A method and system for preparing high-purity rubidium or cesium metal

Abstract

The present invention provides a method and system for preparing high-purity rubidium or cesium metal. In this method, rubidium or cesium metal is used as the raw material, and molten metal Ag is used as the extraction medium. By utilizing the fact that Na, Li, and K have a certain solubility in metal Ag while rubidium and cesium are insoluble in Ag, the contents of impurities Na, Li, and K in the rubidium or cesium metal raw material are reduced, and then high-purity rubidium or cesium metal is obtained through vacuum distillation. The present invention purifies and removes impurities from rubidium or cesium metal through melt extraction, can process the rubidium or cesium metal raw material to obtain high-purity rubidium or cesium metal products. Among them, the purification rates of Na and Li are above 80%, the purification rate of K is above 50%, the purity of the prepared high-purity rubidium is above 99.90%, the purity of the prepared high-purity cesium is above 99.95%, the yield is above 95%, and the process flow is short and the equipment is simple, solving the problems of low traditional distillation efficiency and unobvious impurity removal effect.

Description

Technical Field

[0001] The present invention relates to the technical field of non-ferrous metal purification, and in particular to a method and system for preparing high-purity metal rubidium or cesium. Background Art

[0002] Atomic clocks are key technologies for astronomical research, rocket launch and recovery, and the development of high-precision lasers, directly determining the depth of astronomical research and the key guarantee for rocket launch. Especially during the takeoff and landing phases of an aircraft, ground ranging is a safety guarantee for aircraft takeoff and landing. In terms of controlling the reaction intensity of a reactor, it directly determines the safety of the reactor body.

[0003] Metallic rubidium and cesium are a kind of room-temperature liquid metals used to manufacture phototubes and atomic clocks. The purification technology of metallic rubidium and cesium is a key technology for the development of high-end metallic rubidium and cesium clocks and precision phototubes. Currently, the preparation methods of metallic rubidium and cesium mainly use compounds of rubidium and cesium as raw materials and carry out high-temperature reduction reactions under the action of reducing agents. During the preparation of metallic rubidium and cesium, the removal of impurities Li, Na, and K is a key factor affecting the high purity of metallic rubidium or cesium. This is because metals Li, Na, and K are associated metals of rubidium and cesium, and during the preparation process, the mutual doping between Li, Na, K and rubidium or cesium is inevitable. Moreover, the atomic radii of Na, K, and rubidium are similar and their properties are similar, making the separation difficult. In order to meet the requirements of high-end and precision, a more simple method is needed to remove the impurities Li, Na, and K doped in metallic rubidium or cesium, so as to obtain higher-purity metallic rubidium or cesium. Summary of the Invention

[0004] The present invention provides a method and system for preparing high-purity metal rubidium or cesium. Through the method of metal melt extraction, the metal raw materials rubidium and cesium can be processed to obtain high-purity metal rubidium or cesium products, solving the problems of low traditional distillation efficiency and unclear impurity removal effect.

[0005] In a first aspect, the present invention provides a method for preparing high-purity metal rubidium or cesium, the raw material of which contains impurities; the impurities include one or more of Li, Na, and K, and the method includes the following.

[0006] Mix the raw material with Ag, heat the obtained mixture to above the melting point of Ag and keep it warm under the protection and sealing of a rare gas, and cool it to below the boiling point of the high-purity metal after the heat preservation ends; after the cooling ends, heat it again to below 600°C under a vacuum state to form vapor of rubidium or cesium, and the vapor is condensed and collected to obtain the high-purity metal.

[0007] Experiments have found that although there are many metals that can form eutectics, only Ag can selectively dissolve impurity elements Li, Na, and K without dissolving the main elements rubidium or cesium. Almost all other metal melts will dissolve the main metals rubidium or cesium. Based on this discovery, the present invention proposes a method of metal melt extraction, using Ag as the extraction medium. Under sealed and rare gas protection conditions, it is heated to the above specific temperature and kept warm. At this time, rubidium or cesium is in a gaseous state, while the impurity elements are fully dissolved in the extraction medium. If the temperature is too low at this time, Ag is not in a molten state and melt extraction cannot be carried out. Then, after cooling to below the boiling point of the metal to be purified, rubidium or cesium condenses. By further strictly controlling the vacuum pumping and heating to below 600 °C, the metal to be purified can gradually form steam and be separated from the mixture. The steam is collected after condensation, and the content of impurity elements in the obtained product is significantly reduced.

[0008] There are three reasons why the second heating needs to be carried out under vacuum. First, it reduces the boiling points of rubidium and cesium, thereby reducing the reaction temperature and energy consumption. Second, it keeps the system in a negative pressure environment, preventing external air from entering the reaction system and contaminating the product. Third, under vacuum, the evaporation rate of rubidium or cesium is faster, which can reduce the reaction time and increase efficiency.

[0009] Preferably, the purity of the raw material is below 99.70%.

[0010] More preferably, when the metal is rubidium, the purity is 99.50% - 99.70%, and when the metal is cesium, the purity is 99.950 - 99.970%.

[0011] Preferably, the weight ratio of the raw material to the Ag is 1:2 - 1:8.

[0012] Preferably, the temperature above the melting point of Ag to which it is heated is denoted as the first temperature, the first temperature is 1000 - 1350 °C, and the holding time at the first temperature is 4 - 6 h.

[0013] And / or, the temperature to which it is heated again to below 600 °C under vacuum is denoted as the second temperature, the second temperature is 300 - 600 °C, and the holding time at the second temperature is 3 - 6 h.

[0014] Preferably, the purity of the Ag ≥ 99.99%.

[0015] Preferably, the vacuum state is a pressure below 1.0×10 -2 Pa.

[0016] Preferably, the purity of the rare gas ≥ 99.999%.

[0017] More preferably, the rare gas is argon.

[0018] Preferably, the method for preparing high-purity metal is as follows.

[0019] Mix the raw materials and Ag in a weight ratio of 1:2 to 1:8 to obtain a mixture.

[0020] The mixture is kept at the first temperature of 970°C to 1500°C for 2 to 10 h under the protection of a rare gas and in a sealed state, and after the heat preservation is completed, it is cooled to room temperature.

[0021] After the cooling is completed, it is heated again to the second temperature of 50°C to 600°C under the condition that the pressure is not greater than 1.0×10 -2 Pa, and kept warm for 2 to 8 h, during which the condensate is continuously collected to obtain the high-purity metal.

[0022] The present invention discovers that the impurities Na, Li, and K in rubidium or cesium metals have a certain solubility in metallic Ag, while rubidium or cesium metals have no solubility in metallic Ag. As an example: at a temperature of 1000°C, the mass fractions of the impurity elements Li, Na, and K in rubidium or cesium metals in molten metallic Ag are 100 wt.%, 100 wt.%, and 1 wt.%, respectively. The difference can be utilized to extract the impurity elements Li, Na, and K in rubidium or cesium with molten Ag.

[0023] At the same time, the melting point of rubidium metal is 39.5°C and the boiling point is 688°C; the melting point of cesium metal is 28.5°C and the boiling point is 668 - 705°C; the melting point of metallic Ag is 961.93°C. After extracting the Li, Na, and K impurities, the difference between the boiling points of rubidium or cesium and the melting point of Ag can be further utilized to distill and separate high-purity rubidium or cesium under a vacuum state. In principle, when the second temperature is at most 600°C, it is sufficient to separate the eutectic from rubidium or cesium, and higher temperatures can also be used but will significantly increase energy consumption.

[0024] In a second aspect, the present invention provides a preparation system for high-purity rubidium or cesium metal, the raw materials of which contain impurities; the impurities include one or more of Li, Na, and K, and the system includes the following parts.

[0025] A reaction vessel for keeping the mixture of raw materials and Ag at the first temperature of 970°C to 1500°C for more than 2 h under the protection of a rare gas and in a sealed state, and after the heat preservation is completed, cooling it to below the boiling point of the high-purity metal; after the cooling is completed, heating it again to the second temperature below 600°C under a vacuum state to form rubidium or cesium vapor.

[0026] A condensation device communicated with the reaction vessel, which is used to receive and condense the vapor.

[0027] A vacuum device for making the reaction vessel and / or the condensation device in a vacuum state.

[0028] Preferably, the above system further includes.

[0029] A collection device for collecting the condensation products formed by the steam.

[0030] A heating device for heating the reaction vessel.

[0031] A sealing device for sealing the reaction vessel.

[0032] Preferably, the condensation device includes a condenser tube at an angle of 20-30° to the horizontal direction; the vacuum device is connected to the condenser tube.

[0033] The above design makes the installation and operation of the preparation system convenient, the cleaning inside the reaction vessel more convenient and safe, which not only improves the recovery rate and production efficiency of rubidium or cesium metal, but also is more suitable for continuous industrial production.

[0034] Preferably, the reaction vessel is sequentially cleaned with 3-5% hydrochloric acid and deionized water before use, rinsed with ethanol and then dried.

[0035] The method and system for preparing high-purity rubidium or cesium metal provided by the present invention remove alkali metal impurities Na, Li, K in rubidium or cesium by the method of metal melt extraction, and obtain high-purity rubidium or cesium metal products. Among them, the purification rates of Na and Li are above 80%, the purification rate of K is above 50%, the purity of the obtained high-purity rubidium is above 99.90%, the purity of the obtained high-purity cesium is above 99.95%, and the yield is above 95%. And the equipment is simple, the installation and operation are convenient, and it is suitable for continuous industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0037] Figure 1 It is a process schematic diagram of the method for preparing high-purity metal provided by the present invention.

[0038] Figure 2 It is a structural diagram of the system for preparing high-purity metal of the present invention.

[0039] The reference numerals are as follows.

[0040] 1: Furnace body; 2: Reaction vessel; 3: Metal raw material and Ag; 4: Condensation device; 5: Collection device; 6: Vacuum device. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] To make the objectives, technical solutions, and advantages of the present invention more clear, the following will, in conjunction with the accompanying drawings of the present invention, clearly and completely describe the technical solutions in the present invention. Apparently, the described embodiments are part of the embodiments of the present invention, rather than all of them. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0042] The embodiments of the present invention first provide a system for preparing high-purity rubidium or cesium metal, the structure of which is as Figure 2 shown, including the following parts.

[0043] It includes a furnace body 1, a reaction vessel 2 installed in the furnace body 1, a collection device 5 connected to the reaction vessel 2 through a condensation device 4, and a vacuum device 6 connected to the condensation device. The condensation tube forms an angle of 25° with the horizontal direction.

[0044] The present invention provides a specific implementation method for preparing high-purity rubidium or cesium metal, the process of which is as Figure 1 shown, including the following steps.

[0045] S1. Under argon protection, place metallic Ag in the reaction vessel in the glove box. Secondly, transfer the vacuum-sealed vial containing liquid metallic raw material rubidium or cesium to the glove box, open the vial cap, and transfer the liquid metallic raw material rubidium or cesium to the reaction vessel containing metallic Ag.

[0046] S2. Close the valve of the reaction vessel, heat the reaction vessel that has completed the furnace loading operation, raise the furnace temperature to 970 °C - 1500 °C, and keep it warm for 2 - 10 h.

[0047] S3. After the insulation in S2 ends and the temperature drops to room temperature, open the valve of the reaction vessel, evacuate to below 1.0×10 -2 Pa, maintain the vacuum, raise the furnace temperature to 50 °C - 600 °C, keep it warm for 2 - 8 h, then stop evacuating. The purified rubidium or cesium vapor condenses to form liquid metal and is collected by the collection device, thus obtaining high-purity rubidium or cesium metal.

[0048] The present invention also provides the preparation system used in the above method, the structure of which is as Figure 2 shown, and the specific embodiments are as follows.

[0049] Example 1

[0050] In the metallic rubidium to be purified in this example, the impurity elements include elements such as Li, K, and Na. Among them, the mass percentage content of Li is 93×10 -4 %, the mass percentage content of K is 652×10 -4 %, and the mass percentage content of Na is 82×10 -4 %.

[0051] The method for purifying rubidium metal in this embodiment is carried out by using the above system for preparing high-purity rubidium or cesium metal, and the specific steps are as follows.

[0052] Before use, the reaction vessel is successively cleaned with 3-5% hydrochloric acid and deionized water, rinsed with ethanol and then dried.

[0053] Take 100 g of metal Ag (purity 99.99%) material and place it in the reaction vessel in the glove box. Secondly, transfer the vial with 50 g of liquid metal raw material rubidium (purity 99.50%) sealed under vacuum to the glove box protected by argon (purity 99.999%). Open the vial cap of the vial and transfer the liquid metal raw material rubidium to the reaction vessel containing metal Ag. Close the valve of the reaction vessel, start the heating system, heat up to 1000 °C, keep the temperature for 6 h, and then cool down to room temperature after the heat preservation ends.

[0054] After the heat preservation ends and the temperature drops to room temperature, open the valve of the reaction vessel and start to evacuate. Wait until the pressure in the furnace drops below 1.0×10 -2 Pa, keep the vacuum, start the heating system, heat up to 400 °C, keep the temperature for 4 h. After the heat preservation ends, stop evacuating. The purified rubidium vapor condenses in the condensation device to form liquid rubidium metal, which is collected through the collection container, and high-purity rubidium metal is obtained.

[0055] Close the valve of the reaction vessel, remove the collection tank, and then remelt it in the glove box for sub-packaging and sampling analysis. A total of 48.3 g of metal is obtained in the collection tank, and the overall yield is 96.6%.

[0056] As shown in Table 1, this batch of metal raw material is rubidium raw material, and the impurity content table of the high-purity rubidium metal collected in the collection tank after the above process. After impurity removal, the purity of the rubidium metal is increased to 99.92%.

[0057]

[0058] Example 2

[0059] The impurity elements in the rubidium metal to be purified in this embodiment include elements such as Li, K, and Na. Among them, the mass percentage content of Li is 89×10 -4 %, the mass percentage content of K is 563×10 -4 %, and the mass percentage content of Na is 94×10 -4 %.

[0060] The method for purifying rubidium metal in this embodiment includes the following steps.

[0061] Before use, the reaction vessel is successively cleaned with 3-5% hydrochloric acid and deionized water, rinsed with ethanol and then dried.

[0062] Take 150 g of metallic Ag (purity 99.99%) material and place it in a reaction vessel inside a glove box. Next, transfer a vial with a vacuum seal containing 50 g of liquid metallic raw material rubidium (purity 99.62%) to the glove box protected by argon (purity 99.999%). Open the vial cap of the metallic raw material rubidium liquid and transfer it to the reaction vessel containing metallic Ag. Close the valve of the reaction vessel, start the heating system, raise the temperature to 1200 °C, keep the temperature for 5 h, and after the heat preservation ends, cool down to room temperature.

[0063] After the heat preservation ends and the temperature drops to room temperature, open the valve of the reaction vessel and start to evacuate. Wait until the pressure inside the furnace drops below 1.0×10 -2 Pa, maintain the vacuum, start the heating system, raise the temperature to 500 °C, keep the temperature for 3 h. After the heat preservation ends, stop evacuating. The purified rubidium vapor condenses in the condensation device to form liquid metallic rubidium, and is collected through a collection container, thus obtaining high-purity metallic rubidium.

[0064] Close the valve of the said reaction vessel, remove the said collection tank, and remelt it again in the glove box for sub-packaging and sampling analysis. A total of 48.8 g of metal is obtained in the collection tank, and the overall yield is 97.6%.

[0065] As shown in Table 2, this batch of metallic raw material is rubidium raw material, and it is the impurity content table of the high-purity metallic rubidium collected in the collection tank after the above process. After impurity removal, the purity of the metallic rubidium is increased to 99.95%.

[0066]

[0067] Example 3

[0068] The impurity elements in the metallic rubidium to be purified in this example include elements such as Li, K, Na, etc. Among them, the mass percentage content of Li is 81×10 -4 %, the mass percentage content of K is 742×10 -4 %, and the mass percentage content of Na is 89×10 -4 %.

[0069] The method for purifying metallic rubidium in this example includes the following steps.

[0070] Before use, wash the reaction vessel successively with 3 - 5% hydrochloric acid and deionized water, and rinse with ethanol and then dry.

[0071] Take 200 g of metal Ag (purity 99.99%) material and place it in a reaction vessel inside a glove box. Secondly, transfer a vial containing 50 g of liquid metal raw material rubidium (purity 99.55%) under vacuum seal to the glove box protected by argon (purity 99.999%). Open the vial cap of the metal raw material rubidium liquid and transfer it to the reaction vessel containing metal Ag. Close the valve of the reaction vessel, start the heating system, raise the temperature to 1200 °C, keep the temperature for 5 h, and after the heat preservation ends, cool down to room temperature.

[0072] After the heat preservation ends and the temperature drops to room temperature, open the valve of the reaction vessel and start pumping vacuum. Wait until the pressure in the furnace drops below 1.0×10 -2 Pa, maintain the vacuum, start the heating system, raise the temperature to 500 °C, keep the temperature for 4 h. After the heat preservation ends, stop pumping vacuum. The purified rubidium vapor condenses in the condensation device to form liquid metal rubidium, and is collected through a collection container, thus obtaining high-purity metal rubidium.

[0073] Close the valve of the reaction vessel, remove the collection tank, and remelt it in the glove box for sub-packaging and sampling analysis. A total of 48.1 g of metal is obtained in the collection tank, and the overall yield is 96.2%.

[0074] As shown in Table 3, this batch of metal raw material is rubidium raw material, and it is the impurity content table of the high-purity metal rubidium collected in the reaction vessel after the above process. After impurity removal, the purity of the metal rubidium is increased to 99.94%.

[0075]

[0076] Example 4

[0077] In the metal cesium to be purified in this example, the impurity elements include elements such as Li, K, Na, etc. Among them, the mass percentage content of Li is 92×10 -4 %, the mass percentage content of K is 183×10 -4 %, and the mass percentage content of Na is 82×10 -4 %.

[0078] The method for purifying metal cesium in this example includes the following steps:

[0079] Before use, clean the reaction vessel successively with 3 - 5% hydrochloric acid and deionized water, and rinse it with ethanol and then dry it.

[0080] Take 150 g of metal Ag (purity 99.99%) material and place it in a reaction vessel inside the glove box. Secondly, transfer a vial containing 50 g of liquid metal raw material cesium (purity 99.950%) sealed under vacuum to the glove box protected by argon (purity 99.999%). Open the vial cap of the cesium and transfer the liquid metal raw material cesium to the reaction vessel containing metal Ag. Close the valve of the reaction vessel, start the heating system, raise the temperature to 1000 °C, keep the temperature for 5 h, and then cool down to room temperature after the heat preservation ends.

[0081] After the heat preservation ends and the temperature drops to room temperature, open the valve of the reaction vessel and start pumping vacuum. Wait until the pressure in the furnace drops below 1.0×10 -2 Pa. Keep the vacuum, start the heating system, raise the temperature to 400 °C, keep the temperature for 5 h. After the heat preservation ends, stop pumping vacuum. The purified cesium vapor condenses in the condensation device to form liquid metal cesium, which is collected through a collection container, and thus high-purity metal cesium is obtained.

[0082] Close the valve of the reaction container, remove the collection tank, and then remelt it in the glove box for sub-packaging and sampling analysis. A total of 49.1 g of metal is obtained in the collection tank, and the overall yield is 98.2%.

[0083] As shown in Table 4, this batch of metal raw material is cesium raw material, and it is the impurity content table of the high-purity metal cesium collected in the reaction vessel after the above process. After impurity removal, the purity of the metal cesium is increased to 99.96%.

[0084]

[0085] Example 5

[0086] The impurity elements in the metal cesium to be purified in this example include elements such as Li, K, Na, etc. Among them, the mass percentage content of Li is 72×10 -4 %, the mass percentage content of K is 265×10 -4 %, and the mass percentage content of Na is 68×10 -4 %.

[0087] The method for purifying metal cesium in this example includes the following steps.

[0088] Before use, wash the reaction vessel successively with 3 - 5% hydrochloric acid and deionized water, and rinse it with ethanol and then dry it.

[0089] Take 100 g of metallic Ag (purity 99.99%) material and place it in a reaction vessel inside a glove box. Secondly, transfer a vial containing 50 g of liquid metallic cesium (purity 99.950%) under vacuum seal into the glove box protected by argon (purity 99.999%). Open the vial cap of the metallic cesium liquid and transfer it into the reaction vessel containing metallic Ag. Close the valve of the reaction vessel, start the heating system, raise the temperature to 1200 °C, keep the temperature for 6 h, and after the heat preservation ends, cool down to room temperature.

[0090] After the heat preservation ends and the temperature drops to room temperature, open the valve of the reaction vessel and start to evacuate. Wait until the pressure inside the furnace drops below 1.0×10 -2 Pa. Keep the vacuum, start the heating system, raise the temperature to 450 °C, keep the temperature for 4 h. After the heat preservation ends, stop evacuating. The purified cesium vapor condenses in the condensation device to form liquid metallic cesium, which is collected through a collection container, and thus high-purity metallic cesium is obtained.

[0091] Close the valve of the said reaction vessel, remove the said collection tank, and remelt it in the glove box for sub-packaging and sampling analysis. A total of 47.9 g of metal is obtained in the collection tank, and the overall yield is 95.8%.

[0092] As shown in Table 5, this batch of metal raw material is cesium raw material, and it is the impurity content table of the high-purity metallic cesium collected in the reaction vessel after the above process. After impurity removal, the purity of the metallic cesium is increased to 99.96%.

[0093]

[0094] Example 6

[0095] The impurity elements in the metallic cesium to be purified in this example include elements such as Li, K, Na, etc. Among them, the mass percentage content of Li is 63×10 -4 %, the mass percentage content of K is 148×10 -4 %, and the mass percentage content of Na is 69×10 -4 %.

[0096] The method for purifying metallic cesium in this example includes the following steps.

[0097] Before use, wash the reaction vessel successively with 3 - 5% hydrochloric acid and deionized water, and rinse it with ethanol and then dry it.

[0098] Take 200 g of metallic Ag (purity 99.99%) material and place it in a reaction vessel inside a glove box. Secondly, transfer a vial with 50 g of liquid metallic raw material Cs (purity 99.960%) sealed under vacuum to the glove box protected by argon (purity 99.999%). Open the vial cap of the vial and transfer the liquid metallic raw material Cs to the reaction vessel containing metallic Ag. Close the valve of the reaction vessel, start the heating system, raise the temperature to 1350 °C, keep the temperature for 6 h, and then cool down to room temperature after the heat preservation is over.

[0099] After the heat preservation is over and the temperature drops to room temperature, open the valve of the reaction vessel and start vacuum pumping. Wait until the pressure inside the furnace drops below 1.0×10 -2 Pa. Keep the vacuum, start the heating system, raise the temperature to 500 °C, keep the temperature for 5 h. After the heat preservation is over, stop vacuum pumping. The purified Cs vapor condenses in the condensation device to form liquid metallic Cs, which is collected through a collection container, and thus high-purity metallic Cs is obtained.

[0100] Close the valve of the said reaction vessel, remove the said collection tank, and then remelt it in the glove box for sub-packaging and sampling analysis. A total of 48.7 g of metal is obtained in the collection tank, and the overall yield is 97.4%.

[0101] As shown in Table 6, this batch of metallic raw material is Cs raw material, and it is the impurity content table of the high-purity metallic Cs collected in the reaction vessel after the above process. After impurity removal, the purity of the metallic Cs is increased to 99.97%.

[0102]

[0103] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing high-purity rubidium or cesium metal, the raw material of which contains impurities; the impurities include one or more of Li, Na, and K, characterized in that, The method includes: Mixing the raw material and Ag, heating the obtained mixture to a temperature above the melting point of Ag under the protection of a noble gas and in a sealed state, keeping the temperature for a certain period after reaching the required temperature, and then cooling to a temperature below the boiling point of the high-purity metal; after the cooling is completed, heating again to a temperature below 600 °C in a vacuum state to form a vapor of rubidium or cesium, and collecting the condensed vapor to obtain the high-purity metal; The weight ratio of the raw material to Ag is 1:2 to 1:

8.

2. The preparation method according to claim 1, wherein The purity of the raw material is 99.70% or less.

3. The preparation method according to claim 1, wherein Denote the temperature heated above the melting point of Ag as the first temperature, the first temperature is 1000 - 1350 °C, and the holding time at the first temperature is 4 - 6 h; And / or, denote the temperature heated again to a temperature below 600 °C in a vacuum state as the second temperature, the second temperature is 300 - 600 °C, and the holding time at the second temperature is 3 - 6 h.

4. The preparation method according to claim 1, characterized in that, The purity of the Ag ≥ 99.99%.

5. The preparation method according to claim 1, characterized in that, The vacuum state is a pressure below 1.0×10 -2 Pa.

6. The preparation method according to any one of claims 1 to 5, characterized in that, It includes: Mixing the raw material and Ag in a weight ratio of 1:2 to 1:8 to obtain a mixture; The mixture is kept at a temperature of 970 °C - 1500 °C for 2 - 10 h under the protection of a noble gas and in a sealed state, and after the holding is completed, it is cooled to room temperature; After the temperature reduction ends, the temperature is raised again to a second temperature of 50°C to 600°C under the condition that the pressure is not greater than 1.0×10 -2 Pa, and heat is kept for 2 to 8 hours. During this period, condensate is continuously collected to obtain the high-purity metal.

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