Preparation method and application of rare earth molybdate ceramic material synthesized by molten salt method
Rare earth molybdate ceramic materials were synthesized by the molten salt method, using a mixture of lithium molybdate and sodium molybdate as the molten salt system. This solved the problem of high-temperature and long-term sintering in existing technologies, and enabled low-temperature rapid synthesis and industrial production, while also improving the luminescent properties of the materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- INST OF HIGH ENERGY PHYSICS CHINESE ACAD OF SCI
- Filing Date
- 2023-11-29
- Publication Date
- 2026-07-07
AI Technical Summary
Existing methods for preparing rare earth molybdate ceramic materials suffer from problems such as high sintering temperature, long reaction time, difficulty in controlling morphology and uniformity, and are not conducive to industrial production.
Rare earth molybdate ceramic materials were synthesized using a molten salt method. A mixture of lithium molybdate and sodium molybdate binary salts was used as the molten salt system, with rare earth oxides as the RE source. The reaction was carried out at a relatively low temperature to synthesize rare earth molybdate ceramic materials with the chemical formula RExMoO(3x+6)/2.
This method enables the simple and efficient synthesis of rare earth molybdate ceramic materials at lower temperatures, reducing preparation temperature and time, minimizing impurity residues, making it suitable for industrial production, and improving luminescence performance.
Smart Images
Figure CN117902898B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of new materials technology, and in particular to a method for preparing rare earth molybdate ceramic materials by molten salt synthesis and their application. Background Technology
[0002] Compounds in the rare earth molybdate family possess luminescent, catalytic, and semiconductor properties due to their unique crystal and electronic structures. Their applications in luminescent materials, environmentally friendly dyes, ferroelectric materials, microwave ceramics, and catalysis have attracted considerable attention, leading to extensive and in-depth research in the past. Among these, pure RE... x MoO (3x+6) / 2 and doped RE x MoO (3x+6) / 2 These compounds, due to their good catalytic and luminescent properties and their oxygen ion and proton conductivity, have potential applications in catalysis, high-performance luminescent materials, and solid oxide fuel cells.
[0003] Current reports about RE x MoO (3x+6) / 2 Most methods for preparing ceramic materials involve solid-state reactions (SCR), typically at sintering temperatures of 1200–1600 °C. These high temperatures and long reaction times are detrimental to controlling the morphology and maintaining uniformity of the products. Therefore, scientists both domestically and internationally have developed "soft chemistry" synthesis methods, such as the hydrothermal method and the sol-gel process, to prepare REs with different morphologies and sizes. x MoO (3x+6) / 2 Ceramic materials are available, but their synthesis methods are complex, involve the introduction of organic matter, and require high reaction temperatures, making them unsuitable for industrial production.
[0004] Therefore, this invention is proposed. Summary of the Invention
[0005] The molten salt method uses different types of inorganic molten salts as the reaction medium. Compared with conventional solvents, these salts possess sufficient electrical conductivity, high thermal conductivity, high thermal stability, and a certain viscosity, thus exhibiting high reactivity towards different inorganic components. Furthermore, the eutectic salts have low melting points, making them suitable for preparing inorganic ceramic materials. Compared to the methods mentioned above, the molten salt method is simpler, requires lower synthesis temperatures, shorter reaction times, and leaves fewer impurities, making it a more economical synthesis method.
[0006] This invention provides a method for preparing and applying rare earth molybdate ceramic materials via a molten salt method. Using a mixture of lithium molybdate and sodium molybdate binary salts as the molten salt system, rare earth oxides as the RE source, and a mixture of binary salts and / or MoO3 as the Mo source, RE is synthesized simply and efficiently at relatively low temperatures. x MoO (3x+6) / 2 Ceramic materials.
[0007] Specifically, this invention provides a method for preparing rare earth molybdate ceramic materials, comprising: reacting a RE source and a Mo source in a molten salt system using a molten salt method to synthesize a material with the chemical formula RE. x MoO (3x+6) / 2 Rare earth molybdate ceramic materials, wherein RE is selected from one or more of La, Nd, Sm, Eu, Gd, Dy, Ho, Er and Yb, and 0 < x ≤ 6.
[0008] According to the preparation method of the rare earth molybdate ceramic material provided by the present invention, the molten salt system is mainly composed of a binary salt mixture of lithium molybdate and sodium molybdate.
[0009] Compared to other salts, the lithium molybdate and sodium molybdate used in this invention can not only serve as sources of Mo, reducing the use of other Mo raw materials, but also, compared to using lithium molybdate or sodium molybdate alone, using a mixture of the two can effectively reduce the preparation temperature of rare earth molybdates.
[0010] Preferably, the mass ratio of lithium molybdate to sodium molybdate is 1:10 to 10:1; more preferably, the mass ratio of lithium molybdate to sodium molybdate is 22:25.
[0011] According to the preparation method of the rare earth molybdate ceramic material provided by the present invention, rare earth oxides are used as the RE source;
[0012] Preferably, the RE source includes one or more of La2O3, Nd2O3, Sm2O3, Eu2O3, Gd2O3, Dy2O3, Ho2O3, Er2O3, and Yb2O3;
[0013] More preferably, the RE source is two of La2O3, Nd2O3, Sm2O3, Eu2O3, Gd2O3, Dy2O3, Ho2O3, Er2O3 and Yb2O3;
[0014] Most preferably, the RE source is a mixture of Sm2O3 and Gd2O3; or, the RE source is a mixture of Eu2O3 and Gd2O3.
[0015] Compared to a single RE source, when using a mixture of Sm2O3 and Gd2O3 or a mixture of Eu2O3 and Gd2O3, luminescent rare-earth ion-doped rare-earth molybdate materials can be synthesized, which have further improved luminescent performance compared to pure rare-earth molybdates.
[0016] According to the preparation method of the rare earth molybdate ceramic material provided by the present invention, the binary salt mixture and / or MoO3 are used as the Mo source;
[0017] Preferably, the binary salt mixture is used as the Mo source.
[0018] The method for preparing the rare earth molybdate ceramic material according to the present invention includes:
[0019] The mixture is heated and melted into a binary salt mixture mainly composed of lithium molybdate and sodium molybdate; then, raw materials containing RE source are added to the molten binary salt mixture and reacted at 462-1000℃ to obtain rare earth molybdate ceramic materials; the raw materials containing RE source are mainly composed of RE source and MoO3 in a molar ratio of 1:0-10.
[0020] More specifically, the dried binary salt mixture is placed in a high-temperature device, heated to 462-1000℃, and kept at the temperature for several hours (e.g., more than 1 hour) to completely melt the binary salt mixture. Then, raw materials containing RE source are added, and the mixture is kept at 462-1000℃ for several hours (e.g., more than 2 hours) and then cooled to obtain rare earth molybdate ceramic material.
[0021] Alternatively, a binary salt mixture mainly composed of lithium molybdate and sodium molybdate is mixed with a raw material containing a RE source and reacted at 462–1000 °C to obtain rare earth molybdate ceramic material; the raw material containing the RE source is mainly composed of a RE source and MoO3 in a molar ratio of 1:0–10.
[0022] During the heating process described above, the reaction system can be carried out under an air atmosphere or a protective gas atmosphere.
[0023] The method for preparing the rare earth molybdate ceramic material according to the present invention includes:
[0024] The binary salt mixture, mainly composed of lithium molybdate and sodium molybdate, is pretreated and then heated and melted. The pretreatment includes: mixing lithium molybdate and sodium molybdate evenly to obtain a binary salt mixture, placing it in a corrosion-resistant crucible (such as a corundum crucible), and then drying it at a temperature below 200°C to remove moisture.
[0025] Alternatively, the product after the reaction can be post-processed to obtain rare earth molybdate ceramic powder;
[0026] Preferably, the post-processing includes: washing the product with water, filtering to obtain a precipitate; drying the precipitate at a temperature below 200°C to obtain rare earth molybdate ceramic powder.
[0027] The high-temperature equipment in this invention refers to a device that can provide sufficient temperature and heat the reaction system under the action of an air atmosphere or a protective gas, such as a muffle furnace or an atmosphere furnace, all of which are applicable to this invention, with a muffle furnace being preferred.
[0028] The protective gas in this invention refers to a gas that can prevent external gases from interfering with the reaction of this invention. Generally, an inert gas, such as helium or argon, is introduced into the reaction equipment to isolate the reactants from the outside environment. An argon atmosphere is preferred.
[0029] The crucible in this invention is used only as a reaction vessel and needs to have properties such as corrosion resistance and high temperature resistance. Generally speaking, corundum crucibles are preferred.
[0030] The method for preparing the rare earth molybdate ceramic material according to the present invention includes:
[0031] The raw material containing the RE source has a molar ratio of RE source to MoO3 of 1:0 to 5; the raw material containing the RE source is obtained by grinding in an agate mortar.
[0032] Preferably, the mass of the raw material containing the RE source is 1% to 20% of the binary salt mixture.
[0033] According to the method for preparing the rare earth molybdate ceramic material provided by the present invention, the heating rate during the reaction process is 5-50℃ / min.
[0034] Secondly, the present invention also provides a rare earth molybdate ceramic material prepared by the method described above, which has the chemical formula RE. x MoO (3x+6) / 2 Rare earth molybdate ceramic materials, wherein RE is selected from one or more of La, Nd, Sm, Eu, Gd, Dy, Ho, Er and Yb, and 0 < x ≤ 6;
[0035] Preferably, the rare earth molybdate ceramic material has the chemical formula La2MoO6 or Nd6MoO. 12 Sm2MoO6, Eu2MoO6, Gd 1.8 Sm 0.2 MoO6 or Gd 1.8 Eu 0.2 MoO6.
[0036] Thirdly, the present invention also provides the application of the rare earth molybdate ceramic materials described above in environmentally friendly dyes, ferroelectric materials, microwave ceramic materials, catalytic materials, luminescent materials or solid oxide fuel cells.
[0037] This invention provides a method for preparing rare earth molybdate ceramic materials using a molten salt method and its application. The method employs a molten salt method to prepare materials with the chemical formula RE. x MoO (3x+6) / 2 The rare earth molybdate ceramic material uses a mixture of lithium molybdate and sodium molybdate as the melt. It has advantages such as low reaction temperature, simple process, short synthesis time, low impurity residue, no pollution and low cost.
[0038] In addition, the melt is also one of the sources of Mo. In some embodiments, the rare earth molybdate ceramic material can be prepared without introducing MoO3 powder.
[0039] Furthermore, in some embodiments, luminescent rare-earth ion-doped rare-earth molybdate materials can also be synthesized, which have further improved luminescent properties compared to pure rare-earth molybdates.
[0040] Therefore, this invention is expected to be used for the preparation of rare earth molybdate ceramic materials on an engineering scale. Attached Figure Description
[0041] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0042] Figure 1 The image shows the XRD pattern of La2MoO6 prepared in Example 1.
[0043] Figure 2 The Nd6MoO prepared in Example 2 12 XRD pattern;
[0044] Figure 3 The image shows the XRD pattern of Sm2MoO6 prepared in Example 3;
[0045] Figure 4 The image shows the XRD pattern of Eu2MoO6 prepared in Example 4;
[0046] Figure 5 The Gd prepared in Example 5 1.8 Sm 0.2 XRD pattern of MoO6;
[0047] Figure 6 The Gd prepared in Example 6 1.8 Eu 0.2 XRD pattern of MoO6;
[0048] Figure 7 The fluorescence spectra of the ceramic powders prepared in Examples 3 and 5 are shown.
[0049] Figure 8 The images show the fluorescence spectra of the ceramic powders prepared in Examples 4 and 6. Detailed Implementation
[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.
[0051] The following is combined with Figures 1-8 This invention describes the preparation method and application of rare earth molybdate ceramic materials synthesized by the molten salt method.
[0052] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.
[0053] Example 1
[0054] A method for preparing rare earth molybdate ceramic materials by molten salt synthesis, the specific steps of which are as follows:
[0055] Step 1: Mix lithium molybdate and sodium molybdate in a mass ratio of 22:25 until homogeneous, place the mixture in a corundum crucible and dry it in a vacuum oven at 150°C for more than 24 hours to obtain a binary eutectic salt.
[0056] Step 2: Place the crucible from Step 1 into a muffle furnace, introduce argon gas, heat to 550°C at a rate of 5°C / min, and hold at this temperature for 1 hour to allow the eutectic salt to completely melt. Then add La2O3, the mass of which is 1% of the mass of the binary eutectic salt, and hold at 550°C for 5 hours before naturally cooling to room temperature.
[0057] Step 3: The product obtained in Step 2 was washed with deionized water at room temperature, filtered, and the precipitate was dried in a vacuum oven at 150°C for at least 6 hours to obtain dry La2MoO6 ceramic powder. The XRD test results of the powder are as follows: Figure 1 As shown.
[0058] Example 2
[0059] A method for preparing rare earth molybdate ceramic materials by molten salt synthesis is basically the same as that in Example 1, except that La2O3 is replaced by Nd2O3 in equal mass to obtain dry Nd6MoO. 12 The ceramic powder, and the XRD test results of the powder are as follows: Figure 2 As shown.
[0060] Example 3
[0061] A method for preparing rare earth molybdate ceramic materials by molten salt synthesis is disclosed. The specific steps are basically the same as in Example 1, except that: an equal mass of La2O3 is replaced with a mixture of Sm2O3 and MoO3 in a molar ratio of 1:1. The mass of this mixture is 1% of the mass of the binary eutectic salt, resulting in dry Sm2MoO6 ceramic powder. The XRD test results of this powder are as follows: Figure 3 As shown.
[0062] Figure 7 (Solid line) shows the emission spectrum of the target sample prepared in Example 3 under 319nm laser excitation and the excitation spectrum at 640nm. It can be seen that under 319nm wavelength excitation, the prepared sample exhibits red light emission at 640nm.
[0063] Example 4
[0064] A method for preparing rare earth molybdate ceramic materials by molten salt synthesis is disclosed. The specific steps are basically the same as in Example 1, except that: an equal mass of La₂O₃ is replaced with a mixture of Eu₂O₃ and MoO₃ in a molar ratio of 1:1. The mass of this mixture is 1% of the mass of the binary eutectic salt. Dry Eu₂MoO₆ ceramic powder is obtained, and the XRD test results of this powder are as follows: Figure 4 As shown.
[0065] Figure 8 (Solid lines) show the emission spectrum of the target sample prepared in Example 4 under 306nm laser excitation and the excitation spectrum at 614nm. It can be seen that under 306nm wavelength excitation, the prepared sample exhibits red light emission at 614nm.
[0066] Example 5
[0067] A method for preparing rare earth molybdate ceramic materials by molten salt synthesis is disclosed. The specific steps are basically the same as in Example 1, except that: La₂O₃ is replaced by an equal mass of a mixture of Sm₂O₃, Gd₂O₃, and MoO₃ (molar ratio 0.1:0.9:1.0), and the mass of this mixture is 1% of the mass of the binary eutectic salt, yielding dried Gd₂O₃. 1.8 Sm0.2 MoO6 ceramic powder, the XRD test results of this powder are as follows: Figure 5 As shown.
[0068] Figure 7 (Dashed lines) show the emission spectrum of the target sample prepared in Example 5 under 319 nm laser excitation and the excitation spectrum at 640 nm. It can be seen that under 319 nm wavelength excitation, the prepared sample exhibits red light emission at 640 nm, and its fluorescence intensity is stronger than that of Example 3.
[0069] Example 6
[0070] A method for preparing rare earth molybdate ceramic materials by molten salt synthesis is disclosed. The specific steps are basically the same as in Example 1, except that: La₂O₃ is replaced by an equal mass of a mixture of Eu₂O₃, Gd₂O₃, and MoO₃ (molar ratio 0.1:0.9:1.0), and the mass of this mixture is 1% of the mass of the binary eutectic salt, yielding dried Gd₂O₃. 1.8 Eu 0.2 MoO6 ceramic powder, the XRD test results of this powder are as follows: Figure 6 As shown.
[0071] Figure 8 (Dashed lines) show the emission spectrum of the target sample prepared in Example 6 under 306 nm laser excitation and the excitation spectrum at 614 nm. It can be seen that under 306 nm wavelength excitation, the prepared sample exhibits red light emission at 614 nm. Furthermore, its excitation spectrum indicates that the excitation band at 614 nm is wider than that of Example 4.
[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing a rare earth molybdate ceramic material, characterized in that, include: The RE source and Mo source were reacted in a molten salt system using a molten salt method to synthesize a substance with the chemical formula RE. x MoO (3x+6) / 2 Rare earth molybdate ceramic materials, wherein RE is selected from one or more of La, Nd, Sm, Eu, Gd, Dy, Ho, Er and Yb, and 0 < x ≤ 6; The molten salt system is a binary salt mixture composed of lithium molybdate and sodium molybdate. The mass ratio of lithium molybdate to sodium molybdate is 1:10 to 10:
1.
2. The method for preparing rare earth molybdate ceramic material according to claim 1, characterized in that, Rare earth oxides are used as RE sources.
3. The method for preparing rare earth molybdate ceramic material according to claim 2, characterized in that, The RE source includes one or more of La2O3, Nd2O3, Sm2O3, Eu2O3, Gd2O3, Dy2O3, Ho2O3, Er2O3, and Yb2O3.
4. The method for preparing rare earth molybdate ceramic material according to claim 3, characterized in that, The RE source is two of the following: La2O3, Nd2O3, Sm2O3, Eu2O3, Gd2O3, Dy2O3, Ho2O3, Er2O3, and Yb2O3.
5. The method for preparing rare earth molybdate ceramic material according to claim 4, characterized in that, The RE source is a mixture of Sm2O3 and Gd2O3; or, the RE source is a mixture of Eu2O3 and Gd2O3.
6. The method for preparing the rare earth molybdate ceramic material according to any one of claims 1 to 5, characterized in that, The binary salt mixture and / or MoO3 are used as the Mo source.
7. The method for preparing the rare earth molybdate ceramic material according to any one of claims 1 to 5, characterized in that, include: A binary salt mixture consisting of lithium molybdate and sodium molybdate is heated and melted; then, a raw material containing a RE source is added to the molten binary salt mixture and reacted at 462~1000℃ to obtain rare earth molybdate ceramic material; the raw material containing the RE source is a material composed of a RE source and MoO3 in a molar ratio of 1:0~10. Alternatively, a binary salt mixture consisting of lithium molybdate and sodium molybdate is mixed with a raw material containing a RE source and reacted at 462~1000℃ to obtain a rare earth molybdate ceramic material; the raw material containing the RE source is a material composed of a RE source and MoO3 in a molar ratio of 1:0~10.
8. The method for preparing rare earth molybdate ceramic material according to claim 7, characterized in that, include: The binary salt mixture composed of lithium molybdate and sodium molybdate is pretreated and then heated and melted. The pretreatment includes: mixing lithium molybdate and sodium molybdate evenly to obtain the binary salt mixture, placing it in a crucible, and then drying it at a temperature below 200°C to remove moisture. Alternatively, the product after the reaction may be post-processed to obtain rare earth molybdate ceramic powder.
9. The method for preparing rare earth molybdate ceramic material according to claim 8, characterized in that, The post-processing includes: washing the product with water, filtering to obtain a precipitate; drying the precipitate at a temperature below 200°C to obtain rare earth molybdate ceramic powder.
10. The method for preparing the rare earth molybdate ceramic material according to claim 8, characterized in that, include: The molar ratio of RE source to MoO3 in the raw material containing RE source is 1:0~5.
11. The method for preparing rare earth molybdate ceramic material according to claim 10, characterized in that, The mass of the raw material containing the RE source is 1% to 20% of the binary salt mixture.
12. The method for preparing the rare earth molybdate ceramic material according to claim 8, characterized in that, The heating rate during the reaction process is 5~50℃ / min.
13. A rare earth molybdate ceramic material prepared by the method of any one of claims 1 to 12, having the chemical formula RE x MoO (3x+6) / 2 Rare earth molybdate ceramic materials, among which, RE is selected from one or more of La, Nd, Sm, Eu, Gd, Dy, Ho, Er, and Yb, where 0 < x ≤ 6.
14. The rare earth molybdate ceramic material according to claim 13, characterized in that, The rare earth molybdate ceramic material has the chemical formula La2MoO6 or Nd6MoO6. 12 Sm2MoO6, Eu2MoO6, Gd 1.8 Sm 0.2 MoO6 or Gd 1.8 Eu 0.2 MoO6.
15. The application of the rare earth molybdate ceramic material of claim 13 or 14 in environmentally friendly dyes, ferroelectric materials, microwave ceramic materials, catalytic materials, luminescent materials or solid oxide fuel cells.