Potassium sodium niobate-based ceramic material with excellent fatigue resistance and preparation method thereof

Abstract

The potassium sodium niobate-based ceramic material with excellent fatigue resistance disclosed in the present invention has a general chemical composition formula of: (1-x)K 0.5 Na 0.5 NbO3‑x(Sr 0.7 La 0.2 )(Mg 1 / 3 Nb 2 / 3 )O3; x represents the number of moles, and x is 0.03 to 0.12; the ceramic has a perovskite structure, a breakdown electric field of 230 to 400 kV / cm, and a maximum polarization strength of 29.6 to 34.1 μC / cm 2 , the residual polarization intensity is 4.1~7.4μC / cm 2 The present invention discloses a method for preparing a potassium sodium niobate-based ceramic material with excellent fatigue resistance, comprising the following steps: batching, primary ball milling, pre-sintering, secondary ball milling, tableting, cold isostatic pressing, and pressureless closed sintering. The potassium sodium niobate-based ceramic material of the present invention exhibits excellent energy storage performance and fatigue resistance. The ceramic material preparation method of the present invention is simple, reproducible, and has a high yield.

Description

Technical Field

[0001] The present invention belongs to the technical field of ferroelectric ceramic materials, relates to a potassium sodium niobate-based ceramic material with excellent fatigue resistance, and also relates to a preparation method of the potassium sodium niobate-based ceramic material with excellent fatigue resistance. Background Art

[0002] Ferroelectric materials are materials that exhibit spontaneous polarization (without an applied electric field), and the direction of this spontaneous polarization can change with an applied electric field. These materials are called ferroelectrics, and this property is called ferroelectricity. Ferroelectric ceramics are ceramic materials that exhibit ferroelectricity. Due to their excellent ferroelectric and mechanical properties, ferroelectric ceramics are used in large-capacity capacitors, high-frequency microcapacitors, multilayer capacitors, and semiconductor ceramic capacitors.

[0003] The ferroelectric ceramics widely studied at present all have perovskite structure, among which K 0.5 Na 0.5 NbO3 (KNN) based ceramics have a relatively high breakdown field strength due to their unique submicron particles and are considered to be one of the most promising lead-free ferroelectric ceramics. 0.5 Na 0.5 NbO3 (KNN) is a solid solution formed between ferroelectric KNbO3 and antiferroelectric NaNbO3. Previous research on KNN-based ceramics focused on piezoelectric and photoelectric properties. In 2016, Du et al. first reported a KNN-based ceramic with submicron grains (~5μm) and an effective energy storage density of 2.6J / cm 3 0.8K 0.5 Na 0.5 NbO3-0.2Sr(Sc 0.5 Nb 0.5 )O3 relaxor ferroelectrics, and then researchers gradually began to pay attention to the energy storage properties of KNN-based ceramics. 0.5 Na 0.5 NbO3 introduces Bi(Mn 0.5 Ni 0.5 )O3, obtained 1.823 / cm 3 The effective energy storage density is 1.5 GHz, and after 5,000 cycles at a 150 kV / cm electric field, the change in effective energy storage density is 3.7%. In addition to energy storage performance, fatigue resistance is also a key performance indicator for ferroelectric ceramics. After repeated application of an external electric field, ceramic materials find it difficult to maintain their original slender and complete hysteresis loop. Excellent fatigue resistance is a critical issue that urgently needs to be addressed in the practical application of ferroelectric ceramic capacitors.

[0004] In recent years, reports on potassium sodium niobate-based ferroelectric ceramics have shown that by refining the grains and increasing the breakdown field strength, the energy storage performance has been greatly improved, and the fatigue resistance has also been improved. However, there are few reports on potassium sodium niobate-based ferroelectric ceramics that have both high energy storage performance and fatigue resistance. Summary of the Invention

[0005] The present invention aims to provide a potassium sodium niobate-based ceramic material with excellent fatigue resistance, which has the characteristics of high energy storage density and excellent fatigue resistance.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned potassium sodium niobate-based ceramic material with excellent fatigue resistance.

[0007] The technical solution adopted by the present invention is that the potassium sodium niobate-based ceramic material with excellent fatigue resistance has the general chemical composition formula: (1-x)K 0.5 Na 0.5 NbO3-x(Sr 0.7 La 0.2 )(Mg 1 / 3 Nb 2 / 3 )O3;

[0008] Where, x represents (Sr 0.7 La 0.2 )(Mg 1 / 3 Nb 2 / 3 )The number of moles of O3, x is 0.03~0.12.

[0009] The present invention is also characterized in that:

[0010] According to the chemical composition formula (1-x)K 0.5 Na 0.5 NbO3-x(Sr 0.7 La 0.2 )(Mg 1 / 3 Nb 2 / 3 )O3, composed of the following raw materials: Na2CO3 powder, K2CO3 powder, Nb2O5 powder, SrCO3 powder, La2O3 powder, and MgO powder.

[0011] x is 0.07.

[0012] The ceramic has a perovskite structure, a breakdown electric field of 230-400 kV / cm, and a maximum polarization strength of 29.6-34.1 μC / cm. 2 , the residual polarization intensity is 4.1~7.4μC / cm 2 .

[0013] Another technical solution adopted by the present invention is a method for preparing potassium sodium niobate-based ceramic materials with excellent fatigue resistance, which is specifically implemented according to the following steps:

[0014] Step 1: According to the chemical formula (1-x)K 0.5 Na 0.5 NbO3-x(Sr 0.7 La 0.2 )(Mg 1 / 3 Nb 2 / 3 )O3, where x is 0.03 to 0.12, weigh the following raw materials: Na2CO3 powder, K2CO3 powder, Nb2O5 powder, SrCO3 powder, La2O3 powder, and MgO powder;

[0015] Step 2: ball milling, drying, and grinding the raw materials to obtain a raw material mixture;

[0016] Step 3: pre-calcining the raw material mixture, cooling it to room temperature, and grinding it to obtain pre-calcined powder;

[0017] Step 4: ball milling the calcined powder for a second time, drying and grinding the calcined powder to obtain a mixed powder;

[0018] Step 5: tableting and cold isostatic pressing the mixed powder to obtain a cylindrical blank;

[0019] Step 6: Perform pressureless closed sintering on the cylindrical blank and cool it to room temperature to obtain a potassium sodium niobate-based ceramic material with excellent fatigue resistance.

[0020] Another technical solution of the present invention is also characterized in that:

[0021] In step 2, the ball milling medium for the first ball milling is 50 ml of anhydrous 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;

[0022] In step 3, the pre-calcination is carried out by heating the temperature to 850° C. to 900° C. at a heating rate of 3° C. / min and pre-calcining for 3 h to 5 h.

[0023] In step 3, the pre-calcination is performed by heating the temperature to 850° C. at a heating rate of 3° C. / min and pre-calcining for 5 h.

[0024] 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.

[0025] In step 5, the thickness of the tablet is 1.3 mm to 1.5 mm, the applied pressure of the cold isostatic pressing is not less than 200 MPa, and the holding time is not less than 5 minutes;

[0026] In step 6, the cylindrical blank is placed on a zirconia flat plate, the zirconia flat plate is placed in an alumina closed sagger, the temperature is increased to 1180°C to 1200°C at a heating rate of 3°C / min, sintered for 5h to 8h, and then naturally cooled to room temperature in the furnace.

[0027] In step 6, the cylindrical blank is placed on a zirconia plate, the zirconia plate is placed in an alumina closed sagger, and the temperature is increased to 1190° C. at a heating rate of 3° C. / min, sintered for 5 h, and then naturally cooled to room temperature in the furnace.

[0028] The beneficial effects of the present invention are:

[0029] The potassium sodium niobate-based ceramic material with excellent fatigue resistance has good energy storage performance and excellent fatigue resistance. Its breakdown electric field is 230-400 kV / cm and its maximum polarization intensity is 29.6-34.1 μC / cm. 2 , the residual polarization intensity is 4.1~7.4μC / cm 2 , and the highest effective energy storage density of 3.16 J / cm was obtained when x = 0.07. 3 , and also has very excellent anti-fatigue performance, after 10 5 After the first cycle, the energy storage performance of the ceramic sample showed no significant attenuation, and the change rate of the effective energy storage density was only 0.11%. It is a lead-free ferroelectric ceramic with excellent practicality and easy production.

[0030] The preparation method of the potassium sodium niobate-based ceramic material with excellent fatigue resistance is simple, has good repeatability and high yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 1 is the XRD diagram of Examples 1 to 5 of the potassium sodium niobate-based ceramic material with excellent fatigue resistance of the present invention;

[0032] Figure 2 The single-stage hysteresis loop of Examples 1 to 5 of the present invention;

[0033] Figure 3 1 is a graph showing changes in polarization intensity according to Examples 1 to 5 of the present invention;

[0034] Figure 4 1 is a graph showing the change of the single-stage hysteresis loop of Example 3 of the present invention with the number of cycles;

[0035] Figure 5 3 is a graph showing the change in energy storage performance of Example 3 of the present invention with the number of cycles. DETAILED DESCRIPTION

[0036] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] The potassium sodium niobate-based ceramic material with excellent fatigue resistance of the present invention has a general chemical composition formula of: (1-x)K 0.5 Na 0.5 NbO3-x(Sr 0.7 La 0.2 )(Mg 1 / 3 Nb 2 / 3 )O3;

[0038] Where, x represents (Sr 0.7 La 0.2 )(Mg 1 / 3 Nb 2 / 3 ) the number of moles of O3, x is 0.03 to 0.12;

[0039] According to the chemical composition formula (1-x)K 0.5 Na 0.5 NbO3-x(Sr 0.7 La 0.2 )(Mg 1 / 3 Nb 2 / 3 )O3, composed of the following raw materials: Na2CO3 powder, K2CO3 powder, Nb2O5 powder, SrCO3 powder, La2O3 powder, and MgO powder.

[0040] The potassium sodium niobate-based ceramic material with excellent fatigue resistance is prepared by a high-temperature solid-phase method and has a pure perovskite structure, a breakdown electric field of 230 to 400 kV / cm, and a maximum polarization strength of 29.6 to 34.1 μC / cm. 2 , the residual polarization intensity is 4.1~7.4μC / cm 2 When the value of x is 0.07, the breakdown electric field of the ceramic material is 400kV / cm and the polarization difference is 26.7μC / cm 2 , the effective energy storage density is 3.16J / cm 3 , loop 10 5 The energy storage performance was stable after the test, with the change rate of effective energy storage density being only 0.11% and the change rate of energy storage efficiency being 0.28%.

[0041] The preparation method of the potassium sodium niobate-based ceramic material with excellent fatigue resistance of the present invention is specifically implemented according to the following steps:

[0042] Step 1. Ingredients:

[0043] According to the chemical composition formula (1-x)K 0.5 Na 0.5 NbO3-x(Sr 0.7 La 0.2 )(Mg 1 / 3 Nb 2 / 3)O3, where x is 0.03 to 0.12, weigh the following raw materials: Na2CO3 powder, K2CO3 powder, Nb2O5 powder, SrCO3 powder, La2O3 powder, and MgO powder;

[0044] Step 2, primary ball milling: put all raw materials into a ball mill, add 50 ml of anhydrous ethanol as a ball milling medium, mix and ball mill for 20 to 24 hours, dry at 100 to 120 degrees Celsius for 10 to 12 hours, and grind to obtain a raw material mixture;

[0045] Step 3, pre-calcining: placing the raw material mixture in an alumina crucible and covering it, placing it in a muffle furnace, heating it to 850°C to 900°C at a heating rate of 3°C / min, pre-calcining it for 3h to 5h, then naturally cooling it to room temperature in the furnace, and grinding it with a mortar to obtain a pre-calcined powder;

[0046] The preferred pre-firing temperature is 850° C., the pre-firing time is 5 h, and the heating rate is 3° C. / min.

[0047] Step 4, secondary ball milling: Place the calcined powder in a ball mill, add zirconium balls as grinding balls and 45 ml of anhydrous ethanol as a ball milling medium, mix thoroughly and ball mill for 16 to 24 hours, separate the zirconium balls, and then dry at 100 to 120 degrees Celsius for 10 to 12 hours, grind, and obtain a mixed powder;

[0048] Step 5: Tabletting and cold isostatic pressing:

[0049] The mixed powder is placed in a mold and pressed into a cylindrical blank with a thickness of 1.3 mm to 1.5 mm using a powder tablet press. A pressure of not less than 200 MPa is then applied and the pressure is maintained for at least 5 minutes to perform cold isostatic pressing to obtain a cylindrical blank.

[0050] Step 6, pressureless closed sintering: Place the cylindrical blank on a zirconia plate, place the zirconia plate in an alumina closed sagger, heat it to 1180°C ~ 1200°C at a heating rate of 3°C / min, sinter for 5h ~ 8h, and then cool it naturally to room temperature in the furnace to obtain a potassium sodium niobate-based ceramic material with excellent fatigue resistance.

[0051] In step 6, the temperature is preferably increased to 1190° C. at a heating rate of 3° C. / min and sintered for 5 h.

[0052] Example 1: x = 0.03

[0053] Step 1. Ingredients:

[0054] According to 0.97K 0.5 Na 0.5 NbO3-0.03(Sr 0.7 La 0.2 )(Mg 1 / 3Nb 2 / 3 )O3 stoichiometrically, 2.6322 g of 99.999% pure Na2CO3 powder, 3.4327 g of 99.99% pure K2CO3 powder, 13.4760 g of 99.99% pure Nb2O5 powder, 0.3177 g of 99.95% pure SrCO3 powder, 0.1001 g of 99.99% pure La2O3 powder, and 0.0413 g of 99.95% pure MgO powder were weighed as raw materials;

[0055] Step 2: First ball milling:

[0056] The weighed raw materials were placed in a ball mill, and 50 ml of anhydrous ethanol was added to the ball mill. Zirconium balls were used as grinding balls and anhydrous ethanol was used as ball milling media. The mixture was fully mixed and ball milled in a rack ball mill for 24 hours. The zirconium balls were separated, and the raw material mixed slurry was placed in a drying oven at 100°C for 12 hours. The raw material mixture was ground into powder in a mortar for 30 minutes to obtain a raw material mixture.

[0057] Step 3: Pre-burning:

[0058] The raw material mixture ground in step 2 was placed in an alumina crucible, compacted with an agate rod, covered, placed in a resistance furnace, heated to 850°C at a heating rate of 3°C / min, and pre-fired for 5 hours. Then, it was naturally cooled to room temperature in the furnace and ground with a mortar to obtain pre-fired powder.

[0059] Step 4: Secondary ball milling

[0060] The calcined powder was placed in a ball mill, and 45 ml of anhydrous ethanol was added. Zirconium balls were used as grinding balls and anhydrous ethanol was used as ball milling media. The mixture was fully mixed and ball milled for 24 hours. The zirconium balls were separated. The calcined powder was placed in a drying oven at 100°C for 12 hours and ground into powder in a mortar for 20 minutes to obtain a mixed powder.

[0061] Step 5: Tabletting and cold isostatic pressing

[0062] Take 0.4g of the mixed powder and put it into a stainless steel mold with a diameter of 11mm. Use a powder tablet press to press it into a cylindrical blank with a thickness of 1.5mm. The pressed cylindrical blank is evenly placed in a rubber glove and vacuumed. Then, the rubber glove containing the cylindrical blank is placed in a cylinder filled with silicone oil, and a pressure of 200MPa is applied and maintained for 5 minutes for cold isostatic pressing to obtain a cylindrical blank.

[0063] Step 6: Pressureless and sealed sintering

[0064] The cylindrical blank was placed on a zirconia plate, which was placed in an alumina sealed sagger and heated to 1190°C at a heating rate of 3°C / min. The sintering was carried out for 5 hours and then naturally cooled to room temperature in the furnace to prepare a 0.97K 0.5 Na 0.5 NbO3-0.03(Sr 0.7 La 0.2 )(Mg 1 / 3 Nb 2 / 3 )O3 has excellent fatigue resistance.

[0065] Example 2: x=0.06

[0066] Basically the same as Example 1, except that:

[0067] Step 1: Ingredients: According to 0.94K 0.5 Na 0.5 NbO3-0.06(Sr 0.7 La 0.2 )(Mg 1 / 3 Nb 2 / 3 ) O3 stoichiometrically: 2.5337 g of 99.999% pure Na2CO3 powder, 3.3042 g of 99.99% pure K2CO3 powder, 13.2502 g of 99.99% pure Nb2O5 powder, 0.6310 g of 99.95% pure SrCO3 powder, 0.1989 g of 99.99% pure La2O3 powder, and 0.0820 g of 99.95% pure MgO powder were weighed as raw materials;

[0068] In step 6, the temperature was raised to 1180°C at a heating rate of 3°C / min and sintered for 5 hours; the molecular formula was 0.94K 0.5 Na 0.5 NbO3-0.06(Sr 0.7 La 0.2 )(Mg 1 / 3 Nb 2 / 3 )O3 has excellent fatigue resistance.

[0069] Example 3: x=0.07

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

[0071] Step 1: Ingredients: According to 0.93K 0.5 Na 0.5 NbO3-0.07(Sr 0.7 La 0.2 )(Mg 1 / 3 Nb 2 / 3)O3 stoichiometrically, 2.5011 g of 99.999% pure Na2CO3 powder, 3.2617 g of 99.99% pure K2CO3 powder, 13.1756 g of 99.99% pure Nb2O5 powder, 0.7346 g of 99.95% pure SrCO3 powder, 0.2315 g of 99.99% pure La2O3 powder, and 0.0955 g of 99.95% pure MgO powder were weighed as raw materials;

[0072] In step 6, the temperature was raised to 1180°C at a heating rate of 3°C / min and sintered for 5 hours; the molecular formula was 0.93K 0.5 Na 0.5 NbO3-0.07(Sr 0.7 La 0.2 )(Mg 1 / 3 Nb 2 / 3 )O3 has excellent fatigue resistance.

[0073] Example 4: x=0.09

[0074] Basically the same as Example 1, except that:

[0075] Step 1: Ingredients: According to 0.91K 0.5 Na 0.5 NbO3-0.09(Sr 0.7 La 0.2 )(Mg 1 / 3 Nb 2 / 3 ) O3 stoichiometrically, 2.4364 g of 99.999% pure Na2CO3, 3.1774 g of 99.99% pure K2CO3, 13.0274 g of 99.99% pure Nb2O5, 0.9402 g of 99.95% pure SrCO3, 0.2963 g of 99.99% pure La2O3, and 0.1222 g of 99.95% pure MgO were weighed as raw materials;

[0076] In step 6, the temperature was raised to 1180°C at a heating rate of 3°C / min and sintered for 5 hours; the molecular formula was 0.91K 0.5 Na 0.5 NbO3-0.09(Sr 0.7 La 0.2 )(Mg 1 / 3 Nb 2 / 3 )O3 has excellent fatigue resistance.

[0077] Example 5: x=0.12

[0078] Basically the same as Example 1, except that:

[0079] Step 1: Ingredients: According to 0.88K 0.5 Na 0.5 NbO3-0.12(Sr 0.7 La 0.2 )(Mg 1 / 3 Nb 2 / 3 ) O3 stoichiometrically, 2.3405 g of 99.999% pure Na2CO3, 3.0522 g of 99.99% pure K2CO3, 12.8076 g of 99.99% pure Nb2O5, 1.2453 g of 99.95% pure SrCO3, 0.3925 g of 99.99% pure La2O3, and 0.1619 g of 99.95% pure MgO were weighed as raw materials;

[0080] In step 6, the temperature was raised to 1200°C at a heating rate of 3°C / min and sintered for 5 hours; the molecular formula was 0.91K 0.5 Na 0.5 NbO3-0.09(Sr 0.7 La 0.2 )(Mg 1 / 3 Nb 2 / 3 )O3 has excellent fatigue resistance.

[0081] Example 6

[0082] Basically the same as Example 1, except that:

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

[0084] In step 3, the temperature is raised to 870°C at a heating rate of 3°C / min and pre-fired for 4 hours;

[0085] In step 4, the mixture was ball-milled for 20 hours, the zirconium balls were separated, and the calcined powder was dried in a drying oven at 110° C. for 11 hours;

[0086] In step 5, a powder tablet press is used to press the cylindrical blank into a thickness of 1.4 mm. The pressed cylindrical blank is evenly placed in a rubber glove and vacuumed. The rubber glove containing the cylindrical blank is then placed in a cylinder containing silicone oil, and a pressure of 220 MPa is applied and the pressure is maintained for 10 minutes to perform cold isostatic pressing to obtain a cylindrical blank.

[0087] In step 6, the temperature is raised to 1190° C. at a heating rate of 3° C. / min and sintered for 6.5 hours.

[0088] Example 7

[0089] Basically the same as Example 1, except that:

[0090] The mixed slurry in step 2 was ball-milled for 20 hours, and the raw material mixture was placed in a drying oven at 100° C. for 12 hours, and ground into powder in a mortar for 30 minutes to obtain a raw material mixture;

[0091] In step 3, the temperature is raised to 900°C at a heating rate of 3°C / min and pre-fired for 3 hours;

[0092] In step 4, the mixture is ball-milled for 16 hours, the zirconium balls are separated, and the calcined powder is dried in a drying oven at 100° C. for 12 hours;

[0093] In step 5, a powder tablet press is used to press the cylindrical blank into a thickness of 1.3 mm. The pressed cylindrical blank is evenly placed in a rubber glove and vacuumed. The rubber glove containing the cylindrical blank is then placed in a cylinder containing silicone oil. A pressure of 210 MPa is applied and the pressure is maintained for 8 minutes to perform cold isostatic pressing to obtain a cylindrical blank.

[0094] In step 6, the temperature is raised to 1180° C. at a heating rate of 3° C. / min and sintered for 8 hours.

[0095] Example 8

[0096] Basically the same as Example 1, except that:

[0097] The mixed material in step 2 was ball-milled for 22 hours, the raw material mixed slurry was placed in a drying oven at 120° C. for 10 hours, and ground into powder using a mortar for 30 minutes to obtain a raw material mixture;

[0098] In step 3, the temperature is raised to 850°C at a heating rate of 3°C / min and pre-fired for 5 hours;

[0099] In step 4, the mixture is ball-milled for 24 hours, the zirconium balls are separated, and the calcined powder is dried in a drying oven at 120° C. for 10 hours;

[0100] In step 5, a pressure of 230 MPa is applied and the pressure is maintained for 7 minutes to form a cylindrical blank by cold isostatic pressing;

[0101] In step 6, the temperature is increased to 1200° C. at a heating rate of 3° C. / min and sintered for 5 hours.

[0102] From Examples 1 to 5, a potassium sodium niobate-based ceramic sheet with excellent fatigue resistance was selected. The surface was first polished to a thickness of 1 mm with 1200-mesh corundum. Then, both sides of the ceramic material were polished for 20 minutes with 1500-mesh polishing liquid. Finally, it was ultrasonically cleaned with alcohol and ground into powder. XRD test was performed using a Japanese Rigaku MiniFlex600 diffractometer. The results are shown in FIG. Figure 1 .

[0103] From Examples 1 to 5, a potassium sodium niobate-based ceramic sheet with excellent fatigue resistance was selected respectively. The ceramic material was polished to a thickness of 0.15 mm with 1500-mesh corundum. The polished ceramic sample was placed in an ion sputtering instrument. A gold target was selected. The current was 30 mA and the time was 200 s. Gold electrodes with a thickness of 0.02 mm and a diameter of 2 mm were sputtered on the upper and lower surfaces of the ceramic. The AixACCT-TF2000 ferroelectric parameter tester was used to perform a unipolar PE hysteresis loop test and a frequency stability test. The results are shown in FIG. Figure 2 、 Figure 3 、 Figure 4 and Figure 5 shown.

[0104] Depend on Figure 1 It can be seen that the ceramic materials prepared in Examples 1 to 5 all have pure perovskite structures. Figure 2 The single-stage hysteresis loops of Examples 1 to 5 under the critical breakdown electric field are shown. The breakdown electric field of the materials is 230 to 400 kV / cm, and the breakdown electric field of Example 3 is the highest at 400 kV / cm. Figure 3 The polarization intensity variation diagrams of Examples 1 to 5 are shown, wherein P max is the maximum polarization intensity, P r is the remanent polarization intensity, P max -P r is the polarization difference, such as Figure 3 As shown, the maximum polarization intensity of the material is 29.6~34.1μC / cm 2 , the residual polarization intensity is 4.1~7.4μC / cm 2 , the polarization difference is 21.19~26.69μC / cm 2 The polarization difference of Example 3 is the largest, which is 26.698μC / cm 2 , and at the same time has the highest breakdown electric field, so that Example 3 has the best energy storage performance, and its effective energy storage density is 3.16J / cm 3 . Figure 4 The graph showing the change of the single-stage hysteresis loop of Example 3 under an electric field of 150 kV / cm with the number of cycles is as follows: Figure 4 As shown, after 10 5 After the first cycle, the ceramic material of Example 3 still maintains a good and complete hysteresis loop with no difference changes. Figure 5 The graph shows the change of energy storage performance of Example 3 under an electric field of 150 kV / cm with the number of cycles, where W totel is the total energy storage density, W rec is the effective energy storage density, W loss is the lost energy storage density, η is the energy storage efficiency, such as Figure 5As shown, the effective energy storage density change rate of Example 3 is only 0.11%, while the energy storage efficiency change rate is 0.28%. 5 After the first cycle, the ceramic's energy storage performance showed no degradation, demonstrating its exceptionally high fatigue resistance. Therefore, the potassium sodium niobate-based ceramic material with excellent fatigue resistance prepared by the present invention combines excellent fatigue resistance with good energy storage performance, making it a high-performance lead-free ferroelectric ceramic.

Claims

1. Potassium sodium niobate-based ceramic material with excellent fatigue resistance, 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 Nb 2 / 3 )O3; Where, x represents (Sr 0.7 La 0.2 )(Mg 1 / 3 Nb 2 / 3 ) the number of moles of O3, x is 0.03 to 0.12; The ceramic has a perovskite structure, a breakdown electric field of 230-400 kV / cm, and a maximum polarization strength of 29.6-34.1 μC / cm. 2 , the residual polarization intensity is 4.1~7.4μC / cm 2 .

2. The potassium sodium niobate-based ceramic material with excellent fatigue resistance according to claim 1, characterized in that: According to the chemical composition formula (1-x)K 0.5 Na 0.5 NbO3-x(Sr 0.7 La 0.2 )(Mg 1 / 3 Nb 2 / 3 )O3, composed of the following raw materials: Na2CO3 powder, K2CO3 powder, Nb2O5 powder, SrCO3 powder, La2O3 powder, and MgO powder.

3. The potassium sodium niobate-based ceramic material with excellent fatigue resistance according to claim 1, characterized in that: The x is 0.

07.

4. A method for preparing potassium sodium niobate-based ceramic materials with excellent fatigue resistance, characterized in that: Please follow the steps below to implement it: Step 1: According to the chemical formula (1-x)K 0.5 Na 0.5 NbO3-x(Sr 0.7 La 0.2 )(Mg 1 / 3 Nb 2 / 3 )O3, where x is 0.03 to 0.12, weigh the following raw materials: Na2CO3 powder, K2CO3 powder, Nb2O5 powder, SrCO3 powder, La2O3 powder, and MgO powder; Step 2: ball milling, drying, and grinding the raw materials to obtain a raw material mixture; Step 3: pre-calcining the raw material mixture, cooling it to room temperature, and grinding it to obtain pre-calcined powder; Step 4: ball milling the calcined powder for a second time, drying and grinding the calcined powder to obtain a mixed powder; Step 5: tableting and cold isostatic pressing the mixed powder to obtain a cylindrical blank; Step 6: Perform pressureless closed sintering on the cylindrical blank, and cool it to room temperature to obtain a potassium sodium niobate-based ceramic material with excellent fatigue resistance.

5. The method for preparing the potassium sodium niobate-based ceramic material with excellent fatigue resistance according to claim 4, characterized in that: In step 2, the ball milling medium for the first ball milling is 50 ml of anhydrous 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; In step 3, the pre-calcination is to increase the temperature to 850° C. to 900° C. at a heating rate of 3° C. / min and pre-calculate for 3 h to 5 h.

6. The method for preparing the potassium sodium niobate-based ceramic material with excellent fatigue resistance according to claim 4, characterized in that: In step 3, the pre-calcination is performed by heating the temperature to 850° C. at a heating rate of 3° C. / min and pre-calcining for 5 hours.

7. The method for preparing potassium sodium niobate-based ceramic material with excellent fatigue resistance according to claim 4, 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.

8. The method for preparing the potassium sodium niobate-based ceramic material with excellent fatigue resistance according to claim 4, characterized in that: In step 5, the thickness of the pressed sheet is 1.3 mm to 1.5 mm, the applied pressure of the cold isostatic pressing is not less than 200 MPa, and the holding time is not less than 5 minutes; In step 6, the cylindrical blank is placed on a zirconia flat plate, the zirconia flat plate is placed in an alumina closed sagger, the temperature is increased to 1180°C to 1200°C at a heating rate of 3°C / min, sintered for 5h to 8h, and then naturally cooled to room temperature in the furnace.

9. The method for preparing potassium sodium niobate-based ceramic material with excellent fatigue resistance according to claim 4, characterized in that: In step 6, the cylindrical blank is placed on a zirconia flat plate, the zirconia flat plate is placed in an alumina closed sagger, the temperature is increased to 1190° C. at a heating rate of 3° C. / min, sintered for 5 h, and then naturally cooled to room temperature in the furnace.

Images