Sodium niobate antiferroelectric ceramic and preparation method thereof

Abstract

The invention discloses a sodium niobate antiferroelectric ceramic and a preparation method thereof, the stoichiometric formula of the sodium niobate antiferroelectric ceramic is Na < 1-x > Sm < x > NbO < 3 + 4 x-0.1 mol% MnO < 2 >, and x is equal to 0.005-0.07; the preparation method comprises the following steps: weighing Na2CO3, Nb2O5, Sm2O3 and MnO2 according to a stoichiometric equation to form a mixture, carrying out ball milling on the mixture, and calcining at 700-850 DEG C for 4 hours to form a full ingredient; carrying out ball milling, drying and sieving on the whole ingredient to form a sieved material; pressing the sieved material into a cylindrical green body, putting the cylindrical green body on a zirconium oxide flat plate, putting the zirconium oxide flat plate into an aluminum oxide closed sagger, and putting the aluminum oxide closed sagger into a box-type furnace for sintering to obtain the sodium niobate anti-ferroelectric ceramic; the material keeps a stable antiferroelectric phase at room temperature, the breakdown strength of the material is improved, and the material can be applied to precise circuits in the field of electronic and electrical engineering; the preparation process is simple, the material cost is low, and the material is green and environment-friendly and becomes an important candidate material of a lead-free ceramic material with a stable antiferroelectric phase.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of functional materials, and relates to a sodium niobate antiferroelectric ceramic energy storage material, in particular to a sodium niobate antiferroelectric ceramic and a preparation method thereof. BACKGROUND

[0002] At present, the antiferroelectric ceramic has potential application values in high-energy density energy storage devices and pulse power capacitors due to its unique AFE-FE phase transition characteristics and double electric hysteresis loop characteristics. However, the commonly used lead-containing antiferroelectric ceramic such as PbZrO3 has environmental pollution and health risks, which limits its industrial application. As a typical lead-free antiferroelectric ceramic, sodium niobate (NaNbO3) has a low transition field of AFE P phase, which leads to a low energy storage efficiency of AFE P phase, and further reduces the material insulation and breakdown field strength, thereby limiting the energy storage performance and practical application. Therefore, it is necessary to optimize the doping to improve the AFE R phase stability of the NaNbO3-based lead-free antiferroelectric ceramic, so as to improve the energy storage density and breakdown field strength. SUMMARY

[0003] In view of the deficiencies in the prior art, the purpose of the present application is to provide a sodium niobate antiferroelectric ceramic with excellent insulation, high breakdown field strength and high energy density energy storage characteristics, and a preparation method thereof.

[0004] In order to achieve the above-mentioned purpose, the following technical solutions are adopted in the present application:

[0005] A sodium niobate antiferroelectric ceramic, the stoichiometric formula of which is Na 1-x Sm x NbO 3+4x -0.1mol%MnO2, wherein x=0.005-0.07.

[0006] The present application also protects a preparation method of the sodium niobate antiferroelectric ceramic as described above, comprising the following steps:

[0007] Step one, weighing Na2CO3, Nb2O5, Sm2O3 and MnO2 according to the stoichiometric formula to form a mixed material, and calcining the mixed material at 700-850 DEG C for 4h after ball milling to form a full ingredient;

[0008] Step two, re-ball milling, drying and sieving the full ingredient to form a sieved material;

[0009] Step three, pressing the sieved material into a cylindrical green body, placing the cylindrical green body on a zirconia flat plate, placing the zirconia flat plate in an alumina closed box, and placing the alumina closed box in a box-type furnace for sintering to obtain the sodium niobate antiferroelectric ceramic.

[0010] Preferably, the ball milling in step one and step two is that the mixture or full ingredients is mixed with zirconium balls and anhydrous ethanol according to the mass ratio of 1:(2-3):(1-1.5) and then ball milled for 20-24 hours.

[0011] Preferably, the drying in step two is that the mixture is dried in an oven at 80-90 DEG C for 20-24 hours.

[0012] Preferably, the mesh number of the screen in step two is 200-300 mesh.

[0013] Preferably, the sintering mechanism in step three is that the temperature is first increased to 500-600 DEG C at a rate of 5 DEG C / min, then kept for 3 min, then increased to 1000-1100 DEG C at a rate of 5 DEG C / min and kept for 30 min, then increased to 1290-1310 DEG C at a rate of 2 DEG C / min and kept for 120 min, then decreased to 1000 DEG C at a rate of 2 DEG C / min, then decreased to 500 DEG C at a rate of 5 DEG C / min, and finally cooled to room temperature with the furnace.

[0014] Compared with the prior art, the present application has the following technical effects:

[0015] The Na 1-x Sm x NbO 3+4x -0.1mol%MnO2 3+ Doping, verified by first-principle calculation, reduces BO6 octahedral distortion degree (from 33.43 to 32.08), improves b-axis average tilt angle (from 25.26° to 27.23°), realizes stable phase transition from FE Q phase to AFE R phase, improves the band gap of the material from 2.02 eV to 2.60 eV, significantly improves the insulation and breakdown field strength, realizes high energy density storage characteristics, and finally prepares a sodium niobate ceramic material with stable antiferroelectric phase, which maintains stable antiferroelectric phase at room temperature and improves the breakdown strength, and can be applied in precision circuits in the field of electronic and electrical engineering.

[0016] Further, high breakdown strength means that higher operating voltage can be withstood, thereby improving the range of application and the reliability of the equipment, and helping to simplify the design and operation of the equipment.

[0017] The preparation process of the present application is simple, the material cost is low, and the present application is green and environmentally friendly, and becomes an important candidate material for lead-free ceramic materials with stable antiferroelectric phase. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 (a-c) are the electron localization functions of the NaSmNbSbO3 model, (d-f) are the crystal structures, and (g-i) are the band gap.

[0019] Figure 2 Fig. 2 is a schematic diagram of the spatial distribution of Sm atoms in a NaSmNbSbO3 model;

[0020] Figure 3 NaSmNbSbO3 prepared in Example 1 0.995 Sm 0.05 NbO 3+0.2 -0.1mol% MnO2 ceramic;

[0021] Figure 4 NaSmNbSbO3 prepared in Example 2 0.995 Sm 0.005 NbO 3+0.02 -0.1mol% MnO2 ceramic. DETAILED DESCRIPTION

[0022] The specific content of the application is further explained in detail below in combination with examples.

[0023] The application constructs a Sm 3+ The FE Q phase AFE P phase and AFE R phase cell structure model of doped NaNbO3 is calculated by using the first principle to calculate the Sm 3+ The FE Q phase AFE P phase and AFE R phase cell structure model of doped NaNbO3 is calculated by using the first principle to calculate the Sm 3+ The doping of Sm 3+ ) doped NaNbO3, which provides direct theoretical guidance for improving the AFE R phase stability of NaNbO3 structural materials;

[0024] The design method of sodium niobate antiferroelectric ceramic based on the first principle guidance comprises the following steps:

[0025] Step 1, using VESTA software, based on the FE Q phase AFE P phase and AFE R phase cell structure of known NaNbO3, a NaSmNbSbO3 doping model is constructed by atomic replacement, different doping contents are simulated and ordered cell structures are generated; the electronic localization function, crystal structure and band gap of the FE Q phase AFE P phase and AFE R phase of NaSmNbSbO3 under different doping configurations. Figure 1 (a-c) are the electronic localization functions of NaSmNbSbO3 model: (d-f) are the crystal structures and (g-i) are the band gaps;

[0026] Step 2, based on density functional theory, the NaNbO3 and NaSmNbSbO3 crystal cell structures with different doping contents constructed in step 1 are geometrically optimized and convergence test is performed, and the total energy of each configuration is calculated, the oxygen octahedron distortion degree and tilt angle are calculated, and the antiferroelectric phase structure with the lowest energy and the most stable structure is screened.

[0027] The VASP software is used for convergence test of the FE Q phase, AFE P phase and AFE R phase crystal cell structures of NaSmNbSbO3 in step 1, and the Vienna Ab Initio Simulation Package (VASP) with a plane wave basis set is used for density functional theory (DFT) calculation of the model. The projector augmented wave (PAW) method is used to describe the electron-ion interaction. The Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) exchange correlation function is used, and the matrix diagonalization technique is used to solve the electronic ground state. In order to accelerate the convergence of self-consistent loop, Broyden and Pulay density mixing scheme is used in the iteration process. Before performing the performance calculation, parameter test is performed on the ENCUT and k-point grid size, and the cutoff energy of 450eV and the k-point grid of 6x6x8 are obtained. In the process of property calculation, the convergence standard is set to 10 -4 eV / atom for energy and The FE Q phase, AFE P phase and AFE R phase structures of NaSmNbSbO3 are calculated, which are represented by space groups Pmc 21 , Pbcm and Pnma respectively. For the FE Q phase, AFE P phase and AFE R phase, 80-atom supercell corresponding to √2x√2x1 is used. Finally, the stoichiometric formula of the sodium niobate antiferroelectric ceramic corresponding to the antiferroelectric phase structure with the lowest energy and the most stable structure is Na 1-x Sm x NbO 3+δ -0.1mol% MnO2 (x=0.005~0.07).

[0028] Figure 2 It is a schematic diagram of the spatial distribution of Sm atoms in the NaSmNbSbO3 model, which proves that the arrangement of atoms in different positions will cause different energy differences. After systematically analyzing these possibilities, the total energy differences of all considered configurations are provided in Table 1. By analyzing all possible structures, it is found that configuration 1 has the lowest energy and the most stable structure, so configuration 1 is selected as our result. The results show that the AFE R phase has lower energy than the FE Q phase and the AFE P phase, and the BO6 octahedron distortion degree is reduced (from 33.43 to 32.08) and the average tilt angle of b-axis is increased (from 25.26° to 27.23°), which indicates that the doping of Sm atoms is beneficial to stabilize the AFE R phase of sodium niobate;

[0029] Table 1. Energy difference (ΔE) between different phases of NaSmNbSbO3 under different Sm atomic configurations

[0030]

[0031] Example 1

[0032] The present embodiment provides a preparation method of a sodium niobate antiferroelectric ceramic, comprising the following steps:

[0033] Step one, according to the stoichiometric formula Na 0.95 Sm 0.05 NbO 3+0.2 -0.1mol%MnO2, Na2CO3, Nb2O5, Sm2O3 and MnO2 are weighed to form a mixture, the mixture is mixed with zirconium balls and anhydrous ethanol according to a mass ratio of 1:2:1, and then ball milled for 20h, and then calcined at 700℃ for 4h to form a full ingredient;

[0034] Step two, the full ingredient is mixed with zirconium balls and anhydrous ethanol according to a mass ratio of 1:2:1, and then ball milled for 20h, and then placed in an oven for drying at 80℃ for 24h, and then sieved through a 200 mesh sieve to form a sieved material;

[0035] Step three, the sieved material is pressed into a cylindrical green body, the cylindrical green body is placed on a zirconia flat plate, the zirconia flat plate is placed in an alumina closed crucible, and the prepared green body is sintered in a box furnace, and the sintering mechanism is: first heated to 500℃ at a rate of 5℃ / min, kept for 3min, then heated to 1000℃ at a rate of 5℃ / min, kept for 30min, then heated to 1290℃ at a rate of 2℃ / min, kept for 120min, then cooled to 1000℃ at a rate of 2℃ / min, then cooled to 500℃ at a rate of 5℃ / min, and finally cooled to room temperature with the furnace, to obtain a ceramic.

[0036] The prepared ceramic sample is polished and washed, and then Ag electrodes are coated on both sides of the sample, and the silver is burned at 400℃ for 25min, and then tested.

[0037] Figure 3 The polarization P of the Na 0.995 Sm 0.05 NbO 3+0.2 -0.1mol%MnO2 ceramic prepared in Example 1 varies with the applied electric field; the effect of electric field change on polarization P is shown, and after the addition of Sm 3+ , the sample shows a phenomenon of elongated hysteresis loop, which proves that the present application improves the energy storage efficiency of the sodium niobate antiferroelectric ceramic.

[0038] Example 2

[0039] The embodiment provides a preparation method of sodium niobate antiferroelectric ceramic, and comprises the following steps:

[0040] Step one, Na 0.995 Sm 0.005 NbO 3+0.02 -0.1mol%MnO2, Na2CO3, Nb2O5, Sm2O3 and MnO2 are weighed to form a mixture, and the mixture is mixed with zirconium balls and anhydrous ethanol according to a mass ratio of 1:3:1.5, and then ball-milled for 24 hours, and then calcined at 850 DEG C for 4 hours to form a full ingredient;

[0041] Step two, the full ingredient is mixed with zirconium balls and anhydrous ethanol according to a mass ratio of 1:3:1.5, and then ball-milled for 24 hours, and then placed in an oven for drying at 90 DEG C for 20 hours, and then sieved through a 300-mesh sieve to form a sieved material;

[0042] Step three, the sieved material is pressed into a cylindrical green body, the cylindrical green body is placed on a zirconia flat plate, the zirconia flat plate is placed in an alumina closed crucible, and the prepared green body is sintered in a box-type furnace, and the sintering mechanism is as follows: first, the temperature is increased to 600 DEG C at a rate of 5 DEG C / min, and then the temperature is increased to 1100 DEG C at a rate of 5 DEG C / min, and then the temperature is increased to 1310 DEG C at a rate of 2 DEG C / min, and then the temperature is decreased to 1000 DEG C at a rate of 2 DEG C / min, and then the temperature is decreased to 500 DEG C at a rate of 5 DEG C / min, and finally the furnace is cooled to room temperature, and the ceramic is obtained.

[0043] The prepared ceramic sample is polished and cleaned, and then Ag electrodes are coated on both sides of the sample, and the silver is burned at 400 DEG C for 25 min, and then the test is performed.

[0044] Figure 4 The polarization P of the Na 0.995 Sm 0.005 NbO 3+0.02 -0.1mol%MnO2 ceramic prepared in Example 2 is shown in the graph of the change of the polarization P with the external electric field, and the effect of the change of the electric field on the polarization P is shown, and after the addition of Sm 3+ , the sample shows a long hysteresis loop, which proves that the energy storage efficiency of the sodium niobate antiferroelectric ceramic is improved.

[0045] Example 3

[0046] The embodiment provides a preparation method of sodium niobate antiferroelectric ceramic, and comprises the following steps:

[0047] Step one, Na 0.985 Sm 0.015 NbO 3+0.06-0.1mol% MnO2 Na2CO3, Nb2O5, Sm2O3 and MnO2 were weighed to form a mixture, the mixture was mixed with zirconium balls and anhydrous ethanol according to a mass ratio of 1:2.5:1.2, and then ball-milled for 22h, and then calcined at 800℃ for 4h to form a full ingredient;

[0048] Step two, the full ingredient zirconium balls and anhydrous ethanol were mixed according to a mass ratio of 1:2.5:1.2, and then ball-milled for 22h, and then placed in an oven for drying at 85℃ for 22h, and then sieved through a 220 mesh sieve to form a sieved material;

[0049] Step three, the sieved material was pressed into a cylindrical green body, the cylindrical green body was placed on a zirconia flat plate, the zirconia flat plate was placed in an alumina closed crucible, and the prepared green body was sintered in a box furnace, and the sintering mechanism was as follows: first, the temperature was raised to 550℃ at a rate of 5℃ / min, and then the temperature was raised to 1050℃ at a rate of 5℃ / min, and then the temperature was raised to 1300℃ at a rate of 2℃ / min, and then the temperature was raised to 1000℃ at a rate of 2℃ / min, and then the temperature was raised to 500℃ at a rate of 5℃ / min, and finally the furnace was cooled to room temperature, to obtain a ceramic.

[0050] The prepared ceramic sample was polished and cleaned, and then Ag electrodes were coated on both sides of the sample, and the silver was burned at 400℃ for 25min, and then tested.

[0051] Example 4

[0052] The present embodiment provides a preparation method of a sodium niobate antiferroelectric ceramic, comprising the following steps:

[0053] Step one, Na2CO3, Nb2O5, Sm2O3 and MnO2 were weighed according to the stoichiometric formula Na 0.93 Sm 0.07 NbO 3+0.28 -0.1mol% MnO2 Na2CO3, Nb2O5, Sm2O3 and MnO2 were weighed to form a mixture, the mixture was mixed with zirconium balls and anhydrous ethanol according to a mass ratio of 1:2:1, and then ball-milled for 24h, and then calcined at 700℃ for 4h to form a full ingredient;

[0054] Step two, the full ingredient zirconium balls and anhydrous ethanol were mixed according to a mass ratio of 1:2:1, and then ball-milled for 20h, and then placed in an oven for drying at 80℃ for 24h, and then sieved through a 300 mesh sieve to form a sieved material;

[0055] Step three, the sieved material is pressed into a cylindrical green body, the cylindrical green body is placed on a zirconia flat plate, the zirconia flat plate is placed in an alumina closed box and the prepared green body is sintered in a box furnace, the sintering mechanism is: first, the temperature is raised to 600℃ at 5℃ / min, the temperature is kept for 3min, then the temperature is raised to 1100℃ at 5℃ / min, the temperature is kept for 30min, then the temperature is raised to 1310℃ at 2℃ / min, the temperature is kept for 120min, then the temperature is reduced to 1000℃ at 2℃ / min, then the temperature is reduced to 500℃ at 5℃ / min, finally, the furnace is cooled to room temperature, and a ceramic is obtained.

[0056] The prepared ceramic sample is polished and cleaned, and then Ag electrodes are coated on both sides of the sample, the silver is burned for 25min at 400℃, and the test is performed.

[0057] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application and not to limit it, although the present application has been described in detail with reference to the above examples, those skilled in the art should understand that: the specific embodiments of the present application can still be modified or replaced by the equivalent, without departing from the spirit and scope of the present application, any modification or equivalent replacement, which should be covered in the protection scope of the claims of the present application.

Claims

1. A sodium niobate antiferroelectric ceramic, characterized in that, The stoichiometric formula is Na 1-x Sm x NbO 3+4x -0.1 mol% MnO2, where x = 0.005 to 0.

07.

2. A method for preparing sodium niobate antiferroelectric ceramics as described in claim 1, characterized in that, Includes the following steps: Step 1: Weigh Na2CO3, Nb2O5, Sm2O3 and MnO2 according to the stoichiometric formula to form a mixture. After ball milling, calcine the mixture at 700-850℃ for 4 hours to form the complete batch. Step 2: The entire batch of ingredients is ball-milled again, dried, and sieved to form sieved material; Step 3: Press the sieved material into a cylindrical green body, place the cylindrical green body on a zirconia plate, place the zirconia plate in an alumina sealed sagger, and place it in a box furnace for sintering to obtain sodium niobate antiferroelectric ceramic.

3. The method for preparing sodium niobate antiferroelectric ceramics as described in claim 2, characterized in that, The ball milling mentioned in Step 1 and Step 2 involves mixing the mixture or complete feedstock with zirconium balls and anhydrous ethanol at a mass ratio of 1:(2-3):(1-1.5) and then ball milling for 20-24 hours.

4. The method for preparing sodium niobate antiferroelectric ceramics as described in claim 2, characterized in that, The drying process described in step two involves placing the item in an oven at 80–90°C and drying it for 20–24 hours.

5. The method for preparing sodium niobate antiferroelectric ceramics as described in claim 2, characterized in that, The sieve used in step two has a mesh size of 200 to 300.

6. The method for preparing sodium niobate antiferroelectric ceramics as described in claim 2, characterized in that, The sintering mechanism described in step three is as follows: First, the temperature is increased to 500-600℃ at 5℃ / min and held for 3min. Then, the temperature is increased to 1000-1100℃ at 5℃ / min and held for 30min. Next, the temperature is increased to 1290-1310℃ at 2℃ / min and held for 120min. Then, the temperature is decreased to 1000℃ at 2℃ / min. Next, the temperature is decreased to 500℃ at 5℃ / min. Finally, the temperature is cooled to room temperature with the furnace.

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