Sodium Potassium Niobate-based Ceramic Materials with High Energy Storage under Low Electric Field and Their Preparation Methods

Abstract

The potassium sodium niobate-based ceramic material with high energy storage under low electric fields disclosed by the present invention has a chemical composition general formula of (1-x)K 0.5 Na 0.5 NbO3-x(Sr 0.7 La 0.2 )(Mg 1 / 3 Ta 2 / 3 )O3, where x represents the number of moles and x is 0.03 to 0.12; the potassium sodium niobate-based ceramic material is a pure perovskite structure; the preparation method of the potassium sodium niobate-based ceramic material with high energy storage under low electric fields disclosed by the present invention comprises the following steps: batching, primary ball milling, pre-sintering, secondary ball milling, tabletting and cold isostatic pressing, and pressureless airtight sintering. The potassium sodium niobate-based ceramic material with high energy storage under low electric fields of the present invention has very excellent energy storage performance under low electric fields, has strong practicability and is easy to produce, and is a lead-free ferroelectric ceramic with excellent performance; the preparation method of the potassium sodium niobate-based ceramic material with high energy storage under low electric fields of the present invention is simple, has good repeatability and high yield.

Description

Technical Field

[0001] The present invention belongs to the technical field of ferroelectric ceramic materials, relates to a sodium potassium niobate-based ceramic material with high energy storage under low electric fields, and also relates to a preparation method of the sodium potassium niobate-based ceramic material with high energy storage under low electric fields. Background Art

[0002] As a kind of energy storage technology, the working principle of dielectric capacitors is to store and release energy through dielectric polarization and depolarization of an external electric field. Due to its ultra-fast charge and discharge rate, ultra-high power density, and stable working performance, it is widely used in aerospace, new energy power generation, commercial applications, etc.

[0003] Currently, dielectric ceramics for energy storage can be divided into four categories: linear dielectrics, ordinary ferroelectrics, relaxor ferroelectrics, and antiferroelectrics. Among them, ferroelectrics have a relatively high maximum polarization intensity P max due to the presence of large ferroelectric domains. However, due to the clamping of domain walls, the remanent polarization intensity P r is relatively large and the coercive field is relatively high. Antiferroelectrics, on the other hand, have a high P max and a large effective energy storage density W rec , but the energy storage efficiency η is relatively low. Sodium potassium niobate K 0.5 Na 0.5 NbO3 (KNN) is a solid solution formed between the ferroelectric KNbO3 and the antiferroelectric NaNbO3. Its unique sub-micron particles enable KNN-based ferroelectric ceramics to have a relatively high breakdown electric field strength, and theoretically, the synergy of high energy storage density and high energy storage efficiency can be achieved. Since the energy storage performance of KNN-based ceramics was first discovered in 2016, it has attracted the attention of more and more scholars.

[0004] Currently, some studies have further increased the breakdown electric field strength by introducing different components, enabling KNN-based ceramics to obtain a high energy storage density. However, due to the generally high applied electric field and low energy storage efficiency, it will cause a large amount of heat generation and energy waste during the application process. Compared with BNT-based and BT-based ceramics, KNN-based ceramics have a lower maximum polarization intensity P max and a higher remanent polarization intensity P r , resulting in a lower polarization intensity difference for KNN-based ceramics, which is not conducive to achieving high energy storage performance under low electric fields. For example, the Chinese patent "A KNN-based lead-free ferroelectric energy storage ceramic material with ultra-high energy storage efficiency and its preparation method" (CN116003128A, 20230425) discloses a KNN-based energy storage ceramic material and its preparation method. The energy storage efficiency of this invention is as high as 98.17% - 99.32%, but its effective energy storage density is only 0.804 - 1.032 J / cm 3 . Summary of the Invention

[0005] The object of the present invention is to provide a sodium potassium niobate-based ceramic material with high energy storage under low electric fields, which has the characteristic of achieving high energy storage performance under low electric fields.

[0006] Another object of the present invention is to provide a preparation method of the sodium potassium niobate-based ceramic material with high energy storage under low electric fields.

[0007] The technical solution adopted by the present invention is that the sodium potassium niobate-based ceramic material with high energy storage under low electric fields has a chemical composition general formula of (1-x)K 0.5 Na 0.5 NbO3-x(Sr 0.7 La 0.2 )(Mg 1 / 3 Ta 2 / 3 )O3, where x represents the number of moles and x is 0.03 to 0.12.

[0008] The characteristics of the present invention also lie in that:

[0009] The sodium potassium niobate-based ceramic material has a perovskite structure.

[0010] x is 0.09 to 0.12.

[0011] Another technical solution adopted by the present invention is a preparation method of the sodium potassium niobate-based ceramic material with high energy storage under low electric fields, which is specifically implemented according to the following steps:

[0012] Step 1: According to the chemical composition general formula (1-x)K 0.5 Na 0.5 NbO3-x(Sr 0.7 La 0.2 )(Mg 1 / 3 Ta 2 / 3 )O3, where x is 0.03 to 0.12, respectively weigh the following raw materials: Na2CO3 powder, K2CO3 powder, Ta2O5 powder, SrCO3 powder, La2O3 powder, MgO powder, Nb2O5 powder;

[0013] Step 2: Ball-mill the raw materials once, dry and grind them to obtain a raw material mixture;

[0014] Step 3: Pre-sinter the raw material mixture, then cool it to room temperature and grind it to obtain a pre-sintered powder;

[0015] Step 4: Ball-mill the pre-sintered powder a second time, dry and grind it to obtain a mixed powder;

[0016] Step 5: Press and cold isostatically press the mixed powder to form a cylindrical blank;

[0017] Step 6: Sinter the cylindrical blank under no pressure in a sealed manner and cool it to room temperature to obtain a sodium potassium niobate-based ceramic material with high energy storage under low electric fields.

[0018] Another technical solution of the present invention is also characterized in that:

[0019] In step 2, the ball milling medium for the first ball milling is 50 ml of absolute ethanol; the first ball milling time is 20 h to 24 h; the drying temperature is 100 °C to 120 °C, and the drying time is 10 h to 12 h.

[0020] In step 3, the pre-sintering is to raise the temperature to 850 °C to 900 °C at a heating rate of 3 °C per minute and pre-sinter for 3 h to 5 h.

[0021] In step 3, the pre-sintering is to raise the temperature to 850 °C at a heating rate of 3 °C per minute and pre-sinter for 5 h.

[0022] In step 4, the ball milling medium for the second ball milling is 45 ml of absolute ethanol, the second ball milling time is 16 h to 24 h, the drying temperature is 100 °C to 120 °C, and the drying time is 10 h to 12 h.

[0023] In step 5, the thickness of the tablet is 1.3 mm to 1.5 mm, the applied pressure of cold isostatic pressing is not less than 200 MPa, and the pressure holding time is not less than 5 minutes;

[0024] In step 6, place the cylindrical blank on a zirconia flat plate, place the zirconia flat plate in an alumina sealed crucible, raise the temperature to 1200 °C to 1210 °C at a heating rate of 3 °C per minute, sinter for 5 h to 8 h, and then naturally cool to room temperature with the furnace.

[0025] In step 6, place the cylindrical blank on a zirconia flat plate, place the zirconia flat plate in an alumina sealed crucible, raise the temperature to 1200 °C at a heating rate of 3 °C per minute, sinter for 5 h, and then naturally cool to room temperature with the furnace.

[0026] The beneficial effects of the present invention are:

[0027] The sodium potassium niobate-based ceramic material with high energy storage under low electric fields of the present invention has a medium dielectric constant of 1002 to 1844 and has very excellent energy storage performance under low electric fields. When x = 0.09, the effective energy storage density of the ceramic sample is 2.264 J / cm 3 , the energy storage efficiency is 70%, and when x = 0.12, the energy storage efficiency is as high as 86.1% under an electric field of 200 kV / cm; it has strong practicability and is easy to produce, and it is a lead-free ferroelectric ceramic with excellent performance;

[0028] The preparation method of the sodium potassium niobate-based ceramic material with high energy storage under low electric field according to the present invention is simple, has good repeatability and high yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is the XRD pattern of Examples 1-4 of the sodium potassium niobate-based ceramic material with high energy storage under low electric field according to the present invention;

[0030] Figure 2 It is the dielectric constant pattern of Examples 1-4 of the present invention;

[0031] Figure 3 It is the single-stage ferroelectric hysteresis loop pattern of Examples 1-4 of the present invention;

[0032] Figure 4 It is the graph of the change of energy storage performance of Examples 1-4 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention will be described in detail below in conjunction with the drawings and specific embodiments.

[0034] The sodium potassium niobate-based ceramic material with high energy storage under low electric field according to the present invention has a chemical composition general formula of (1-x)K 0.5 Na 0.5 NbO3-x(Sr 0.7 La 0.2 )(Mg 1 / 3 Ta 2 / 3 )O3, where x represents the molar number of (Sr 0.7 La 0.2 )(Mg 1 / 3 Ta 2 / 3 )O3, and x is 0.03-0.12.

[0035] The sodium potassium niobate-based ceramic material with high energy storage under low electric field has a pure perovskite structure, and x is preferably 0.09-0.12.

[0036] When the value of x is 0.09, the sodium potassium niobate-based ceramic material with high energy storage under low electric field obtains an effective energy storage density as high as 2.264 J / cm 3 at an electric field strength of 250 kV / cm, and the energy storage efficiency is 70%. When the value of x is 0.12, the sodium potassium niobate-based ceramic material with high energy storage under low electric field has an energy storage efficiency as high as 86.1% at an electric field of 200 kV / cm.

[0037] The preparation method of the sodium potassium niobate-based ceramic material with high energy storage under low electric field according to the present invention is specifically implemented according to the following steps:

[0038] Step 1, weighing:

[0039] According to the chemical composition general formula (1 - x)K 0.5 Na 0.5 NbO3 - x(Sr 0.7 La 0.2 )(Mg 1 / 3 Ta 2 / 3 )O3, where x is from 0.03 to 0.12. Weigh the following raw materials respectively: Na2CO3 powder, K2CO3 powder, Ta2O5 powder, SrCO3 powder, La2O3 powder, MgO powder, Nb2O5 powder;

[0040] Step 2, primary ball milling: Load the above - mentioned raw materials into a ball - milling tank, add zirconium balls as grinding balls and 50 ml of anhydrous ethanol as the ball - milling medium, mix and ball - mill for 20 h to 24 h, then dry at 100 °C to 120 °C for 10 h to 12 h, and grind to obtain a raw material mixture;

[0041] Step 3, pre - sintering:

[0042] Place the raw material mixture in an alumina crucible and cover it, place it in a muffle furnace, heat it at a heating rate of 3 °C per minute to 850 °C to 900 °C, pre - sinter for 3 h to 5 h, then cool naturally to room temperature with the furnace, and grind with a mortar to obtain pre - sintered powder;

[0043] Preferably, the pre - sintering temperature is 850 °C, the pre - sintering time is 5 hours, and the heating rate is 3 °C per minute.

[0044] Step 4, secondary ball milling:

[0045] Load the pre - sintered powder into a ball - milling tank, add zirconium balls as grinding balls and 45 ml of anhydrous ethanol as the ball - milling medium, fully mix and ball - mill for 16 h to 24 h, separate the zirconium balls, then dry at 100 °C to 120 °C for 10 h to 12 h, and grind to obtain a mixed powder;

[0046] Step 5, tabletting and cold isostatic pressing:

[0047] Put the mixed powder into a mold, press it into a cylindrical blank with a thickness of 1.3 mm to 1.5 mm using a powder press, then apply a pressure of not less than 200 MPa and keep the pressure for at least 5 minutes for cold isostatic pressing to obtain a cylindrical billet;

[0048] Step 6, pressureless airtight sintering:

[0049] Place the cylindrical billet on a zirconia plate, place the zirconia plate in an alumina airtight crucible, heat it at a heating rate of 3 °C per minute to 1200 °C to 1210 °C, sinter for 5 h to 8 h, then cool naturally to room temperature with the furnace.

[0050] The preferred scheme is to heat it at a heating rate of 3 °C per minute to 1200 °C and sinter for 5 h.

[0051] Example 1

[0052] Step 1: Batching

[0053] x = 0.03, according to 0.97K 0.5 Na 0.5 NbO3 - 0.03(Sr 0.7 La 0.2 )(Mg 1 / 3 Ta 2 / 3 )O3, weigh 2.6087 g of Na2CO3 powder with a purity of 99.999%, 3.4020 g of K2CO3 powder with a purity of 99.99%, 0.4485 g of Ta2O5 powder with a purity of 99.99%, 0.3148 g of SrCO3 powder with a purity of 99.95%, 0.0992 g of La2O3 powder with a purity of 99.99%, 0.0409 g of MgO powder with a purity of 99.95%, and 13.0858 g of Nb2O5 powder with a purity of 99.99% as raw materials respectively according to the stoichiometry;

[0054] Step 2: Primary ball milling

[0055] Put the weighed raw materials into the ball milling tank, add 50 ml of anhydrous ethanol into the ball milling tank, use zirconium balls as grinding balls and anhydrous ethanol as the ball milling medium, mix and ball mill fully with a bench-type ball mill for 24 hours, separate the zirconium balls, place the raw material mixed slurry in a drying oven and dry it at 100 °C for 12 hours, and grind it with a mortar for 30 minutes into a powder to obtain a raw material mixture.

[0056] Step 3: Pre-sintering

[0057] Put the raw material mixture ground in Step 1 into an alumina crucible, compact it with an agate rod, cover it, place it in a resistance furnace, heat it to 850 °C at a heating rate of 3 °C per minute for pre-sintering for 5 hours, and then cool it naturally to room temperature with the furnace, and grind it with a mortar to obtain a pre-sintered powder.

[0058] Step 4: Secondary ball milling

[0059] Put the pre-sintered powder into the ball milling tank, add 45 ml of anhydrous ethanol, use zirconium balls as grinding balls and anhydrous ethanol as the ball milling medium, mix and ball mill fully for 24 hours, separate the zirconium balls, place the pre-sintered powder in a drying oven and dry it at 100 °C for 12 hours, and grind it with a mortar for 20 minutes into a powder to obtain a mixed powder.

[0060] Step 5: Tabletting and cold isostatic pressing

[0061] Take 0.4 g of the mixed powder and put it into a stainless-steel mold with a diameter of 11 mm. Press it into a cylindrical green body with a thickness of 1.5 mm using a powder press. Place the pressed green body evenly in a rubber glove and evacuate it. Then, place the rubber glove containing the green body in a cylinder filled with silicone oil, apply a pressure of 200 MPa and hold the pressure for 5 minutes to form a cylindrical green body.

[0062] Step 6, Pressureless Sealed Sintering

[0063] Place the cylindrical green body on a zirconia plate, and place the zirconia plate in an alumina sealed crucible. Heat it to 1200 °C at a heating rate of 3 °C per minute, sinter for 5 hours, and then naturally cool to room temperature in the furnace to prepare a potassium sodium niobate-based ceramic material with high energy storage under low electric fields and a chemical formula of 0.97K 0.5 Na 0.5 NbO3-0.03(Sr 0.7 La 0.2 )(Mg 1 / 3 Ta 2 / 3 )O3.

[0064] Example 2

[0065] Basically the same as Example 1, the difference is:

[0066] Step 1, Batching

[0067] x = 0.06. Weigh 2.4891 g of Na2CO3 powder with a purity of 99.999%, 3.2460 g of K2CO3 powder with a purity of 99.99%, 0.8833 g of Ta2O5 powder with a purity of 99.99%, 0.6199 g of SrCO3 powder with a purity of 99.95%, 0.1954 g of La2O3 powder with a purity of 99.99%, 0.0806 g of MgO powder with a purity of 99.95%, and 12.4857 g of Nb2O5 powder with a purity of 99.99% as raw materials according to the stoichiometry of 0.94K 0.5 Na 0.5 NbO3-0.06(Sr 0.7 La 0.2 )(Mg 1 / 3 Ta 2 / 3 )O3.

[0068] Prepare a potassium sodium niobate-based ceramic material with high energy storage under low electric fields and a chemical formula of 0.94K 0.5 Na 0.5 NbO3-0.06(Sr 0.7 La 0.2 )(Mg 1 / 3 Ta 2 / 3 )O3.

[0069] Example 3

[0070] Basically the same as Example 1, except that:

[0071] Step 1: Ingredients

[0072] x=0.09,according to 0.91K 0.5 Na 0.5 NbO3-0.09(Sr 0.7 La 0.2 )(Mg 1 / 3 Ta 2 / 3 )O3 stoichiometrically: 2.3731 g of Na2CO3 powder with a purity of 99.999%, 3.0948 g of K2CO3 powder with a purity of 99.99%, 1.3048 g of Ta2O5 powder with a purity of 99.99%, 0.9158 g of SrCO3 powder with a purity of 99.95%, 0.2886 g of La2O3 powder with a purity of 99.99%, 0.1190 g of MgO powder with a purity of 99.95%, and 11.9039 g of Nb2O5 powder with a purity of 99.99% were weighed as raw materials,

[0073] In step 6, the temperature is raised to 1210° C. at a heating rate of 3° C. / min, sintered for 5 hours, and then naturally cooled to room temperature in the furnace;

[0074] Prepared with molecular formula of 0.91K 0.5 Na 0.5 NbO3-0.09(Sr 0.7 La 0.2 )(Mg 1 / 3 Ta 2 / 3 )KNO3-based ceramic materials with high energy storage under low electric field of O3.

[0075] Example 4

[0076] Basically the same as Example 1, except that:

[0077] Step 1: Ingredients

[0078] x = 0.12, in the batching step 1 of this embodiment, according to 0.88K 0.5 Na 0.5 NbO3-0.12(Sr 0.7 La 0.2 )(Mg 1 / 3Ta 2 / 3)For the stoichiometry of O3, 2.2606 g of Na2CO3 powder with a purity of 99.999%, 2.9480 g of K2CO3 powder with a purity of 99.99%, 1.7137 g of Ta2O5 powder with a purity of 99.99%, 1.2028 g of SrCO3 powder with a purity of 99.95%, 0.3791 g of La2O3 powder with a purity of 99.99%, 0.1564 g of MgO powder with a purity of 99.95%, and 11.3395 g of Nb2O5 powder with a purity of 99.99% were weighed respectively as raw materials;

[0079] In step 6, it was heated to 1210 °C at a heating rate of 3 °C per minute, sintered for 5 hours, and then naturally cooled to room temperature in the furnace;

[0080] Prepared into a sodium-potassium niobate-based ceramic material with a high energy storage under low electric fields having the molecular formula 0.88K 0.5 Na 0.5 NbO3-0.12(Sr 0.7 La 0.2 )(Mg 1 / 3 Ta 2 / 3 )O3.

[0081] Example 5

[0082] Basically the same as Example 1, the differences are as follows:

[0083] In step 2, it was mixed and ball-milled for 22 hours. The raw material mixed slurry was placed in a drying oven and dried at 110 °C for 11 hours, and then ground in a mortar for 30 minutes to form a powder to obtain a raw material mixture;

[0084] In step 3, it was heated to 870 °C at a heating rate of 3 °C per minute and pre-sintered for 4 hours;

[0085] In step 4, it was ball-milled for a second time and mixed and ball-milled for 20 hours, the zirconia balls were separated, and the pre-sintered powder was placed in a drying oven and dried at 110 °C for 11 hours;

[0086] In step 5, it was pressed into a cylindrical blank with a thickness of 1.4 mm using a powder press. The pressed cylindrical blank was evenly placed in a rubber glove and evacuated, and then the rubber glove containing the cylindrical blank was placed in a cylinder filled with silicone oil, and a pressure of 220 MPa was applied and held for 10 minutes for cold isostatic pressing to form a cylindrical blank;

[0087] In step 6, it was heated to 1205 °C at a heating rate of 3 °C per minute and sintered for 6.5 hours.

[0088] Example 6

[0089] Basically the same as Example 1, the differences are as follows:

[0090] In Step 2, mix and ball mill for 22 hours. Place the raw material mixed slurry in a drying oven and dry it at 110°C for 11 hours. Grind it into powder with a mortar for 30 minutes to obtain a raw material mixture;

[0091] In Step 3, heat it up to 870°C at a heating rate of 3°C per minute and pre-sinter for 4 hours;

[0092] In Step 4, perform secondary ball milling and mix and ball mill for 20 hours. Separate the zirconium balls. Place the pre-sintered powder in a drying oven and dry it at 110°C for 11 hours;

[0093] In Step 5, use a powder press to press it into a cylindrical blank with a thickness of 1.4 mm. Uniformly place the pressed cylindrical blank into a rubber glove and evacuate it. Then place the rubber glove containing the cylindrical blank into a cylinder filled with silicone oil, apply a pressure of 220 MPa and hold the pressure for 10 minutes for cold isostatic pressing to form a cylindrical blank;

[0094] In Step 6, heat it up to 1205°C at a heating rate of 3°C per minute and sinter for 6.5 hours.

[0095] Example 7

[0096] Basically the same as Example 1, the differences are as follows:

[0097] In Step 2, mix and ball mill for 20 hours. Place the raw material mixed slurry in a drying oven and dry it at 120°C for 10 hours. Grind it into powder with a mortar for 30 minutes to obtain a raw material mixture;

[0098] In Step 3, heat it up to 900°C at a heating rate of 3°C per minute and pre-sinter for 3 hours;

[0099] In Step 4, perform secondary ball milling and mix and ball mill for 16 hours. Separate the zirconium balls. Place the pre-sintered powder in a drying oven and dry it at 120°C for 10 hours;

[0100] In Step 5, use a powder press to press it into a cylindrical blank with a thickness of 1.3 mm. Uniformly place the pressed cylindrical blank into a rubber glove and evacuate it. Then place the rubber glove containing the cylindrical blank into a cylinder filled with silicone oil, apply a pressure of 230 MPa and hold the pressure for 8 minutes for cold isostatic pressing to form a cylindrical blank;

[0101] In Step 6, heat it up to 1210°C at a heating rate of 3°C per minute and sinter for 8 hours.

[0102] Select a ceramic sheet of a potassium sodium niobate-based ceramic material with high energy storage under low electric fields from Examples 1 to 4. First, polish the surface with 1200-mesh emery to a thickness of 1 mm, then polish both sides of the ceramic material with 1500-mesh polishing liquid for 20 minutes each. Finally, ultrasonically clean with alcohol, wipe clean, and grind into powder. Perform XRD testing using a Rigaku MiniFlex600 diffractometer in Japan. The results are as Figure 1 shown.

[0103] Select a ceramic sheet of a potassium sodium niobate-based ceramic material with high energy storage under low electric fields from Examples 1 to 4. Grind the ceramic material with 1500-mesh emery to a thickness of 0.7 mm, then polish with 2000-mesh sandpaper until the surface reflects light. Wipe clean with alcohol, and then coat silver paste with a thickness of 0.01 - 0.03 mm on the upper and lower surfaces of the polished ceramic. Place it in a resistance furnace, heat up to 840 °C, hold for 30 minutes, and then naturally cool to room temperature with the furnace. Test the dielectric properties of the ceramic sample using an Agilient 4980A precision impedance analyzer. The results are as Figure 2 shown.

[0104] Finally, select one from each of the ceramic materials prepared in Examples 1 to 4. Grind the ceramic material with 1500-mesh emery to a thickness of 0.15 mm. Place the polished ceramic sample into an ion sputtering instrument, select a gold target, with a current of 30 mA and a time of 200 s, sputter gold electrodes with a thickness of 0.02 mm and a diameter of 2 mm on the upper and lower surfaces of the ceramic. Perform single-pole P-E hysteresis loop testing and frequency stability testing using an AixACCT-TF2000 ferroelectric parameter tester. The results are as Figures 3 to 4 shown.

[0105] It can be seen from Figure 1 that the ceramic materials prepared in Examples 1 to 4 are all pure perovskite structures. Figure 2 Show the curve graph of the dielectric constant varying with temperature at 50 kHz for Examples 1 to 4. Through Figure 2 it can be seen that the dielectric constant of the ceramic material decreases with the increase of the doping amount, so that the ceramic sample has a medium-sized dielectric constant at room temperature. And there is research indicating that a medium-sized dielectric constant is beneficial for achieving high energy storage performance. Figure 3 Show the single-pole hysteresis loop graphs of Examples 1 to 4. Through Figure 3 it can be seen that the corresponding electric field strength and polarization strength are the highest when x = 0.09, and the hysteresis loop is the thinnest when x = 0.12. Summarize the energy storage performance of Examples 1 to 4 to Figure 4 . Among them, W rec is the effective energy storage density, η is the energy storage efficiency. Through Figure 4It can be seen that the ceramic material has very excellent energy storage performance under low electric fields. When x = 0.09, the effective energy storage density of the ceramic sample at an electric field strength of 250 kV / cm is: 2.264 J / cm 3 , and the energy storage efficiency is 70%. When x = 0.12, the energy storage efficiency is as high as 86.1% under an electric field of 200 kV / cm. Therefore, the sodium potassium niobate-based ceramic material with high energy storage under low electric fields of the present invention has very high application value.

Claims

1. A sodium potassium niobate-based ceramic material with high energy storage under low electric fields, characterized in that, The general chemical formula is (1 - x)K 0.5 Na 0.5 NbO3 - x(Sr 0.7 La 0.2 )(Mg 1 / 3 Ta 2 / 3 )O3, where x represents the number of moles of (Sr 0.7 La 0.2 )(Mg 1 / 3 Ta 2 / 3 )O3, and x ranges from 0.09 to 0.12; The sodium potassium niobate-based ceramic material has a perovskite structure.

2. Preparation method of sodium potassium niobate-based ceramic material with high energy storage under low electric field, characterized in that, The specific implementation steps are as follows: Step 1. According to the chemical composition general formula (1-x)K 0.5 Na 0.5 NbO3-x(Sr 0.7 La 0.2 )(Mg 1 / 3 Ta 2 / 3 )O3, where x is 0.03 to 0.12, and weigh the following raw materials respectively: Na2CO3 powder, K2CO3 powder, Ta2O5 powder, SrCO3 powder, La2O3 powder, MgO powder, Nb2O5 powder; Step 2: Perform primary ball milling on the raw materials, dry and grind them to obtain a raw material mixture; Step 3: Pre-sinter the raw material mixture, then cool it to room temperature and grind to obtain a pre-sintered powder; Step 4: Perform secondary ball milling on the pre-sintered powder, dry and grind it to obtain a mixed powder; Step 5: Press and cold isostatically press the mixed powder to form a cylindrical blank; Step 6: Perform pressureless sealed sintering on the cylindrical blank, cool it to room temperature to obtain a sodium potassium niobate-based ceramic material with high energy storage under low electric fields.

3. The preparation method of the sodium potassium niobate-based ceramic material with high energy storage under low electric field according to claim 2, characterized in that, In Step 2, the ball milling medium for the primary ball milling is 50 ml of anhydrous ethanol; the primary ball milling time is 20 h to 24 h; the drying temperature is 100 °C to 120 °C, and the drying time is 10 h to 12 h.

4. The preparation method of the sodium potassium niobate-based ceramic material with high energy storage under low electric field according to claim 2, characterized in that, In Step 3, the pre-sintering is carried out by heating at a heating rate of 3 °C per minute to 850 °C to 900 °C and pre-sintering for 3 h to 5 h.

5. The preparation method of the sodium potassium niobate-based ceramic material with high energy storage under low electric fields according to claim 4, characterized in that, In Step 3, the pre-sintering is carried out by heating at a heating rate of 3 °C per minute to 850 °C and pre-sintering for 5 h.

6. The preparation method of the sodium potassium niobate-based ceramic material with high energy storage under low electric fields according to claim 2, characterized in that, In Step 4, the ball milling medium for the secondary ball milling is 45 ml of anhydrous ethanol, the secondary ball milling time is 16 h to 24 h, the drying temperature is 100 °C to 120 °C, and the drying time is 10 h to 12 h.

7. The preparation method of the sodium potassium niobate-based ceramic material with high energy storage under low electric field according to claim 2, characterized in that, In Step 5, the thickness of the pressed tablet is 1.3 mm to 1.5 mm, the applied pressure for the cold isostatic pressing is not less than 200 MPa, and the pressure holding time is not less than 5 minutes; In Step 6, place the cylindrical blank on a zirconia plate, place the zirconia plate in an alumina sealed crucible, heat it at a heating rate of 3 °C per minute to 1200 °C to 1210 °C, sinter for 5 h to 8 h, and then naturally cool to room temperature in the furnace.

8. The preparation method of the sodium potassium niobate-based ceramic material with high energy storage under low electric fields according to claim 7, characterized in that, In Step 6, place the cylindrical blank on a zirconia plate, place the zirconia plate in an alumina sealed crucible, heat it at a heating rate of 3 °C per minute to 1200 °C, sinter for 5 h, and then naturally cool to room temperature in the furnace.

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