TWI413629B - Process for single crystal phase barium ferrite ceramics and method for increasing ferroelectric and ferromagnetic properties thereof - Google Patents

Abstract

This invention provides a synthesis method of BiFeO3 ceramics, in which ferroelectric and ferromagnetic properties were enhanced. The importance is that the single-phase BiFeO3 can be acquired under certain sintering conditions without cleaning of impurities. This synthesis has an efficient reproducibility to manufacture BiFeO3 ceramics; In addition, this invention can efficiently reduce the electric leakage of BiFeO3 ceramics by using various substitutions of rare-earth elements in BiFeO3 structure and different sintering processes. It can also enhance ferroelectric and ferromagnetic properties.

Description

Process for single crystal phase barium ferrite ceramics and method for increasing ferroelectric and ferromagnetic properties thereof

The invention provides a single crystal phase barium ferrite ceramic process and a method for increasing ferroelectric and ferromagnetic properties, in particular to a process of barium ferrite ceramics, which can improve leakage phenomenon of barium ferrite ceramics and increase ferroelectricity and iron The method of magnetic quality.

In recent years, iron-clad materials have attracted great interest. Among them, barium ferrite is considered to be in information storage, integrated circuits, magnetic sensors and spins because of its ferroelectricity and weak ferromagnetism at room temperature. Electronic devices and the like can be widely used; currently, when barium ferrite is applied to a piezoelectric material, it can replace a lead-containing piezoelectric material to become a new generation of green energy material; barium ferrite (chemical formula: BiFeO ₃ ) iron The electric Curie point is 820 ° C, and the antiferromagnetic Neel point is 370 ° C. It is a very rare iron-based ceramic material that has ferroelectric and ferromagnetic properties above room temperature, but due to the melting point of cerium oxide. Too low, and the oxygen vacancy and current leakage caused by the electron transfer of iron ions, make the material and the actual component application have a very large gap, resulting in the quality of commercially available materials is also uneven.

In addition, although the iron electrodeposition amount of barium ferrite is theoretically higher than 100 μC/cm ² , it is difficult to prepare pure barium ferrite due to its secondary phase and various defects, which makes it difficult to measure its true state. Iron electrodeification, there are many preparation methods, such as solid phase sintering, rapid liquid phase sintering, sol-gel method, hydrothermal method and arc method; among them, solid phase sintering method is to iron oxide powder and cerium oxide The powder is uniformly mixed and sintered at a high temperature, but the melting point of the iron oxide is 1566 ° C, and the melting point of the cerium oxide is 817 ° C. Therefore, when the sintering temperature is higher than the melting point of cerium oxide, a large amount of liquid cerium oxide is volatilized. If the sintering temperature is too low, the reaction between cerium oxide and iron oxide may be incomplete, and in both cases, a large amount of impurities will be generated; although the method for solving this problem is currently used, the method of using nitric acid and barium ferrite The impurity (unreacted cerium oxide or Bi ₂ Fe ₄ O ₉ ) is reacted, and a single crystal phase of barium ferrite is obtained after filtration; however, the barium ferrite powder obtained by washing away the impurities with nitric acid is rather rough in quality. And the re-creation of this process Very poor, it is not the best solution.

Therefore, the above problems will be the difficulties that the technicians in this field want to solve.

Therefore, the inventors of the present invention have proposed a single crystal phase barium ferrite ceramic process and a method of increasing ferroelectric and ferromagnetic properties in view of the above-mentioned deficiencies of the prior art, which mainly have the following objectives: The purpose is to form a single crystal phase by directly forming barium ferrite ceramics with special environmental conditions and sintering methods, and the barium ferrite ceramic can reach a single crystal phase without additional steps of removing impurities, which has excellent performance. The remanufacturability can be produced in large quantities.

The second object of the present invention is to effectively improve the leakage of barium ferrite material. The method provides several kinds of dopants and a synthesis method thereof, and a single crystal phase dopant-containing barium ferrite material can be obtained. The method is to incorporate barium titanate and strontium in the process of manufacturing barium ferrite ceramics, thereby improving the ferroelectric and ferromagnetic properties of barium ferrite ceramics and reducing leakage.

In order to achieve the above objects and effects, only a preferred embodiment will be described herein, and those skilled in the art will be able to carry out the various embodiments.

First, please refer to the first figure, which is a flow chart 1 of the present invention, which clearly indicates the preparation procedure of the ferrite ceramic material barium ferrite ceramic:

(1) firstly mixing cerium oxide powder (purity: 99.99%, particle diameter less than 45 μm) with iron oxide powder (purity: 99.99%, particle size less than 45 μm) in a molar ratio of 1.1:1;

(2) Adding a plurality of grinding balls (aluminum oxide material, diameter 10 mm) and placing them in a ball mill jar (aluminum oxide material, volume 400 ml, inner diameter 74.35 mm), the ratio of the weight of the mixed powder (g) to the number of grinding balls is 1. :1, then adding 99.5% pure alcohol, the ratio of the weight of the mixed powder to the grinding ball mixture (g) to the volume of the alcohol (ml) is 1:0.5, and then the ball grinding pot is placed on a ball mill for grinding, the ball grinding tank The ratio of the inner diameter (mm) to the ball mill speed (rpm) is 1:1.5, and the grinding is continuously performed at a speed of 120 revolutions per minute for 24 hours;

(3) The mixed powder is sent to an oven and baked at a temperature of 120 ° C to remove water in the mixed powder. After the mixed powder is completely dried, it is placed in a shaker and sieved at 70 mesh (pore size: 212 μm). Screening

(4) The mixed powder is placed in a zirconia crucible for calcination, the maximum temperature is 750 ° C to 850 ° C, the calcination time is 1 to 10 hours, and the screen is 70 mesh (pore diameter 212 μm). Sifted, can not be sieved mixed powder, can be polished with stainless steel or agate, crushed, placed in a shaker, shaken to complete sieving, the calcination temperature parameters are shown in Table 1;

(5) Adding a plurality of grinding balls (zirconia material, diameter 3 mm) and placing them in a ball mill jar (zirconia material, volume 250 ml, inner diameter 75.80 mm), the volume ratio of the grinding ball to the grinding pot is 1:3 To 1:4, fill 1/3 of the ball mill jar with a grinding ball, and then add alcohol so that the ratio of the weight (g) of the mixed powder to the grinding ball to the volume of the alcohol (ml) is 1:0.4 to 1:0.6. The ball mill jar is then placed on a ball mill for grinding. The ratio of the inner diameter (mm) to the rotational speed (rpm) of the ball mill tank is between 1:4 and 1:6, and is reversed at 400 rpm and every 30 minutes. In the manner of continuous grinding for 12 hours, baking at 120 ° C, and sieving through a sieve of 70 mesh (pore size: 212 μm);

(6) further adding a polyvinyl alcohol solution, the solution is prepared by mixing polyvinyl alcohol powder and water at a weight ratio of 1:9, and the mixing weight ratio of the mixed powder to the polyvinyl alcohol solution is 10:1, and then Screening of 70 mesh (212 μm pore size);

(7) Reserve a small portion of the mixed powder, and the remaining mixed powder is compressed into a composite block by a tableting machine at a pressure of 5 ton/cm ² ;

(8) Take half of the reserved mixed powder and lay it on the zirconia crucible. Then, the synthetic block is placed on the powdered zirconia crucible, and then the remaining mixed powder is used to cover the composite block to complete the back cover. The upper lid is sent to a high temperature furnace for sintering. The sintering temperature is as shown in Table 2. The maximum temperature is between 800 ° C and 950 ° C. The sintering time is 1 to 10 hours, and then it can be obtained by rapid cooling. For the single crystal phase of barium ferrite ceramics, please refer to the second figure, which is the X-ray diffraction spectrum of barium ferrite, which indicates that the barium ferrite ceramics produced by the method is a single crystal phase.

Please refer to the third figure, which is a flow chart 2 of the present invention. The method for preparing a barium ferrite ceramic doped barium titanate is clearly indicated, and barium titanate is added to barium ferrite to improve the barium ferrite ceramic. Leakage, the method steps are:

(1) firstly mixing cerium oxide powder (purity: 99.99%, particle diameter less than 45 μm) with iron oxide powder (purity: 99.99%, particle size less than 45 μm) in a molar ratio of 1.0:1;

(2) Adding a plurality of grinding balls (aluminum oxide material, diameter 10 mm) and placing them in a ball mill jar (aluminum oxide material, volume 400 ml, inner diameter 74.35 mm), the ratio of the weight of the mixed powder (g) to the number of grinding balls is 1. :1, then adding 99.5% pure alcohol, the ratio of the weight of the mixed powder to the grinding ball mixture (g) to the volume of the alcohol (ml) is 1:0.5, and then the ball grinding pot is placed on a ball mill for grinding, the ball grinding tank The ratio of the inner diameter (mm) to the ball mill rotation speed (rpm) is 1:1.5, thereby continuously grinding for 24 hours;

(3) The mixed powder is sent to an oven and baked at a temperature of 120 ° C to remove water in the mixed powder. After the mixed powder is completely dried, it is placed in a shaker and sieved at 70 mesh (pore size: 212 μm). Screening

(4) The mixed powder is placed in a zirconia crucible for calcination, the maximum temperature is 750 ° C to 850 ° C, the calcination time is 1 to 10 hours, and the screen is 70 mesh (pore diameter 212 μm). Screening

(5) adding barium titanate powder (purity of 99.99%, particle size of less than 45), adding barium titanate powder to the mixed powder, the molar ratio of 2:1 to 19:1;

(6) Adding a plurality of grinding balls and placing them in a ball mill jar, the volume ratio of the grinding balls to the grinding pot is 1:3 to 1:4, and then adding alcohol (purity 99.5%) to make the mixed powder and the grinding ball The ratio of the mixture weight (g) to the alcohol volume (ml) is 1:0.5, and the ball mill can be placed on a ball mill for grinding. The ratio of the inner diameter (mm) to the rotation speed (rpm) of the ball mill tank is 1: 4 to 1:6, the ball mill has a grinding time of 10 to 14 hours, is further baked at 120 ° C, and sieved through a sieve of 70 mesh (pore size: 212 μm);

(7) further adding a polyvinyl alcohol solution, the solution is prepared by mixing polyvinyl alcohol powder and water at a weight ratio of 1:8 to 1:10, and the mixing weight ratio of the mixed powder to the polyvinyl alcohol solution is 8: 1 to 12:1, and then sieved through a sieve of 70 mesh (212 μm pore diameter);

(8) using a tableting machine, pressing the mixed powder into a composite block at a pressure of 5 ton/cm ² ;

(9) The synthetic block is coated with mixed powder on the upper and lower sides, and is placed on a zirconia crucible and sent to a high temperature furnace for sintering. The maximum temperature is between 890 ° C and 1000 ° C, and the sintering time is 1 to 10 In the hour, the calcination temperature parameters are shown in Table 3. The single crystal phase barium ferrite ceramics can be obtained by rapid cooling, and the fourth figure is the X-ray diffraction spectrum of barium ferrite-doped barium titanate. The barium ferrite ceramics produced by the method is a single crystal phase; the fifth figure shows the hysteresis curve of barium ferrite doped barium titanate, and the sixth figure shows the leakage current of barium ferrite doped with 20% barium titanate. Therefore, it can be seen that the barium titanate doped with barium titanate can greatly increase the amount of polarization and obtain better ferroelectric properties.

Please refer to the seventh figure, which is a flow chart 3 of the present invention, which clearly indicates a method for preparing a barium ferrite ceramic doped germanium, which is doped with barium strontium strontium sulphate to improve the leakage phenomenon of barium ferrite ceramics. The method steps are:

(1) First, cerium oxide powder (purity: 99.99%, particle size less than 45 μm) and iron oxide powder (purity: 99.99%, particle size less than 45 μm) and cerium oxide (purity: 99.95%, particle size less than 45 μm) powder, in Mo Ear ratio is 1:1: 0.1 to 1.09: 1:0.01 ratio mixing;

(2) Adding a plurality of grinding balls (aluminum oxide material, diameter 10 mm) and placing them in a ball mill jar (aluminum oxide material, volume 400 ml, inner diameter 74.35 mm), the ratio of the weight of the mixed powder (g) to the number of grinding balls is 1. :1, then adding 99.5% pure alcohol, the ratio of the weight of the mixed powder to the grinding ball mixture (g) to the volume of the alcohol (ml) is 1:0.5, and then the ball grinding pot is placed on a ball mill for grinding, the ball grinding tank The ratio of the inner diameter (mm) to the ball mill rotation speed (rpm) is 1:1.5, thereby continuously grinding for 24 hours;

(3) The mixed powder is sent to an oven and baked at a temperature of 120 ° C to remove water in the mixed powder. After the mixed powder is completely dried, it is placed in a shaker and sieved at 70 mesh (pore size: 212 μm). Screening

(4) The mixed powder is placed in a zirconia crucible for calcination, the maximum temperature is 850 ° C to 950 ° C, the calcination time is 1 to 10 hours, and the sieve is 70 mesh (the pore size is 212 μm). After sieving, the calcination temperature parameters are shown in Table 4;

(5) Adding a plurality of grinding balls (zirconia material, diameter 3 mm) and placing them in a ball mill jar (zirconia material, volume 250 ml, inner diameter 75.80 mm), the volume ratio of the grinding ball to the grinding pot is 1:3 To 1:4, fill 1/3 of the ball mill jar with a grinding ball, and then add alcohol so that the ratio of the weight (g) of the mixed powder to the grinding ball to the volume of the alcohol (ml) is 1:0.4 to 1:0.6. The ball mill jar is then placed on a ball mill for grinding. The ratio of the inner diameter (mm) to the rotational speed (rpm) of the ball mill tank is between 1:4 and 1:6, and is reversed at 400 rpm and every 30 minutes. In the manner of continuous grinding for 12 hours, baking at 120 ° C, and sieving through a sieve of 70 mesh (pore size: 212 μm);

(6) further adding a polyvinyl alcohol solution, the solution is prepared by mixing polyvinyl alcohol powder and water at a weight ratio of 1:9, and the mixing weight ratio of the mixed powder to the polyvinyl alcohol solution is 10:1, and then Screening of 70 mesh (212 μm pore size);

(7) Reserve a small portion of the mixed powder, and the remaining mixed powder is compressed into a composite block by a tableting machine at a pressure of 5 t/cm 2 ;

(8) Take half of the reserved mixed powder and lay it on the zirconia crucible. Then, the synthetic block is placed on the powdered zirconia crucible, and then the remaining mixed powder is used to cover the composite block to complete the back cover. The upper lid is sent to a high temperature furnace for sintering. The sintering temperature is as shown in Table 5. The maximum temperature is between 850 ° C and 950 ° C. The sintering time is 1 to 10 hours, and then it can be obtained by rapid cooling. The single crystal phase barium ferrite ceramics doped with yttrium, please refer to the eighth figure, which is the X-ray diffraction spectrum of the single crystal phase lanthanum ferrite ceramic doped with yttrium, which can explain the doping of yttrium produced by the method. The barium ferrite crystal is a single crystal phase.

In the above, the above is a preferred embodiment of the present invention, and the scope of the patent is not limited thereby, and the scope of the patent should be determined by the scope of the patent application attached below.

S1~S8. . . Flow chart one

A1~a9. . . Flow chart two

B1~b8. . . Flow chart three

The first figure is a flow chart 1 of the present invention.

The second figure is an X-ray diffraction spectrum of the barium ferrite of the present invention.

The third figure is a flow chart 2 of the present invention.

The fourth figure is an X-ray diffraction spectrum of the barium ferrite doped 20% barium titanate of the present invention.

The fifth graph is a graph of the hysteresis of 5% barium titanate doped with barium ferrite of the present invention.

The sixth figure is a graph of the leakage current of the barium ferrite doped 20% barium titanate of the present invention.

The seventh drawing is the third flowchart of the present invention.

The eighth figure is a X-ray diffraction spectrum of 5% bismuth doped with barium ferrite of the present invention.

S1~S8. . . Flow chart one

Claims (13)

A method for preparing a single crystal phase barium ferrite ceramics, wherein the barium ferrite is brought to a single crystal phase without impurities, and the method steps are as follows: (1) a powder mixing step, the cerium oxide powder and the iron oxide powder are in a molar number of 1.0. : a ratio of 1 to 1.2:1; (2) a first powder grinding step, adding abrasive material and alcohol to the grinding vessel, the ratio of the weight (g) of the mixed powder to the abrasive material mixture to the volume of the alcohol (ml) The grinding container is further placed in a grinding machine for continuous grinding for 20 to 24 hours; (3) the baking powder step is baked at a temperature of 120 ° C to remove moisture in the mixed powder, to be mixed powder. After completely drying, it is sieved again; (4) calcining powder step, the mixed powder is calcined, the maximum temperature is 750 ° C to 850 ° C, and the calcination time is 1 to 10 hours, and then sieved; 5) The second powder grinding step, adding the abrasive material and the alcohol to the grinding container, the ratio of the weight (g) of the mixed powder to the abrasive material mixture and the volume of the alcohol (ml) is 1:0.4 to 1:0.6, and then reset Continuous grinding in a grinding machine for 10 to 14 hours, then through temperature 120 Baking and sieving; (6) adding a binder step, adding a polyvinyl alcohol solution, which is prepared by mixing polyvinyl alcohol powder and water at a weight ratio of 1:8 to 1:10, and mixing the powder with the poly The vinyl alcohol solution is mixed in a weight ratio of 8:1 to 12:1, and then sieved; (7) the powder is pressed into a block step, and the mixed powder is pressed into a composite block at a pressure of 1 to 5 ton/cm ² (8) sintering into a single crystal phase barium ferrite ceramic step, the synthetic bulk material is sent to a high temperature furnace for sintering, the highest temperature is between 800 ° C and 950 ° C, the sintering time is 1 to 10 hours, and then A single crystalline phase of barium ferrite ceramics can be obtained by rapid cooling. The method for preparing a single crystal phase barium ferrite ceramic according to claim 1, wherein when the mixed powder is calcined, the mixed powder which cannot be sieved can be ground and then ground using stainless steel or agate honing. Shake the sieve and shake it until it is completely sieved. A method for increasing the ferroelectric and ferromagnetic properties of barium ferrite ceramics by incorporating barium titanate into the barium ferrite crystal to improve the leakage phenomenon of barium ferrite ceramics and increasing the ferroelectric and ferromagnetic properties thereof. The steps are: (1) a powder mixing step of mixing the cerium oxide powder and the iron oxide powder in a molar ratio of 1.0:1 to 1.2:1; (2) the first powder grinding step, adding the abrasive material and the alcohol to the grinding In the container, the ratio of the weight (g) of the mixed powder to the abrasive material mixture to the volume of the alcohol (ml) is 1:0.4 to 1:0.6, and the grinding container is further placed in a grinding machine for continuous grinding for 20 to 24 hours; a baking powder step, baking at a temperature of 120 ° C to remove moisture in the mixed powder, and then sieving after the mixed powder is completely dried; (4) calcining the powder step, calcining the mixed powder, the highest temperature system 750 ° C to 850 ° C, the calcination time is 1 to 10 hours, and then sieved; (5) adding barium titanate powder step, adding barium titanate powder to the mixed powder, the molar ratio is 2 : 1 to 19:1; (6) second powder grinding step, adding abrasive materials and wine In the grinding vessel, the ratio of the weight (g) of the mixed powder to the abrasive material mixture to the volume of the alcohol (ml) is 1:0.4 to 1:0.6, and then placed in a grinding machine for continuous grinding for 10 to 14 hours, and then passed through the temperature. Baking and sieving at 120 ° C; (7) adding a binder step, adding a polyvinyl alcohol solution, which is prepared by mixing polyvinyl alcohol powder with water at a weight ratio of 1:8 to 1:10, and mixing the powder The mixing weight ratio with the polyvinyl alcohol solution is 8:1 to 12:1, and then sieved; (8) the powder is pressed into a block step, and the mixed powder is pressed into a synthesis at a pressure of 1 to 5 ton/cm ² (9) sintering into a single crystal phase barium ferrite ceramic step, the composite block is sent to a high temperature furnace for sintering, the maximum temperature is between 890 ° C and 1000 ° C, the sintering time is 1 to 10 hours Then, a single crystal phase barium ferrite ceramic doped with barium titanate can be obtained by rapid cooling. A method for increasing the ferroelectric and ferromagnetic properties of barium ferrite ceramics by doping germanium in a barium ferrite crystal to improve the leakage phenomenon of the barium ferrite ceramics and increasing the ferroelectric and ferromagnetic properties thereof. : (1) a powder mixing step, first mixing the cerium oxide powder, the iron oxide powder and the cerium oxide in a molar ratio of 1:1:0.1 to 1.09:1:0.01; (2) the first powder grinding step, adding Grinding material and alcohol into the grinding container, the ratio of the weight (g) of the mixed powder to the abrasive material mixture and the volume of the alcohol (ml) is 1:0.4 to 1:0.6, and the grinding container is placed in a grinding machine for continuous grinding 20 (4) baking powder step, baking at a temperature of 120 ° C to remove water in the mixed powder, and then sieving the mixed powder after completely drying; (4) calcining the powder step, mixing the powder For calcination, the maximum temperature is 850 ° C to 950 ° C, the calcination time is 1 to 10 hours, and then sieved; (5) the second powder grinding step, adding the abrasive material and alcohol to the grinding vessel, Weight (g) of mixed powder and abrasive material mixture and alcohol body (ml) ratio of 1:0.4 to 1:0.6, and then placed in a grinding machine for 10 to 14 hours of continuous grinding, and then baked and sifted at a temperature of 120 ° C; (6) adding a binder step, adding polyethylene An alcohol solution prepared by blending a polyvinyl alcohol powder with water at a weight ratio of 1:8 to 1:10, and mixing the powder and the polyvinyl alcohol solution in a weight ratio of 8:1 to 12:1. Screening; (7) powder pressing into a block step, pressing the mixed powder into a composite block at a pressure of 1 to 5 ton/cm ² ; (8) sintering into a single crystal phase barium ferrite ceramic step, the synthetic block The material is sent to a high temperature furnace for sintering, and the maximum temperature is between 850 ° C and 950 ° C, and the sintering time is 1 to 10 hours, and then the single crystal phase barium ferrite ceramic doped with cerium is obtained by rapid cooling. A method for producing a single crystal phase barium ferrite ceramic according to any one of claims 1, 3, or 4, and a method for increasing ferroelectric and ferromagnetic properties, wherein the first powder grinding step, The abrasive material may be a plurality of grinding balls, and the ratio of the weight (g) of the mixed powder to the number of grinding balls is 1:0.8 to 1:1.2. A method for producing a single crystal phase barium ferrite ceramic according to any one of claims 1, 3, or 4, and a method for increasing ferroelectric and ferromagnetic properties, wherein the first powder grinding step, The grinding vessel can be a ball mill tank, and the grinding machine can be a ball mill having a ratio of the inner diameter (mm) of the ball mill tank to the ball mill speed (rpm) of 1:1.5 to 1:2.0. The method for preparing a single crystal phase lanthanum ferrite ceramic according to any one of the preceding claims, wherein the method of baking the powder can be The mixed powder is placed in an oven. A method for producing a single crystal phase lanthanum ferrite ceramic according to any one of the preceding claims, wherein the method of adding a ferroelectric and a ferromagnetic material, wherein the sieving is carried out It was placed in a shaker and sieved through a sieve of 70 mesh (212 μm pore size). A method for preparing a single crystal phase lanthanum ferrite ceramic according to any one of claims 1 to 3, or a method for increasing ferroelectric and ferromagnetic properties, wherein the calcining powder step can be The mixed powder was placed in a zirconia crucible for calcination. A method for producing a single crystal phase lanthanum ferrite ceramic according to any one of claims 1 to 3, or a method for increasing ferroelectric and ferromagnetic properties, wherein the second powder grinding step, The abrasive material may be a plurality of abrasive balls, and the grinding container may be a ball mill tank having a volume ratio of 1:3 to 1:4. A method for producing a single crystal phase barium ferrite ceramic according to any one of claims 1 to 3, or a method for increasing ferroelectric and ferromagnetic properties, wherein the grinding vessel can be a ball mill. The can, and the grinding machine may be a ball mill having a ratio of an inner diameter (mm) of the ball mill to a ball mill speed (rpm) of 1:4 to 1:6. A method for producing a single crystal phase lanthanum ferrite ceramic according to any one of claims 1 to 3, or a method for increasing ferroelectricity and ferromagnetic property, wherein the powder is pressed into a bulk material step, A tablet press can be used. A method for producing a single crystal phase lanthanum ferrite ceramic according to any one of claims 1 to 3, or a method for increasing ferroelectric and ferromagnetic properties, wherein the sintering into a single crystal phase ferrite In the ceramic step, the upper and lower sides of the composite block are coated with a mixed powder and laid flat on a zirconia crucible for sintering.