CN103771848B - La0.1Bi0.9FeO3/CoFe2O4 magneto-electricity compound powder body and preparation method thereof - Google Patents

Abstract

The invention relates to a La0.1Bi0.9FeO3/CoFe2O4 magneto-electricity compound powder body and a preparation method thereof. The preparation method comprises the steps: according to a chemical general formula xLa0.1Bi0.9FeO3/(1-x)CoFe2O4, adding analytical-grade Fe(NO3)3.9H2O, Bi(NO3)3.9H2O, La (NO3)3.6H2O and Co(NO3)2.6H2O in distilled water to prepare a solution, wherein x is a mass percent of the La0.1Bi0.9FeO3, and is not less than 0.6 and not more than 0.9; adding citric acid in the solution, uniformly stirring, adjusting the pH value to obtain a uniform sol B; and drying the sol B and calcining. The invention is a method for rapidly preparing the La0.1Bi0.9FeO3/CoFe2O4 magneto-electricity compound powder body at a lower temperature; and the method is simple in process and energy-saving; and the prepared magneto-electricity compound powder body is better in uniformity.

Description

A kind of La0.1Bi0.9FeO3/CoFe2O4 magnetoelectric composite powder and its preparation method

technical field

The invention belongs to the field of material science, and specifically relates to a La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder and a preparation method thereof.

Background technique

Multiferroic materials are a large class of very important advanced functional materials. Components made of multiferroic materials have the functions of converting, transmitting, processing information, storing energy, saving energy, etc., and are widely used in energy, telecommunications, automatic Control, communication, household appliances, biology, medical and health, light industry, mineral processing, physical prospecting, military industry and other fields. With the rapid development of mobile communication and computer technology, all kinds of electronic equipment are required to become more highly integrated, multi-functional, miniaturized and fast-responsive, thus putting forward higher standards for materials, requiring components not only with large capacity , miniaturization, high speed, and has the characteristics of reliability, durability, vibration resistance and low cost, which requires the development of new materials with two or more functions at the same time, multiferroic materials have also become a A new hot research field in the world, in which BiFeO ₃ with a perovskite structure has become an important material for everyone to study, because BiFeO ₃ is the only material that has both ferroelectricity and antiferromagnetism above room temperature, and its ferroelectricity ranks The inner temperature is TC=830°C, the antiferromagnetic Niel temperature is TN=370°C, and there is a coupling effect between the two ferrotypes, that is, the electrical properties are adjusted by the magnetic field, or the magnetic properties are controlled by the electric field.

At present, there are three prominent problems in BiFeO ₃ : (1) Since Bi is easy to volatilize, the balance of kinetics and thermodynamics must be taken into consideration during synthesis, so it is difficult to obtain pure phase BiFeO ₃ . The control of BiFeO ₃ growth process and conditions has become a challenging work; (2) The large leakage current makes it difficult to measure the ferroelectricity; (3) The special G-type antiferromagnetic structure of BiFeO ₃ makes the macroscopic size of BiFeO ₃ It exhibits very weak antiferromagnetism at room temperature, which seriously hinders the development of _BiFeO3 for practical applications. Now in industrial production, spherical magnetoelectric materials should have as large a coercive field as possible, high saturation magnetization and high magnetoelectric coupling coefficient, etc., in order to obtain magnetoelectric materials with high saturation magnetization and high coercive force, Usually people choose to use doping modification or compound with different materials to achieve this purpose. For example, a hard magnetic/soft magnetic compound is composed of a hard magnetic phase and a soft magnetic phase, and there is a strong exchange coupling between them. In the reverse magnetization process, affected by the magnetic moment of the hard magnetic layer, the distribution of the deflection direction of the magnetic moment in the soft magnetic layer is continuous. The larger the reverse magnetization field or the farther away from the interface, the closer the magnetic moment is to the direction of the external field, and The magnetic moment can rotate reversibly when the magnetic field is less than the exchange coupling critical field. For the ABO ₃ -type cachinite ferroelectric material, the substitution of A-site ions and B-site ions can realize its structure adjustment, and finally achieve the purpose of changing the performance. Doping BiFeO ₃ with certain elements can reduce the leakage current and improve the bismuth ferrite. Magnetic and electrical properties; CoFe ₂ O ₄ has high coercive field and saturation magnetization, and the introduction of CoFe ₂ O ₄ can improve the magnetic properties of BiFeO ₃ .

Usually, the method for preparing magnetoelectric composite powders is to prepare each single-phase powders separately by solid-phase method firstly, and then perform mechanical mixing. This method not only requires a high calcination temperature due to the complex process, but also the prepared composite powder is mixed on the grain size, resulting in relatively poor uniformity, which ultimately directly affects the performance of the composite powder.

Contents of the invention

The object of the present invention is to overcome the problems in the prior art and provide La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder and its preparation method, which has a relatively low preparation temperature and simple method, and the prepared La _0.1 Bi The uniformity of _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder is better.

To achieve the above object, the present invention adopts the following technical solutions:

A preparation method of La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder, comprising the following steps:

1) According to the general chemical formula xLa _0.1 Bi _0.9 FeO ₃ /(1-x)CoFe ₂ O ₄ , analytically pure Fe(NO ₃ ) ₃ ·9H ₂ O, Bi(NO ₃ ) ₃ ·9H ₂ O, La (NO ₃ ) ₃ ·6H ₂ O and Co(NO ₃ ) ₂ ·6H ₂ O were added to distilled water to prepare a solution; wherein, x is the mass percentage of La _0.1 Bi _0.9 FeO ₃ , and 0.6≤x≤0.9;

2) Add citric acid to the solution in step 1), heat and stir at 80-100°C to obtain sol A, wherein the molar amount of citric acid added is the total amount of iron ions, bismuth ions, lanthanum ions, and cobalt ions in the solution. 2-4 times the molar weight;

3) Under stirring, adjust the pH value of sol A to 6.5-7.5 to obtain uniform sol B;

4) Sol B was dried at 180-200°C to obtain a dark brown loose xerogel;

5) After grinding the xerogel, calcining at 700-800°C for 1-4h to obtain La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder.

The heating in the step 2) is realized by heating in a water bath.

The stirring time in the step 2) is 1-2 hours.

The pH value in the step 3) is adjusted by using ethylenediamine or ammonia water.

The drying time in step 4) is 2-4 hours.

The drying in step 4) is carried out in a vacuum oven.

Calcination in step 5) is carried out in an electric furnace.

A La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder, characterized in that the general chemical formula of the La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder is xLa _0.1 Bi _0.9 FeO ₃ /(1-x)CoFe ₂ O ₄ , wherein, x is the mass percentage of La _0.1 Bi _0.9 FeO ₃ , and 0.6≤x≤0.9.

Compared with the prior art, the present invention has beneficial effects: the present invention uses Fe(NO ₃ ) ₃ ·9H ₂ O, Bi(NO ₃ ) ₃ ·9H ₂ O, La(NO ₃ ) ₃ ·6H ₂ O, Co (NO ₃ ) ₂ ·6H ₂ O and citric acid are used as raw materials, adjusted pH, dried, and calcined at 700-800°C to obtain La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder; prepared by the present invention The temperature is low, the method is simple, and energy is saved; the La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder prepared by the present invention has better uniformity, and as the content of CoFe ₂ O ₄ in the composite powder increases, The saturation magnetization increased from 4.8emu/g to 26.1emu/g, and the coercive field increased from 1260.14 Oersted to 1930.73 Oersted, which overcomes the high synthesis temperature and the obtained composite powder in the existing method for preparing composite powder. The problem of poor powder performance.

Description of drawings

Figure 1 is the XRD pattern of the composite powder calcined at 700°C when the mass percentage of La _0.1 Bi _0.9 FeO ₃ is 90% and the mass percentage of CoFe ₂ O ₄ is 10%.

Figure 2 is the XRD pattern of the composite powder calcined at 700°C when the mass percentage of La _0.1 Bi _0.9 FeO ₃ is 80% and the mass percentage of CoFe ₂ O ₄ is 20%.

Figure 3 is the XRD pattern of the composite powder calcined at 700°C when the mass percentage of La _0.1 Bi _0.9 FeO ₃ is 70% and the mass percentage of CoFe ₂ O ₄ is 30%.

Figure 4 is the XRD pattern of the composite powder calcined at 700°C when the mass percentage of La _0.1 Bi _0.9 FeO ₃ is 60% and the mass percentage of CoFe ₂ O ₄ is 40%.

Figure 5 is an SEM image of the composite powder calcined at 700°C when the mass percentage of La _0.1 Bi _0.9 FeO ₃ is 90% and the mass percentage of CoFe ₂ O ₄ is 10%.

Fig. 6 is an SEM image of the composite powder calcined at 700°C when the mass percentage of La _0.1 Bi _0.9 FeO ₃ is 80% and the mass percentage of CoFe ₂ O ₄ is 20%.

Figure 7 is an SEM image of the composite powder calcined at 700°C when the mass percentage of La _0.1 Bi _0.9 FeO ₃ is 70% and the mass percentage of CoFe ₂ O ₄ is 30%.

Figure 8 is an SEM image of the composite powder calcined at 700°C when the mass percentage of La _0.1 Bi _0.9 FeO ₃ is 60% and the mass percentage of CoFe ₂ O ₄ is 40%.

Figure 9 is the hysteresis loop of the composite powder calcined at 700°C when the mass ratio of La _0.1 Bi _0.9 FeO ₃ is 90% and the mass ratio of CoFe ₂ O ₄ is 10%.

Figure 10 is the hysteresis loop of the composite powder calcined at 700°C when the mass ratio of La _0.1 Bi _0.9 FeO ₃ is 80% and the mass ratio of CoFe ₂ O ₄ is 20%.

Figure 11 is the hysteresis loop of the composite powder calcined at 700°C when the mass ratio of La _0.1 Bi _0.9 FeO ₃ is 70% and the mass ratio of CoFe ₂ O ₄ is 30%.

Figure 12 is the hysteresis loop of the composite powder calcined at 700°C when the mass ratio of La _0.1 Bi _0.9 FeO ₃ is 60% and the mass ratio of CoFe ₂ O ₄ is 40%.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

Example 1

1) According to the general chemical formula xLa _0.1 Bi _0.9 FeO ₃ /(1-x)CoFe ₂ O ₄ , analytically pure Fe(NO ₃ ) ₃ ·9H ₂ O, Bi(NO ₃ ) ₃ ·9H ₂ O, La (NO ₃ ) ₃ 6H ₂ O and Co(NO ₃ ) ₂ 6H ₂ O were added to distilled water to prepare a solution; where, x is the mass percentage of La _0.1 Bi _0.9 FeO ₃ , and x=0.9;

2) Add citric acid to the solution in step 1), and stir for 1 h under heating in a water bath at 80°C to obtain sol A, wherein the molar amount of citric acid added is the four metals in the solution: iron ions, bismuth ions, lanthanum ions, and cobalt ions 2 times the total molar mass of ions;

3) Under stirring, use ethylenediamine to adjust the pH value of sol A to 6.5 to obtain uniform sol B;

4) Put sol B into a vacuum drying oven and dry at 200°C for 2 hours to obtain a dark brown loose xerogel;

5) Put the dry gel into a crucible after grinding, and place the crucible in an electric furnace for calcination at 700°C for 1 hour to obtain La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder.

The general chemical formula of the magnetoelectric composite powder prepared in this example is xLa _0.1 Bi _0.9 FeO ₃ /(1-x)CoFe ₂ O ₄ , where x is the mass percentage of La _0.1 Bi _0.9 FeO ₃ , and x= 0.9.

It can be seen from Figure 1 that the magnetoelectric composite powder prepared in this example contains perovskite-type La _0.1 Bi _0.9 FeO ₃ and spinel-type CoFe ₂ O ₄ .

It can be seen from Figure 5 that the distribution of two-phase grains in the La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder prepared in this example is relatively uniform, and the two-phase grains are well developed, among which La _0.1 Bi The grain size of _0.9 FeO ₃ is about 200nm, and the grain size of CoFe ₂ O ₄ is less than 100nm.

It can be seen from Figure 9 that the hysteresis loop of the La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder prepared in this example is relatively smooth, the saturation magnetization is 4.8emu/g, and the coercive field is 1411.39 oersted.

Example 2

1) According to the general chemical formula xLa _0.1 Bi _0.9 FeO ₃ /(1-x)CoFe ₂ O ₄ , analytically pure Fe(NO ₃ ) ₃ ·9H ₂ O, Bi(NO ₃ ) ₃ ·9H ₂ O, La (NO ₃ ) ₃ 6H ₂ O and Co(NO ₃ ) ₂ 6H ₂ O were added to distilled water to prepare a solution; wherein, x is the mass percentage of La _0.1 Bi _0.9 FeO ₃ , and x=0.8;

2) Add citric acid to the solution in step 1), and stir for 1 hour under heating in a water bath at 100°C to obtain sol A, wherein the molar amount of citric acid added is the four metals in the solution: iron ions, bismuth ions, lanthanum ions, and cobalt ions 3 times the total molar mass of ions;

3) Under stirring, use ethylenediamine to adjust the pH value of Sol A to 7.5 to obtain uniform Sol B;

4) Put Sol B into a vacuum drying oven and dry at 190°C for 3 hours to obtain a dark brown loose xerogel;

5) Put the dry gel into a crucible after being ground, and place the crucible in an electric furnace for calcination at 700°C for 4 hours to obtain La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder.

The general chemical formula of the magnetoelectric composite powder prepared in this example is xLa _0.1 Bi _0.9 FeO ₃ /(1-x)CoFe ₂ O ₄ , where x is the mass percentage of La _0.1 Bi _0.9 FeO ₃ , and x= 0.8.

It can be seen from Fig. 2 that the magnetoelectric composite powder prepared in this example contains perovskite-type La _0.1 Bi _0.9 FeO ₃ and spinel-type CoFe ₂ O ₄ .

It can be seen from Figure 6 that the distribution of two-phase grains in the La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder prepared in this example is relatively uniform, and the two-phase grains are well developed, among which La _0.1 Bi The grain size of _0.9 FeO ₃ is about 200nm, and the grain size of CoFe ₂ O ₄ is less than 100nm.

It can be seen from Figure 10 that the hysteresis loop of the La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder prepared in this example is relatively smooth, the saturation magnetization is 9.9emu/g, and the coercive field is 1260.14 oersted.

Example 3

1) According to the general chemical formula xLa _0.1 Bi _0.9 FeO ₃ /(1-x)CoFe ₂ O ₄ , analytically pure Fe(NO ₃ ) ₃ ·9H ₂ O, Bi(NO ₃ ) ₃ ·9H ₂ O, La (NO ₃ ) ₃ 6H ₂ O and Co(NO ₃ ) ₂ 6H ₂ O were added to distilled water to prepare a solution; wherein, x is the mass percentage of La _0.1 Bi _0.9 FeO ₃ , and x=0.7;

2) Add citric acid to the solution in step 1), and stir for 2 hours under heating in a water bath at 90°C to obtain sol A, wherein the molar amount of citric acid added is the four metals in the solution: iron ion, bismuth ion, lanthanum ion, and cobalt ion 4 times the total molar mass of ions;

3) Under stirring, use ethylenediamine to adjust the pH value of sol A to 7 to obtain uniform sol B;

4) Put sol B into a vacuum drying oven and dry at 180°C for 4 hours to obtain a dark brown loose xerogel;

5) Put the dry gel into a crucible after grinding, and place the crucible in an electric furnace for calcination at 700°C for 2 hours to obtain La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder.

The general chemical formula of the magnetoelectric composite powder prepared in this example is xLa _0.1 Bi _0.9 FeO ₃ /(1-x)CoFe ₂ O ₄ , where x is the mass percentage of La _0.1 Bi _0.9 FeO ₃ , and x= 0.7.

It can be seen from Fig. 3 that the magnetoelectric composite powder prepared in this example contains perovskite-type La _0.1 Bi _0.9 FeO ₃ and spinel-type CoFe ₂ O ₄ .

It can be seen from Figure 7 that the distribution of two-phase grains in the magnetoelectric composite powder prepared in this example is relatively uniform, and the development of two-phase grains is better, among which the grain size of La _0.1 Bi _0.9 FeO ₃ is about 200nm, and the grain size of CoFe The grain size of ₂ O ₄ is less than 100nm.

It can be seen from Figure 11 that the hysteresis loop of the La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder prepared in this example is relatively smooth, the saturation magnetization is 16.8emu/g, and the coercive field is 1485.92 oersted.

Example 4

1) According to the general chemical formula xLa _0.1 Bi _0.9 FeO ₃ /(1-x)CoFe ₂ O ₄ , analytically pure Fe(NO ₃ ) ₃ ·9H ₂ O, Bi(NO ₃ ) ₃ ·9H ₂ O, La (NO ₃ ) ₃ 6H ₂ O and Co(NO ₃ ) ₂ 6H ₂ O were added to distilled water to prepare a solution; wherein, x is the mass percentage of La _0.1 Bi _0.9 FeO ₃ , and x=0.6;

2) Add citric acid to the solution in step 1), and stir for 1.5 hours under heating in a water bath at 85°C to obtain sol A. 3 times the total molar weight of metal ions;

3) Under stirring, use ethylenediamine to adjust the pH value of sol A to 6.5 to obtain uniform sol B;

4) Put sol B into a vacuum drying oven and dry at 195°C for 2 hours to obtain a dark brown loose xerogel;

5) Grind the xerogel and put it into a crucible, place the crucible in an electric furnace and calcinate at 700°C for 3 hours to obtain La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder.

The general chemical formula of the magnetoelectric composite powder prepared in this example is xLa _0.1 Bi _0.9 FeO ₃ /(1-x)CoFe ₂ O ₄ , where x is the mass percentage of La _0.1 Bi _0.9 FeO ₃ , and x= 0.6.

It can be seen from Figure 4 that the La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder prepared in this example contains perovskite-type La _0.1 Bi _0.9 FeO ₃ and spinel-type CoFe ₂ O ₄ .

It can be seen from Figure 8 that the distribution of two-phase grains in the La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder prepared in this example is relatively uniform, and the two-phase grains are well developed, among which La _0.1 Bi The grain size of _0.9 FeO ₃ is about 200nm, and the grain size of CoFe ₂ O ₄ is less than 100nm.

It can be seen from Figure 12 that the hysteresis loop of the La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder prepared in this example is relatively smooth, the saturation magnetization is 22.6emu/g, and the coercive field is 1930.73 oersted.

Example 5

1) According to the general chemical formula xLa _0.1 Bi _0.9 FeO ₃ /(1-x)CoFe ₂ O ₄ , analytically pure Fe(NO ₃ ) ₃ ·9H ₂ O, Bi(NO ₃ ) ₃ ·9H ₂ O, La (NO ₃ ) ₃ 6H ₂ O and Co(NO ₃ ) ₂ 6H ₂ O were added to distilled water to prepare a solution; wherein, x is the mass percentage of La _0.1 Bi _0.9 FeO ₃ , and x=0.9;

2) Add citric acid to the solution in step 1), and stir for 1 hour under heating in a water bath at 100°C to obtain sol A, wherein the molar amount of citric acid added is the four metals in the solution: iron ions, bismuth ions, lanthanum ions, and cobalt ions 2 times the total molar mass of ions;

3) Under stirring, adjust the pH value of sol A to 6.5 with ammonia water to obtain uniform sol B;

4) Put sol B into a vacuum drying oven and dry at 180°C for 4 hours to obtain a dark brown loose xerogel;

5) Put the dry gel into a crucible after being ground, and place the crucible in an electric furnace for calcination at 800°C for 1 hour to obtain La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder.

The general chemical formula of the magnetoelectric composite powder prepared in this example is xLa _0.1 Bi _0.9 FeO ₃ /(1-x)CoFe ₂ O ₄ , where x is the mass percentage of La _0.1 Bi _0.9 FeO ₃ , and x= 0.9.

Example 6

1) According to the general chemical formula xLa _0.1 Bi _0.9 FeO ₃ /(1-x)CoFe ₂ O ₄ , analytically pure Fe(NO ₃ ) ₃ .9H ₂ O, Bi(NO ₃ ) ₃ .9H ₂ O, La (NO ₃ ) ₃ .6H ₂ O and Co(NO ₃ ) ₂ .6H ₂ O were added to distilled water to prepare a solution; wherein, x is the mass percentage of La _0.1 Bi _0.9 FeO ₃ , and x=0.8;

2) Add citric acid to the solution in step 1), and stir for 1.5 hours under heating in a water bath at 95°C to obtain sol A. 3 times the total molar weight of metal ions;

3) Under stirring, adjust the pH value of sol A to 7.5 with ammonia water to obtain uniform sol B;

4) Put Sol B into a vacuum drying oven and dry at 185°C for 3 hours to obtain a dark brown loose xerogel;

5) The dry gel was ground and put into a crucible, and the crucible was placed in an electric furnace and calcined at 720°C for 4 hours to obtain La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder.

The general chemical formula of the magnetoelectric composite powder prepared in this example is xLa _0.1 Bi _0.9 FeO ₃ /(1-x)CoFe ₂ O ₄ , where x is the mass percentage of La _0.1 Bi _0.9 FeO ₃ , and x= 0.8.

Example 7

1) According to the general chemical formula xLa _0.1 Bi _0.9 FeO ₃ /(1-x)CoFe ₂ O ₄ , analytically pure Fe(NO ₃ ) ₃ ·9H ₂ O, Bi(NO ₃ ) ₃ ·9H ₂ O, La (NO ₃ ) ₃ 6H ₂ O and Co(NO ₃ ) ₂ 6H ₂ O were added to distilled water to prepare a solution; wherein, x is the mass percentage of La _0.1 Bi _0.9 FeO ₃ , and x=0.7;

2) Add citric acid to the solution in step 1), and stir for 1.5 hours under heating in a water bath at 87°C to obtain sol A, wherein the molar amount of citric acid added is four kinds of iron ions, bismuth ions, lanthanum ions, and cobalt ions in the solution 4 times the total molar weight of metal ions;

3) Under stirring, adjust the pH value of sol A to 7 with ammonia water to obtain uniform sol B;

4) Put sol B into a vacuum drying oven and dry at 190°C for 2 hours to obtain a dark brown loose xerogel;

5) Grind the xerogel and put it into a crucible, place the crucible in an electric furnace and calcinate at 750°C for 3 hours to obtain La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder.

The general chemical formula of the magnetoelectric composite powder prepared in this example is xLa _0.1 Bi _0.9 FeO ₃ /(1-x)CoFe ₂ O ₄ , where x is the mass percentage of La _0.1 Bi _0.9 FeO ₃ , and x= 0.7.

Example 8

1) According to the general chemical formula xLa _0.1 Bi _0.9 FeO ₃ /(1-x)CoFe ₂ O ₄ , analytically pure Fe(NO ₃ ) ₃ ·9H ₂ O, Bi(NO ₃ ) ₃ ·9H ₂ O, La (NO ₃ ) ₃ 6H ₂ O and Co(NO ₃ ) ₂ 6H ₂ O were added to distilled water to prepare a solution; wherein, x is the mass percentage of La _0.1 Bi _0.9 FeO ₃ , and x=0.6;

2) Add citric acid to the solution in step 1), and stir for 2 hours under heating in a water bath at 80°C to obtain sol A. 3 times the total molar mass of ions;

3) Under stirring, adjust the pH value of sol A to 6.5 with ammonia water to obtain uniform sol B;

4) Put sol B into a vacuum drying oven and dry at 200°C for 2 hours to obtain a dark brown loose xerogel;

5) Put the dry gel into a crucible after grinding, and place the crucible in an electric furnace for calcination at 770°C for 2 hours to obtain La _0.1 Bi _0.9 FeO ₃ /CoFe ₂ O ₄ magnetoelectric composite powder.

The general chemical formula of the magnetoelectric composite powder prepared in this example is xLa _0.1 Bi _0.9 FeO ₃ /(1-x)/CoFe ₂ O ₄ , where x is the mass percentage of La _0.1 Bi _0.9 FeO ₃ , and x =0.6.

Claims (7)

1. a La _0.1bi _0.9feO ₃/ CoFe ₂o ₄the preparation method of magnetoelectricity composite granule, is characterized in that, comprises the following steps:

1) by chemical general formula xLa _0.1bi _0.9feO ₃/ (1-x) CoFe ₂o ₄, by analytically pure Fe (NO ₃) ₃9H ₂o, Bi (NO ₃) ₃9H ₂o, La (NO ₃) ₃6H ₂o and Co (NO ₃) ₂6H ₂o joins in distilled water and is mixed with solution; Wherein, x is La _0.1bi _0.9feO ₃mass percent, and 0.6≤x≤0.9;

2) to step 1) solution in add citric acid, heat at 80-100 DEG C and stir, obtaining Sol A, wherein, the molar weight adding citric acid be iron ion in solution, bismuth ion, lanthanum ion, cobalt ion integral molar quantity 2-4 doubly;

3), under stirring, the pH value of Sol A is adjusted to 6.5-7.5, obtains uniform sol B;

4) sol B is dry at 180-200 DEG C, obtain chocolate and to loosen shape xerogel;

5), after xerogel being ground, at 700-800 DEG C, calcine 1-4h obtain La _0.1bi _0.9feO ₃/ CoFe ₂o ₄magnetoelectricity composite granule;

Described step 3) in pH value be adopt quadrol regulate.

2. a kind of La according to claim 1 _0.1bi _0.9feO ₃/ CoFe ₂o ₄the preparation method of magnetoelectricity composite granule, is characterized in that, described step 2) in heating realized by heating in water bath.

3. a kind of La according to claim 1 _0.1bi _0.9feO ₃/ CoFe ₂o ₄the preparation method of magnetoelectricity composite granule, is characterized in that, described step 2) in stir time be 1 ~ 2 hour.

4. a kind of La according to claim 1 _0.1bi _0.9feO ₃/ CoFe ₂o ₄the preparation method of magnetoelectricity composite granule, is characterized in that, described step 4) in the dry time be 2-4 hour.

5. a kind of La according to claim 1 _0.1bi _0.9feO ₃/ CoFe ₂o ₄the preparation method of magnetoelectricity composite granule, is characterized in that, described step 4) in drying carry out in vacuum drying oven.

6. a kind of La according to claim 1 _0.1bi _0.9feO ₃/ CoFe ₂o ₄the preparation method of magnetoelectricity composite granule, is characterized in that, described step 5) in calcining carry out in electric furnace.

7. the La for preparing of method as claimed in claim 1 _0.1bi _0.9feO ₃/ CoFe ₂o ₄magnetoelectricity composite granule, is characterized in that, this La _0.1bi _0.9feO ₃/ CoFe ₂o ₄the chemical general formula of magnetoelectricity composite granule is xLa _0.1bi _0.9feO ₃/ (1-x) CoFe ₂o ₄, wherein, x is La _0.1bi _0.9feO ₃mass percent, and 0.6≤x≤0.9.