WO2021109858A1

WO2021109858A1 - Gallium ferrite nanofiber, manufacturing method for gallium ferrite nanofiber, and use of gallium ferrite nanofiber

Info

Publication number: WO2021109858A1
Application number: PCT/CN2020/129163
Authority: WO
Inventors: 訾孟飞; 钟高阔; 李江宇; 任传来; 安峰
Original assignee: 中国科学院深圳先进技术研究院
Priority date: 2019-12-03
Filing date: 2020-11-16
Publication date: 2021-06-10
Also published as: CN111733483A; CN111733483B

Abstract

The present invention relates to a gallium ferrite nanofiber, a manufacturing method for the gallium ferrite nanofiber, and use of the gallium ferrite nanofiber. The gallium ferrite nanofiber is a ferroelectric and ferromagnetic gallium ferrite nanofiber having room temperature single-phase multiferroic properties, the chemical formula of the composition thereof is Ga_xFe_2-xO₃, the numerical value range of x is 0.6-1.0, and the diameter of the gallium ferrite nanofiber is less than 300 nm. The method comprises the following steps: preparing a gallium ferrite precursor solution by using a sol-gel method; performing electrospinning on a fully aged gallium ferrite precursor solution to obtain a gallium ferrite precursor fiber having a first fiber structure diameter; and performing heat treatment on the gallium ferrite precursor fiber to obtain the gallium ferrite nanofiber. The gallium ferrite nanofiber has the ferroelectricity and ferromagnetism of the room temperature single-phase multiferroic properties, and has a second fiber structure diameter, and the second fiber structure diameter is less than 300 nm. The gallium ferrite nanofiber has both the ferroelectricity and ferromagnetism at room temperature, and can be applied to an electronic device.

Description

Gallium ferrite nanofiber, manufacturing method and application of gallium ferrite nanofiber

Technical field

The present invention relates to the technical field of gallium ferrite, in particular to the manufacturing method and application of gallium ferrite nanofibers and gallium ferrite nanofibers.

Background technique

As we all know, ferroelectricity realizes the storage of digital information through the spontaneous polarization formed by the displacement of atoms in the ferroelectric crystal; in contrast, ferromagnetism realizes the storage of information through the orderly arrangement of the electron spins in the ferromagnetic material. Magnetoelectric coupling multiferroic material (Magnetoelectric Coupling multiferroics) refers to compounds that have both ferroelectricity (electric sequence) and ferromagnetism (magnetic sequence). Multiferroic materials have the following characteristics: (1) Ferroelectric and ferromagnetic coexistence, and the charge ordering and spin ordering have a strong correlation coupling; (2) The magnetic polarization state is changed by adjusting the electric field, and it is applied to high density. Among the information storage, the generated Joule heat can be reduced. The application of magnetoelectric materials will help solve the problem of high energy consumption of this kind of memory, and realize the functions of low energy consumption, fast storage, processing, etc.; (3) Multiferroic materials have two degrees of freedom of charge and spin. The magnetic field controls them separately, which can be used to design and develop ternary or quaternary storage devices to realize high-density storage of information. The above-mentioned advantages of multiferroic materials make them have great application prospects for non-volatile storage, magnetic sensors, tunable microwave devices and spintronic devices.

In transition metal oxides, the electric polarization needs to satisfy the electrons of the d-electron orbital to be zero, while the long-range magnetic order needs to satisfy the d-electron orbital with some electrons. Therefore, in principle, it is difficult for ferroelectricity and long-range magnetic order to coexist and regulate each other in the same material system. Therefore, single-phase multiferroic materials are very rare, and they are often limited by antiferromagnetic order and low-temperature conditions, making their application in actual devices face huge challenges. At present, the most studied multiferroic material is BiFeO ₃ material, but it also has the shortcomings of weak ferromagnetism and large leakage current. Therefore, it is necessary to find a new type of multiferroic material.

Ga _x Fe _2-x O ₃ is a room temperature piezoelectric and low temperature submagnetic material. Because Fe ³⁺ and Ga ^{3+ have} similar radii, the two ions can be randomly distributed in the four cation sites. When Fe ions are excessive At this time, excessive Fe ions may replace Ga ions in the Ga2 position, and the relatively strong antiferromagnetic superexchange interaction between Fe1 and Ga2 between adjacent Fe ions may enhance the ferrimagnetic spin ordering and ferromagnetism. Therefore, by adjusting the stoichiometric ratio of Fe and Ga, the magnetic transition temperature can be raised above room temperature. Therefore, Ga _x Fe _2-x O ₃ is a potential room temperature single-phase multiferroic material. More and more attention. However, it is currently disclosed that Ga _x Fe _2-x O ₃ materials can have ferromagnetism at room temperature, but the piezoelectric performance does not meet the requirements of non-volatile storage, magnetic sensors, tunable microwave devices, spintronic devices, etc.

Chinese invention patent CN101410331B discloses a magnetic material, which has X-ray diffraction peaks _{corresponding to the crystalline structure of ε-Fe 2} O ₃ ^{, and contains Ga 3+} ions instead of part of Fe ³⁺ ions of ε-Fe ₂ O _{3 crystals} It is a crystal of ε-Ga _x Fe _{2-xO3 formed} by locating, where 0<X<1, and contains fine powder particles whose average particle volume measured by TEM photography is 20000 nm ^{3 or less.} The piezoelectric properties of the ε-Ga _x Fe _2-xO3 powder particles obtained by the above solution do not meet the requirements of non-volatile storage, magnetic sensors, tunable microwave devices, spintronic devices, and the like.

In the prior art, gallium ferrite material is also made into a thin film, but the film is restricted by the substrate, which will also significantly affect the ferroelectric properties of the material.

technical problem

The first objective of the present invention is to provide a gallium ferrite nanofiber with a larger aspect ratio, good ferroelectric and ferromagnetic properties at room temperature, and conforms to non-volatile storage, magnetic sensor, adjustable Requirements for microwave equipment or spintronic equipment.

The second objective of the present invention is to provide a method for manufacturing gallium ferrite nanofibers. The prepared gallium ferrite nanofibers are not restricted by the substrate, and can amplify the displacement caused by the piezoelectric effect or the magnetostrictive effect. It has both ferromagnetic and ferroelectric properties; it meets the requirements of non-volatile storage, magnetic sensors, tunable microwave equipment, and spintronic equipment.

The third objective of the present invention is to provide the application of the gallium ferrite nanofibers in non-volatile storage, magnetic sensors, tunable microwave devices or spintronic devices.

Technical solutions

The first objective of the present invention is achieved through the following technical solutions: a gallium ferrite nanofiber, which is a ferroelectric and ferromagnetic gallium ferrite nanofiber with single-phase multiferroic properties at room temperature, gallium ferrite nanofiber The composition chemical formula of the wire is Ga _x Fe _2-x O ₃ , the value of x is in the range of 0.6-1.0, and the diameter of the gallium ferrite nanofiber wire is below 300 nm.

By adopting the above technical solutions, the prepared gallium ferrite nanofibers have a larger aspect ratio, can amplify the displacement caused by the piezoelectric effect or the magnetostrictive effect, are not restricted by the substrate, and have better physical, Chemical properties, but also has a more significant magneto-electric coupling effect. It has good ferroelectric and ferromagnetic properties at room temperature and meets the requirements of non-volatile storage, magnetic sensors, tunable microwave equipment or spintronic equipment. After testing, when the number of x is in the above range, it can simultaneously ensure that the gallium ferrite nanofiber wire has good ferroelectric and ferromagnetic properties at room temperature.

The present invention is further set as follows: the diameter of the second fiber structure of the gallium ferrite nanofiber wire is 100-250 nm.

After testing, the above-mentioned diameter is easier to control, and the structure is more stable.

The second objective of the present invention is achieved through the following technical solutions: the manufacturing method of gallium ferrite nanofibers includes the following steps:

The sol-gel method is used to prepare the solution of the gallium ferrite precursor;

Electrospinning the fully aged gallium ferrite precursor solution to obtain a gallium ferrite precursor fiber filament with the first fiber structure diameter;

The gallium ferrite precursor fiber filaments are heat-treated to obtain gallium ferrite nanofiber filaments. The gallium ferrite nanofiber filaments have single-phase multiferroic ferroelectricity and ferromagnetism at room temperature and have a second fiber structure diameter The diameter of the second fiber structure is smaller than the diameter of the first fiber structure, and the diameter of the second fiber structure of the gallium ferrite nanofiber filaments is less than 300 nm.

By fully aging the gallium ferrite precursor fiber, the components are fully reacted, and then heat-treated to obtain the gallium ferrite precursor fiber filament, which is regular in shape and uniform in composition, and has a larger long diameter compared to the gallium ferrite nanofiber film. Compared with the nanofiber structure, it is not restricted by the substrate, and can amplify the displacement caused by the piezoelectric effect or the magnetostrictive effect. It has both ferromagnetic and ferroelectric properties at room temperature; it has better physical and chemical properties, and also It has a more significant magneto-electric coupling effect and meets the requirements of non-volatile storage, magnetic sensors, tunable microwave equipment and spintronic equipment. The preparation method of the invention is simple, the device used is relatively simple, the operation is convenient, and the repeatability is high.

The second fiber structure of the gallium ferrite nanofiber filament obtained after heat treatment is smaller in diameter, and it is not easy to break during the shrinking process, and it is easier to obtain the gallium ferrite nanofiber filament with excellent performance.

The present invention is further configured as follows: the diameter shrinkage rate of the second fiber structure relative to the diameter of the first fiber structure is 20 to 80%.

By controlling the ratio of raw materials to control the shrinkage rate, it is found through testing that when the shrinkage rate is 20 to 80%, it is less likely to break.

The present invention is further configured as follows: the diameter shrinkage rate of the second fiber structure relative to the diameter of the first fiber structure is 30-60%.

By controlling the ratio of raw materials to control the shrinkage rate, it is found through testing that when the shrinkage rate is 30-60%, it is less likely to break. In the electrospinning process, the fiber filaments are less likely to agglomerate, and the yield rate obtained is higher.

The present invention is further configured as follows: the concentration of the gallium ferrite precursor solution is 0.2-0.5 mol/L.

Through the above technical solution, it is possible to ensure that the filament is not easily broken during the electrospinning process, and it is not easy to block the syringe used in the electrospinning process.

The present invention is further provided that: preparing the gallium ferrite precursor solution includes the following steps:

Dissolve ferric nitrate and gallium nitrate in a mixed solvent of deionized water and absolute ethanol, stir to fully dissolve the above components; then add organic acid for complexation reaction, where the organic acid is one of citric acid and oxalic acid Or two;

Add the spinning aid to the above mixed solvent, stir evenly and let it stand for 1 to 3 days to obtain a uniform, stable and transparent gallium ferrite precursor solution.

The volatility of deionized water and absolute ethanol is suitable, and the precursor solution of gallium ferrite is more likely to form Taylor cones at the nozzle, and it is not easy to cause clogging of the nozzle, and the fiber filaments are not easy to stick together. And after testing, it was found that by mixing deionized water and absolute ethanol before dissolving other components, the fiber filaments obtained are more regular and uniform in shape, and less likely to break; deionized water and absolute ethanol are environmentally friendly, energy-saving, and cost-effective. low.

The present invention is further configured as follows: the volume ratio of deionized water and absolute ethanol in the step of preparing the gallium ferrite precursor solution is 1:1; the molar ratio of gallium nitrate, ferric nitrate, and citric acid is x: (2-x): 2.

After testing, it was found that when the volume ratio of deionized water and absolute ethanol was 1:1, the shape of the fiber filaments was more regular, uniform, and less likely to break. When the total molar amount of ferric nitrate and gallium nitrate and the molar amount of citric acid are 1:1, the formed components are uniform, and the viscosity and surface tension are more suitable, and the obtained fiber filaments are longer and not easy to break.

The present invention is further set as follows: the spinning aid is polyvinylpyrrolidone with a molecular weight of 1 to 1.5 million; and the concentration of polyvinylpyrrolidone in the gallium ferrite precursor solution is 0.04 to 0.05 g/mL.

Polyvinylpyrrolidone (PVP) is a synthetic water-soluble polymer compound. It has the general properties of water-soluble polymer compounds, such as colloidal protection, film-forming, adhesiveness, hygroscopicity, solubilization or aggregation. The invention uses PVP to dissolve better with mixed solvents, and the K value of PVP with a molecular weight of 1 to 1.5 million is 81.0-97.2, and the viscosity is appropriate. Then, by adjusting the concentration of PVP, the fiber filament is not easy to be used in the electrospinning process. Fracture, the diameter distribution of the first fiber structure and the diameter of the second fiber structure are more uniform.

The present invention further provides that: electrospinning the gallium ferrite precursor solution includes the following steps:

Put an appropriate amount of gallium ferrite precursor solution into the syringe and fix it on the syringe pump, and set the speed of the syringe pump to 0.2~0.5mL/h;

Place a substrate for receiving the precursor fiber filaments of gallium ferrite on the receiving plate;

Adjust the distance between the needle tip and the base to be 8~15cm;

Turn on the high-voltage power supply for spinning to obtain the precursor fiber filaments of gallium ferrite, where the high-voltage power supply is 10-15kV.

In electrospinning, when the voltage applied to the solution reaches a certain critical value, the charge repulsion on the surface of the solution is greater than its surface tension, jets are ejected and stretched into filaments. A suitable voltage is not only beneficial to the maintenance and stability of the ejected Taylor cone, but also to maintain the distribution of the diameter of the first fiber structure of the gallium ferrite precursor filament; the distance between the needle tip and the substrate will directly affect the electric field strength, which is suitable for the present invention. The distance can not only ensure the full volatilization of the solvent in the air, it is not easy to cause the bonding of fiber filaments, but also can obtain finer uniform fiber filaments; through the joint limitation of the speed of the syringe pump, the distance between the needle tip and the substrate, and the size of the high-voltage power supply, The shape of the Taylor cone at the tip of the needle will be better, and the filament will be more stable, which can maintain the topographic structure of the fiber surface. The first fiber structure of the precursor fiber of gallium ferrite has a smaller diameter and is more uniform.

The present invention is further provided as follows: the substrate is aluminum foil, YSZ/ITO or SiO ₂ /Si.

The above-mentioned substrate does not significantly interfere with the growth of fiber filaments, nor does it easily affect the piezoelectric properties of the fiber filaments; the aluminum foil has low cost and is convenient for large-scale use.

The present invention is further provided that: heat-treating the gallium ferrite precursor fiber filament includes the following steps:

Dry to remove deionized water and absolute ethanol contained in the precursor filaments of gallium ferrite;

Plastic discharging, heat the dried gallium ferrite precursor filament to 380~420 ^o C and keep it for 0.5~1h to remove the organic matter in the gallium ferrite precursor filament to obtain the first product of gallium ferrite filament;

Annealing treatment, the first product of gallium ferrite fiber after plasticization is heated to 750~850 ^o C and then kept for 1.5~2.5h to obtain gallium ferrite nanofiber wire.

Drying to remove deionized water and absolute ethanol, and then plastic removal to remove organic matter, so that the components in the gallium ferrite precursor filaments are slowly removed, which can better maintain the structure and morphology of the gallium ferrite filaments. Easy to break. Through annealing treatment, the growth of gallium ferrite grains is promoted, and the structure of gallium ferrite filaments is better obtained. Moreover, the diameter of the second fiber structure of gallium ferrite filaments is smaller, and the gallium ferrite filaments have a larger aspect ratio. , Has better physical and chemical properties.

The present invention is further set as follows: in the steps of plastic ejection and annealing treatment, the heating rate is 5-10°C/min.

By controlling the heating rate, the growth of gallium ferrite grains can be better promoted, and the structure and morphology of the gallium ferrite fiber can be maintained, and it is not easy to break.

The third objective of the present invention is achieved through the following technical solutions: the application of the gallium ferrite nanofibers described in the above solutions in non-volatile storage, magnetic sensors, tunable microwave devices or spintronic devices.

Beneficial effect

In summary, at least one beneficial technical effect of the present invention is:

1. The gallium ferrite precursor fiber is gelatinized, and then heat treated to obtain the gallium ferrite precursor fiber. The nanofiber structure is regular in shape, uniform in composition, and has a larger aspect ratio. It is not restricted by the substrate and can be enlarged. The displacement caused by the piezoelectric effect or the magnetostrictive effect has both ferromagnetic and ferroelectric properties at room temperature; it has better physical and chemical properties, and also has a more significant magnetoelectric coupling effect, which is in line with non-volatility Requirements for storage, magnetic sensors, tunable microwave equipment and spintronics equipment.

2. The second fiber structure of the gallium ferrite nanofiber filaments obtained after heat treatment is smaller in diameter, and it is not easy to break during the shrinking process, and it is easier to obtain gallium ferrite nanofiber filaments with excellent performance.

3. The preparation method of the present invention is simple, the device used is relatively simple, the operation is convenient, and the repeatability is high.

4. The volatility of deionized water and absolute ethanol is suitable. The precursor solution of gallium ferrite is more likely to form Taylor cones at the nozzle, and it is not easy to cause clogging of the nozzle and the fiber filaments are not easy to stick together. And after testing, it was found that by mixing deionized water and absolute ethanol before dissolving other components, the fiber filaments obtained are more regular and uniform in shape, and less likely to break; deionized water and absolute ethanol are environmentally friendly, energy-saving, and cost-effective. low.

5. The selected PVP of the present invention can better dissolve with mixed solvents, and the K value of PVP with a molecular weight of 1 to 1.5 million is 81.0-97.2, and the viscosity is appropriate. Then, by adjusting the concentration of PVP, the fiber filaments in the electrospinning process will be better. It is not easy to break, and the diameter distribution of the first fiber structure and the diameter of the second fiber structure are more uniform.

6. Through the joint limitation of the speed of the syringe pump, the distance between the needle tip and the substrate, and the size of the high-voltage power supply, the shape of the Taylor cone at the needle tip will be better, the wire will be more stable, and the morphological structure of the fiber surface can be maintained, the precursor of gallium ferrite The first fiber structure of the fiber yarn has a smaller diameter and is more uniform.

7. Drying to remove deionized water and absolute ethanol, and then plastic removal to remove organic matter, so that the components in the precursor filaments of gallium ferrite are slowly removed, which can better maintain the structure and morphology of the gallium ferrite filaments , Not easy to break. Through annealing treatment, the growth of gallium ferrite grains is promoted, and the structure of gallium ferrite filaments is better obtained. Moreover, the diameter of the second fiber structure of gallium ferrite filaments is smaller, and the gallium ferrite filaments have a larger aspect ratio. , Has better physical and chemical properties.

8. When _{the value range of x in Ga x} Fe _2-x O ₃ is 0.6-1.0, it can simultaneously ensure that the gallium ferrite nanofiber wire has good ferroelectric and ferromagnetic properties at room temperature.

Description of the drawings

Figure 1 is a schematic diagram of the preparation process of gallium ferrite nanofibers in experimental examples 1, 2, and 3 of the present invention;

Figure 2 is an X-ray powder diffraction (XRD) graph of gallium ferrite nanofibers in experimental examples 1, 2, and 3 of the present invention;

Figure 3 is a scanning electron microscope (SEM) image of gallium ferrite nanofibers in experimental examples 1, 2, and 3 of the present invention;

4 is a transmission electron microscope (TEM) image of gallium ferrite nanofibers in Experimental Example 3 of the present invention.

Figure 5 shows the magnetic susceptibility-temperature (M-T) curve and hysteresis curve (M-H) of the gallium ferrite nanofibers in test examples 1, 2, and 3;

Figure 6 is a second harmonic imaging (SHG) image of gallium ferrite nanofibers in experimental examples 1, 2, and 3.

Embodiments of the present invention

Glossary

YSZ refers to the single crystal substrate ZrO _{2 of} high-temperature superconducting thin film;

ITO conductive glass is made of soda-lime-based or silicon-boron-based substrate glass and coated with a layer of indium tin oxide (commonly known as ITO) film by magnetron sputtering;

The K value represents the corresponding PVP average molecular weight range, and the K value is a characteristic value related to the relative viscosity of the PVP aqueous solution.

In the magnetic susceptibility-temperature curve, the FC mode is to first heat up to greater than the Curie temperature (Tc) without applying a magnetic field, and then use the magnetic field to cool down the measurement; the ZFC mode is to first heat up without a magnetic field, then cool down without a magnetic field, and then add a small magnetic field to heat up measuring.

Second harmonic generation (Second Harmonic Generation, SHG for short)

In order to more conveniently understand the technical solution of the present invention, the manufacturing method of the gallium ferrite nanofibers of the present invention will be described in further detail below, but it is not as the protection scope defined by the present invention.

One embodiment of the present invention is a gallium ferrite nanofiber, a gallium ferrite nanofiber, which is a ferroelectric and ferromagnetic gallium ferrite nanofiber wire with single-phase multiferroic properties at room temperature, and a gallium ferrite nanofiber wire The chemical formula of the composition is Ga _x Fe _2-x O ₃ , the value range of x is 0.6-1.0, and the diameter of gallium ferrite nanofiber filaments is below 300 nm. Preferably, the diameter of the gallium ferrite nanofiber filaments is 100-250 nm.

The second embodiment of the present invention discloses a manufacturing method of gallium ferrite nanofibers, which includes the following steps:

Step 1. Use the sol-gel method to prepare the gallium ferrite precursor solution;

Step 2: Electro-spinning the fully aged gallium ferrite precursor solution to obtain the gallium ferrite precursor filament with the first fiber structure diameter;

Step 3. Heat the gallium ferrite precursor fiber filaments to obtain gallium ferrite nanofiber filaments. The gallium ferrite nanofiber filaments have single-phase multiferroic ferroelectricity and ferromagnetism at room temperature and have second The diameter of the fiber structure, the diameter of the second fiber structure is smaller than the diameter of the first fiber structure, and the diameter of the second fiber structure of the gallium ferrite nanofiber filaments is less than 300 nm.

Preferably, the diameter shrinkage rate of the second fiber structure relative to the diameter of the first fiber structure is 20 to 80%. Preferably, the diameter shrinkage rate of the second fiber structure relative to the diameter of the first fiber structure is 30-60%. Preferably, the diameter shrinkage rate of the second fiber structure relative to the diameter of the first fiber structure is 37.5-50%.

Regarding the preparation of the gallium ferrite precursor solution in step 1, in a preferred example, the following steps are included:

Add the spinning aid to the above-mentioned mixed solvent, stir evenly and let it stand for 1 to 3 days, fully aging, fully reacting each component, and obtaining a uniform, stable and transparent gallium ferrite precursor solution.

Among them, the volume ratio of deionized water and absolute ethanol is 1:1; the molar ratio of gallium nitrate, ferric nitrate, and citric acid is x:(2-x):2. The concentration of gallium ferrite precursor solution is 0.2~0.5 mol/L.

Regarding the possible types of spinning aids in step 1, in a preferred example, the spinning aid is polyvinylpyrrolidone with a molecular weight of 1 to 1.5 million; preferably, the concentration of the polyvinylpyrrolidone in the solution of the gallium ferrite precursor is 0.04~0.05g/mL.

Regarding the electrospinning in step 2, in a preferred example, the following steps are included:

Adjust the distance between the needle tip and the base to be 8~15cm;

Among them, the substrate is aluminum foil, YSZ/ITO or SiO ₂ /Si.

Regarding the heat treatment in step three, in a preferred example, the following steps are included:

Among them, the heating rate in the steps of plastic ejection and annealing treatment is 5-10°C/min.

The third embodiment of the present invention discloses the application of gallium ferrite nanofibers in non-volatile storage, magnetic sensors, tunable microwave equipment or spintronic equipment in the above scheme.

The following three test examples are combined with the drawings for specific description

Test Example 1

As shown in Figure 1, a gallium ferrite nanofiber and a preparation method thereof. The target product is prepared by a combination of a sol-gel method and an electrospinning method, including the following steps:

(1) Prepare precursor solution by sol-gel method: first, take 4.2986g iron nitrate (Fe(NO ₃ ) ₃ ·9H ₂ O), 1.3708g gallium nitrate (Ga(NO ₃ ) ₃ ·xH ₂ O), 3.3622 g citric acid (C ₆ H ₈ O ₇ ·H ₂ O) was dissolved in 20 mL mixed solvent of deionized water and absolute ethanol with a volume ratio of 1:1, and the molar ratio of each substance was Fe(NO ₃ ) ₃ ·9H ₂ O:Ga(NO ₃ ) ₃ ·xH ₂ O:C ₆ H ₈ O ₇ ·H ₂ O=1.33:0.67:2; then use a magnetic stirrer to stir for 6 hours to fully dissolve; then, take 0.8g of polyvinylpyrrolidone (PVP) with a molecular weight of 1.3 million was added to the solution. The concentration of PVP in the resulting solution was 0.04 g/mL. Continue stirring with a magnetic stirrer for 7 hours. Finally, let the solution stand for 2 days to fully age the solution. The components reacted sufficiently to obtain a uniform, stable and transparent gallium ferrite precursor solution with a concentration of 0.4 mol/L.

(2) Electrospinning to prepare gallium ferrite precursor filaments: first, take an appropriate amount of the fully aged gallium ferrite precursor solution obtained in step (1) into the syringe, and fix it on the syringe pump, and set the syringe pump speed to 0.3 mL/h; Then, an aluminum foil is placed on the receiving plate as a substrate to receive the spun gallium ferrite precursor fiber filaments, where the distance between the needle tip and the substrate is 12cm; finally, the high-voltage power supply is turned on for spinning, and the gallium ferrite precursor is obtained. Body fiber yarn, the high-voltage power supply is 12kV.

(3) Heat treatment of the gallium ferrite precursor filaments: first, put the gallium ferrite precursor filaments in a 60 ^o C constant temperature drying oven for 12 hours to remove the deionization contained in the gallium ferrite precursor filaments Water, anhydrous ethanol; then, put it into a muffle furnace for annealing treatment, at a heating rate of 6 ^o C/min, first heat up from room temperature to 400 ^o C and then keep it for 1 hour to remove the precursor fiber of gallium ferrite The organic matter in the silk; finally, the temperature is increased to 800 ^o C and the temperature is maintained for 2 h to obtain gallium ferrite nanofiber silk with a diameter of 100-250 nm.

Test Example 2

As shown in Figure 1, the present invention discloses a gallium ferrite nanofiber and a preparation method thereof. The target product is prepared by a combination of a sol-gel method and an electrospinning method, and includes the following steps:

(1) Prepare precursor solution by sol-gel method: first, take 3.8784g iron nitrate (Fe(NO ₃ ) ₃ ·9H ₂ O), 1.6367g gallium nitrate (Ga(NO ₃ ) ₃ ·xH ₂ O), 3.3622 g citric acid (C ₆ H ₈ O ₇ ·H ₂ O) was dissolved in 20 mL mixed solvent of deionized water and absolute ethanol with a volume ratio of 1:1, and the molar ratio of each substance was Fe(NO ₃ ) ₃ ·9H ₂ O:Ga(NO ₃ ) ₃ ·xH ₂ O:C ₆ H ₈ O ₇ ·H ₂ O=1.2:0.8:2; then use a magnetic stirrer to stir for 6 hours to make it fully dissolved; then, Take 0.8g of polyvinylpyrrolidone (PVP) with a molecular weight of 1.3 million and add it to the solution. The PVP concentration in the resulting solution is 0.04 g/mL. Continue stirring with a magnetic stirrer for 7 hours. Finally, let it stand for 2 days to fully age the solution. A uniform, stable and transparent gallium ferrite precursor solution with a concentration of 0.4 mol/L.

(2) Electrospinning to prepare gallium ferrite precursor filaments: First, take an appropriate amount of the fully aged gallium ferrite precursor solution obtained in step (1) into the syringe and fix it on the syringe pump, and set the syringe pump speed to 0.3 mL /h; Then, an aluminum foil is placed on the receiving plate as the substrate to receive the spun gallium ferrite precursor fiber filaments, where the distance between the needle tip and the substrate is 12 cm; finally, the high-voltage power supply is turned on for spinning, and the gallium ferrite precursor is obtained Body fiber yarn, the high-voltage power supply is 12 kV.

(3) Heat treatment of the precursor nanofibers: First, put the gallium ferrite precursor fibers into a 60 ^o C constant temperature drying oven for 12 hours to remove the deionized water and the deionized water contained in the gallium ferrite precursor fiber filaments. Anhydrous ethanol; then, put it into a muffle furnace for annealing treatment, at a heating rate of 6 ^o C/min, first heat up from room temperature to 400 ^o C and then keep it for 1 h to remove the precursor fiber filaments of gallium ferrite Finally, the temperature is increased to 800 ^o C and the temperature is kept for 2 h to obtain gallium ferrite nanofibers with a diameter of 100-250nm.

Test Example 3

(1) Prepare precursor solution by sol-gel method: first, take 3.2320g iron nitrate (Fe(NO ₃ ) ₃ ·9H ₂ O), 2.0459g gallium nitrate (Ga(NO ₃ ) ₃ ·xH ₂ O), 3.3622 g citric acid (C ₆ H ₈ O ₇ ·H ₂ O) was dissolved in 20 mL mixed solvent of deionized water and absolute ethanol with a volume ratio of 1:1, and the molar ratio of each substance was Fe(NO ₃ ) ₃ ·9H ₂ O:Ga(NO ₃ ) ₃ ·xH ₂ O:C ₆ H ₈ O ₇ ·H ₂ O=1:1:2; then use a magnetic stirrer to stir for 6 h to make it fully dissolved; then, Take 0.8g of polyvinylpyrrolidone (PVP) with a molecular weight of 1.3 million and add it to the solution. The concentration of PVP in the resulting solution is 0.04 g/mL. Continue stirring with a magnetic stirrer for 7 hours. Finally, let it stand for 2 days to fully age the solution. The components reacted sufficiently to obtain a uniform, stable and transparent gallium ferrite precursor solution with a concentration of 0.4 mol/L.

(3) Heat treatment of the gallium ferrite precursor filaments: First, put the gallium ferrite precursor filaments in a 60 ^o C constant temperature drying oven for 12 hours to remove the gallium ferrite precursor filaments. Ionized water, absolute ethanol; then, put it into a muffle furnace for annealing treatment, at a heating rate of 6 ^o C/min, first heat up from room temperature to 400 ^o C and then keep it for 1 h, before removing gallium ferrite The organic matter in the body filaments; finally, the temperature is raised to 800 ^o C and the temperature is maintained for 2 h to obtain gallium ferrite nanofibers with a diameter of 100-250 nm.

Performance Testing

As shown in Figure 2, from top to bottom are the X-ray powder diffraction patterns of the gallium ferrite nanofiber filaments of Test Example 1-3 and the standard pattern of the standard PDF card GaFeO ₃ -PDF#76-1005. The test is carried out The gallium ferrite nanofibers prepared in Examples 1-3 have good crystallinity. Compared with the standard PDF card GaFeO ₃ -PDF#76-1005, it can be seen that most of the diffraction peaks come from the orthogonal structure of gallium ferrite. And gallium ferrite with different iron content has little effect on crystallinity.

As shown in Figure 3, Figures 3(a), 3(b), and 3(c) are the corresponding morphologies of the unsintered gallium ferrite precursor filaments prepared in experimental examples 1, 2, and 3. Figures 3(d), 3(e), and 3(f) are the corresponding morphology diagrams of the gallium ferrite nanofibers obtained after sintering the gallium oxide precursor filaments prepared in Examples 1, 2, and 3, respectively. It can be clearly seen from the figure that the unsintered gallium ferrite precursor fiber has a smooth surface and a uniform diameter, approximately between 200-400 nm; while the gallium ferrite nanofibers obtained after sintering become rougher, and The diameter is reduced to about 100-250 nm, and the aspect ratio increases. The morphology of the nanofiber filaments with different iron content did not change significantly. They were all regular in shape, the diameter of the fiber filaments were relatively close, the overall arrangement was neat, there was no obvious bending, and there were no many broken filaments.

As shown in Figure 4, Figures 4(a) and 4(b) are low-magnification and high-magnification TEM images of gallium ferrite nanofibers prepared in Experimental Example 3. The fine microstructure and regular shape can be seen The diameters of the fiber filaments are also relatively close. The lattice fringe in Figure 4(c) shows that its plane spacing is 0.336 nm, which is consistent with the orthorhombic gallium ferrite (130) plane. Figures 4(d), 4(e), and 4(f) respectively show that Fe, Ga, and O are uniformly distributed in the nanofiber filaments. It can be clearly seen that the components are very uniform, indicating that the fiber filaments obtained are very stable. it is good.

As shown in Figure 5, it can be clearly seen from the magnetic susceptibility-temperature curve of Figure 5(a) that whether it is in the FC mode or the ZFC mode, the Curie temperature of Test Example 1 is 305K, and the Curie temperature of Test Example 2 is 305K. The inner temperature is 364K, and the Curie temperature of test example 1 has exceeded 400K, which is 403K. Therefore, the Curie temperature of the gallium ferrite nanofiber filaments prepared in test examples 1-3 are all above room temperature, and with the increase of Fe content Increasing the Curie temperature also increases, which fully proves that the gallium ferrite nanofiber wire prepared by the present invention has good ferromagnetic properties at room temperature. It can be seen from the hysteresis curve of Fig. 5(b) that with the increase of iron content, its residual magnetization and coercive field will also increase, which further proves that the gallium ferrite nanofibers prepared by the present invention have good properties at room temperature. The ferromagnetic properties.

As shown in Figure 6, Figures 6(a), 6(b), and 6(c) are the SHG in the p-out polarization direction of the gallium ferrite nanofibers prepared in experimental examples 1, 2, and 3, respectively. Intensity diagram, it can be seen from Figure 6 that the obtained SHG signal has a bisymmetric structure, indicating that the gallium ferrite nanofiber filaments have spontaneous polarization. The larger the SHG signal, the greater the polarization of the sample. When x=0.67, the polarization of the fiber is the largest. When x=1.0, the symmetry of the SHG signal is not obvious, indicating that the polarization is weaker. The SHG diagram macroscopically illustrates the ferroelectricity of _{Ga x} Fe _2x O _{3 fibers.}

The examples of this specific implementation manner are all preferred examples of the present invention, rather than all the examples, and do not limit the scope of protection of the present invention accordingly. Therefore: everything is obtained in the form of equivalent substitutions or equivalent transformations of the present invention. All technical solutions should be covered by the protection scope of the present invention.

Claims

A gallium ferrite nanofiber, which is characterized in that it is a ferroelectric and ferromagnetic gallium ferrite nanofiber wire with room temperature single-phase polyferroicity, and the composition chemical formula of the gallium ferrite nanofiber wire is Ga x Fe 2- The value range of x O 3 , x is 0.6-1.0, and the diameter of gallium ferrite nanofiber filaments is below 300 nm.
The gallium ferrite nanofiber according to claim 1, wherein the diameter of the gallium ferrite nanofiber filament is 100-250 nm.
The manufacturing method of gallium ferrite nanofiber is characterized in that it includes the following steps:

The sol-gel method is used to prepare the solution of the gallium ferrite precursor;

Electrospinning the fully aged gallium ferrite precursor solution to obtain a gallium ferrite precursor fiber filament with the first fiber structure diameter;

The gallium ferrite precursor fiber filaments are heat-treated to obtain gallium ferrite nanofiber filaments. The gallium ferrite nanofiber filaments have single-phase multiferroic ferroelectricity and ferromagnetism at room temperature and have a second fiber structure diameter The diameter of the second fiber structure is smaller than the diameter of the first fiber structure, and the diameter of the second fiber structure of the gallium ferrite nanofiber filaments is less than 300 nm.
The method for manufacturing gallium ferrite nanofibers according to claim 3, wherein the diameter shrinkage rate of the second fiber structure relative to the diameter of the first fiber structure is 30-60%.
The method for manufacturing gallium ferrite nanofibers according to claim 3, wherein the concentration of the gallium ferrite precursor solution is 0.2-0.5 mol/L.
The method for manufacturing gallium ferrite nanofibers according to claim 5, wherein the preparation of the gallium ferrite precursor solution comprises the following steps:

Dissolve ferric nitrate and gallium nitrate in a mixed solvent of deionized water and absolute ethanol, stir to fully dissolve the above components; then add organic acid for complexation reaction, where the organic acid is one of citric acid and oxalic acid Or two;

Add the spinning aid to the above mixed solvent, stir evenly and let it stand for 1 to 3 days to obtain a uniform, stable and transparent gallium ferrite precursor solution.
The method for manufacturing gallium ferrite nanofibers according to claim 6, wherein the volume ratio of deionized water and absolute ethanol in the step of preparing the gallium ferrite precursor solution is 1:1; gallium nitrate, ferric nitrate, The molar ratio of citric acid is x:(2-x):2.
The method for manufacturing gallium ferrite nanofibers according to claim 6, wherein the spinning aid is polyvinylpyrrolidone with a molecular weight of 1 to 1.5 million; and the concentration of polyvinylpyrrolidone in the gallium ferrite precursor solution is 0.04 ~0.05g/mL.
The method for manufacturing gallium ferrite nanofibers according to claim 3, wherein the electrospinning of the gallium ferrite precursor solution comprises the following steps:

Put an appropriate amount of gallium ferrite precursor solution into the syringe and fix it on the syringe pump, and set the speed of the syringe pump to 0.2~0.5mL/h;

Place a substrate for receiving the precursor fiber filaments of gallium ferrite on the receiving plate;

Adjust the distance between the needle tip and the base to be 8~15cm;

Turn on the high-voltage power supply for spinning to obtain the precursor fiber filaments of gallium ferrite, where the high-voltage power supply is 10-15kV.
The method of manufacturing a gallium iron acid nanofiber according to claim 9, wherein the substrate is an aluminum foil, YSZ / ITO or SiO 2 / Si.
The method for manufacturing gallium ferrite nanofibers according to any one of claims 6-10, wherein the heat treatment of the gallium ferrite precursor filaments comprises the following steps:

Dry to remove deionized water and absolute ethanol contained in the precursor filaments of gallium ferrite;

Plastic discharging, heat the dried gallium ferrite precursor filament to 380~420 o C and keep it for 0.5~1h to remove the organic matter in the gallium ferrite precursor filament to obtain the first product of gallium ferrite filament;

Annealing treatment, the first product of gallium ferrite fiber after plasticization is heated to 750~850 o C and then kept for 1.5~2.5h to obtain gallium ferrite nanofiber wire.
The method for manufacturing gallium ferrite nanofibers according to claim 11, wherein the temperature increase rate in the steps of plastic ejection and annealing treatment is 5-10° C./min.
The use of the gallium ferrite nanofibers of any one of claims 1-2 in non-volatile storage, magnetic sensors, tunable microwave devices or spintronic devices.