CN112456535A - Gadolinium oxyfluoride and preparation method and application thereof - Google Patents
Gadolinium oxyfluoride and preparation method and application thereof Download PDFInfo
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Abstract
The invention relates to fluorinated gadolinium hydroxide and a preparation method and application thereof. Gadolinium fluorohydroxide has the general formula: gd (OH)yF3‑yWherein y is 0.5 to 2.5.
Description
Technical Field
The invention relates to the field of materials, and particularly relates to fluorinated gadolinium hydroxide and a preparation method and application thereof.
Background
The traditional gas compression refrigeration technology is widely applied to daily life of people, but along with the continuous improvement of the living standard of people, the low efficiency of the traditional gas compression refrigeration machine can not meet the requirements of people. Meanwhile, the refrigerant Freon used by the traditional refrigerator can also seriously damage the ozone layer, so people begin to search for a novel refrigeration technology which has the advantages of high efficiency, energy conservation and no environmental pollution.
In 1997, the Ames laboratory, department of energy in the United states, discovered that an alloy consisting of Gd, Si, Ge showed a great magnetocaloric effect at room temperature, and since then, the American aerospace company began to develop a new refrigerator based on magnets without using a compressor. As compared with the traditional gas compression refrigeration refrigerator, the refrigerator has the advantages of no need of a compressor, small vibration noise, high reliability, long working period, high efficiency, no pollution, wide working temperature and cold quantity range and the like, more attention is paid to the field of magnetic refrigerationAnd the magnetic refrigeration research is gradually transited to the low-temperature and even extremely low-temperature magnetic refrigeration research based on coordination compounds. The magnetic refrigeration materials in the temperature range mainly have two types: paramagnetic salts and rare earth metal compounds. Gadolinium gallium garnet (GGG, Gd) as representative of paramagnetic salts3Ga5O12) Dysprosium aluminum garnet (DAG, Dy)3Al5O12) Gadolinium gallium aluminum garnet (GGA, Gd)3(Ga1- xAl2)5O12And x is 0.1 to 0.4). Among them, GGG has achieved commercial application by virtue of its excellent properties as a front stage refrigeration for production of He II stream and He liquefaction.
There is a need in the art for better performing magnetic refrigeration materials.
Disclosure of Invention
The inventor has conducted extensive research to develop a fluorinated gadolinium hydroxide material having a significant magnetocaloric effect (MCE).
In some aspects, the present disclosure provides a fluorinated gadolinium hydroxide material having the general formula: gd (OH)yF3-yWherein y is 0.5 to 2.5. For example, y is 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, or 2.5, and in some embodiments, y is 1 to 2, preferably y is 1.5 to 2, and more preferably y is 1, 1.5, or 2.
In some embodiments, the fluorinated gadolinium hydroxide material is crystalline.
In some embodiments, the fluorinated gadolinium hydroxide material has the following crystalline form characteristics: which belongs to the hexagonal system.
In some embodiments, the fluorinated gadolinium hydroxide material has a space group of P63/m。
In some embodiments, the fluorinated gadolinium hydroxide material has a unit cell volume of
(e.g. in
)。
In some embodiments, the calculated density of crystals of the fluorinated gadolinium hydroxide material, ρcalcd5.5 to 6.5g/cm3(e.g., 5.8 to 6.2 g/cm)3)。
In some embodiments, the fluorinated gadolinium hydroxide material has the following unit cell parameters:
In some embodiments, the fluorinated gadolinium hydroxide material has the following unit cell parameters:
α＝90°；
β＝90°；
γ＝120°。
in some embodiments, the fluorinated gadolinium hydroxide material has an XRD powder diffraction pattern (Cu target) including a characteristic peak P1～P4Wherein, in the step (A),
characteristic peak P1The 2 θ value of (a) is 16.5 ° to 17.5 ° (e.g., 16.5 °, 16.6 °, 16.7 °, 16.8 °, 16.9 °, 17.0 °, 17.1 °, 17.2 °, 17.3 °, 17.4 °, or 17.5 °);
characteristic peak P2The 2 θ value of (a) is 29.5 ° -30.5 ° (e.g., 29.5 °, 29.6 °, 29.7 °, 29.8 °, 29.9 °, 30.0 °, 30.1 °, 30.2 °, 30.3 °, 30.4 °, or 30.5 °);
characteristic peak P3The 2 θ value of (a) is 42.0 ° to 43.0 ° (e.g., 42.0 °, 42.1 °, 42.2 °, 42.3 °, 42.4 °, 42.5 °, 42.6 °, 42.7 °, 42.8 °, or 42.9 °);
the 2 θ value of characteristic peak P4 is 51.4 ° to 52.4 ° (e.g., 51.4 °, 51.5 °, 51.6 °, 51.7 °, 51.8 °, 51.9 °, 52.0 °, 52.1 °, 52.2 °, 52.3 °, or 52.4 °); .
In some embodiments, the fluorinated gadolinium hydroxide material further comprises one or more of the following characteristic peaks P in its XRD powder diffractogram5～P9Wherein, in the step (A),
characteristic peak P5The 2 theta value of (a) is 33.5 DEG to 34.5 DEG (e.g., 33.5 DEG, 33.6 DEG, 33.7 DEG, 33.8 DEG, 33.9 DEG, 34.0 DEG, 34.1 DEG, 34.2 DEG, 34.3 DEG, 34.4 DEG, 34.5 DEG);
characteristic peak P6The 2 theta value of (a) is 38.0 DEG to 39.0 DEG (e.g., 38.0 DEG, 38.1 DEG, 38.2 DEG, 38.3 DEG, 38.4 DEG, 38.5 DEG, 38.6 DEG, 38.7 DEG, 38.8 DEG, 38.9 DEG, 39.0 DEG);
characteristic peak P7The 2 theta value of (a) is 45.0 DEG to 46.0 DEG (e.g., 45.0 DEG, 45.1 DEG, 45.2 DEG, 45.3 DEG, 45.4 DEG, 45.5 DEG, 45.6 DEG, 45.7 DEG, 45.8 DEG, 45.9 DEG, 46.0 DEG);
characteristic peak P8The 2 theta value of (a) is 49.5-50.5 deg. (e.g. 49.5 deg., 49.6 deg., 49.7 deg., 49.8 deg., 49.9 deg., 50.0 deg., 50.1 deg., 50.2 deg., 50.3 deg., 50.4 deg., 50.5 deg.);
characteristic peak P9Has a 2 theta value of 52.8 deg. -53.3 deg. (e.g. 52.8 deg., 52.9 deg., 53.0 deg., 53.1 deg., 53.2 or 53.3 deg.).
In some embodiments, the fluorinated gadolinium hydroxide material has an XRD powder diffraction pattern including characteristic peaks with the following 2 theta values: 16.6 +/-0.1 degrees, 29.0 +/-0.1 degrees, 29.8 +/-0.1 degrees, 33.6 +/-0.1 degrees, 38.3 +/-0.1 degrees, 42.1 +/-0.1 degrees, 45.0 +/-0.1 degrees, 50.2 +/-0.1 degrees, 51.9 +/-0.1 degrees and 53.2 +/-0.1 degrees.
In some embodiments, the fluorinated gadolinium hydroxide material has an XRD powder diffraction pattern including characteristic peaks with the following 2 theta values: 16.9 +/-0.1 degrees, 29.4 +/-0.1 degrees, 29.8 +/-0.1 degrees, 34.1 +/-0.1 degrees, 38.5 +/-0.1 degrees, 42.4 +/-0.1 degrees, 45.6 +/-0.1 degrees, 50.0 +/-0.1 degrees, 52.2 +/-0.1 degrees and 53.1 +/-0.1 degrees.
In some embodiments, the fluorinated gadolinium hydroxide material has an XRD powder diffraction pattern including characteristic peaks with the following 2 theta values: 16.9 +/-0.1 degrees, 29.8 +/-0.1 degrees, 34.2 +/-0.1 degrees, 38.6 +/-0.1 degrees, 42.5 +/-0.1 degrees, 45.8 +/-0.1 degrees, 50.0 +/-0.1 degrees, 52.4 +/-0.1 degrees and 53.2 +/-0.1 degrees.
In some embodiments, the fluorinated gadolinium hydroxide material has a crystal structure comprising a plurality of Gd-centered N-topped gdns9Tetrakaidecahedron, multiple GdN9Forming a three-dimensional skeletal network structure in a manner sharing a vertex N, wherein N is OH-Or F-。
In some embodiments, the fluorinated gadolinium hydroxide material has a magnetic entropy change value- Δ S at a temperature of 2K and a magnetic field change Δ H of 7TmIs 70J kg-1K-1Above, e.g., 70 to 80J kg-1K-1。
In some aspects, the present disclosure provides a method for preparing fluorinated gadolinium hydroxide, comprising
(1) Providing a composition containing Gd3+And F-An aqueous solution of (a);
(2) mixing the liquid obtained in the last step with alkali until the pH of the mixed liquid is 5-8 (such as 5-6, 6-7 or 7-8);
(3) putting the liquid obtained in the last step into a pressure-resistant hydrothermal kettle for closed hydrothermal treatment, wherein the hydrothermal treatment temperature is 180-220 ℃, and the heat preservation time is 1-5 days;
optionally, performing solid-liquid separation on the product obtained in the last step, and collecting solid matters;
further optionally, the solids are treated by one or more of: and (5) washing and drying.
In some embodiments, in step (1), the aqueous solution contains GdCl3。
In some embodiments, in step (1), the aqueous solution contains HF or NaF.
In some embodiments, in step (1), Gd3+And F-Is 1:0.5 to 2.5, such as 1:1 to 2, such as 1: 1.5.
In some embodiments, in step (1), Gd3+The concentration of (b) is 0.1 to 0.3 mol/L.
In some embodiments, in step (2), the base is a hydroxide, such as an alkali metal hydroxide or an alkaline earth metal hydroxide.
In some embodiments, in step (2), the base is an aqueous sodium hydroxide solution, for example, an aqueous 2-3 mol/L sodium hydroxide solution.
In some embodiments, the fluorinated gadolinium hydroxide materials of the present disclosure are prepared from the methods of the present disclosure.
In some embodiments, drying refers to drying at 100 to 120 ℃.
In some embodiments, the drying time is 8 to 12 hours.
In some aspects, the present disclosure provides an adiabatic demagnetization refrigerant comprising the gadolinium oxyfluoride material of any one of the above.
In some aspects, the present disclosure provides the use of the gadolinium oxyfluoride as described above for adiabatic demagnetization refrigeration.
In some embodiments, the gadolinium oxyfluoride hydroxide described above is used as a refrigerant in an adiabatic demagnetization refrigerator.
In some embodiments, the fluorinated gadolinium hydroxide materials described above are used to achieve temperatures below 1K.
Interpretation of terms
The Magnetocaloric Effect (MCE) refers to the reversible adiabatic change of the applied magnetic field to the temperature of a material.
Adiabatic Demagnetization (Adiabatic Demagnetization) refers to a process in which a magnetic field is applied to a refrigerant to align its magnetic moments regularly in the direction of the magnetic field, and then the magnetic field is removed adiabatically to obtain a lower temperature.
Advantageous effects
The disclosed methods or products have one or more of the following advantages:
1) the synthetic method of the gadolinium oxyfluoride is convenient and fast, is easy to operate and has a wide application prospect;
2) gadolinium fluorohydroxide has a significant magnetocaloric effect (MCE), for example with a large magnetic entropy variation;
3) gadolinium fluorohydroxide has a significant magnetocaloric effect (MCE) at low temperature conditions, for example, has a large magnetic entropy change;
4) gadolinium oxyfluoride has a significant magnetocaloric effect (MCE) in a weak magnetic field, for example, has a large magnetic entropy change value;
5) the fluorinated gadolinium hydroxide has good thermal stability;
6) the gadolinium oxyfluoride has a high rare earth/ligand mass ratio, and further has high magnetic density and enhanced magnetocaloric effect.
Drawings
FIG. 1 is an SEM photograph of a fluorinated gadolinium hydroxide material of an embodiment;
FIG. 2 is an XRD spectrum of a fluorinated gadolinium hydroxide material of an example;
FIG. 3 a shows Gd of a fluorinated gadolinium hydroxide material of an embodiment3+B of fig. 3 shows a schematic plan view of the three-dimensional structure of the crystal projected on the paper surface along the c-axis;
FIG. 4 is a thermogravimetric plot of the gadolinium fluorohydroxide material of the example;
FIG. 5 is a graph of temperature change magnetic susceptibility and a graph of temperature change field magnetization (shown inset) for a fluorinated gadolinium hydroxide material of an example;
FIG. 6 is a graph showing the magnetic entropy change of a gadolinium oxyfluoride magnetic refrigeration material.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.
Example 1
(1) GdCl was added to 5ml of water3(0.371g,1.0mmol) and HF solution (0.043mL, containing HF 1mmol) to obtain a mixed solution;
(2) adding NaOH water into the mixed solutionSolution (2.5mol L)-1) To a system pH of about 7.
(3) The product was transferred to a pressure-resistant stainless steel autoclave with a polytetrafluoroethylene liner having a volume of 25mL, heated to 200 ℃ and kept at this temperature for 3 days (72 hours). After hydrothermal treatment, the obtained product was subjected to solid-liquid separation, the solid was collected, washed with deionized water 3 times, and then air-dried at 100 ℃ overnight to obtain the solid material of example 1.
Example 2
Example 2 differs from example 1 in that the aqueous HF solution used in step (1) was 0.066mL in volume, corresponding to 1.5mmol of HF.
The other steps and parameters were the same as in example 1 to obtain a solid material of example 2.
Example 3
Example 3 differs from example 1 in that the aqueous HF solution used in step (1) was 0.086mL in volume, corresponding to 2mmol of HF.
The other steps and parameters were the same as in example 1 to obtain a solid material of example 3.
Analytical testing
(1) Topography analysis
Fig. 1 a and d show SEM photographs of the solid material of example 1.
Fig. 1 b and e show SEM photographs of the solid material of example 2.
Fig. 1 c and f show SEM photographs of the solid material of example 3.
From the SEM photographs, it can be seen that the materials of examples 1-3 have uniform morphology and no impurities.
(2) XRD analysis
The powdery solid materials of examples 1 to 3 were subjected to structural characterization at 298K using a Rigaku Ultima type IV X-ray powder diffractometer (copper target). Fig. 2 a, b and c show XRD curves of the powdery solid materials of examples 1, 2 and 3, respectively. Their characteristic peak 2 θ values (unit: °) are shown in table 1 below:
TABLE 1
| Characteristic peak/2 theta | |
| Example 1 | 16.6、29.0、29.8、33.6、38.3、42.1、45.0、50.2、51.9、53.2 |
| Example 2 | 16.9、29.4、29.8、34.1、38.5、42.4、45.6、50.0、52.2、53.1 |
| Example 3 | 16.9、29.8、34.2、38.6、42.5、45.8、50.0、52.4、53.2 |
| Y(OH)1.57F1.43 | 16.9、29.4、30.4、42.8、52.8 |
| Gd(OH)3 | 16.0、28.0、29.3、32.5、41.2、43.5、49.8、50.4 |
Analysis of the XRD profile of FIG. 2 revealed that the profile of this material was consistent with Gd (OH)3(card number JCPDS #83-2037) and Y (OH)1.57F1.43(the spectrum of card number JCPDS #80-2008) was similar, from which it was deduced that the solid product of examples 1-3 was Gd (OH)3Part of OH-Quilt F-The product obtained by substitution, i.e. having the following general formula: gd (OH)yF3-y。
Using the General Structure Analysis System (GSAS) program, with Y (OH)1.57F1.43As initial structural formForm, the XRD curves were fitted by Rietveld method and the results are shown in table 2 below. Fitting accuracy χ of examples 1, 2, and 321.32, 1.07 and 1.05, respectively, indicating that the fitting results are very close to the experimental values. Gd (OH) is also shown in Table 23For comparison with the solid materials of examples 1 to 3.
FIG. 3 a shows Gd for the fluorinated gadolinium hydroxide materials of examples 1 to 33+The geometric configuration diagram of (1). In this structure, each Gd3+Coordinated to nine ligands N (ligand N is-OH or F)-) And three Gd are attached per ligand N (OH-or F-)3+And periodically and repeatedly forming a three-dimensional framework in space.
B of fig. 3 shows a schematic plan view of the three-dimensional structure of the crystal projected on the paper along the c-axis. In the figure, arrows a and b indicate the directions of the a-axis and the b-axis of the hexagonal system, respectively. In the projection view, Gd3+Enclosing to form a plane hexagon.
(3) Energy spectrum analysis (EDS)
The compositions of the solid materials of examples 1-3 were identified by energy dispersive X-ray spectroscopy (EDS). The results showed that O, F and Gd elements were present in the solid materials of examples 1 to 3. The solid material of each example was subjected to at least 3 EDS tests with the following results:
TABLE 3
| Atomic ratio of F to Gd | |
| Example 1 | 1.083±0.226 |
| Example 2 | 1.534±0.231 |
| Example 3 | 2.125±0.283 |
According to the above analysis results, the atomic ratio of F to Gd was close to 1:1, 1.5:1 and 2:1 for the solid materials of examples 1 to 3.
(4) Thermogravimetric analysis (TG)
Thermogravimetric (TG) analysis was performed on the solid materials of examples 1 to 3 using an SDT-Q600 thermal analyzer at a temperature range of 30 ℃ to 800 ℃ in an air atmosphere. The thermogravimetric analysis curves g, h and i in FIG. 4 show the solid materials of examples 1 to 3, respectively. The results show that the weight loss of the solid materials of examples 1-3 in the temperature rising region of 200-550 ℃ is respectively 8.54%, 6.01% and 4.26%, and the weight loss is reduced in sequence. From the above-mentioned energy spectrum analysis and XRD analysis, it was found that the solid materials of examples 1 to 3 had higher doping ratios of F atoms. Therefore, the results of thermogravimetric analysis are in agreement with those of XRD and EDS analyses.
The thermogravimetric analysis result shows that 3 compounds show an obvious thermal weight loss phenomenon at 250 ℃, and the material has better thermal stability before 250 ℃.
(5) Magnetocaloric performance analysis
And testing the fluorinated gadolinium hydroxide material by adopting a Quantum Design SQUID MPMS magnetometer under the external magnetic field condition that the temperature range is 2-300K and 1000 Oe.
FIGS. 5 a, c, and e are graphs of the temperature swing susceptibility of the fluorinated gadolinium hydroxide materials of examples 1, 2, and 3, with the abscissa being temperature, the unit K, and the ordinate being χMT, unit cm3 K mol-1。
FIG. 5 a, c, e show the χ of fluorinated gadolinium hydroxide material at room temperatureMT value of 7.99cm3 K mol-1(examples of the invention)1)，7.97cm3 K mol-1(example 2), 7.96cm3 K mol-1(example 3) calculation of Individual Gd according to Curie's theorem3+MT theoretical value obtained by ion of 7.88cm3 mol-1K is close. In the temperature range of 300-100K, the MT value hardly changes with the decrease of the temperature, the MT value starts to decrease slowly below 100K, the MT value decreases more rapidly with the decrease of the temperature, and the MT value is 4.59cm when the temperature reaches 2K3 K mol-1(example 1), 5.29cm3 K mol-1(example 2), 5.80cm3 K mol-1(example 3).
Within the range of 2-300K, is right XMThe curves from T to T are fitted according to the Curie-Weiss theorem to obtain:
C＝8.04cm3 K mol-1θ ═ 1.31K (example 1);
C＝8.07cm3 K mol-1θ ═ 0.95K (example 2);
C＝8.03cm3 K mol-1θ ═ 0.53K (example 3);
the negative weiss constant also illustrates the antiferromagnetic coupling of the gadolinium fluorohydroxide material from the side.
The inset graphs of a, c, e in FIG. 5 are plots of the magnetization intensity of the fluorinated gadolinium hydroxide materials of examples 1, 2 and 3 obtained by testing at a temperature of 2-10K and a magnetic field of 0-7T, respectively, with the abscissa being the magnetic field intensity and the ordinate being the magnetization intensity and the unit being N μΒ. As shown in the figure, the magnetization intensity of the fluorinated gadolinium hydroxide material gradually increases along with the increase of the magnetic field intensity, and reaches a saturation value of 7.07N mu at a temperature of 2K and a magnetic field of 7TΒExample 1, 7.03 N.mu.ΒExample 2, 7.05 N.mu.Β(example 3), this and the theoretical value of 7N μΒAre very close.
B, d and f in FIG. 6 are graphs of magnetic entropy change of gadolinium oxyfluoride material, with the abscissa being temperature, the unit K, and the left and right ordinates being magnetic entropy change (unit mass, unit volume) and the unit J kg-1K-1、mJ cm-3K-1. Practice ofThe magnetic entropy change values of the fluorinated gadolinium hydroxide materials of examples 1, 2 and 3 can be determined according to Maxwell formula
The magnetization data of the temperature and the change field are used for estimation.
B, d and f in fig. 6 show that the magnetic entropy value of the fluorinated gadolinium hydroxide material is increased in the test range, and the magnetic entropy change value (- Δ S) is 7T at 2K Δ Hm) Reaches the maximum of 72.4J kg-1K-1Example 1, 74.3J kg-1K-1Example 2, 76.1J kg-1K-1(example 3).
In particular, the gadolinium oxyfluoride material of example 3 has a magnetic entropy change value (- Δ S) at 2K, Δ H ═ 3Tm) Also can reach 55.4J kg-1K-1. It is noted that the gadolinium oxyfluoride material of example 3 has a magnetic entropy change (- Δ S) of 7T at 2K Δ Hm) Up to 76.1Jkg-1K-1The material with the largest magnetic entropy change value is known at present.
Table 4 shows the fluorinated gadolinium hydroxide materials and Gd (OH) of examples 1, 2 and 33Magnetic entropy variation (- Δ S) at 2K/3K Δ H ═ 7Tm)。
TABLE 4
As shown in Table 4, the magnetic entropy change values of the materials of examples 1 to 3 were significantly higher than those of Gd (OH)3。
While specific embodiments of the invention have been described in detail, those skilled in the art will understand that: various modifications may be made in the details within the teachings of the disclosure, and these variations are within the scope of the invention. The full scope of the invention is given by the appended claims and any equivalents thereof.
Claims (14)
1. A fluorinated gadolinium hydroxide material having the general formula: gd (OH)yF3-yWherein y is 0.5～2.5。
2. The material according to claim 1, wherein y is 1-2, preferably 1.5-2, more preferably 1, 1.5 or 2.
3. The material of claim 1, which is crystalline, having the following crystalline form characteristics: it belongs to the hexagonal system, preferably its space group is P63/m。
4. The material of claim 3, having one or more of the following characteristics:
a unit cell volume of
(e.g. in
)；
-its calculated density of crystals ρcalcd5.5 to 6.5g/cm3(e.g., 5.8 to 6.2 g/cm)3)。
5. The material of claim 4, having the following unit cell parameters:
6. The material of claim 4, having the following unit cell parameters:
α＝90°；
β＝90°；
γ＝120°。
7. the material of claim 1, having an XRD powder diffraction pattern comprising a characteristic peak P1～P4Wherein, in the step (A),
characteristic peak P1The 2 θ value of (a) is 16.5 ° to 17.5 ° (e.g., 16.5 °, 16.6 °, 16.7 °, 16.8 °, 16.9 °, 17.0 °, 17.1 °, 17.2 °, 17.3 °, 17.4 °, or 17.5 °);
characteristic peak P2The 2 θ value of (a) is 29.5 ° -30.5 ° (e.g., 29.5 °, 29.6 °, 29.7 °, 29.8 °, 29.9 °, 30.0 °, 30.1 °, 30.2 °, 30.3 °, 30.4 °, or 30.5 °);
characteristic peak P3The 2 θ value of (a) is 42.0 ° to 43.0 ° (e.g., 42.0 °, 42.1 °, 42.2 °, 42.3 °, 42.4 °, 42.5 °, 42.6 °, 42.7 °, 42.8 °, or 42.9 °);
characteristic peak P4The 2 θ value of (a) is 51.4 ° -52.4 ° (e.g., 51.4 °, 51.5 °, 51.6 °, 51.7 °, 51.8 °, 51.9 °, 52.0 °, 52.1 °, 52.2 °, 52.3 °, or 52.4 °);
preferably, the XRD powder diffraction pattern of the material also comprises one or more of the following characteristic peaks P5～P9Wherein, in the step (A),
characteristic peak P5The 2 θ value of (a) is 33.5 ° -34.5 ° (e.g., 33.5 °, 33.6 °, 33.7 °, 33.8 °, 33.9 °, 34.0 °, 34.1 °, 34.2 °, 34.3 °, 34.4 °, or 34.5 °);
characteristic peak P6The 2 θ value of (a) is 38.0 ° -39.0 ° (e.g., 38.0 °, 38.1 °, 38.2 °, 38.3 °, 38.4 °, 38.5 °, 38.6 °, 38.7 °, 38.8 °, 38.9 °, or 39.0 °);
characteristic peak P7The 2 θ value of (a) is 45.0 ° to 46.0 ° (e.g., 45.0 °, 45.1 °, 45.2 °, 45.3 °, 45.4 °, 45.5 °, 45.6 °, 45.7 °, 45.8 °, 45.9 °, or 46.0 °);
characteristic peak P8The 2 θ value of (a) is 49.5 ° -50.5 ° (e.g., 49.5 °, 49.6 °, 49.7 °, 49.8 °, 49.9 °, 50.0 °, 50.1 °, 50.2 °, 50.3 °, 50.4 °, or 50.5 °);
characteristic peak P9Has a 2 theta value of 52.8 DEG to 53.3 DEG (e.g., 52.8 DEG, 52.9 DEG, 53.0 DEG, 53.1 DEG, 53.2 DEG or 53.3 DEG).
8. The material of claim 1, the material having a crystal structure comprising a plurality of Gd-centered N-topped gdns9Tetrakaidecahedron, multiple GdN9Forming a three-dimensional skeletal network structure in a manner sharing a vertex N, wherein N is OH-Or F-。
9. The material as claimed in claim 1, wherein the magnetic entropy change value- Δ Sm is 70J kg at the temperature of 2K and the magnetic field change Δ H-7T-1K-1Above, e.g., 70 to 80J kg-1K-1。
10. A preparation method of fluorinated gadolinium hydroxide material comprises
(1) Providing a composition containing Gd3+And F-An aqueous solution of (a);
(2) mixing the liquid obtained in the last step with alkali until the pH of the mixed liquid is 5-8;
(3) putting the liquid obtained in the last step into a pressure-resistant hydrothermal kettle for closed hydrothermal treatment, wherein the hydrothermal treatment temperature is 180-220 ℃, and the heat preservation time is 1-5 days;
optionally, performing solid-liquid separation on the product obtained in the last step, and collecting solid matters;
further optionally, the solids are treated by one or more of: and (5) washing and drying.
11. The method of claim 10, wherein one or more of the following features:
step (1), wherein the aqueous solution contains GdCl3；
-in step (1), the aqueous solution contains HF or NaF;
in step (1), Gd3+And F-Is 1:0.5 to 2.5, such as 1:1 to 2, such as 1:1.
In step (1), Gd3+The concentration of (A) is 0.1-0.3 mol/L;
in step (2), the alkali is an aqueous sodium hydroxide solution, for example, an aqueous sodium hydroxide solution of 2 to 3 mol/L.
12. The method according to claim 10, wherein the drying is drying at 100-120 ℃; preferably, the drying time is 8 to 12 hours.
13. An adiabatic demagnetization refrigerant, comprising the fluorinated gadolinium hydroxide material according to any one of claims 1 to 9.
14. Use of a fluorinated gadolinium hydroxide material according to any one of claims 1 to 9 for adiabatic demagnetization refrigeration;
preferably, the use of said gadolinium oxyfluoride as a refrigerant for an adiabatic demagnetization refrigerator.
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| CN113277545A (en) * | 2021-05-12 | 2021-08-20 | 厦门大学 | Gadolinium fluorocarbonate, and preparation method and application thereof |
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