Lead-free multiferroic material with relaxor ferroelectric property 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 with relaxor ferroelectric properties3CoMn x1-Cr x O6(0.05≤xLess than or equal to 0.15) and a preparation method.
Background
The multiferroic material refers to a material with two or more than two iron orderings, and the material can simultaneously have spontaneous polarization sequences and spin sequences at a certain temperature, so that the multiferroic material has certain special physical properties due to the magnetoelectric coupling effect. The ferroelectric material has the characteristic of having a spontaneous polarization phenomenon in the absence of an external electric field, and the direction of the spontaneous polarization can be reversed or reoriented by the external electric field. Among ferroelectrics, one class is called relaxor ferroelectrics, and the materials have high dielectric constant and large electrostrictive effect, so that the materials have wide application prospect in the fields of micro positioners, actuators, smart structures and the like. In addition, the relaxation ferroelectric material has excellent pyroelectric performance, so that the relaxation ferroelectric material can be applied to infrared detectors and the like, and the relaxation ferroelectric material has piezoelectric performance, so that the relaxation ferroelectric material can be applied to high-frequency sonar equipment and used as a receiving transducer. The dielectric properties of the material are widely applied to the aspects of large-capacity capacitors, tunable microwave devices, thermosensitive elements and the like. Meanwhile, for a multiferroic material, the multiferroic material often has a higher magnetoelectric coupling coefficient in a magnetic phase transition temperature region or a ferroelectric phase transition temperature region, and compared with a normal ferroelectric, the multiferroic material with relaxivity ferroelectric characteristics can enhance the magnetoelectric coupling effect in a wider temperature range due to the wider ferroelectric phase transition temperature region, thereby widening the application range.
However, most of the currently applied relaxor ferroelectric materials are lead-based single crystals or ceramics, and the toxicity of lead brings great harm to the environment and human health, so that the finding of novel lead-free relaxor ferroelectric materials is of great significance.
In view of the above, the present invention is particularly proposed.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a relaxor ferroelectric material with characteristics of relaxation ferroelectricsCalcium-based lead-free multiferroic material3CoMn x1-Cr x O6(0.05≤xNot more than 0.15) and preparation method thereof, Ca obtained3CoMn x1-Cr x O6(0.05≤xNot more than 0.15) is crystallized into a single-phase orthorhombic structure, which not only has multiferroic characteristics, but also has obvious relaxation property in ferroelectric phase transition.
In order to solve the technical problems, the invention adopts the following technical scheme:
a lead-free multiferroic material with relaxor ferroelectric properties, with chemical formula of 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.
The preparation method of the lead-free multiferroic material with the relaxor ferroelectric property comprises the following steps of:
(1) at 10-30 deg.C for CaCO3、C4H6CoO4·4H2O、C4H6MnO4·4H2O、CrN3O9According 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、CrN3O9Dissolving in citric acid solution, and performing ultrasonic dispersion to obtain mixed solution;
(3) adding glycol into the mixed solution obtained in the step (2) to enhance the viscosity of the solution so as to prevent metal cations and OH in the solution in the later deionized water evaporation process-Precipitate is generated by root combination, and proper amount of analytically pure nitric acid or ammonia water is added to adjust the pH value of the solution, so that the pH value of the solution is kept between 3 and 5;
(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。
Further, 1-2mL of deionized water is needed per gram of citric acid in the step (1).
Further, according to the content of the solution, the volume ratio of the ethylene glycol to the mixed solution in the step (3) is 1:4-1: 3.
Further, the magnetic stirring speed in the step (4) is 5-15 r/s, and the stirring time is 1-2 hours.
Further, the temperature of the water bath kettle in the step (4) is 90-100 ℃, and the heating time is 10-15 hours.
Further, the temperature of the constant temperature drying oven in the step (5) is set to be 150-.
Further, the pre-sintering temperature in the step (6) is 700-.
Further, the sintering temperature in the step (6) is 1000-1200 ℃, and the sintering time is 12-24 hours.
Ca produced by the method of the present invention3CoMn x1-Cr x O6(0.05≤xNot more than 0.15), not only has multiferroic characteristics, but also has obvious relaxation characteristics in ferroelectric phase transition, is a lead-free relaxor ferroelectric material, and overcomes the defect that the toxicity of the lead-based relaxor ferroelectric material has great harm to human bodies and the environment.
The invention has the beneficial effects that: 1. the lead-free multiferroic material Ca prepared by the invention3CoMn x1-Cr x O6(0.05≤x≤0.15)The crystal is a single-phase rhombic structure, the sample particles are uniform in size, and the crystal not only has multiferroic characteristics, but also has obvious relaxation characteristics in ferroelectric phase transition. 2. Ca3CoMn x1-Cr x O6(0.05≤xLess than or equal to 0.15) the ferroelectric polarization comes from the exchange contraction effect between magnetic moments, and Ca can be realized by regulating the order degree of magnetic ions3CoMn x1-Cr x O6(0.05≤xLess than or equal to 0.15) regulating and controlling the phase change type. 3. Ca3CoMn x1-Cr x O6(0.05≤xLess than or equal to 0.15) as a multiferroic material, the relaxation characteristic of the ferroelectric phase transition characteristic of the multiferroic material can better enable Ca to be added3CoMn x1-Cr x O6The magnetic field has strong magnetoelectric coupling effect in a wide temperature area, and the electric dipole moment of the magnetic field is regulated and controlled, so that the application of the magnetic field in multifunctional devices is promoted. In addition, the preparation process is simple, the cost is low, and mass production can be realized.
Drawings
FIG. 1 shows a lead-free multiferroic material Ca with relaxor ferroelectric properties3CoMn x1-Cr x O6(0.05≤xLess than or equal to 0.15); FIG. 2 shows Ca3CoMn x1-Cr x O6(0.05≤x≦ 0.15) dielectric constant of the material, dielectric dissipation factor, and temperature, wherein (a)x=0.05, (b)x=0.1, (c)x=0.15。
FIG. 3 shows Ca3CoMn x1-Cr x O6(0.05≤xLess than or equal to 0.15) material dielectric constant and dielectric loss factor with magnetic field, wherein (a)x=0.05, (b)x=0.1, (c)x=0.15。
Detailed Description
The present invention will be further described with reference to the following examples. It is to be understood that the following examples are illustrative only and are not intended to limit the scope of the invention, which is to be given numerous insubstantial modifications and adaptations by those skilled in the art based on the teachings set forth above.
The lead-free multiferroic material Ca with relaxor ferroelectric properties of this example3CoMn x1-Cr x O6(0.05≤xLess than or equal to 0.15) is prepared as follows:
the first step is to carry out reaction on CaCO at the temperature of 25 DEG C3、C4H6CoO4·4H2O、C4H6MnO4·4H2O、CrN3O9According to the ratio of 3:1:1-x: x (xAccurately weighing the stoichiometric ratio of =0.05, 0.1, 0.15), and simultaneously weighing citric acid with 2 times of the amount of the metal cation substance to be dissolved in deionized water (1-2 ml of the deionized water is calculated according to the principle of each gram of the citric acid);
second, the previously weighed CaCO3、C4H6CoO4·4H2O、C4H6MnO4·4H2O、CrN3O9Dissolving in the prepared citric acid solution, and performing ultrasonic dispersion to obtain a mixed solution;
thirdly, adding a certain amount of ethylene glycol (CH) into the mixed solution according to the content of the mixed solution2OH)2(the volume ratio of the glycol to the mixed solution is 1: 4) to enhance the viscosity of the solution;
the fourth step, in order to prevent metal cations and OH in the solution during the later stage of the evaporation of the deionized water-Precipitate is generated by root combination, and proper amount of analytically pure nitric acid or ammonia water is added to adjust the pH value of the solution, so that the pH value of the solution is kept at 4;
fifthly, under the condition of 25 ℃, the solution is fully and uniformly mixed by magnetic stirring for 2 hours at the stirring speed of 10 revolutions per second;
sixthly, after stirring, putting the uniformly mixed solution into a water bath kettle with the temperature set to 95 ℃ for heating for 12 hours to change the solution into jelly-like wet gel;
seventhly, putting the wet gel into a constant-temperature drying oven at 150 ℃ for drying for 8 hours to obtain dry gel;
eighthly, grinding the obtained xerogel into powder, and presintering for 24 hours at the temperature of 900 ℃;
and step nine, grinding the pre-sintered powder for the second time, tabletting and sintering at 1000 ℃ for 12 hours.
The lead-free multiferroic material Ca prepared by the invention3CoMn x1-Cr x O6(0.05≤xLess than or equal to 0.15), the crystal is a single-phase orthorhombic structure, and the crystal not only has multiferroic characteristics, but also has obvious relaxation property in ferroelectric phase transition. In addition, the preparation process is simple, the cost is low, and mass production can be realized.
And (3) characterizing the microstructure of the sample, and analyzing the phase of the sample by using an X-ray diffractometer (XRD). The lead-free multiferroic material Ca prepared in the example was used3CoMn x1-Cr x O6(x=0.05, 0.1, 0.15), as can be seen from fig. 1, the sample diffraction peak is sharp, the crystallization is good, and no other impurities are generated.
Lead-free multiferroic material Ca with relaxor ferroelectric properties3CoMn x1-Cr x O6(0.05≤xNot more than 0.15) is crystallized into an orthorhombic structure, the space group R-3c is formed, and the lattice parameters of all samples are respectivelyx=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。
FIG. 2 shows a lead-free multiferroic material Ca with relaxor ferroelectric properties3CoMn x1-Cr x O6(0.05≤x≦ 0.15) as a function of temperature, it can be seen that the sample has a significant relaxor ferroelectric characteristic.
FIG. 3 shows Ca3CoMn x1-Cr x O6(0.05≤xLess than or equal to 0.15) material dielectric constant is changed with the magnetic field, so that the dielectric property of the sample can be effectively regulated and controlled by the magnetic field.
According to the preparation method of the lead-free multiferroic material with the relaxor ferroelectric property, the proportion of each raw material and the specific reaction condition can be adaptively adjusted within the proportion range defined by the invention, so that an expected target product can be obtained. The foregoing shows and describes the general principles and features of the present invention, together with the advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.