CN113087514B - Lead-free multiferroic material with relaxor ferroelectric property and preparation method thereof - Google Patents

Abstract

The invention discloses a lead _- free _{multiferroic material} with _{relaxor ferroelectric} properties and a preparation method thereof. Group R‑3c. Dissolve the weighed CaCO ₃ , C ₄ H ₆ CoO ₄ · 4H ₂ O, C ₄ H ₆ MnO ₄ · 4H ₂ O, CrN ₃ O ₉ in the citric acid solution, and add ethylene glycol to enhance the viscosity of the solution , then adjust the pH of the mixed solution to 3-5, put it in a water bath and heat to make the solution into a jelly-like wet gel; dry the wet gel to obtain a dry gel; Sheet, sintered to obtain lead-free multiferroic material. The particle size of the sample is uniform, and it not only has the characteristics of multiferroics, but also has obvious relaxation characteristics of its ferroelectric phase transition. Its electric dipole moment is regulated by a magnetic field, which promotes its application in multifunctional devices.

Description

A kind of lead-free multiferroic material with relaxor ferroelectric properties and preparation method thereof

technical field

The invention relates to the field of relaxor ferroelectric materials and multiferroic materials, in particular to a lead-free multiferroic material Ca ₃ CoMn _{1- x} Cr _x O ₆ (0.05≤x≤0.15 ) with relaxor ferroelectric properties and Preparation.

Background technique

Multiferroic materials refer to materials with two or more ferrous orders at the same time. Such materials can coexist with spontaneous polarization order and spin order at a certain temperature, and the magnetoelectric coupling effect caused by them makes multiferroic materials. Materials have some special physical properties. The characteristic of ferroelectric materials is that they have spontaneous polarization when no external electric field is applied, and the direction of their spontaneous polarization can be reversed or redirected by an external electric field. Among ferroelectrics, there is a class called relaxor ferroelectrics, which have high dielectric constant and large electrostrictive effect, so they have broad application prospects in the fields of micropositioners, actuators and smart structures. . In addition, the excellent pyroelectric properties of relaxor ferroelectric materials enable them to be used in infrared detectors, and their piezoelectric properties enable them to be used in high-frequency sonar devices as receiving transducers. The dielectric properties of these materials are also widely used in large-capacity capacitors, tunable microwave devices, and thermal elements. At the same time, for multiferroic materials, they tend to have higher magnetoelectric coupling coefficients in the magnetic phase transition or ferroelectric phase transition temperature region. Compared with normal ferroelectrics, multiferroic materials with relaxor ferroelectric characteristics Due to its wide ferroelectric phase transition temperature range, the magnetic material can enhance its magnetoelectric coupling effect in a wider temperature range and broaden its application range.

However, the currently used relaxor ferroelectric materials are mostly lead-based single crystals or ceramics. Since the toxicity of lead will bring great harm to the environment and human health, it is of great significance to find new lead-free relaxor ferroelectric materials.

In view of this, the present invention is proposed.

SUMMARY OF THE INVENTION

In view of the problems existing in the prior art, the present invention provides a lead-free multiferroic material Ca ₃ CoMn _{1- x} Cr _x O ₆ (0.05≤x≤0.15 ) with relaxor ferroelectric properties and a preparation method thereof. The lead-free multiferroic material of Ca ₃ CoMn _{1- x} Cr _x O ₆ (0.05≤x ≤0.15) crystallizes into a single-phase orthorhombic structure, which not only has multiferroic characteristics, but also has obvious relaxation in its ferroelectric phase transition. characteristic.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical solutions:

A lead-free multiferroic material with relaxor ferroelectric properties, the chemical formula is Ca ₃ CoMn _{1- x} Cr _x O ₆ , wherein 0.05≤x ≤0.15, and the crystal of Ca ₃ CoMn _{1- x} Cr _x O ₆ is orthorhombic structure , space group R-3c.

The preparation method of the lead-free multiferroic material with relaxor ferroelectric properties according to the present invention comprises the following steps:

(1) Under the temperature condition of 10-30℃, the molar ratio of CaCO ₃ , C ₄ H ₆ CoO ₄ · 4H ₂ O, C ₄ H ₆ MnO ₄ · 4H ₂ O, CrN ₃ O ₉ is 3:1:1 - x : x is accurately weighed, and at the same time, citric acid 1.5-2 times the amount of the metal cation substance is weighed and dissolved in deionized water to obtain a citric acid solution;

(2) Dissolve the weighed CaCO ₃ , C ₄ H ₆ CoO ₄ · 4H ₂ O, C ₄ H ₆ MnO ₄ · 4H ₂ O and CrN ₃ O ₉ in the citric acid solution, and perform ultrasonic dispersion to obtain a mixed solution ;

(3) Add ethylene glycol to the mixed solution obtained in step (2) to enhance the viscosity of the solution. In order to prevent the combination of metal cations and OH ^- radicals in the solution during the later evaporation of deionized water to form a precipitate, an appropriate amount of analytically pure nitric acid is added. Or ammonia water to adjust the pH of the solution to keep the pH value of the solution between 3-5;

(4) At a temperature of 20-30 °C, magnetically stir the mixed solution obtained after adjusting the pH in step (3) to make it evenly mixed, and then put it in a water bath to heat to make the solution into a jelly-like wet gel;

(5) Dry the wet gel in a constant temperature drying oven to obtain a dry gel;

(6) Grind the obtained xerogel into powder, and then pre-sinter the pre-sintered powder for secondary grinding, tableting, and sintering to obtain a lead-free multiferroic material Ca ₃ CoMn _{1- x} Cr _x O ₆ , where 0.05≤x≤0.15 .

Further, 1-2 mL of deionized water is required per gram of citric acid in the step (1).

Further, according to the content of the solution, the volume ratio of ethylene glycol to the mixed solution in the step (3) is 1:4-1:3.

Further, in the step (4), the speed of magnetic stirring is 5-15 revolutions per second, and the stirring time is 1-2 hours.

Further, in the step (4), the temperature of the water bath is 90-100° C., and the heating time is 10-15 hours.

Further, in the step (5), the temperature of the constant temperature drying box is set to 150-170° C., and the drying time is 6-10 hours.

Further, the calcination temperature in the step (6) is 700-900° C., and the calcination time is 10-24 hours.

Further, the sintering temperature in the step (6) is 1000-1200° C., and the sintering time is 12-24 hours.

The Ca ₃ CoMn _{1- x} Cr _x O ₆ (0.05≤x≤0.15) prepared by the method of the present invention not only has multiferroic characteristics, but also has obvious relaxation characteristics in its ferroelectric phase transition, which is a kind of The lead-free relaxor ferroelectric material overcomes the shortcoming that the toxicity of lead-based relaxor ferroelectric material is harmful to the human body and the environment.

Beneficial effects of the present invention: 1. The lead-free multiferroic material Ca ₃ CoMn _{1- x} Cr _x O ₆ (0.05≤x≤0.15) prepared by the present invention has a single-phase orthorhombic structure, and the particle size of the sample is uniform. It not only has multiferroic characteristics, but also its ferroelectric phase transition has obvious relaxation characteristics. 2. The ferroelectric polarization of Ca ₃ CoMn _{1- x} Cr _x O ₆ (0.05≤x ≤0.15) originates from the exchange contraction effect between the magnetic moments. By adjusting the order degree of the magnetic ions, the Ca ₃ CoMn should be controlled Control of _{1- x} Cr _x O ₆ (0.05≤x≤0.15) phase transition types. 3. As a multiferroic material, Ca ₃ CoMn _{1- x} Cr _x O ₆ (0.05≤x ≤ 0.15), its relaxation characteristics of ferroelectric phase transition characteristics can make Ca ₃ CoMn _{1- x} Cr _x O ₆ It has a strong magnetoelectric coupling effect in a wide temperature range, and its electric dipole moment is regulated by a magnetic field, which promotes its application in multifunctional devices. In addition, the preparation process of the present invention is simple, the cost is low, and mass preparation and production can be realized.

Description of drawings

Fig. 1 is the XRD pattern of the lead-free multiferroic material Ca ₃ CoMn _{1- x} Cr _x O ₆ (0.05≤x ≤ 0.15) with relaxor ferroelectric properties; Fig. 2 is the XRD pattern of Ca ₃ CoMn _{1- x} Cr _x O ₆ ( 0.05≤x≤0.15 ) The graph of the relationship between the dielectric constant and the dielectric loss factor of the material and temperature, where (a) x =0.05, (b) x =0.1, (c) x =0.15.

Figure 3 is a graph showing the relationship between the dielectric constant and dielectric loss factor of Ca ₃ CoMn _{1- x} Cr _x O ₆ (0.05≤x ≤0.15) material with magnetic field, where (a) x =0.05, (b) x = 0.1, (c) x = 0.15.

Detailed ways

The present invention will be further described below with reference to specific embodiments. It should be understood that the following examples are only used to illustrate the present invention rather than to limit the scope of the present invention, and those skilled in the art can make some non-essential improvements and adjustments according to the content of the above invention.

The preparation method of the lead-free multiferroic material Ca ₃ CoMn _{1- x} Cr _x O ₆ (0.05≤x≤0.15) with relaxor ferroelectric properties in this embodiment is as follows:

In the first step, under the temperature condition of 25℃, for CaCO ₃ , C ₄ H ₆ CoO ₄ · 4H ₂ O, C ₄ H ₆ MnO ₄ · 4H ₂ O, CrN ₃ O ₉ according to 3:1:1- x : The stoichiometric ratio of x ( x = 0.05, 0.1, 0.15) is accurately weighed, and at the same time, 2 times the amount of citric acid of the metal cation substance is dissolved in deionized water (the principle is that each gram of citric acid corresponds to 1 -2ml);

In the second step, previously weighed CaCO ₃ , C ₄ H ₆ CoO ₄ ·4H ₂ O, C ₄ H ₆ MnO ₄ ·4H ₂ O, CrN ₃ O ₉ were dissolved in the prepared citric acid solution, and carried out Ultrasonic dispersion to obtain a mixed solution;

In the third step, according to the content of the mixed solution, add a certain amount of ethylene glycol (CH ₂ OH) ₂ to the mixed solution (the volume ratio of ethylene glycol and the mixed solution is 1:4) to enhance the viscosity of the solution;

In the fourth step, in order to prevent the combination of metal cations and OH ^- radicals in the solution in the later deionized water evaporation process to form a precipitate, add an appropriate amount of analytical pure nitric acid or ammonia water to adjust the pH of the solution, so that the pH value of the solution is maintained at 4;

The fifth step, under the condition of a temperature of 25 ° C, magnetic stirring for 2 hours to fully and uniformly mix the solution, and the stirring speed is 10 rpm;

The sixth step, after the stirring, put the uniformly mixed solution into a water bath with a temperature of 95°C and heat for 12 hours, so that the solution becomes a jelly-like wet gel;

The seventh step is to put the wet gel into a constant temperature drying oven at 150° C. to dry for 8 hours to obtain a dry gel;

In the eighth step, the obtained xerogel is ground into powder, and pre-fired at 900 ° C for 24 hours;

In the ninth step, the pre-fired powder is ground for a second time, pressed into tablets, and then sintered at 1000° C. for 12 hours.

The lead-free multiferroic material Ca ₃ CoMn _{1- x} Cr _x O ₆ (0.05≤x≤0.15) prepared by the invention has a single-phase orthorhombic structure, which not only has the characteristics of multiferroics, but also has a ferroelectric phase transition. has obvious relaxation properties. In addition, the preparation process of the present invention is simple, the cost is low, and mass preparation and production can be realized.

The microstructure of the samples was characterized, and the phase was analyzed by X-ray diffractometer (XRD). Using the lead-free multiferroic material Ca ₃ CoMn _{1- x} Cr _x O ₆ ( x =0.05, 0.1, 0.15) prepared in the example, it can be seen from Figure 1 that the sample has sharp diffraction peaks, good crystallization, and no other impurities generate.

The lead-free multiferroic material Ca ₃ CoMn _{1- x} Cr _x O ₆ (0.05≤x ≤0.15) with relaxor ferroelectric properties crystallizes in an orthorhombic structure, space group R-3c, and the lattice parameters of each sample are x = 0.05: a=9.1260Å, c=10.5730Å; x =0.1: a=9.1264Å; c=10.5711Å; x =0.15: a=9.1258Å, c=10.5711Å.

Figure 2 shows the relationship between the dielectric constant and temperature of the lead-free multiferroic material Ca ₃ CoMn _{1- x} Cr _x O ₆ (0.05≤x≤0.15) with relaxor ferroelectric properties. It can be seen that the sample has A pronounced relaxor ferroelectric signature.

Figure 3 shows the relationship between the dielectric constant of Ca ₃ CoMn _{1- x} Cr _x O ₆ (0.05≤x ≤0.15) material as a function of magnetic field. It can be seen that the magnetic field can effectively control the dielectric properties of the sample.

In the preparation method of the lead-free multiferroic material with relaxor ferroelectric properties of the present invention, the ratio of each raw material and the specific reaction conditions can be adaptively adjusted within the proportion range defined by the present invention, and the expected target product can be obtained. The foregoing has shown and described the basic principles and main features of the present invention, as well as the advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments. The above-mentioned embodiments and descriptions only illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have Various changes and modifications fall within the scope of the claimed invention. The claimed scope of the present invention is defined by the appended claims and their equivalents.

Claims (9)

1. A lead-free multiferroic material having relaxor ferroelectric properties, characterized by: the chemical formula of the lead-free multiferroic material is Ca₃CoMn _x1-Cr _x O₆Wherein 0.05 is less than or equal tox≤0.15，Ca₃CoMn _x1-Cr _x O₆The crystal is in an orthorhombic structure and has a space group R-3 c.

2. The method for preparing a lead-free multiferroic material with relaxor ferroelectric properties as claimed in claim 1, characterized by the steps of:

(1) at 10-30 deg.C for CaCO₃、C₄H₆CoO₄·4H₂O、C₄H₆MnO₄·4H₂O、Cr(NO₃)₃According to the molar ratio of 3:1:1-x:xAccurately weighing, and simultaneously weighing citric acid with the amount of 1.5-2 times that of the metal cation substances, and dissolving the citric acid in deionized water to obtain a citric acid solution;

(2) weighed CaCO₃、C₄H₆CoO₄·4H₂O、C₄H₆MnO₄·4H₂O、Cr(NO₃)₃Dissolving in citric acid solution, and performing ultrasonic dispersion to obtain mixed solution;

(3) adding ethylene glycol into the mixed solution obtained in the step (2) to enhance the viscosity of the solution, and then adjusting the pH =3-5 of the mixed solution;

(4) magnetically stirring the mixed solution obtained after the pH value is adjusted in the step (3) at the temperature of 20-30 ℃ to uniformly mix the mixed solution, and then putting the mixed solution into a water bath kettle to heat the mixed solution to change the solution into jelly-like wet gel;

(5) putting the wet gel into a constant-temperature drying box for drying to obtain dry gel;

(6) grinding the obtained dry gel into powder, then pre-burning, carrying out secondary grinding on the pre-burned powder, tabletting and sintering to obtain the lead-free multiferroic material Ca₃CoMn _x1-Cr _x O₆Wherein 0.05 is less than or equal tox≤0.15。

3. The method for preparing a lead-free multiferroic material with a relaxor ferroelectric property as claimed in claim 2, characterized in that: in the step (1), 1-2mL of deionized water is needed per gram of citric acid.

4. The method for preparing a lead-free multiferroic material with a relaxor ferroelectric property as claimed in claim 2, characterized in that: the volume ratio of the ethylene glycol to the mixed solution in the step (3) is 1:4-1: 3.

5. The method for preparing a lead-free multiferroic material with a relaxor ferroelectric property as claimed in claim 2, characterized in that: the magnetic stirring speed in the step (4) is 5-15 r/s, and the stirring time is 1-2 hours.

6. The method for preparing a lead-free multiferroic material with a relaxor ferroelectric property as claimed in claim 2, characterized in that: the temperature of the water bath in the step (4) is 90-100 ℃, and the heating time is 10-15 hours.

7. The method for preparing a lead-free multiferroic material with a relaxor ferroelectric property as claimed in claim 2, characterized in that: the temperature of the constant-temperature drying box in the step (5) is set to be 150 ℃ and 170 ℃, and the drying time is 6-10 hours.

8. The method for preparing a lead-free multiferroic material with a relaxor ferroelectric property as claimed in claim 2, characterized in that: the pre-sintering temperature in the step (6) is 700-900 ℃, and the pre-sintering time is 10-24 hours.

9. The method for preparing a lead-free multiferroic material with a relaxor ferroelectric property as claimed in claim 2, characterized in that: the sintering temperature in the step (6) is 1000-1200 ℃, and the sintering time is 12-24 hours.

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