CN112125281A - Method for preparing lanthanide oxide material by using coprecipitation combined with molten salt deposition method and application thereof - Google Patents
Method for preparing lanthanide oxide material by using coprecipitation combined with molten salt deposition method and application thereof Download PDFInfo
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Abstract
The invention provides a method for preparing Ln by using coprecipitation combined with molten salt deposition2M2O7A method of forming an oxide material and uses thereof, the method comprising: lanthanide series nuclide salt, actinide series nuclide salt and M salt are subjected to coprecipitation pretreatment according to a certain proportion to generate a precursor material, and then the precursor material and composite nitric acid molten salt formed by sodium nitrate and potassium nitrate are uniformly sintered to obtain the catalyst; the M elements are Ti, Zr and Hf, lanthanide ions, actinide ions and M element ions are weighed according to a certain stoichiometric ratio, and the mass ratio of the precursor material to the composite molten nitrate salt is 1: 1-1: 50. The invention changes the traditional molten salt methodThe method has the advantages of low preparation material cost, simple equipment, high preparation efficiency, greatly reduced synthesis temperature, large actinide package capacity and great advantage in synthesizing lanthanide pyrochlore structure or defective fluorite structure materials for actinide storage.
Description
Technical Field
The invention relates to a spent fuel treatment method in the field of nuclear energy utilization, in particular to a method for preparing Ln by using coprecipitation combined with a molten salt growth method2M2O7A method of forming an oxide material and its use.
Background
Nuclear energy is a very powerful way of energy utilization. One very important aspect of the development of the nuclear power nuclear industry is nuclear spent fuel processing. Pyrochlore has attracted considerable attention as a naturally stable mineral as a cure for actinides. The structure generally has high receptivity to actinides, can keep a stable state under the conditions of high temperature, high pressure, strong acid and strong alkali, has very low ion leaching rate under natural conditions, can stably exist for hundreds of years to tens of thousands of years, and has excellent radiation (mainly alpha, beta and gamma particles) resistance when a matrix contains radioactive elements. These advantages make pyrochlore and its derived structures a highly desirable direction for nuclear spent fuel processing.
Ln2M2O7Oxide, generally denoted A2B2O6±σAnd O' is Fd-3m or Fm-3 m. The former is about twice the unit cell size of the latter. The former parent possesses two different cationic sites, the a site at 16d, usually shown in valence state as +3, and the B site at 16c, usually shown in valence state as + 4. O is at position 48f and O' is at position 8 b. A number of oxygen vacancies exist in the pyrochlore structure at the 8a site, corresponding to 8 b. In the case of coordination, the a site forms an 8-coordinate hexahedron (8 oxygen atoms containing 6 long bonds a-O and 2 short bonds a-O) and the B site forms a regular hexa-coordinate B-O octahedron, the system will, by the incorporation of actinides, adjust the X site of O48f to switch between the two structures, giving good containment capacity for actinides. Both structures A, B incorporate actinides in different valences to represent the most realistic solidification environment.
The conventional methods for synthesizing pyrochlore compounds include a solid phase method, a sol-gel method, a combustion synthesis method and the like. The size of the pyrochlore material prepared by the method is large and is about 100-2000 nm, the calcining temperature is generally over 1000 ℃, and secondary calcining can be carried out at a higher temperature, so that huge energy waste is caused.
Disclosure of Invention
The invention aims to provide a method for preparing Ln by using coprecipitation combined with a molten salt method2M2O7Method for forming oxide material and application thereof, thereby solving problem of Ln in the prior art2M2O7The synthesis of the type oxide material requires higher temperature, which causes huge energy waste.
In order to solve the technical problems, the invention adopts the following technical scheme:
according to a first aspect of the present invention, there is provided a method for preparing Ln using coprecipitation in combination with a molten salt method2M2O7The method of the oxide material comprises the steps of carrying out coprecipitation pretreatment on lanthanide series nuclide salt, actinide series nuclide salt and M salt according to a certain proportion to generate a precursor material, and then uniformly sintering the precursor material and a composite nitric acid molten salt formed by sodium nitrate and potassium nitrate; the M elements are Ti, Zr and Hf, lanthanide ions, actinide ions and M element ions are weighed according to a certain stoichiometric ratio, and the mass ratio of the precursor material to the composite molten nitrate salt is 1: 1-1: 50.
According to a preferred embodiment of the present invention, the method comprises the steps of: s1: weighing lanthanide nitrate or chloride salt or acetate, M nitrate or chloride salt or acetate, and actinide nitrate or chloride salt or acetate according to a stoichiometric ratio, dissolving in distilled water, stirring for dissolving, slowly adding 2-10% diluted ammonia water, continuing stirring, filtering flocculent precipitate, and drying at 50-80 ℃ to obtain a dry precursor material; s2: weighing the precursor material and the composite molten nitrate salt according to the mass ratio of 1: 1-1: 50, grinding and stirring for 1-6 h, then putting the mixed material into a reaction boat and placing the reaction boat into a reaction furnace, setting the heating rate and the heat preservation time to carry out high-temperature reaction, and naturally cooling; and S3: centrifuging or suction-filtering and cleaning the product obtained in the step S2 by using distilled water to obtain Ln2M2O7A type oxide material.
Ln prepared according to the invention2M2O7The type oxide material is a pyrochlore structure or a defective fluorite structure, it being understood that both the pyrochlore structure and the defective fluorite structure are A2B2O7±σType oxide material, generally denoted A2B2O6±σAnd O', the space groups are Fd-3m and Fm-3m respectively. The former is about twice the unit cell size of the latter. The former parent structure possesses two different cationic sites, the A site is located at 16d, the valence is usually + 2- +5, the B site is located at 16c, and the valence is usually + 3- + 6. O is at position 48f and O' is at position 8 b. A number of oxygen vacancies exist in the pyrochlore structure at the 8a site, corresponding to 8 b. In terms of coordination, the A site forms an 8-coordinate hexahedron (8 oxygen atoms contain 6 long bonds A-O and 2 short bonds A-O), the B site forms a regular six-coordinate B-O octahedron, the pyrochlore structure material is in a pyrochlore structure when the xO48f is positioned at about 0.3125 by adjusting the site of O48f, and the structure becomes a defective fluorite structure when the structure is close to 0.375. Therefore, the pyrochlore structure is not different from the basic preparation method of the defective fluorite structure, and the final formed structure mainly depends on the ion radius ratio of the A site to the B site and other complex factors. The pyrochlore structure is a superlattice structure of a defective fluorite structure, and the pyrochlore structure and the defective fluorite structure can be mutually converted under certain conditions.
Wherein, the lanthanide is La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc and Y, the actinide is Ac, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No and Lr.
According to the invention, the mass ratio of the precursor to the composite molten nitrate salt is preferably 1:1 to 1:50, when the mass ratio of the precursor to the composite molten nitrate salt is in the range, pyrochlore or defective fluorite structure can be prepared, and when the mass ratio of the precursor to the composite molten nitrate salt is too large or too small near two ends, the crystallinity and purity of the sample can be reduced, so that the material purity and crystallinity can be improved when the mass ratio of the precursor to the composite molten nitrate salt is 1:1 to 1: 50.
Preferably, in step S1, the amount of distilled water per mole of raw material is 100 to 500L, the raw material is stirred and dissolved for 6 to 12 hours, and the diluted ammonia water is added and then the stirring is continued for 6 to 12 hours.
Preferably, in step S2, the set value of the reaction temperature of the high-temperature reaction is 0 to 500 ℃ higher than the melting point of the composite molten nitrate salt, and the holding time is 0.5 to 10 hours.
Preferably, in the step S2, the reaction temperature of the high-temperature reaction is 650-850 ℃, and the temperature is kept for 3-10 hours.
According to a preferable scheme of the invention, in the step S2, the mixed material is placed in a reaction furnace, heated from room temperature to 150 ℃ at the heating rate of 5 ℃/min, and is kept at the temperature for 1h, and then heated from room temperature to 650-850 ℃ at the heating rate of 5 ℃/min, and is kept at the temperature for 3-10 h.
Preferably, in step S2, the reaction boat is an alumina crucible, a quartz crucible, or a platinum crucible.
Preferably, in step S3, after cooling, the reactant is washed with distilled water for 1-5 times, centrifuged, filtered, dried, and ground.
According to a second aspect of the present invention, there is provided a method for preparing Ln using coprecipitation in combination with a molten salt method as described above2M2O7Use of a method of forming an oxide material in the storage solidification of actinides.
Ln prepared according to the invention2M2O7The type oxide material is a cubic structure with a particle size of 10-50 nm, wherein the ratio of actinides is 0.1-2.0. E.g. Ln2M2O7The Ln site is substituted for 0.1U element, the chemical formula is Ln1.9U0.1M2O7And substitution of Ln site by 2.0 means that one of the sites is completely substituted and represented by the formula U2M2O7Namely, the complete site substitution of the Ln element, and the substitution site is the Ln site or the M site. The material is very stable, can resist high temperature, acid and alkali, can resist irradiation, and is an ideal actinide host material.
According to the invention, the nitrates of salts of lanthanide series nuclidesIs Ln (NO)3)3·nH2O, in the form of a compound, is more complex in the form of the nitrate of actinide salts, e.g. UO as the nitrate of uranium2(NO3)2·nH2O, chloride and acetate salts are similar.
According to a preferable embodiment of the invention, the molar ratio of sodium nitrate to potassium nitrate in the composite molten nitrate salt is 1: about 1, as a cosolvent. According to the phase diagram, when the sodium nitrate and the potassium nitrate are mixed in the ratio of 1:1, the melting point can be reduced to the maximum extent, the mixture becomes molten salt, and the reaction efficiency is improved.
According to the invention, the nitrate, chloride salt, acetate, ammonia water, potassium nitrate, sodium nitrate and other raw materials are proportioned according to the stoichiometric ratio, namely, the product Ln2M2O7The ion ratio of (a) is a standard.
Preferably, the ammonia water is 100-400 liters of 2.8 percent ammonia water per mole of raw materials, the total mass ratio of the precursor to the sodium nitrate and the potassium nitrate is weighed according to 1: 1-1: 50, and the molar ratio of the sodium nitrate to the potassium nitrate is about 1: 1.
Preferably, in step S3, the material obtained in step S2 is ground, washed with deionized water, centrifuged, and dried in air to obtain Ln2M2O7And (3) powder.
The key points of the invention mainly lie in the following aspects: 1) firstly preparing a precursor containing actinides by coprecipitation, then using NaNO3、KNO3The mixed salt is used as a fluxing agent, so that the traditional preparation temperature can be greatly reduced, the holding capacity of the actinides is greatly improved, and the holding capacity of the actinides is greatly improved compared with the traditional actinide holding capacity. Of particular importance is the use of NaNO3、KNO3The mixed salt as a fluxing agent can greatly improve the holding capacity of the structure to the actinide elements, and even can achieve the improvement of the capacity of 100 percent of one site of the mixed salt to completely replace the original elements; 2) according to the method provided by the invention, the reaction temperature is reduced to below 850 ℃ from above 1000 ℃ in the traditional method, and the high-temperature time is shortened to below 10h from above 24h in the traditional method.
The technical difficulties to be overcome by the invention mainly lie in that: firstly, the method comprises the following steps: the material has high preparation temperature, long heat preservation time and high cost, and the preparation cost is greatly reduced by the method of the invention; II, secondly: the previous preparation of such actinide doped materials has been impure or otherwise numerous, which is a hidden danger for maintaining structural stability, and then according to the invention it is possible to prepare a completely pure phase pyrochlore structure, or a defective fluorite structure or a transition form structure of both; thirdly, the method comprises the following steps: in the prior art, the high-concentration doping of actinides is difficult to achieve, the doping without impurity is generally difficult to achieve more than a few tenths or 1, and the invention achieves the effect that a certain point is completely substituted, namely the occupation ratio is 2, or the pure phase structure, so the invention has obvious superiority compared with the prior art.
In conclusion, according to the present invention, Ln is prepared by using the modified molten salt method2M2O7Pyrochlore or deficient fluorite materials are useful for storage curing of actinides. Compared with a solid phase method process, the method does not need ball milling and high-energy reaction processes, and has the advantages of simple process, high synthesis rate and low cost; meanwhile, the method is beneficial to refining and improving the dispersibility of the powder; the particle size of the powder obtained by the invention is 10-50 nm, the powder has good stability, can resist high temperature, acid, alkali and irradiation, and is an ideal actinide host material. The invention improves the traditional molten salt method, has low preparation material cost, simple equipment, high preparation efficiency, greatly reduced synthesis temperature, large volume for actinides, and great advantages in synthesizing lanthanide pyrochlore materials or defective fluorite structures for actinide storage.
Drawings
FIG. 1 shows La synthesized by a modified molten salt method2Zr2O7XRD pattern of pyrochlore powder material;
FIG. 2 shows La synthesized by a modified molten salt method2Zr1.8U0.2O7XRD pattern of pyrochlore powder material;
FIG. 3 shows Pr synthesized by a modified molten salt method2Zr1.8U0.2O7XRD pattern of pyrochlore powder material;
FIG. 4 shows Nd synthesized by a modified molten salt method2Zr1.8U0.2O7XRD pattern of pyrochlore powder material;
FIG. 5 shows La synthesized by using precursors with different mass ratios and composite molten nitrate salt in the modified molten salt method2Zr2O7XRD pattern of pyrochlore powder material.
Detailed Description
The present invention is described below by way of examples, but the content of the present invention is not limited thereto.
The raw materials used in the examples are conventional raw materials, and the equipment used is conventional equipment, commercially available products.
Example 1:
lanthanum nitrate hexahydrate 1moL (about 433g) and zirconyl nitrate dihydrate 1moL (about 267g) were added to 18 M.OMEGA.deionized water (i.e., ultrapure water) in a molar ratio of 1:1 to prepare 200L of a homogeneous mixed solution, and 200L of dilute ammonia (NH)4OH:H2O ═ 1:9(v/v)) solution was added uniformly and slowly to the mixed solution, and the whole process was carried out on a stirrer for 24 hours. And after stirring, centrifuging the generated gel precipitate by using a centrifuge, transferring a centrifugal product to an oven for drying, and drying at the temperature of 55 ℃ for 72h to obtain a blocky precursor. Taking 1moL (about 421g) of dry precursor and 15moL (NaNO) of composite molten nitrate salt3About 1275g, KNO3About 1515 g; NaNO3With KNO3The molar ratio is 1:1), fully grinding for 15 minutes, transferring into a box type heating furnace, and preserving heat for 6 hours at the temperature of 650-750 ℃. Naturally cooling, taking out the product, washing with distilled water for multiple times, transferring into a vacuum drying oven, and keeping the temperature at 55 ℃ for 12h to obtain La2Zr2O7Pyrochlore powder products. The mass ratio of the precursor to the mixed salt is about 1:6.6, the actinides are not doped in this example, and pure phase undoped materials are prepared for subsequent doping by the preferred optimal temperature of the example. In particular, fig. 1 shows the XRD patterns of the product at different temperatures, and the results show that pure phase structures can be prepared at 650-750 ℃, wherein the optimal synthesis temperature is about 750 ℃.
Example 2:
mixing with six kinds of waterLanthanum nitrate 1moL (about 433g), zirconyl nitrate dihydrate 0.9moL (about 240g), uranyl nitrate hexahydrate 0.1moL (about 50g) (in a molar ratio of 2: 1.8: 0.2) were added to 18 M.OMEGA.deionized water to prepare 200L of a uniform mixed solution, and 200L of dilute ammonia (NH)4OH:H2O ═ 1:9(v/v)) solution was added uniformly and slowly to the mixed solution, and the whole process was carried out on a stirrer for 24 hours. And after stirring, centrifuging the generated gel precipitate by using a centrifuge, transferring a centrifugal product to an oven for drying, and drying at the temperature of 55 ℃ for 72h to obtain a blocky precursor. Taking 1moL (about 424g) of dry precursor and 15moL (NaNO) of composite molten nitrate salt3About 1275g, KNO3About 1515 g; NaNO3With KNO3The molar ratio is 1:1), fully grinding for 15 minutes, and transferring into a box type heating furnace for heat preservation at 700 ℃ for 6 hours. Naturally cooling, taking out the product, washing with distilled water for multiple times, transferring into a vacuum drying oven, and keeping the temperature at 55 ℃ for 12h to obtain La2Zr1.8U0.2O7Pyrochlore powder product of La2Zr1.8U0.2O7The XRD pattern of the pyrochlore powder material is shown in figure 2. The mass ratio of the precursor to the composite molten nitrate salt in this example is about 1:6.6, and the actinides are incorporated in this example, indicating that the synthesis conditions of the parent material can be used to prepare pure phase pyrochlore or defective fluorite materials incorporating actinides.
Example 3:
praseodymium nitrate hexahydrate 1moL (about 433g), zirconyl nitrate dihydrate 0.9moL (about 240g), and acyl nitrate hexahydrate 0.1moL (about 50g) (in a molar ratio of 2: 1.8: 0.2) were added to 18 M.OMEGA.deionized water to prepare 200L of a uniform mixed solution, and 200L of dilute ammonia (NH) (NH 2: 1.8: 0.2) was added4OH:H2O ═ 1:9(v/v)) solution was added uniformly and slowly to the mixed solution, and the whole process was carried out on a stirrer for 24 hours. And after stirring, centrifuging the generated gel precipitate by using a centrifuge, transferring a centrifugal product to an oven for drying, and drying at the temperature of 55 ℃ for 72h to obtain a blocky precursor. Taking 1moL (about 426g) of dry precursor and 15moL (NaNO) of composite molten nitrate salt3About 1275g, KNO3About 1515 g; NaNO3With KNO3Mixing at a molar ratio of 1:1), grinding thoroughly for 15 minutes, transferring into a boxThe temperature of the heating furnace is kept for 6h at 750 ℃. Naturally cooling, taking out the product, washing with distilled water for many times, transferring into vacuum drying oven, and keeping the temperature at 55 deg.C for 12h to obtain Pr2Zr1.8U0.2O7Pyrochlore powder product, the Pr2Zr1.8U0.2O7The XRD pattern of the pyrochlore powder material is shown in figure 3. The mass ratio of the precursor to the composite molten nitrate salt is about 1:6.6 in the embodiment, the lanthanide is doped in the embodiment, the preparation method has lanthanide universality, and other lanthanide parent materials can be used for preparing pure-phase pyrochlore or defective fluorite materials doped with actinide.
Example 4:
1moL (about 436g) of neodymium nitrate hexahydrate, 0.9moL (about 240g) of zirconyl nitrate dihydrate, and 0.1moL (about 50g) of uranyl nitrate hexahydrate were added to 18 M.OMEGA.deionized water in a molar ratio of 2: 1.8: 0.2 to prepare 200L of a uniform mixed solution, and 200L of dilute ammonia (NH) was added4OH:H2O ═ 1:9(v/v)) solution was added uniformly and slowly to the mixed solution, and the whole process was carried out on a stirrer for 24 hours. And after stirring, centrifuging the generated gel precipitate by using a centrifuge, transferring a centrifugal product to an oven for drying, and drying at the temperature of 55 ℃ for 72h to obtain a blocky precursor. Taking 1moL (about 429g) of dry precursor and 15moL (NaNO) of composite molten nitrate salt3About 1275g, KNO3About 1515 g; NaNO3With KNO3Mixing according to the molar ratio of 1:1), fully grinding for 15 minutes, and transferring into a box type heating furnace for heat preservation at 750 ℃ for 6 hours. Naturally cooling, taking out the product, washing with distilled water for many times, transferring into a vacuum drying oven, and keeping the temperature at 55 ℃ for 12h to obtain Nd2Zr1.8U0.2O7Pyrochlore powder products of the formula Nd2Zr1.8U0.2O7The XRD pattern of the pyrochlore powder material is shown in figure 4. The mass ratio of the precursor material to the composite molten nitrate salt in the embodiment is about 1:6.6, the lanthanide is doped in the embodiment, the preparation method has lanthanide universality, other lanthanide parent materials can be used for preparing pure-phase pyrochlore or defective fluorite materials doped with actinide, and the preparation temperature has preparation universality at about 750 ℃.
Example 5:
lanthanum nitrate hexahydrate 1moL (about 433g) and zirconyl nitrate dihydrate 1moL (about 267g) were added to 18 M.OMEGA.deionized water (i.e., ultrapure water) in a molar ratio of 1:1 to prepare 200L of a homogeneous mixed solution, and 200L of dilute ammonia (NH)4OH:H2O ═ 1:9(v/v)) solution was added uniformly and slowly to the mixed solution, and the whole process was carried out on a stirrer for 24 hours. And after stirring, centrifuging the generated gel precipitate by using a centrifuge, transferring a centrifugal product to an oven for drying, and drying at the temperature of 55 ℃ for 72h to obtain a blocky precursor. Taking 1moL (about 421g) of dry precursor and 2.3moL, 45.5moL and 113.6moL of composite molten nitrate salt (respectively corresponding to NaNO)3About 194g, 3880g, 9700g, KNO3About 227g, 4547g, 11367 g; NaNO3With KNO3Mixing according to the molar ratio of 1:1), fully grinding for 15 minutes, and transferring into a box type heating furnace for heat preservation at 750 ℃ for 6 hours. Naturally cooling, taking out the product, washing with distilled water for multiple times, transferring into a vacuum drying oven, and keeping the temperature at 55 ℃ for 12h to obtain La2Zr2O7Pyrochlore powder product of La2Zr2O7The XRD pattern of the pyrochlore powder material is shown in figure 5. The embodiment illustrates that the pyrochlore or defective fluorite structure can be prepared when the mass ratio of the precursor to the composite molten nitrate salt is 1:1 to 1:50, and when the mass ratio of the precursor to the composite molten nitrate salt is 1:1 and 1:50, the crystallinity and the purity of a sample are reduced, so that the material purity and the crystallinity are improved by approaching to an intermediate ratio.
The above embodiments are merely preferred embodiments of the present invention, which are not intended to limit the scope of the present invention, and various changes may be made in the above embodiments of the present invention. All simple and equivalent changes and modifications made according to the claims and the content of the specification of the present application fall within the scope of the claims of the present patent application. The invention has not been described in detail in order to avoid obscuring the invention.
Claims (10)
1. Preparation of Ln by using coprecipitation and molten salt method2M2O7A process for forming an oxide material, characterized in that it consists of a salt of a lanthanide or actinideAnd performing coprecipitation pretreatment on the M salt according to a certain proportion to generate a precursor material, and then uniformly sintering the precursor material and a composite molten nitrate salt formed by sodium nitrate and potassium nitrate; the M elements are Ti, Zr and Hf, lanthanide ions, actinide ions and M element ions are weighed according to a certain stoichiometric ratio, and the mass ratio of the precursor material to the composite molten nitrate salt is 1: 1-1: 50.
2. Method according to claim 1, characterized in that it comprises the following steps:
s1: weighing lanthanide nitrate or chloride salt or acetate, M nitrate or chloride salt or acetate, and actinide nitrate or chloride salt or acetate according to a stoichiometric ratio, dissolving in distilled water, stirring for dissolving, slowly adding 2-10% diluted ammonia water, continuing stirring, filtering flocculent precipitate, and drying at 50-80 ℃ to obtain a dry precursor material;
s2: weighing the precursor material and the composite molten nitrate salt according to the mass ratio of 1: 1-1: 50, grinding and stirring for 1-6 h, then putting the mixed material into a reaction boat and placing the reaction boat into a reaction furnace, setting the heating rate and the heat preservation time to carry out high-temperature reaction, and naturally cooling;
s3: centrifuging or suction-filtering and cleaning the product obtained in the step S2 by using distilled water to obtain Ln2M2O7A type oxide material.
3. The method of claim 1, wherein the Ln is defined as2M2O7The type oxide material is a pyrochlore structure or a defective fluorite structure.
4. The method of claim 2, wherein the lanthanide is La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, and Y, and the actinide is Ac, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No, Lr.
5. The method according to claim 2, wherein in step S1, the amount of distilled water per mole of raw material is 100-500L, the raw material is stirred and dissolved for 6-12 h, and the stirring is continued for 6-12 h after the dilute ammonia water is added.
6. The method according to claim 2, wherein in step S2, the reaction temperature of the high-temperature reaction is set to a value 0 to 500 ℃ higher than the melting point of the molten salt of the composite nitric acid, and the holding time is 0.5 to 10 hours.
7. The method according to claim 6, wherein in step S2, the reaction temperature of the high-temperature reaction is 650-850 ℃, and the temperature is maintained for 3-10 h.
8. The method according to claim 7, wherein in step S2, the mixed material is placed in a reaction furnace, heated from room temperature to 150 ℃ at a heating rate of 5 ℃/min, and then kept at the temperature for 1h, and then heated from room temperature to 650-850 ℃ at a heating rate of 5 ℃/min, and kept at the temperature for 3-10 h.
9. The method of claim 2, wherein in step S2, the reaction boat is an alumina crucible, a quartz crucible, or a platinum crucible.
10. Ln prepared by using coprecipitation combined with molten salt deposition method according to any one of claims 1 to 92M2O7Use of a method of forming an oxide material in the storage solidification of actinides.
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