Method for preparing magnetoelectric composite ceramic with mosaic structure through segmented crystallization

Abstract

The invention discloses a method for preparing magnetoelectric multiphase ceramic with a mosaic structure through segmented crystallization, and relates to a preparation method of multiphase ceramic. The invention aims to solve the technical problem that the leakage current of the current multiphase multiferroic material is higher than that of the single-phase multiferroic material by a plurality of orders of magnitude. The magnetoelectric composite ceramic with the mosaic structure is characterized in that a ferromagnetic phase bCoFe2O4 is inlaid in a ferroelectric phase aPb < 0.9625 > Sm < 0.025 > (Mg < 1 / 3 > Nb < 2 / 3 >) < 0.7 > Ti < 0.3 > O < 3 >. The method comprises the following steps: 1, preparing sol A; 2, preparing sol B; 3, preparing sol C; 4, preparing sol D; 5, preparing sol E; 6, drying; 7, carbonizing; 8, calcining; 9, grinding; 10, granulating; 11, tabletting; 12, discharging glue; and 13, sintering. According to the invention, the mosaic structure is designed, that is, the ferromagnetic phase is uniformly inlaid in the ferroelectric phase, so that the ferromagnetic phase cannot be agglomerated on a grain boundary, and current leakage after agglomeration is avoided.

Description

Technical Field

[0001] The present invention relates to a method for preparing a multiphase ceramic. Background Art

[0002] Multiferroic materials refer to materials that simultaneously exhibit ferroelectricity and ferromagnetism, and are functional materials that can exhibit two or more ferroic orderings (such as ferroelectricity, ferromagnetism, ferroelasticity, etc.) in the same phase and have a coupling effect. Such materials can utilize both their coupling properties and certain individual properties, and will show significant responses under the action of an electric field and a magnetic field, having broad application potential. They can be used in multiple fields such as information storage, logic devices, and microwaves.

[0003] Multiferroic materials can be classified into single-phase multiferroic materials, multiphase multiferroic materials, layered multiferroic materials, organic-inorganic hybrid multiferroic materials, and two-dimensional multiferroic materials according to their components. Currently, multiphase multiferroic materials have received attention due to their good magnetoelectric coupling performance.

[0004] For multiphase multiferroic materials (taking the ferroelectric-ferromagnetic two-phase composite as an example), the current composite methods between the two phases are 0-3 (particle-block) type, 1-3 (cylinder-block) type, and 2-2 (layer-layer) type. Different composite methods result in different magnetoelectric coupling performances, but none of the three composite methods can solve the leakage current problem: the ferromagnetic phase exists at the grain boundaries of the ferroelectric phase, causing a leakage current that is several orders of magnitude higher than that of single-phase multiferroic materials. Summary of the Invention

[0005] The purpose of the present invention is to solve the technical problem of the leakage current of current multiphase multiferroic materials being several orders of magnitude higher than that of single-phase multiferroic materials, and to provide a method for preparing a magnetoelectric multiphase ceramic with an inlaid structure by segmented crystallization.

[0006] A method for preparing a magnetoelectric multiphase ceramic with an inlaid structure by segmented crystallization, wherein the magnetoelectric multiphase ceramic with an inlaid structure is ferroelectric phase aPb 0.9625 Sm 0.025 (Mg 1 / 3 Nb 2 / 3 ) 0.7 Ti 0.3 O3 inlaid with ferromagnetic phase bCoFe2O4, where a is the amount of substance of Pb 0.9625 Sm 0.025 (Mg 1 / 3 Nb 2 / 3 ) 0.7 Ti 0.3 O3, b is the amount of substance of CoFe2O4, and 0.5 ≤ a ≤ 0.95, 0.05 ≤ b ≤ 0.5, a + b = 1; The method is specifically completed according to the following steps:

[0007] I. Preparation of Sol A:

[0008] ①. Add lead acetate, magnesium acetate and samarium nitrate into anhydrous acetic acid, heat and stir for a period of time, then add tetrabutyl titanate, and stir at room temperature for a period of time to obtain Sol A;

[0009] In the Sol A described in Step I①, the molar ratio of lead element, magnesium element, samarium element and titanium element is

[0010] II. Preparation of Sol B:

[0011] ①. Add niobium hydroxide and oxalic acid into deionized water, heat and stir for a period of time to obtain niobium oxalate salt solution;

[0012] ②. Mix hydrogen peroxide and citric acid, stir at room temperature for a period of time, and then adjust the pH value of the solution to 1 with dilute nitric acid to obtain Mixed Solution I;

[0013] ③. Add the niobium oxalate salt solution obtained in Step II① into the Mixed Solution I obtained in Step II②, stir evenly to obtain Sol B;

[0014] III. Preparation of Sol C:

[0015] ①. Add ammonia water and citric acid into deionized water, stir at room temperature for a period of time to obtain Mixed Solution II;

[0016] ②. Mix Sol A, Sol B and Mixed Solution II, heat and stir for a period of time to obtain Sol C;

[0017] In the Sol C described in Step III②, the molar ratio of lead element, magnesium element, samarium element, titanium element and niobium element is

[0018] In the Sol C described in Step III②, the molar ratio of the amount of substance of ammonia water to the total molar mass of lead element, magnesium element and titanium element is 50:1;

[0019] IV. Preparation of Sol D:

[0020] Weigh cobalt salt as Raw Material 1; weigh iron nitrate as Raw Material 2; add Raw Material 1 and Raw Material 2 into deionized water, and stir at room temperature until the cobalt salt and iron nitrate are completely dissolved in deionized water to obtain Sol D;

[0021] V. Preparation of Mixed Sol E:

[0022] Fully mix Sol D and Sol C, heat and stir for a period of time to obtain Sol E;

[0023] The molar ratio of sol C to sol D described in Step 5 is a:b, where 0.5 ≤ a ≤ 0.95, 0.05 ≤ b ≤ 0.5, and a + b = 1;

[0024] VI. Drying:

[0025] Place sol E in a dust-free environment and keep it at 80 °C for a period of time to obtain a mixed xerogel;

[0026] VII. Carbonization:

[0027] Keep the mixed xerogel obtained in Step VI at 180 - 200 °C for a period of time to obtain a foamy black xerogel;

[0028] VIII. Calcination:

[0029] Heat the foamy black xerogel obtained in Step VII from room temperature to 150 °C - 400 °C and keep it at this temperature for a period of time, then heat it to 650 °C - 850 °C and keep it at this temperature for a period of time, and then cool it to room temperature with the furnace to obtain ceramic powder;

[0030] IX. Grinding:

[0031] Place the ceramic powder obtained in Step VIII in a mortar for grinding, and then sieve it to obtain ceramic powder with a particle size of 100 - 160 mesh;

[0032] X. Granulation:

[0033] Mix polyvinyl alcohol and deionized water evenly, heat and stir until the polyvinyl alcohol is completely dissolved to obtain an aqueous polyvinyl alcohol solution; mix the ceramic powder with a particle size of 100 - 160 mesh and the aqueous polyvinyl alcohol solution and then grind them to obtain a uniform powder;

[0034] XI. Tabletting:

[0035] Place the uniform powder obtained in Step X into a mold and press it into a block;

[0036] XII. Debinding:

[0037] Heat the block obtained in Step XI from room temperature to 500 °C - 600 °C and keep it at this temperature for a period of time, and then cool it to room temperature with the furnace to obtain a ceramic green body block without polyvinyl alcohol;

[0038] XIII. Sintering:

[0039] In an oxygen atmosphere, the ceramic green body block without polyvinyl alcohol obtained in Step 12 is embedded with the ceramic powder having a particle size of 100-160 mesh sieve obtained in Step 9, heated from room temperature to 1150 °C - 1300 °C in an oxygen atmosphere, held for a period of time under the conditions of an oxygen atmosphere and a temperature of 1150 °C - 1300 °C, and then cooled to room temperature with the furnace in an oxygen atmosphere to obtain a magnetoelectric composite ceramic with an embedded structure.

[0040] Advantages of the present invention:

[0041] 1. In the magnetoelectric composite ceramic with an embedded structure prepared by the present invention, the ferromagnetic phase is embedded in the ferroelectric phase, less appears at the grain boundaries of the ferroelectric phase or does not appear at the grain boundaries of the ferroelectric phase, and its leakage current is less than that of the ceramic block prepared by other methods with the same composition;

[0042] 2. The sol-gel method used in the present invention has a stable process and uniform properties of the products;

[0043] 3. The sol-gel method used in the present invention has a stable process, a short cycle, low energy consumption, and the preparation process does not involve high-pressure reactions, with a high safety factor;

[0044] 4. The present invention can obtain a magnetoelectric composite ceramic with an embedded structure, and its leakage current is less than that of 0-3, 1-3, and 2-2 type multiferroic composite ceramics. Description of the drawings

[0045] Figure 1 Backscattered electron image of the scanning electron microscope of the magnetoelectric composite ceramic with an embedded structure prepared in Example 1;

[0046] Figure 2 Hysteresis loop diagram of the magnetoelectric composite ceramic with an embedded structure prepared in Example 1;

[0047] Figure 3 Electric hysteresis loop diagram of the magnetoelectric composite ceramic with an embedded structure prepared in Example 1;

[0048] Figure 4 Magnetoelectric coupling coefficient diagram of the magnetoelectric composite ceramic with an embedded structure prepared in Example 1. Detailed implementation manners

[0049] Detailed implementation manner 1: A method for preparing a magnetoelectric composite ceramic with an embedded structure by fractional crystallization in this implementation manner. The magnetoelectric composite ceramic with an embedded structure is ferroelectric phase aPb 0.9625 Sm 0.025 (Mg 1 / 3 Nb 2 / 3 ) 0.7 Ti 0.3The ferromagnetic phase bCoFe2O4 is embedded in O3, where a is Pb 0.9625 Sm 0.025 (Mg 1 / 3 Nb 2 / 3 ) 0.7 Ti 0.3 The amount of substance of 0.7 Ti 0.3 O3 is b, and the amount of substance of CoFe2O4 is b, and 0.5 ≤ a ≤ 0.95, 0.05 ≤ b ≤ 0.5, a + b = 1; The method is specifically completed according to the following steps:

[0050] I. Preparation of sol A:

[0051] ①. Add lead acetate, magnesium acetate and samarium nitrate to anhydrous acetic acid, heat and stir for a period of time, then add tetrabutyl titanate, and stir at room temperature for a period of time to obtain sol A;

[0052] In the sol A described in step I ①, the molar ratio of lead element, magnesium element, samarium element and titanium element is

[0053] II. Preparation of sol B:

[0054] ①. Add niobium hydroxide and oxalic acid to deionized water, heat and stir for a period of time to obtain a niobium oxalate salt solution;

[0055] ②. Mix hydrogen peroxide and citric acid, stir at room temperature for a period of time, and then adjust the pH value of the solution to 1 with dilute nitric acid to obtain a mixed solution I;

[0056] ③. Add the niobium oxalate salt solution obtained in step II ① to the mixed solution I obtained in step II ②, stir evenly to obtain sol B;

[0057] III. Preparation of sol C:

[0058] ①. Add ammonia water and citric acid to deionized water, stir at room temperature for a period of time to obtain a mixed solution II;

[0059] ②. Mix sol A, sol B and the mixed solution II, heat and stir for a period of time to obtain sol C;

[0060] In the sol C described in step III ②, the molar ratio of lead element, magnesium element, samarium element, titanium element and niobium element is

[0061] In the sol C described in step III ②, the molar ratio of the amount of substance of ammonia water to the total molar mass of lead element, magnesium element and titanium element is 50:1;

[0062] IV. Preparation of sol D:

[0063] Weigh a cobalt salt as raw material 1; weigh ferric nitrate as raw material 2; add raw material 1 and raw material 2 into deionized water, and stir at room temperature until the cobalt salt and ferric nitrate are completely dissolved in the deionized water to obtain sol D;

[0064] 5. Preparation of mixed sol E:

[0065] Sol D and Sol C are fully mixed, heated and stirred for a period of time to obtain Sol E;

[0066] The molar ratio of sol C and sol D in step 5 is a:b, wherein 0.5≤a≤0.95, 0.05≤b≤0.5, a+b=1;

[0067] 6. Drying:

[0068] Sol E was placed in a dust-free environment and kept at 80°C for a period of time to obtain a mixed dry gel;

[0069] 7. Carbonization:

[0070] The mixed xerogel obtained in step 6 is kept at 180-200° C. for a period of time to obtain a foamy black xerogel;

[0071] 8. Calcination:

[0072] The foamy black xerogel obtained in step 7 is heated from room temperature to 150°C to 400°C, and kept at this temperature for a period of time, then heated to 650°C to 850°C, and kept at this temperature for a period of time, and then cooled to room temperature with the furnace to obtain a ceramic powder;

[0073] 9. Grinding:

[0074] Grinding the ceramic powder obtained in step eight in a mortar, and then sieving to obtain ceramic powder with a particle size of 100 to 160 mesh;

[0075] 10. Granulation:

[0076] The polyvinyl alcohol and deionized water are uniformly mixed, and the polyvinyl alcohol is heated and stirred until the polyvinyl alcohol is completely dissolved to obtain a polyvinyl alcohol aqueous solution; the ceramic powder with a particle size of 100 to 160 meshes and the polyvinyl alcohol aqueous solution are mixed and ground to obtain a uniform powder;

[0077] 11. Tableting:

[0078] The uniform powder obtained in step 10 is placed in a mold and pressed into a block;

[0079] 12. Debonding:

[0080] Heat the bulk obtained in Step 11 from room temperature to 500 °C - 600 °C, hold at this temperature for a period of time, and then cool to room temperature in the furnace to obtain a ceramic green body block without polyvinyl alcohol.

[0081] XIII. Sintering:

[0082] Under an oxygen atmosphere, embed the ceramic green body block without polyvinyl alcohol obtained in Step 12 with the ceramic powder having a particle size of 100 - 160 mesh obtained in Step 9. Heat from room temperature to 1150 °C - 1300 °C under an oxygen atmosphere, hold for a period of time under an oxygen atmosphere and at a temperature of 1150 °C - 1300 °C, and then cool to room temperature in the furnace under an oxygen atmosphere to obtain a magnetoelectric composite ceramic with an inlaid structure.

[0083] In this embodiment, lead acetate needs to be in excess.

[0084] Specific Embodiment 2: The difference between this embodiment and Specific Embodiment 1 is that: the molar ratio of lead acetate to the volume of glacial acetic acid in Step 1① is 0.9625 mmol : (5 mL - 15 mL); the heating and stirring temperature in Step 1① is 55 °C - 65 °C, and the heating and stirring speed is 100 r / min - 300 r / min; the stirring speed at room temperature in Step 1① is 100 r / min - 300 r / min, and the stirring time at room temperature is 60 min - 120 min. Other steps are the same as those in Specific Embodiment 1.

[0085] Specific Embodiment 3: The difference between this embodiment and one of Specific Embodiments 1 or 2 is that: the heating and stirring speed in Step 2① is 100 r / min - 300 r / min, the heating and stirring time is 20 min - 40 min, and the heating and stirring temperature is 75 °C - 85 °C; the molar ratio of niobium hydroxide to oxalic acid in Step 2① is 1:5; the molar ratio of niobium hydroxide to the volume of deionized water in Step 2① is 0.467 mmol : (5 mL - 15 mL). Other steps are the same as those in Specific Embodiment 1 or 2.

[0086] Specific Embodiment 4: The difference between this embodiment and one of Specific Embodiments 1 to 3 is that: the concentration of dilute nitric acid in Step 2② is 2 mol / L - 4 mol / L; the molar ratio of H2O2 in hydrogen peroxide to oxalic acid in Step 2① in Step 2② is 13:1; the molar ratio of niobium hydroxide in Step 2① to citric acid in Step 2② is 1:4; the stirring speed in Step 2② is 100 r / min - 300 r / min, and the stirring time is 20 min - 40 min. Other steps are the same as those in Specific Embodiments 1 to 3.

[0087] Specific Embodiment 5: The difference between this embodiment and any one of Specific Embodiments 1 to 4 is as follows: In step 2③, the volume ratio of the niobium oxalate solution to the mixed solution I is 1:1; in step 3①, the molar ratio of ammonia water to citric acid in the mixed solution II is 50:1; in step 3①, the mass fraction of the ammonia water is 20% - 30%; in step 3①, the stirring speed is 100 r / min - 300 r / min, and the stirring time is 20 min - 40 min; in step 3①, the volume ratio of the ammonia water to deionized water is 5:2. Other steps are the same as those in Specific Embodiments 1 to 4.

[0088] Specific Embodiment 6: The difference between this embodiment and any one of Specific Embodiments 1 to 5 is as follows: In step 3②, the heating and stirring speed is 100 r / min - 300 r / min, the heating and stirring time is 20 min - 40 min, and the heating and stirring temperature is 75°C - 85°C; in step 4①, the molar ratio of raw material 1 to raw material 2 is 1:2; in step 4①, the cobalt salt is cobalt nitrate or cobalt acetate; in step 4①, the stirring speed is 100 r / min - 300 r / min; in step 4, the volume ratio of the total amount of substance of raw material 1 and raw material 2 to deionized water is 3 mmol:(2 mL - 10 mL). Other steps are the same as those in Specific Embodiments 1 to 5.

[0089] Specific Embodiment 7: The difference between this embodiment and any one of Specific Embodiments 1 to 6 is as follows: In step 5, the heating and stirring temperature is 70°C - 80°C, the heating and stirring speed is 100 r / min - 300 r / min, and the heating and stirring time is 60 min - 75 min; in step 6, the heat preservation time is 18 h - 36 h. Other steps are the same as those in Specific Embodiments 1 to 6.

[0090] Specific Embodiment 8: The difference between this embodiment and any one of Specific Embodiments 1 to 7 is as follows: In step 7, the heat preservation time is 60 min - 70 min; in step 8, the foamy black xerogel is heated from room temperature to 150°C - 400°C at a heating rate of 1°C / min - 5°C / min, and is kept at this temperature for 1 h - 3 h, and then heated to 650°C - 850°C at a heating rate of 5°C / min - 15°C / min, and is kept at this temperature for 1 h - 2 h. Other steps are the same as those in Specific Embodiments 1 to 7.

[0091] Embodiment 9: The difference between this embodiment and any one of Embodiments 1 to 8 is as follows: In Step 10, the temperature for heating and stirring is 50°C to 100°C, and the stirring speed is 100 r / min to 300 r / min; in Step 10, the volume ratio of the ceramic powder with a particle size of 100 to 160 mesh sieves to the aqueous polyvinyl alcohol solution is 5:2; in Step 10, the mass fraction of the aqueous polyvinyl alcohol solution is 5% to 15%. Other steps are the same as those in Embodiments 1 to 8.

[0092] Embodiment 10: The difference between this embodiment and any one of Embodiments 1 to 9 is as follows: In Step 11, the uniform powder obtained in Step 10 is placed in a mold and kept under pressure for 2 min to 4 min at a pressure of 8 MPa to 10 MPa to form a block; in Step 12, the block obtained in Step 11 is heated from room temperature to 500°C to 600°C at a heating rate of 0.5°C / min to 1.5°C / min and kept at this temperature for 30 min to 120 min; in Step 13, the heating rate is 5°C / min to 10°C / min; in Step 13, the holding time is 15 min to 120 min. Other steps are the same as those in Embodiments 1 to 9.

[0093] The following examples are used to verify the beneficial effects of the present invention:

[0094] Example 1: A method for preparing a magnetoelectric composite ceramic with an inlaid structure by fractional crystallization. The magnetoelectric composite ceramic with an inlaid structure is ferroelectric phase aPb 0.9625 Sm 0.025 (Mg 1 / 3 Nb 2 / 3 ) 0.7 Ti 0.3 O3 inlaid with ferromagnetic phase bCoFe2O4, where a is the amount of substance of Pb 0.9625 Sm 0.025 (Mg 1 / 3 Nb 2 / 3 ) 0.7 Ti 0.3 O3, b is the amount of substance of CoFe2O4, and a = 0.70, b = 0.30, a + b = 1. Co is cobalt element, Fe is iron element, O is oxygen element, Ti is titanium element, Pb is lead element, Sm is samarium element, Mg is magnesium element, and Nb is niobium element. The method is specifically completed according to the following steps:

[0095] I. Preparation of Sol A:

[0096] ①. Add lead acetate, magnesium acetate, and samarium nitrate to glacial acetic acid, heat and stir for a period of time, then add tetrabutyl titanate, and stir at room temperature for a period of time to obtain Sol A;

[0097] The molar ratio of lead element, magnesium element, samarium element and titanium element in sol A described in Step 1 ① is

[0098] The molar ratio of lead acetate to the volume of glacial acetic acid described in Step 1 ① is 0.67375 mmol: 7 mL;

[0099] The temperature of heating and stirring described in Step 1 ① is 60 °C, and the speed of heating and stirring is 200 r / min;

[0100] The speed of stirring at room temperature described in Step 1 ① is 150 r / min, and the time of stirring at room temperature is 60 min;

[0101] II. Preparation of sol B:

[0102] ①. Add niobium hydroxide and oxalic acid to deionized water, heat and stir for a period of time to obtain niobium oxalate solution;

[0103] The speed of heating and stirring described in Step 2 ① is 200 r / min, the time of heating and stirring is 20 min, and the temperature of heating and stirring is 85 °C;

[0104] The molar ratio of niobium hydroxide to oxalic acid described in Step 2 ① is 1:5;

[0105] The molar ratio of niobium hydroxide to the volume of deionized water described in Step 2 ① is 0.3269 mmol: 7 mL;

[0106] ②. Mix hydrogen peroxide and citric acid, stir at room temperature for a period of time, and then adjust the pH value of the solution to 1 with dilute nitric acid to obtain mixed solution I;

[0107] The concentration of dilute nitric acid described in Step 2 ② is 2 mol / L;

[0108] The molar ratio of H2O2 in hydrogen peroxide to oxalic acid described in Step 2 ① in Step 2 ② is 13:1;

[0109] The molar ratio of niobium hydroxide described in Step 2 ① to citric acid described in Step 2 ② is 1:4;

[0110] The speed of stirring described in Step 2 ② is 200 r / min, and the time of stirring is 40 min;

[0111] ③. Add the niobium oxalate solution obtained in Step 2 ① to the mixed solution I obtained in Step 2 ②, stir evenly to obtain sol B;

[0112] The volume ratio of the niobium oxalate solution to the mixed solution I described in Step 2 ③ is 1:1;

[0113] III. Preparation of Sol C:

[0114] ①. Add ammonia water and citric acid to deionized water, stir for a period of time at room temperature to obtain mixed solution II;

[0115] In the mixed solution II described in step III ①, the molar ratio of ammonia water to citric acid is 50:1;

[0116] In the ammonia water described in step III ①, the mass fraction is 25%;

[0117] In the stirring described in step III ①, the speed is 200 r / min and the time is 20 min;

[0118] In the ammonia water described in step III ①, the volume ratio to deionized water is 5:2;

[0119] ②. Mix sol A, sol B and mixed solution II, heat and stir for a period of time to obtain sol C;

[0120] In the heating and stirring described in step III ②, the speed is 100 r / min - 300 r / min, the time is 20 min - 40 min, and the temperature is 80 °C;

[0121] In the sol C described in step III ②, the molar ratio of lead element, magnesium element, samarium element, titanium element and niobium element is

[0122] In the sol C described in step III ②, the molar ratio of the amount of substance of ammonia water to the total molar mass of lead element, magnesium element and titanium element is 50:1;

[0123] IV. Preparation of Sol D:

[0124] ①. Weigh cobalt salt as raw material 1; weigh ferric nitrate as raw material 2; add raw material 1 and raw material 2 to deionized water, stir at room temperature until the cobalt salt and ferric nitrate are completely dissolved in deionized water to obtain sol D;

[0125] In the raw material 1 and raw material 2 described in step IV ①, the molar ratio is 1:2;

[0126] In the cobalt salt described in step IV ①, it is cobalt nitrate;

[0127] In the stirring described in step IV ①, the speed is 250 r / min;

[0128] In the raw material 1 and raw material 2 described in step IV ①, the total amount of substance and the volume ratio of deionized water is 0.9 mmol:2 mL;

[0129] V. Preparation of Mixed Sol E:

[0130] Sol D and Sol C are fully mixed, heated and stirred for a period of time to obtain Sol E;

[0131] The molar ratio of Sol C and Sol D described in step 5 is a:b, a=0.70, b=0.30, a+b=1;

[0132] The heating and stirring temperature in step 5 is 80°C, the heating and stirring speed is 200r / min, and the heating and stirring time is 60min;

[0133] 6. Drying:

[0134] Sol E was placed in a dust-free environment and kept at 80°C for a period of time to obtain a mixed dry gel;

[0135] The insulation time described in step 6 is 24h;

[0136] 7. Carbonization:

[0137] The mixed xerogel obtained in step 6 is kept at 180° C. for a period of time to obtain a foamy black xerogel;

[0138] The insulation time described in step 7 is 60 minutes;

[0139] 8. Calcination:

[0140] The foamy black xerogel obtained in step 7 is heated from room temperature to 350°C and kept at this temperature for a period of time, then heated to 850°C and kept at this temperature for a period of time, and then cooled to room temperature in the furnace to obtain a ceramic powder;

[0141] In step eight, the foamy black xerogel is heated from room temperature to 350°C at a heating rate of 1°C / min, and kept at this temperature for 3 hours, and then heated to 850°C at a heating rate of 5°C / min, and kept at this temperature for 2 hours;

[0142] 9. Grinding:

[0143] Grind the ceramic powder obtained in step eight in a mortar, and then sieve to obtain ceramic powder with a particle size of 100 mesh;

[0144] 10. Granulation:

[0145] The polyvinyl alcohol and deionized water are uniformly mixed, and the polyvinyl alcohol is heated and stirred until the polyvinyl alcohol is completely dissolved to obtain a polyvinyl alcohol aqueous solution; the ceramic powder with a particle size of 100 mesh sieve and the polyvinyl alcohol aqueous solution are mixed and ground to obtain a uniform powder;

[0146] The heating and stirring temperature in step 10 is 75° C. and the stirring speed is 100 r / min;

[0147] The volume ratio of the ceramic powder with a particle size of 100 - mesh sieve to the polyvinyl alcohol aqueous solution described in Step Ten is 5:2;

[0148] The mass fraction of the polyvinyl alcohol aqueous solution described in Step Ten is 5%;

[0149] XI. Tabletting:

[0150] Place the uniform powder obtained in Step Ten into a mold and press it into a block;

[0151] In Step Eleven, place the uniform powder obtained in Step Ten into a mold, hold the pressure at 10 MPa for 3 min, and press it into a block;

[0152] XII. Debinding:

[0153] Heat the block obtained in Step Eleven from room temperature to 300 °C at a heating rate of 1 °C / min, then heat from 300 °C to 550 °C at a heating rate of 0.5 °C / min, then hold for 1 h, and finally cool from 550 °C to room temperature at a cooling rate of 5 °C / min to obtain a ceramic green body block without polyvinyl alcohol;

[0154] XIII. Sintering:

[0155] Under an oxygen atmosphere, embed the ceramic green body block without polyvinyl alcohol obtained in Step Twelve with the ceramic powder with a particle size of 100 - mesh sieve obtained in Step Nine, heat from room temperature to 1200 °C under an oxygen atmosphere, hold for a period of time under an oxygen atmosphere at a temperature of 1200 °C, and then cool to room temperature with the furnace under an oxygen atmosphere to obtain a magnetoelectric composite ceramic with an inlaid structure;

[0156] The heating rate described in Step Thirteen is 5 °C / min;

[0157] The holding time described in Step Thirteen is 15 min.

[0158] Figure 1 It is the backscattered electron image of the scanning electron microscope of the magnetoelectric composite ceramic with an inlaid structure prepared in Example 1;

[0159] Figure 1 It shows the grain morphology of the magnetoelectric composite ceramic with an inlaid structure prepared in Example 1. There are two types of grains in total, that is, small tetragonal grains are distributed inside large equiaxed grains. In addition, it also shows that the two types of grains present different colors. The light - colored small tetragonal grains are evenly dispersed in the large dark - colored equiaxed grains, and the light - colored small grains are completely inlaid inside the dark - colored large equiaxed grains, forming an inlaid structure. The light - colored grains are ferroelectric phase Pb 0.9625 Sm 0.025 (Mg 1 / 3 Nb2 / 3 ) 0.7 Ti 0.3 O3 is embedded with ferromagnetic phase CoFe2O4; black CoFe2O4 crystals are dispersed in light-colored Pb 0.9625 Sm 0.025 (Mg 1 / 3 Nb 2 / 3 ) 0.7 Ti 0.3 O3 grains present the expected embedded structure inside.

[0160] Figure 2 Hysteresis loop diagram of the magnetoelectric composite ceramic with an embedded structure prepared for Example 1;

[0161] From Figure 2 it can be seen that the magnetoelectric composite ceramic with an embedded structure prepared for Example 1 has good magnetic properties.

[0162] Figure 3 Electric hysteresis loop diagram of the magnetoelectric composite ceramic with an embedded structure prepared for Example 1;

[0163] From Figure 3 it can be seen that its remanent polarization intensity is 35.2 (μC / cm 2 ), and the electric hysteresis loop of the embedded structure multiferroic composite ceramic has a high squareness ratio and a small leakage current.

[0164] Figure 4 Magnetoelectric coupling coefficient diagram of the magnetoelectric composite ceramic with an embedded structure prepared for Example 1;

[0165] From Figure 4 it can be seen that the magnetoelectric composite ceramic with an embedded structure prepared for Example 1 has good magnetoelectric coupling performance.

Claims

1. A method for preparing a magnetoelectric composite ceramic with an inlaid structure by fractional crystallization, characterized in that The magnetoelectric composite ceramic with an inlaid structure is a ferroelectric phase aPb 0.9625 Sm 0.025 (Mg 1 / 3 Nb 2 / 3 ) 0.7 Ti 0.3 O3 inlaid with a ferromagnetic phase bCoFe2O4, where a is the amount of substance of Pb 0.9625 Sm 0.025 (Mg 1 / 3 Nb 2 / 3 ) 0.7 Ti 0.3 O3, b is the amount of substance of CoFe2O4, and 0.5 ≤ a ≤ 0.95, 0.05 ≤ b ≤ 0.5, a + b = 1; The method is specifically completed according to the following steps: I. Preparation of Sol A: ①. Add lead acetate, magnesium acetate, and samarium nitrate into anhydrous acetic acid, heat and stir for a period of time, then add tetrabutyl titanate, and stir at room temperature for a period of time to obtain Sol A; The molar ratio of lead element, magnesium element, samarium element and titanium element in sol A described in Step 1① is II. Preparation of Sol B: ①. Add niobium hydroxide and oxalic acid into deionized water, heat and stir for a period of time to obtain a niobium oxalate salt solution; ②. Mix hydrogen peroxide and citric acid, stir at room temperature for a period of time, and then adjust the pH value of the solution to 1 with dilute nitric acid to obtain Mixed Solution I; ③. Add the niobium oxalate salt solution obtained in step II① into the Mixed Solution I obtained in step II②, stir evenly to obtain Sol B; III. Preparation of Sol C: ①. Add ammonia water and citric acid into deionized water, stir at room temperature for a period of time to obtain Mixed Solution II; ②. Mix Sol A, Sol B, and Mixed Solution II, heat and stir for a period of time to obtain Sol C; The molar ratio of lead element, magnesium element, samarium element, titanium element and niobium element in the sol C described in Step 3② is In the Sol C described in step III②, the molar ratio of ammonia water to the total molar mass of lead element, magnesium element, and titanium element is 50:1; IV. Preparation of Sol D: Weigh cobalt salt as Raw Material 1; weigh iron nitrate as Raw Material 2; add Raw Material 1 and Raw Material 2 into deionized water, and stir at room temperature until the cobalt salt and iron nitrate are completely dissolved in deionized water to obtain Sol D; V. Preparation of Mixed Sol E: Fully mix Sol D and Sol C, heat and stir for a period of time to obtain Sol E; In step V, the molar ratio of Sol C to Sol D is a:b, where 0.5 ≤ a ≤ 0.95, 0.05 ≤ b ≤ 0.5, and a + b = 1; VI. Drying: Place Sol E in a dust-free environment, keep it at 80°C for a period of time to obtain a mixed dry gel; VII. Carbonization: Keep the mixed dry gel obtained in step VI at 180 - 200°C for a period of time to obtain a foamy black dry gel; VIII. Calcination: Heat the foamy black dry gel obtained in step VII from room temperature to 150°C - 400°C, keep it at this temperature for a period of time, then heat it to 650°C - 850°C, keep it at this temperature for a period of time, and cool it to room temperature with the furnace to obtain ceramic powder; IX. Grinding: Put the ceramic powder obtained in step VIII in a mortar for grinding, and then sieve it to obtain ceramic powder with a particle size of 100 - 160 mesh; X. Granulation: Mix polyvinyl alcohol and deionized water evenly, heat and stir until the polyvinyl alcohol is completely dissolved to obtain a polyvinyl alcohol aqueous solution; mix the ceramic powder with a particle size of 100 - 160 mesh and the polyvinyl alcohol aqueous solution, and then grind them to obtain a uniform powder; XI. Tabletting: Put the uniform powder obtained in step X into a mold and press it into a block; XII. Debinding: Heat the block obtained in step XI from room temperature to 500°C - 600°C, keep it at this temperature for a period of time, and cool it to room temperature with the furnace to obtain a ceramic green body block without polyvinyl alcohol; XIII. Sintering: In an oxygen atmosphere, the ceramic green body block without polyvinyl alcohol obtained in Step 12 is embedded with the ceramic powder having a particle size of 100-160 mesh obtained in Step 9, heated from room temperature to 1150°C - 1300°C in an oxygen atmosphere, held for a period of time under the conditions of an oxygen atmosphere and a temperature of 1150°C - 1300°C, and then cooled to room temperature with the furnace in an oxygen atmosphere to obtain a magnetoelectric composite ceramic with an inlaid structure.

2. A method for preparing a magnetoelectric composite ceramic with an inlaid structure by fractional crystallization according to claim 1, characterized in that The molar ratio of lead acetate to the volume of glacial acetic acid described in Step 1① is 0.9625 mmol:(5 mL - 15 mL); the temperature of heating and stirring described in Step 1① is 55°C - 65°C, and the speed of heating and stirring is 100 r / min - 300 r / min; the speed of stirring at room temperature described in Step 1① is 100 r / min - 300 r / min, and the stirring time at room temperature is 60 min - 120 min.

3. A method for preparing a magnetoelectric composite ceramic with an inlaid structure by fractional crystallization according to claim 1, characterized in that The speed of heating and stirring described in Step 2① is 100 r / min - 300 r / min, the heating and stirring time is 20 min - 40 min, and the heating and stirring temperature is 75°C - 85°C; the molar ratio of niobium hydroxide to oxalic acid described in Step 2① is 1:5; the molar ratio of niobium hydroxide to the volume of deionized water described in Step 2① is 0.467 mmol:(5 mL - 15 mL).

4. A method for preparing a magnetoelectric composite ceramic with an inlaid structure by fractional crystallization according to claim 1, characterized in that The concentration of dilute nitric acid described in Step 2② is 2 mol / L - 4 mol / L; the molar ratio of H2O2 in hydrogen peroxide to oxalic acid described in Step 2① is 13:1; the molar ratio of niobium hydroxide described in Step 2① to citric acid described in Step 2② is 1:4; the speed of stirring described in Step 2② is 100 r / min - 300 r / min, and the stirring time is 20 min - 40 min.

5. A method for preparing a magnetoelectric composite ceramic with an inlaid structure by fractional crystallization according to claim 1, characterized in that The volume ratio of niobium oxalate solution to Mixed Solution Ⅰ described in Step 2③ is 1:1; the molar ratio of ammonia water to citric acid in Mixed Solution Ⅱ described in Step 3① is 50:1; the mass fraction of ammonia water described in Step 3① is 20% - 30%; the speed of stirring described in Step 3① is 100 r / min - 300 r / min, and the stirring time is 20 min - 40 min; the volume ratio of ammonia water to deionized water described in Step 3① is 5:

2.

6. A method for preparing a magnetoelectric composite ceramic with an inlaid structure by fractional crystallization according to claim 1, characterized in that The speed of heating and stirring described in Step 3② is 100 r / min - 300 r / min, the heating and stirring time is 20 min - 40 min, and the heating and stirring temperature is 75°C - 85°C; the molar ratio of Raw Material 1 to Raw Material 2 described in Step 4① is 1:2; the cobalt salt described in Step 4① is cobalt nitrate or cobalt acetate; the speed of stirring described in Step 4① is 100 r / min - 300 r / min; the total molar amount of Raw Material 1 and Raw Material 2 described in Step 4 and the volume ratio of deionized water is 3 mmol:(2 mL - 10 mL).

7. A method for preparing a magnetoelectric composite ceramic with an inlaid structure by fractional crystallization according to claim 1, characterized in that The temperature of heating and stirring described in Step 5 is 70°C to 80°C, the speed of heating and stirring is 100 r / min to 300 r / min, and the time of heating and stirring is 60 min to 75 min; the time of heat preservation described in Step 6 is 18 h to 36 h.

8. A method for preparing a magnetoelectric composite ceramic with an inlaid structure by fractional crystallization according to claim 1, characterized in that The time of heat preservation described in Step 7 is 60 min to 70 min; in Step 8, the foamy black xerogel is heated from room temperature to 150°C to 400°C at a heating rate of 1°C / min to 5°C / min, and heat preservation is carried out at this temperature for 1 h to 3 h, and then heated to 650°C to 850°C at a heating rate of 5°C / min to 15°C / min, and heat preservation is carried out at this temperature for 1 h to 2 h.

9. A method for preparing a magnetoelectric composite ceramic with an inlaid structure by fractional crystallization according to claim 1, characterized in that The temperature of heating and stirring described in Step 10 is 50°C to 100°C, and the stirring speed is 100 r / min to 300 r / min; the volume ratio of the ceramic powder with a particle size of 100 to 160 mesh sieve to the polyvinyl alcohol aqueous solution in Step 10 is 5:2; the mass fraction of the polyvinyl alcohol aqueous solution described in Step 10 is 5% to 15%.

10. A method for preparing a magnetoelectric composite ceramic with an inlaid structure by fractional crystallization according to claim 1, characterized in that In Step 11, the uniform powder obtained in Step 10 is placed in a mold, and pressure is maintained for 2 min to 4 min under the condition of a pressure of 8 MPa to 10 MPa to form a block; in Step 12, the block obtained in Step 11 is heated from room temperature to 500°C to 600°C at a heating rate of 0.5°C / min to 1.5°C / min, and heat preservation is carried out at this temperature for 30 min to 120 min; the heating rate described in Step 13 is 5°C / min to 10°C / min; the time of heat preservation described in Step 13 is 15 min to 120 min.

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