out the sample, and grinding and polishing to obtain the alpha-SiAlON high-entropy transparent ceramic.

7. The preparation method of the alpha-SiAlON high-entropy transparent ceramic material as claimed in claim 6, wherein when the ball milling in the step 2 is carried out for one time, the weight ratio of the raw materials, the absolute ethyl alcohol and the silicon nitride grinding balls is 1; the ball milling speed is 250-350 r/min, and the ball milling time is 10-36 h.

8. The preparation method of the alpha-SiAlON high-entropy transparent ceramic material as claimed in claim 6, wherein, during the secondary ball milling in the step 4, the weight ratio of the pre-sintered powder, the absolute ethyl alcohol and the silicon nitride grinding balls is 1; the ball milling speed is 250-350 r/min, and the ball milling time is 10-96 h.

9. The method for preparing the alpha-SiAlON high-entropy transparent ceramic material as claimed in claim 6, wherein when the annealing treatment is carried out in the step 6, the annealing temperature is 700-900 ℃, and the annealing time is 2-5 h; the protective atmosphere in the annealing is air.