A B-site doped NaNbO3 high entropy ceramic material and preparation method thereof

Abstract

The present invention discloses a B-doped NaNbO3 high entropy ceramic material and a preparation method thereof, belonging to the technical field of high entropy ceramic materials. The chemical formula of the high entropy ceramic is Na(Nb 0.25 Ta 0.25 V 0.25 W 0.25 )O3, the preparation process is to weigh the raw material powders of Na2CO3, Nb2O5, Ta2O5, V2O5, and WO3 according to the designed stoichiometric ratio, and then carry out wet ball milling, drying, calcination, secondary ball milling, drying, grinding, tableting, and finally sintering at 1100°C in air for 4 hours to obtain high entropy ceramics. When tested at a frequency of 1kHz, the high entropy ceramic has a dielectric loss of less than 0.05 at room temperature and a dielectric constant of 223. At room temperature, when the test frequency increases from 1kHz to 1MHz, the dielectric constant of the high entropy ceramic remains stable, and it has broad application potential in the field of ceramic capacitors.

Description

Technical Field

[0001] The invention relates to a B-site doped NaNbO3 high-entropy ceramic material and a preparation method thereof, belonging to the technical field of high-entropy ceramics. Background Art

[0002] Sodium niobate (NaNbO3) is a typical dielectric ceramic material. After doping, the dielectric constant can be increased and the dielectric loss can be reduced.

[0003] High entropy ceramic materials are multi-principal component solid solution ceramics formed by doping five or more elements in equal or approximately equal proportions. After in-depth research, single-phase solid solution ceramics formed by doping four principal components in equal proportions can also be called high entropy ceramics. In the field of dielectric ceramics, there has never been any research or report on the high entropy design of sodium niobate. This patent is to perform a high entropy design on the B-site of sodium niobate, and dope four elements with similar chemical properties in equal molar ratios into the B-site lattice of sodium niobate, causing the sodium niobate to produce a lattice distortion effect, increase its disorder, and improve its dielectric constant. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing a B-doped NaNbO3 high entropy ceramic material, wherein the chemical formula of the ceramic is: Na(Nb 0.25 Ta 0.25 V 0.25 W 0.25 )O3.

[0005] The preparation method comprises the following steps:

[0006] (1) According to Na(Nb 0.25 Ta 0.25 V 0.25 W 0.25 )O3 chemical formula weigh Na2CO3, Nb2O5, Ta2O5, V2O5, and WO3 raw material powders respectively.

[0007] (2) The above powders are placed in a ball mill for wet ball milling and mixing, followed by drying and calcining to obtain high entropy ceramic powder, which is then ball milled again, dried, ground, and pressed into tablets.

[0008] (3) The pressed high-entropy ceramic block is placed in a muffle furnace and sintered in air.

[0009] Preferably, the conditions for wet ball milling and secondary ball milling in step (2) of the present invention are: the rotation speed of the ball mill is 15 to 35 rpm, the ball milling time is 36 to 72 hours, the ball milling medium is distilled water and zirconia balls, and the ratio of balls: materials: distilled water is (2 to 3): 1: 1. The mass ratio of large zirconia balls, medium balls, and small balls is 1: (2 to 3): 1.

[0010] Preferably, the drying conditions in step (2) of the present invention are: the drying temperature in step (2) is 80 to 120° C., and the drying time is 12 to 30 hours.

[0011] Preferably, the calcination conditions in step (2) of the present invention are: calcination at 780-820° C. for 2-3 hours.

[0012] Preferably, the mesh size of the sieving in step (2) of the present invention is 80 to 200 meshes.

[0013] Preferably, the grinding conditions in step (2) of the present invention are: putting the dried mixed powder into a grinding jar and grinding it for 20 to 50 minutes.

[0014] Preferably, the diameter of the mold used for tableting in step (2) of the present invention is 16-18 mm, the uniaxial pressure is 180-200 MPa, and the holding time is 5-15 minutes.

[0015] Preferably, during the sintering process of step (3) of the present invention: the temperature is raised from room temperature to 1080-1120°C at a heating rate of 5°C / min, kept in the muffle furnace for 3.8-4.2 hours, then cooled to a low temperature with the furnace and taken out.

[0016] Beneficial effects of the present invention

[0017] (1) The preparation process of the present invention is simple and does not require atmosphere protection. It only needs to use an ordinary muffle furnace for sintering, which has the characteristics of short sintering time, energy saving, simple process, low production cost, short production cycle, high efficiency, etc.

[0018] (2) The Na(Nb) prepared by the present invention 0.25 Ta 0.25 V 0.25 W 0.25 )O3 high entropy ceramics do not require the addition of any binders, sintering aids and dispersants.

[0019] (3) Na(Nb) prepared by the present invention 0.25 Ta 0.25 V 0.25 W 0.25 )The dielectric constant of O3 high entropy ceramics remains stable at room temperature and test frequencies from 1kHz to 1MHz. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. However, the protection scope of the present invention is not limited to the above contents. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The Na(Nb) after calcination in Example 1 0.25Ta 0.25 V 0.25 W 0.25 )XRD pattern of O3 high entropy powder.

[0022] Figure 2 For example 1Na(Nb 0.25 Ta 0.25 V 0.25 W 0.25 )SEM image of O3 high entropy ceramics.

[0023] Figure 3 For example 1Na(Nb 0.25 Ta 0.25 V 0.25 W 0.25 ) Dielectric constant diagram of O3 high entropy ceramics at room temperature.

[0024] Figure 4 For example 1Na(Nb 0.25 Ta 0.25 V 0.25 W 0.25 ) Dielectric loss diagram of O3 high entropy ceramics at room temperature.

[0025] Example 1

[0026] A method for preparing a B-doped NaNbO3 high entropy ceramic material, wherein the sintering temperature is 1100°C, and the specific steps are as follows:

[0027] (1) The chemical formula of the ceramic is: Na(Nb 0.25 Ta 0.25 V 0.25 W 0.25 )O3 high entropy ceramics. The preparation process is to weigh the raw material powders of Na2CO3, Nb2O5, Ta2O5, V2O5 and WO3 respectively according to the designed stoichiometric ratio.

[0028] The weighed powder was placed in a ball mill for wet milling and mixing. The speed of the ball mill was 30 rpm, the ball milling time was 43 hours, the ball milling medium was distilled water and zirconia balls, and the ball: material: distilled water ratio was 2:1:1. The mass ratio of large zirconia balls, medium balls, and small balls was 1:2:1. The drying temperature was 92°C and the drying time was 16h. The second ball milling was performed, and the ball milling parameters were the same as those of the first ball milling. The mixed slurry was placed in an oven and dried at 90°C for 20 hours. The dried powder was placed in a grinding jar and ground for 34 minutes.

[0029] The dried mixed powder was put into a grinding jar and ground for 31 minutes, and the ground mixed powder was sieved with a mesh size of 180 meshes.

[0030] (2) After grinding, the ceramic powder was pressed into a ceramic block with a diameter of 16 mm under a uniaxial pressure of 190 MPa.

[0031] (3) The pressed unsintered ceramic sheet is placed in a muffle furnace. The temperature is raised from room temperature to 1100°C at a heating rate of 5°C / min, and the temperature is kept in the muffle furnace for 4 hours. After that, the sheet is cooled to a low temperature and then taken out.

[0032] Example 2

[0033] A method for preparing a B-doped NaNbO3 high entropy ceramic material, wherein the sintering temperature is 1080°C, and the specific steps are as follows:

[0034] (1) The chemical formula of the ceramic is: Na(Nb 0.25 Ta 0.25 V 0.25 W 0.25 )O3 high entropy ceramics. The preparation process is to weigh Na2CO3, Nb2O5, Ta2O5, V2O5, and WO3 according to the designed stoichiometric ratio.

[0035] The weighed powder was placed in a ball mill for wet ball milling. The speed of the ball mill was 28 rpm, the ball milling time was 52 hours, the ball milling medium was distilled water and zirconia balls, and the ball: material: distilled water ratio was 2:1:1. The mass ratio of large zirconia balls, medium balls, and small balls was 1:2:2. After drying, the drying temperature was 94°C and the drying time was 16 hours. After the second ball milling, the ball milling parameters were the same as those of the first ball milling. The mixed slurry was placed in an oven and dried at 90°C for 20 hours. The dried powder was placed in a grinding jar and ground for 30 minutes.

[0036] The dried mixed powder was placed in a grinding jar and ground for 31 minutes, and the ground mixed powder was sieved with a mesh size of 200 meshes.

[0037] (2) After grinding, the ceramic powder was pressed into a ceramic block with a diameter of 16 mm under a uniaxial pressure of 180 MPa.

[0038] (3) The pressed unsintered ceramic sheet is placed in a muffle furnace. The temperature is raised from room temperature to 1080°C at a heating rate of 5°C / min, and the heat preservation time in the muffle furnace is 3.8 hours. After that, the sheet is cooled to a low temperature and then taken out.

[0039] Example 3

[0040] A method for preparing a B-doped NaNbO3 high entropy ceramic material, wherein the sintering temperature is 1120°C, and the specific steps are as follows:

[0041] (1) The chemical formula of the ceramic is: Na(Nb0.25 Ta 0.25 V 0.25 W 0.25 )O3 high entropy ceramics. The preparation process is to weigh Na2CO3, Nb2O5, Ta2O5, V2O5, and WO3 according to the designed stoichiometric ratio.

[0042] The weighed powder was placed in a ball mill for wet milling and mixing. The speed of the ball mill was 28 rpm, the ball milling time was 60 hours, the ball milling medium was distilled water and zirconia balls, and the ball: material: distilled water ratio was 2:1:1. The mass ratio of large zirconia balls, medium balls, and small balls was 1:2:1. After drying, the drying temperature was 94°C and the drying time was 16h. After the second ball milling, the ball milling parameters were the same as those of the first ball milling; the mixed slurry was placed in an oven and dried at 90°C for 20 hours, and the dried powder was placed in a grinding jar and ground for 30 minutes.

[0043] The dried mixed powder was placed in a grinding jar and ground for 32 minutes, and the ground mixed powder was sieved with a mesh size of 180 meshes.

[0044] (2) After grinding, the ceramic powder was pressed into a ceramic block with a diameter of 16 mm under a uniaxial pressure of 200 MPa.

[0045] (3) The pressed unsintered ceramic sheet is placed in a muffle furnace. The temperature is raised from room temperature to 1120°C at a heating rate of 5°C / min, and the heat preservation time in the muffle furnace is 3.9 hours. After that, the sheet is cooled to a low temperature and then taken out.

[0046] Figure 1 The Na(Nb) prepared in Example 1 0.25 Ta 0.25 V 0.25 W 0.25 )O3 high entropy ceramic powder spectrum after calcination. It can be seen from the spectrum that after calcination, Na(Nb 0.25 Ta 0.25 V 0.25 W 0.25 )O3 high entropy ceramics have a single-phase structure and almost no impurity peaks can be seen.

[0047] Figure 2 The Na(Nb) prepared in Example 1 0.25 Ta 0.25 V 0.25 W 0.25 )O3 high entropy ceramic SEM microstructure. As can be seen from the figure, the relative density is high, the element distribution is very uniform, and there is no element segregation phenomenon.

[0048] Figure 3 The Na(Nb) prepared in Example 10.25 Ta 0.25 V 0.25 W 0.25 )O3 high entropy ceramic room temperature dielectric constant diagram; It can be seen from the figure that at room temperature, under 1kHz frequency test, Na(Nb 0.25 Ta 0.25 V 0.25 W 0.25 )The dielectric constant of O3 high entropy ceramics is 223. As the test frequency increases, the dielectric constant is very stable and the variation range is small.

[0049] Figure 4 The Na(Nb) prepared in Example 1 0.25 Ta 0.25 V 0.25 W 0.25 )O3 high entropy ceramic room temperature dielectric loss diagram; It can be seen from the figure that at room temperature, Na(Nb 0.25 Ta 0.25 V 0.25 W 0.25 )O3 high entropy ceramics is 223. Under the 1kHz frequency test, the dielectric loss is 0.04. As the test frequency increases, the dielectric loss drops to about 0.03, and the dielectric loss is also very small. Na(Nb 0.25 Ta 0.25 V 0.25 W 0.25 )O3 high entropy ceramics have the potential to become a new generation of lead-free ceramic capacitors.

Claims

1. A B-doped NaNbO3 high entropy ceramic material, characterized in that: The high entropy ceramic is designed with high entropy at the B position, and the chemical formula of the high entropy ceramic is: Na(Nb 0.25 Ta 0.25 V 0.25 W 0.25 )O3.

2. The method for preparing the B-doped NaNbO3 high entropy ceramic material according to claim 1, characterized in that: The following steps are involved: (1) According to Na(Nb 0.25 Ta 0.25 V 0.25 W 0.25 )O3 chemical formula weigh Na2CO3, Nb2O5, Ta2O5, V2O5, WO3 raw material powders respectively; (2) placing the above powders in a ball mill for wet ball milling and mixing, followed by drying and calcining to obtain high entropy ceramic powder, and then ball milling, drying, grinding, and tableting for a second time; (3) The pressed high-entropy ceramic block is placed in a muffle furnace and sintered in air.

3. The method for preparing the B-doped NaNbO3 high entropy ceramic material according to claim 2, characterized in that: The conditions for the first ball milling and the second ball milling in step (2) are: the rotation speed of the ball mill is 15-35 rpm, the ball milling time is 36-72 hours, the ball milling medium is distilled water and zirconia balls, the ball: material: distilled water is (2-3):1:1; the mass ratio of large zirconia balls, medium balls, and small balls is 1:(2-3):

1.

4. The method for preparing the B-doped NaNbO3 high entropy ceramic material according to claim 2, characterized in that: The drying temperature in step (2) is 80-120°C and the drying time is 12-30 h.

5. The method for preparing the B-doped NaNbO3 high entropy ceramic material according to claim 2, characterized in that: The grinding conditions in step (2) are as follows: the dried mixed powder is placed in a grinding jar and ground for 20 to 50 minutes; the ground mixed powder is sieved with a mesh size of 80 to 200 meshes.

6. The method for preparing the B-doped NaNbO3 high entropy ceramic material according to claim 2, characterized in that: The calcination conditions in step (2) are: calcination at 780-820° C. for 2-3 hours.

7. The method for preparing the B-doped NaNbO3 high entropy ceramic material according to claim 2, characterized in that: The diameter of the mold used for tableting in step (2) is 16-18 mm, the uniaxial pressure is 180-200 MPa, and the holding time is 5-15 minutes.

8. The method for preparing the B-doped NaNbO3 high entropy ceramic material according to claim 3, characterized in that: During the sintering process of step (3): the temperature is raised from room temperature to 1080-1120°C at a heating rate of 5°C / min, and the temperature is kept in the muffle furnace for 3.8-4.2 hours. The crucible is then cooled to a low temperature and taken out with crucible tongs.

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