CN117049494A - Negative thermal expansion material and preparation method thereof - Google Patents
Negative thermal expansion material and preparation method thereof Download PDFInfo
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- CN117049494A CN117049494A CN202311021795.XA CN202311021795A CN117049494A CN 117049494 A CN117049494 A CN 117049494A CN 202311021795 A CN202311021795 A CN 202311021795A CN 117049494 A CN117049494 A CN 117049494A
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- 239000000463 material Substances 0.000 title claims abstract description 121
- 238000002360 preparation method Methods 0.000 title claims abstract description 29
- 239000000126 substance Substances 0.000 claims abstract description 12
- 229910052700 potassium Inorganic materials 0.000 claims abstract description 4
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 3
- 239000011812 mixed powder Substances 0.000 claims description 45
- 238000010438 heat treatment Methods 0.000 claims description 27
- 238000001816 cooling Methods 0.000 claims description 25
- 239000003795 chemical substances by application Substances 0.000 claims description 24
- 239000013078 crystal Substances 0.000 claims description 23
- 238000001354 calcination Methods 0.000 claims description 22
- 229910019142 PO4 Inorganic materials 0.000 claims description 18
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 18
- 239000010452 phosphate Substances 0.000 claims description 18
- 229910052788 barium Inorganic materials 0.000 claims description 16
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 claims description 16
- 229910017052 cobalt Inorganic materials 0.000 claims description 16
- 239000010941 cobalt Substances 0.000 claims description 16
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 16
- 238000000034 method Methods 0.000 claims description 12
- 238000002156 mixing Methods 0.000 claims description 11
- 238000004519 manufacturing process Methods 0.000 claims description 9
- 230000004907 flux Effects 0.000 claims description 5
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 3
- 230000008859 change Effects 0.000 abstract description 4
- 239000000155 melt Substances 0.000 description 10
- 238000002425 crystallisation Methods 0.000 description 9
- 230000008025 crystallization Effects 0.000 description 9
- 239000000843 powder Substances 0.000 description 9
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 7
- 239000007788 liquid Substances 0.000 description 6
- 230000008569 process Effects 0.000 description 6
- 239000002994 raw material Substances 0.000 description 4
- AFCARXCZXQIEQB-UHFFFAOYSA-N N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CCNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 AFCARXCZXQIEQB-UHFFFAOYSA-N 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- AIYUHDOJVYHVIT-UHFFFAOYSA-M caesium chloride Chemical compound [Cl-].[Cs+] AIYUHDOJVYHVIT-UHFFFAOYSA-M 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- FGDZQCVHDSGLHJ-UHFFFAOYSA-M rubidium chloride Chemical compound [Cl-].[Rb+] FGDZQCVHDSGLHJ-UHFFFAOYSA-M 0.000 description 2
- 229910052708 sodium Inorganic materials 0.000 description 2
- 229910018068 Li 2 O Inorganic materials 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 235000005811 Viola adunca Nutrition 0.000 description 1
- 240000009038 Viola odorata Species 0.000 description 1
- 235000013487 Viola odorata Nutrition 0.000 description 1
- 235000002254 Viola papilionacea Nutrition 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052792 caesium Inorganic materials 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 229910052701 rubidium Inorganic materials 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/26—Phosphates
- C01B25/45—Phosphates containing plural metal, or metal and ammonium
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Compositions Of Oxide Ceramics (AREA)
Abstract
The invention discloses a negative thermal expansion material and a preparation method thereof, wherein the chemical formula of the negative thermal expansion material is A 2 BaCo(PO 4 ) 2 Wherein A is selected from one of Li, na, K, rb, cs. The invention provides a chemical formula A for the first time 2 BaCo(PO 4 ) 2 The negative thermal expansion material has no structural phase change in a temperature range of 4-300K and shows a negative expansion characteristic of a single a-axis. Among them, the negative expansion characteristic of the single a-axis is most remarkable in the range of 100 to 300K.
Description
Technical Field
The invention relates to the technical field of negative thermal expansion materials, in particular to a negative thermal expansion material and a preparation method thereof.
Background
The negative thermal expansion material has a linear expansion coefficient or a bulk expansion coefficient of a negative value in a certain temperature range, and by utilizing the characteristics of the negative thermal expansion material and compounding with other materials, the expansion coefficient of the material can be controlled to manufacture a zero expansion or low expansion material, so that the negative thermal expansion material can be used for manufacturing precision mechanical devices, optical devices, electronic devices and the like, and has wide application prospects in the high-tech fields of aerospace, photoelectrons and the like.
Therefore, more negative thermal expansion materials need to be developed to meet the needs of different fields.
Disclosure of Invention
Based on the shortcomings of the prior art, the invention aims to provide a novel negative thermal expansion material, and aims to develop more negative thermal expansion materials so as to meet the demands of different fields.
The technical scheme of the invention is as follows:
in a first aspect of the present invention, there is provided a negative thermal expansion material, wherein the negative thermal expansion material has a chemical formula of a 2 BaCo(PO 4 ) 2 Wherein A is selected from one of Li, na, K, rb, cs.
Optionally, the negative thermal expansion material is a single crystal negative thermal expansion material or a polycrystalline negative thermal expansion material.
In a second aspect of the present invention, there is provided a method for producing a negative thermal expansion material according to the present invention as described above, comprising the steps of:
mixing the source A, the source B, the source C and the fluxing agent to obtain mixed powder;
and calcining the mixed powder to obtain the negative thermal expansion material.
Optionally, the preparation method of the negative thermal expansion material specifically comprises the following steps:
according to A 2 BaCo(PO 4 ) 2 The stoichiometric ratio of each element in the preparation method is that an A source, a barium source, a cobalt source and a phosphate source are taken;
mixing the source A, the source B, the source C and the source P with a fluxing agent to obtain mixed powder; wherein, the mol ratio of the fluxing agent to the Ba element is (0.3-0.8): 1, a step of;
calcining the mixed powder at a first preset temperature for a first preset time, and naturally cooling to room temperature to obtain the monocrystalline negative thermal expansion material.
Optionally, the step of calcining the mixed powder at a first preset temperature for a first preset time, and naturally cooling to room temperature to obtain the monocrystalline negative thermal expansion material specifically comprises the following steps:
and (3) placing the mixed powder into a muffle furnace, heating to 700-900 ℃ at a heating rate of 60-70 ℃/h, calcining at 700-900 ℃ for 80-100h, and naturally cooling to room temperature to obtain the monocrystalline negative thermal expansion material.
Optionally, the preparation method of the negative thermal expansion material specifically comprises the following steps:
step A, according to A 2 BaCo(PO 4 ) 2 The stoichiometric ratio of each element in the preparation method is that an A source, a barium source, a cobalt source and a phosphate source are taken; wherein the A source is in excess of 3-8%;
step B, mixing the source A, the source barium, the source cobalt, the source phosphate and the fluxing agent to obtain mixed powder; the mol ratio of the fluxing agent to the Ba element is (1-2): 1, a step of;
step C, calcining the mixed powder at a second preset temperature for a second preset time, and naturally cooling to room temperature;
and D, repeating the step C for a plurality of times to obtain the polycrystalline negative thermal expansion material.
Optionally, the step C specifically includes:
and (3) placing the mixed powder into a muffle furnace, heating to 600-800 ℃ at a heating rate of 60-70 ℃/h, calcining at 600-800 ℃ for 24-48 h, and naturally cooling to room temperature.
Optionally, step C is repeated 2-3 times.
Optionally, the fluxing agent comprises NH 4 Cl。
Optionally, the a source comprises at least one of carbonate of a, chloride of a, oxide of a; and/or the number of the groups of groups,
the barium source comprises BaCO 3 、BaO、BaCl 2 At least one of (a) and (b); and/or the number of the groups of groups,
the cobalt source comprises CoCO 3 、CoO、CoCl 2 At least one of (a) and (b); and/or the number of the groups of groups,
the phosphate source comprises (NH) 4 ) 2 HPO 4 。
The beneficial effects are that: the invention provides a chemical formula A for the first time 2 BaCo(PO 4 ) 2 The negative thermal expansion material has a chemical formula of Li 2 BaCo(PO 4 ) 2 、Na 2 BaCo(PO 4 ) 2 、K 2 BaCo(PO 4 ) 2 、Rb 2 BaCo(PO 4 ) 2 Or Cs 2 BaCo(PO 4 ) 2 . The negative thermal expansion materials are concretely uniaxial negative thermal expansion materials, have no structural phase change in the temperature range of 4-300K, and show negative expansion characteristics of a single a axis. Among them, the negative expansion characteristic of the single a-axis is most remarkable in the range of 100 to 300K.
Drawings
FIG. 1 is a graph showing the morphology of the uniaxial negative thermal expansion material prepared in example 1.
Fig. 2 is an XRD pattern of the uniaxial negative thermal expansion material prepared in example 1.
FIG. 3 is a graph showing the unit cell parameters of the uniaxial negative thermal expansion material prepared in example 1 with temperature.
Detailed Description
The invention provides a negative thermal expansion material and a preparation method thereof, which are used for making the purposes, technical schemes and effects of the invention clearer and more definite, and the invention is further described in detail below. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
The embodiment of the invention provides a novel negative thermal expansion material, wherein the chemical formula of the negative thermal expansion material is A 2 BaCo(PO 4 ) 2 Wherein A is selected from Li. Na, K, rb, cs.
The invention provides a chemical formula A for the first time 2 BaCo(PO 4 ) 2 The negative thermal expansion material has a chemical formula of Li 2 BaCo(PO 4 ) 2 、Na 2 BaCo(PO 4 ) 2 、K 2 BaCo(PO 4 ) 2 、Rb 2 BaCo(PO 4 ) 2 Or Cs 2 BaCo(PO 4 ) 2 . The negative thermal expansion materials are concretely uniaxial negative thermal expansion materials, have no structural phase change in the temperature range of 4-300K, and show negative expansion characteristics of a single a axis. Among them, the negative expansion characteristic of the single a-axis is most remarkable in the range of 100 to 300K.
In some embodiments, the negative thermal expansion material is a single crystalline negative thermal expansion material or a polycrystalline negative thermal expansion material. In this embodiment, the chemical formula is A 2 BaCo(PO 4 ) 2 Which may be a single crystal; or may be polycrystalline, in particular in powder form.
The embodiment of the invention also provides a preparation method of the negative thermal expansion material, which is provided by the embodiment of the invention, and comprises the following steps:
mixing the source A, the source B, the source C and the fluxing agent to obtain mixed powder;
and calcining the mixed powder to obtain the negative thermal expansion material.
The embodiment of the invention adopts a fluxing method to prepare the negative thermal expansion material. When calcining, the fluxing agent is melted to form a liquid fluxing agent, so that the source A, the source Ba, the source Co and the phosphate exist in the liquid fluxing agent, then in the cooling process, the energy of the system is reduced, when the temperature reaches the crystallization temperature, the solution reaches a supersaturation state, crystallization is started immediately, when the temperature is continuously reduced, the higher the supersaturation degree is, the crystallization speed is also high, the crystals are continuously grown, and the negative thermal expansion material is formed.
In some embodiments, when the negative thermal expansion material is a single crystal, the preparation method of the negative thermal expansion material specifically includes the steps of:
step S11, according to A 2 BaCo(PO 4 ) 2 The stoichiometric ratio of each element in the preparation method is that an A source, a barium source, a cobalt source and a phosphate source are taken;
step S12, mixing the source A, the source B, the source C, the source P and the fluxing agent to obtain mixed powder; wherein, the mol ratio of the fluxing agent to the Ba element is (0.3-0.8): 1 (which may be, for example, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, or 0.8:1, etc.);
and S13, calcining the mixed powder at a first preset temperature for a first preset time, and naturally cooling to room temperature to obtain the monocrystalline negative thermal expansion material.
Specifically, in step S13, the step of calcining the mixed powder at a first preset temperature for a first preset time, and naturally cooling to room temperature to obtain the single crystal negative thermal expansion material specifically includes:
and (3) placing the mixed powder into a muffle furnace, heating to 700-900 ℃ at a heating rate of 60-70 ℃/h (such as 700 ℃, 750 ℃, 800 ℃, 850 ℃ or 900 ℃), calcining at 700-900 ℃ for 80-100h (such as 80h, 85h, 90h, 92h, 94h, 96h, 98h or 100 h), and naturally cooling to room temperature to obtain the single crystal negative thermal expansion material.
Through the preparation steps and the proportion of the raw materials provided in the embodiment, the monocrystalline negative thermal expansion material can be prepared, has the advantages of good integrity, no macroscopic defect, high success rate (about 100%), easy control of crystal size and appearance, difficult cracking of crystals, short preparation period (within 5 days), and capability of ensuring the quality of the material to meet various application requirements. Specifically, the fluxing agent is NH 4 Cl is described. NH (NH) 4 Cl has a melting point of 340 ℃, NH when the temperature exceeds 340 DEG C 4 Cl melts to form a liquid flux (providing a melt environment), in which case the source A, the source Ba, the source Co and the source phosphate are present in the liquid flux, and the raw materials are thoroughly mixed after severe thermal motion in the melt environment during the course of 80-100h at a temperature of 700-900 ℃ and then inThe energy of the whole material system can be reduced in the cooling process, when the temperature is reduced to the crystallization temperature, the melt is supersaturated, crystallization starts, the higher the melt is, the faster the crystallization speed is, and the crystals are continuously grown in the process of continuously reducing the temperature, so that the monocrystalline negative thermal expansion material is obtained.
In some embodiments, when the negative thermal expansion material is polycrystalline, the preparation method of the negative thermal expansion material specifically includes the steps of:
s21 according to A 2 BaCo(PO 4 ) 2 The stoichiometric ratio of each element in the preparation method is that an A source, a barium source, a cobalt source and a phosphate source are taken; wherein the a source is in excess of 3-8% (e.g., may be 3%, 4%, 5%, 6%, 7% or 8%) to inhibit the impurity phase;
s22, mixing the source A, the source barium, the source cobalt, the source phosphate and the fluxing agent to obtain mixed powder; the mol ratio of the fluxing agent to the Ba element is (1-2): 1 (which may be, for example, 1:1, 1.2:1, 1.4:1, 1.5:1, 1.6:1, 1.8:1, or 2:1, etc.);
s23, calcining the mixed powder at a second preset temperature for a second preset time, and naturally cooling to room temperature;
s24, repeating the step S23 for a plurality of times to obtain the polycrystalline negative thermal expansion material.
Specifically, the step S23 specifically includes:
the mixed powder is placed in a muffle furnace, heated to 600-800 ℃ at a heating rate of 60-70 ℃/h (such as 600 ℃, 650 ℃, 700 ℃, 750 ℃ or 800 ℃), calcined at 600-800 ℃ for 24-48 h (such as 24h, 30h, 35h, 40h, 44h or 48 h), and naturally cooled to room temperature.
Specifically, step S232-3 is repeated.
Through the preparation steps and the proportion of the raw materials provided in the embodiment, the powder polycrystalline negative thermal expansion material can be prepared, and the powder polycrystalline negative thermal expansion material is high in purity and can meet various application requirements. Specifically, the fluxing agent is NH 4 Cl is described. NH (NH) 4 Cl with a melting point of 340 ℃ and a working temperatureWhen the temperature exceeds 340 ℃, NH 4 Cl melts to form a liquid flux (providing a melt environment), at this time, an A source, a barium source, a cobalt source and a phosphate source exist in the liquid flux, and in the process of keeping at 600-800 ℃ for 24-48 hours, all raw materials are fully mixed after intense thermal motion in the melt environment, then the energy of the whole material system can be reduced in the process of cooling, when the temperature is reduced to the crystallization temperature, the melt is supersaturated, crystallization starts, the higher the melt is, the faster the crystallization speed is, and crystals grow continuously in the process of continuously reducing the temperature, so as to obtain the polycrystalline negative thermal expansion material.
In step S21, as an example, according to A 2 BaCo(PO 4 ) 2 When the molar ratio of the A source to the barium source to the cobalt source to the phosphate source is 1:1:1:2, if the A source is excessive by 5%, the molar ratio of the A source to the barium source to the cobalt source to the phosphate source is 1.05:1:1:2.
In steps S12 and S22, in some embodiments, the step of mixing the a source, the barium source, the cobalt source, the phosphate source, and the fluxing agent to obtain a mixed powder specifically includes:
mixing the source A, the source B, the source C and the source P with a fluxing agent, and grinding to obtain the mixed powder.
In some embodiments, the fluxing agent comprises NH 4 Cl。
In some embodiments, the source of a comprises at least one of a carbonate, a chloride, an oxide of a.
In some embodiments, the a source comprises Li 2 CO 3 、Na 2 CO 3 、K 2 CO 3 、Rb 2 CO 3 、Cs 2 CO 3 、LiCl、NaCl、KCl、RbCl、CsCl、Li 2 O、Na 2 O、K 2 O、Rb 2 O、Cs 2 One of O.
In some embodiments, the barium source comprises BaCO 3 、BaO、BaCl 2 At least one of them.
In some embodiments, the cobalt source comprises CoCO 3 、CoO、CoCl 2 At least one of them.
In some embodiments, the phosphate source comprises (NH 4 ) 2 HPO 4 。
The invention is further illustrated by the following specific examples.
Li in the following examples 2 CO 3 、BaCO 3 、CoO、(NH 4 ) 2 HPO 4 、NH 4 Cl is powder, and the purity is 99.99%, spectral Purity (SP), 99.9%, 99% and 98.5% respectively.
Example 1
The embodiment provides a preparation method of a uniaxial negative thermal expansion material, which comprises the following steps:
li is mixed with 2 CO 3 、BaCO 3 、CoO、(NH 4 ) 2 HPO 4 、NH 4 Cl is uniformly mixed according to the mol ratio of 1:1:1:2:0.5, and is fully ground for 15 minutes in an agate mortar to obtain mixed powder;
placing the mixed powder into an alumina crucible, covering a cover, placing into a box-type muffle furnace, heating to 800 ℃ at a heating rate of 60 ℃/h, preserving heat for 4 days (namely 96 h), naturally cooling to room temperature, and squeezing by a bench vice to obtain Li 2 BaCo(PO 4 ) 2 And (3) single crystal, namely the uniaxial negative thermal expansion material.
Li in example 1 2 BaCo(PO 4 ) 2 The morphology of the single crystal is shown in figure 1, and the single crystal is a quasi-two-dimensional blue-violet crystal with good integrity and no macroscopic defect, and the size is 1cm multiplied by 1cm.
Li in example 1 2 BaCo(PO 4 ) 2 The XRD pattern of the single crystal is shown in fig. 2, and the lattice constant is a=b=0.50279 nm, and c= 14.4500nm.
Li in example 1 2 BaCo(PO 4 ) 2 The unit cell parameters of the single crystal are shown in FIG. 3, wherein circles are measured values, and solid lines are fitted curves, and as can be seen from FIG. 3, li 2 BaCo(PO 4 ) 2 Single crystal with 4-300K unstructured phase transitionAnd as the temperature increases, the unit cell parameter a gradually decreases, exhibiting negative expansion characteristics of the single a-axis, wherein the negative expansion characteristics of the single a-axis are most remarkable in the temperature range of 100 to 300K.
Example 2
The embodiment provides a preparation method of a uniaxial negative thermal expansion material, which comprises the following steps:
li is mixed with 2 CO 3 、BaCO 3 、CoO、(NH 4 ) 2 HPO 4 、NH 4 Cl is uniformly mixed according to the molar ratio of 1.05:1:1:2:1 to obtain mixed powder;
placing the mixed powder into an alumina crucible, covering a cover, placing into a box-type muffle furnace, heating to 700 ℃ at a heating rate of 60 ℃/h, preserving heat for 1 day (24 h), naturally cooling to room temperature, and repeatedly calcining for 3 times to obtain Li 2 BaCo(PO 4 ) 2 And (3) polycrystal powder, namely the uniaxial negative thermal expansion material.
The uniaxial negative thermal expansion material in example 2 has a single a-axis negative thermal expansion characteristic and XRD results similar to those of the uniaxial negative thermal expansion material in example 1.
Example 3
The embodiment provides a preparation method of a uniaxial negative thermal expansion material, which comprises the following steps:
li is mixed with 2 CO 3 、BaCO 3 、CoO、(NH 4 ) 2 HPO 4 、NH 4 Cl is uniformly mixed according to the molar ratio of 1:1:1:2:0.5 to obtain mixed powder;
placing the mixed powder into an alumina crucible, covering a cover, placing into a box-type muffle furnace, heating to 800 ℃ at a heating rate of 60 ℃/h, preserving heat for 100h, naturally cooling to room temperature, and extruding and crushing by a bench vice to obtain Li 2 BaCo(PO 4 ) 2 And (3) single crystal, namely the uniaxial negative thermal expansion material. The uniaxial negative thermal expansion material in example 3 was similar in single a-axis negative thermal expansion characteristic, morphology, and XRD result to the uniaxial negative thermal expansion material in example 1.
Example 4
The embodiment provides a preparation method of a uniaxial negative thermal expansion material, which comprises the following steps:
li is mixed with 2 CO 3 、BaCO 3 、CoO、(NH 4 ) 2 HPO 4 、NH 4 Cl is uniformly mixed according to the molar ratio of 1.05:1:1:2:1 to obtain mixed powder;
placing the mixed powder into an alumina crucible, covering a cover, placing into a box-type muffle furnace, heating to 700 ℃ at a heating rate of 60 ℃/h, preserving heat for 2 days (48 h), naturally cooling to room temperature, and repeatedly calcining for 3 times to obtain Li 2 BaCo(PO 4 ) 2 And (3) polycrystal powder, namely the uniaxial negative thermal expansion material.
The uniaxial negative thermal expansion material in example 4 has a single a-axis negative thermal expansion characteristic and XRD results similar to those of the uniaxial negative thermal expansion material in example 1.
Example 5
The embodiment provides a preparation method of a uniaxial negative thermal expansion material, which comprises the following steps:
li is mixed with 2 CO 3 、BaCO 3 、CoO、(NH 4 ) 2 HPO 4 、NH 4 Cl is uniformly mixed according to the molar ratio of 1:1:1:2:0.6 to obtain mixed powder;
placing the mixed powder into an alumina crucible, covering a cover, placing into a box-type muffle furnace, heating to 800 ℃ at a heating rate of 60 ℃/h, preserving heat for 4 days (namely 96 h), naturally cooling to room temperature, and squeezing by a bench vice to obtain Li 2 BaCo(PO 4 ) 2 And (3) single crystal, namely the uniaxial negative thermal expansion material. The uniaxial negative thermal expansion material in example 5 was similar in single a-axis negative thermal expansion characteristic, morphology, and XRD result to the uniaxial negative thermal expansion material in example 1.
Example 6
The embodiment provides a preparation method of a uniaxial negative thermal expansion material, which comprises the following steps:
li is mixed with 2 CO 3 、BaCO 3 、CoO、(NH 4 ) 2 HPO 4 、NH 4 Cl is uniformly mixed according to the mol ratio of 1.06:1:1:2:1 to obtain mixed powder;
placing the mixed powder into aluminaPlacing the crucible into a box-type muffle furnace after covering a cover, heating to 700 ℃ at a heating rate of 60 ℃/h, preserving heat for 1 day (24 h), naturally cooling to room temperature, and repeating calcination for 3 times to obtain Li 2 BaCo(PO 4 ) 2 And (3) polycrystal powder, namely the uniaxial negative thermal expansion material.
The uniaxial negative thermal expansion material in example 6 was similar in single a-axis negative thermal expansion characteristic and XRD result to the uniaxial negative thermal expansion material in example 1.
Example 7
The embodiment provides a preparation method of a uniaxial negative thermal expansion material, which comprises the following steps:
li is mixed with 2 CO 3 、BaCO 3 、CoO、(NH 4 ) 2 HPO 4 、NH 4 Cl is uniformly mixed according to the molar ratio of 1:1:1:2:0.5 to obtain mixed powder;
placing the mixed powder into an alumina crucible, covering the crucible with a cover, placing into a box-type muffle furnace, heating to 800 ℃ at a heating rate of 70 ℃/h, preserving heat for 4 days (namely 96 h), naturally cooling to room temperature, and squeezing and crushing by a bench vice to obtain Li 2 BaCo(PO 4 ) 2 And (3) single crystal, namely the uniaxial negative thermal expansion material.
The uniaxial negative thermal expansion material in example 7 was similar in single a-axis negative thermal expansion characteristic, morphology, and XRD result to the uniaxial negative thermal expansion material in example 1.
Example 8
The embodiment provides a preparation method of a uniaxial negative thermal expansion material, which comprises the following steps:
li is mixed with 2 CO 3 、BaCO 3 、CoO、(NH 4 ) 2 HPO 4 、NH 4 Cl is uniformly mixed according to the mol ratio of 1.06:1:1:2:1.5 to obtain mixed powder;
placing the mixed powder into an alumina crucible, covering a cover, placing into a box-type muffle furnace, heating to 700 ℃ at a heating rate of 60 ℃/h, preserving heat for 1 day (24 h), naturally cooling to room temperature, and repeatedly calcining for 3 times to obtain Li 2 BaCo(PO 4 ) 2 And (3) polycrystal powder, namely the uniaxial negative thermal expansion material.
The uniaxial negative thermal expansion material in example 8 was similar in single a-axis negative thermal expansion characteristic, morphology, and XRD result to the uniaxial negative thermal expansion material in example 1.
In summary, the present invention provides for the first time a compound of formula A 2 BaCo(PO 4 ) 2 The negative thermal expansion material has a chemical formula of Li 2 BaCo(PO 4 ) 2 、Na 2 BaCo(PO 4 ) 2 、K 2 BaCo(PO 4 ) 2 、Rb 2 BaCo(PO 4 ) 2 Or Cs 2 BaCo(PO 4 ) 2 . The negative thermal expansion materials are concretely uniaxial negative thermal expansion materials, have no structural phase change in the temperature range of 4-300K, and show negative expansion characteristics of a single a axis. Among them, the negative expansion characteristic of the single a-axis is most remarkable in the range of 100 to 300K. At the same time, the invention provides a chemical formula A 2 BaCo(PO 4 ) 2 The preparation method of the negative thermal expansion material specifically adopts a melting-assisting method, and the preparation period is as short as 5 days. The prepared monocrystal negative thermal expansion material has good integrity, no macroscopic defect, high success rate (about 100%), easy control of crystal size and appearance and difficult cracking; the prepared powder polycrystal negative thermal expansion material has high purity.
It is to be understood that the invention is not limited in its application to the examples described above, but is capable of modification and variation in light of the above teachings by those skilled in the art, and that all such modifications and variations are intended to be included within the scope of the appended claims.
Claims (10)
1. A negative thermal expansion material is characterized in that the chemical formula of the negative thermal expansion material is A 2 BaCo(PO 4 ) 2 Wherein A is selected from one of Li, na, K, rb, cs.
2. The negative thermal expansion material according to claim 1, wherein the negative thermal expansion material is a single crystal negative thermal expansion material or a polycrystalline negative thermal expansion material.
3. A method of producing the negative thermal expansion material according to any one of claims 1 to 2, comprising the steps of:
mixing the source A, the source B, the source C and the fluxing agent to obtain mixed powder;
and calcining the mixed powder to obtain the negative thermal expansion material.
4. The method for producing a negative thermal expansion material according to claim 3, wherein the method for producing a negative thermal expansion material specifically comprises the steps of:
according to A 2 BaCo(PO 4 ) 2 The stoichiometric ratio of each element in the preparation method is that an A source, a barium source, a cobalt source and a phosphate source are taken;
mixing the source A, the source B, the source C and the source P with a fluxing agent to obtain mixed powder; wherein, the mol ratio of the fluxing agent to the Ba element is (0.3-0.8): 1, a step of;
calcining the mixed powder at a first preset temperature for a first preset time, and naturally cooling to room temperature to obtain the monocrystalline negative thermal expansion material.
5. The method of producing a negative thermal expansion material according to claim 4, wherein said step of calcining said mixed powder at a first predetermined temperature for a first predetermined time and naturally cooling to room temperature to obtain said single crystal negative thermal expansion material comprises:
and (3) placing the mixed powder into a muffle furnace, heating to 700-900 ℃ at a heating rate of 60-70 ℃/h, calcining at 700-900 ℃ for 80-100h, and naturally cooling to room temperature to obtain the monocrystalline negative thermal expansion material.
6. The method for producing a negative thermal expansion material according to claim 3, wherein the method for producing a negative thermal expansion material specifically comprises the steps of:
step A, according to A 2 BaCo(PO 4 ) 2 The stoichiometric ratio of each element in the preparation method is that an A source, a barium source, a cobalt source and a phosphate source are taken; wherein the A source is in excess of 3-8%;
step B, mixing the source A, the source barium, the source cobalt, the source phosphate and the fluxing agent to obtain mixed powder; the mol ratio of the fluxing agent to the Ba element is (1-2): 1, a step of;
step C, calcining the mixed powder at a second preset temperature for a second preset time, and naturally cooling to room temperature;
and D, repeating the step C for a plurality of times to obtain the polycrystalline negative thermal expansion material.
7. The method for preparing a negative thermal expansion material according to claim 6, wherein said step C specifically comprises:
and (3) placing the mixed powder into a muffle furnace, heating to 600-800 ℃ at a heating rate of 60-70 ℃/h, calcining at 600-800 ℃ for 24-48 h, and naturally cooling to room temperature.
8. The method of producing a negative thermal expansion material according to claim 6, wherein step C2-3 is repeated.
9. The method for producing a negative thermal expansion material according to any one of claims 3 to 8, wherein the flux comprises NH 4 Cl。
10. The method for producing a negative thermal expansion material according to any one of claims 3 to 8, wherein,
the A source comprises at least one of carbonate of A, chloride of A and oxide of A; and/or the number of the groups of groups,
the barium source comprises BaCO 3 、BaO、BaCl 2 At least one of (a) and (b); and/or the number of the groups of groups,
the cobalt source comprises CoCO 3 、CoO、CoCl 2 At least one of (a) and (b); and/or the number of the groups of groups,
the phosphate source comprises (NH) 4 ) 2 HPO 4 。
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