Preparation method of high-purity double perovskite oxide Sr2CrReO6

Abstract

The invention discloses a preparation method of a double perovskite oxide Sr2CrReO6 with high purity. According to the method, strontium carbonate and rhenium heptoxide are taken as raw materials and are subjected to high-temperature reaction under the protection of argon to synthesize an intermediate product; then mixing with chromium sesquioxide and elemental chromium powder, and carrying out high-temperature reaction under a vacuum tube sealing condition to obtain a crude product; and finally, carrying out heat treatment for multiple times in an inert atmosphere, and removing an impurity phase to obtain high-purity Sr2CrReO6 powder. By optimizing the temperature and time of the high-temperature reaction and introducing the heat treatment step, the impurity content is remarkably reduced, and the product purity is improved. According to the compact ceramic prepared from the high-purity powder through a spark plasma sintering technology, the antisite defect is 13.5%, the Curie temperature reaches 610 K, and the saturation magnetization is 0.84 microB / f.u. The method is easy and convenient to operate, low in equipment requirement, high in safety and suitable for laboratory-scale high-quality material preparation.

Description

Technical Field

[0001] The present invention belongs to the technical field of material preparation, relates to the preparation of high-purity materials, and specifically relates to a method for preparing high-purity double perovskite oxide Sr2CrReO6. Background Art

[0002] Due to their rich structural variants and unique magnetoelectric properties, double perovskite oxides have important application prospects in the field of spintronics. Among them, Sr2CrReO6 has received extensive attention due to its relatively high Curie temperature and high spin polarization rate.

[0003] For the preparation of high-purity Sr2CrReO6 polycrystalline ceramics, it is usually necessary to first synthesize a high-purity powder sample and then prepare it into ceramics under high-temperature and high-pressure conditions. Common synthesis methods for preparing high-purity Sr2CrReO6 powder include the solid-state reaction method and the sol-gel method. In the existing solid-state reaction method, after mixing the precursor powders, the synthesis is usually carried out in a high-temperature reducing atmosphere above 1300 °C, and the conditions are relatively harsh, requiring high requirements for experimental equipment. The sol-gel method has very complex steps, and the reaction process involves the use of strong corrosive chemicals such as aqueous nitric acid solution, which poses certain safety hazards. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the present invention proposes a method for preparing high-purity double perovskite oxide Sr2CrReO6, providing a preparation method with strong operability, high reliability, and capable of improving the purity of the product.

[0005] The method for preparing high-purity double perovskite oxide Sr2CrReO6 specifically includes the following steps:

[0006] Step 1: Using strontium carbonate (SrCO3) and rhenium heptoxide (Re2O7) as raw materials, mixing them evenly in a glove box under argon protection in a molar ratio of 1:4, transferring them to an alumina crucible, and heating and reacting in a muffle furnace. After cooling, an intermediate product Sr2ReO 5.5 .

[0007] Preferably, the heating rate of the heating reaction is set to 5 °C / min, the reaction temperature is 1000 °C, and the holding time is 2 h.

[0008] Step 2: Weigh Sr2ReO 5.5 , chromium(III) oxide (Cr2O3), and elemental chromium powder (Cr) in a molar ratio of 6:1:4, mix and grind them evenly in a glove box under argon protection, then transfer them to an alumina crucible, place the crucible in a quartz tube and seal it under vacuum, and heat and react the sealed quartz tube in a muffle furnace. After cooling, a crude Sr2CrReO6 powder is obtained.

[0009] Preferably, the pressure of the vacuum-sealed tube is less than 5×10 -5 Pa.

[0010] Preferably, the heating rate for heating the sealed quartz tube is 5 °C / min, the reaction temperature is 1200 °C, and the heat preservation time is 10 h.

[0011] Step 3: Grind the as-prepared crude Sr2CrReO6 powder obtained in Step 2 uniformly, transfer it to an alumina crucible, place it in a tube furnace, and perform multiple heat treatments under an inert gas atmosphere to reduce residual impurity phases and obtain high-purity Sr2CrReO6 powder.

[0012] Preferably, the inert gas atmosphere is an argon atmosphere.

[0013] Preferably, the heating rate for the heat treatment is set to 5 °C / min, the reaction temperature is 1150 °C, and the heat preservation time is 12 h.

[0014] A method for preparing high-purity Sr2CrReO6 ceramics. Seal the high-purity Sr2CrReO6 powder obtained in Step 3 into a customized graphite mold, and perform spark plasma sintering (SPS) under high temperature and high pressure. After cooling, a dense ceramic sample is obtained.

[0015] Preferably, the spark plasma sintering is carried out at 800 °C and 40 MPa.

[0016] Preferably, the heating rate is set to 100 °C / min and the heat preservation time is 10 min.

[0017] Preferably, the cooling method is natural cooling.

[0018] The present invention has the following beneficial effects:

[0019] Compared with the existing preparation methods, this method has simpler steps, higher safety, strong operability, and can meet the equipment conditions and safety requirements of most laboratories. At the same time, this preparation process effectively reduces the impurity phases in the sample, improves the purity of Sr2CrReO6, and is suitable for laboratory-scale production. The anti-site defect (AS) of the ceramic sample prepared based on the high-purity Sr2CrReO6 powder is 13.5%, and the Curie temperature (T C ) reaches 610 K, and the saturation magnetization intensity (M S ) is 0.84 μ B / f.u. Description of the Drawings

[0020] Figure 1 It is the X-ray diffraction pattern of the crude Sr2CrReO6 powder in Comparative Example 1.

[0021] Figure 2 The change of impurity phases in Sr2CrReO6 powder before and after heat treatment in Example 1.

[0022] Figure 3 XRD refinement pattern of Sr2CrReO6 ceramic in Example 2.

[0023] Figure 4 High-temperature field-cooled-zero-field-cooled graph of Sr2CrReO6 ceramic in Example 2.

[0024] Figure 5 Hysteresis loop graph of Sr2CrReO6 ceramic at 2K in Example 2. Detailed implementation mode

[0025] The present invention will be further explained below with reference to the accompanying drawings; it should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0026] Comparative Example 1

[0027] This comparative example provides a method for preparing crude Sr2CrReO6 powder for comparison. The specific steps are as follows:

[0028] Step 1. Inside an argon glove box, mix SrCO3 (99.95%, Macklin) and Re2O7 (99.99%, Aladdin) in a molar ratio of 1:4, and after thorough grinding, transfer them to an alumina crucible. Keep them in a muffle furnace at 1000 °C in an air environment for 2 h, and obtain an intermediate product Sr2ReO 5.5 .

[0029] Step 2. Inside an argon glove box, mix the intermediate product Sr2ReO 5.5 with Cr2O3 (99.95%, Aladdin) and elemental Cr powder (99.5%, -100 mesh) in a molar ratio of 6:1:4, grind them evenly and transfer them to a cylindrical alumina crucible. Place the crucible in a quartz tube and seal it under a pressure of less than 5×10 -5 Pa. Place the sealed quartz tube in a muffle furnace and heat it to 1200 °C at a rate of 5 °C / min and keep it for 10 h. After natural cooling, obtain black crude Sr2CrReO6 powder. Its X-ray diffraction (XRD) pattern is as Figure 1 shown, and Re impurities are included in the crude Sr2CrReO6 powder.

[0030] Example 1

[0031] This example provides a preparation method of high-purity double perovskite oxide Sr2CrReO6, which specifically includes the following steps:

[0032] Step 1. Inside an argon glove box, mix SrCO3 (99.95%, Macklin) and Re2O7 (99.99%, Aladdin) in a molar ratio of 1:4, grind them thoroughly, and transfer the mixture to an alumina crucible. Heat the crucible in a muffle furnace at 1000 °C in an air environment for 2 h, and then let it cool naturally to obtain an intermediate product Sr2ReO 5.5 .

[0033] Step 2. Inside an argon glove box, mix the intermediate product Sr2ReO 5.5 with Cr2O3 (99.95%, Aladdin) and elemental Cr powder (99.5%, -100 mesh) in a molar ratio of 6:1:4, grind the mixture evenly, and transfer it to a cylindrical alumina crucible. Place the crucible in a quartz tube and seal it under a pressure less than 5×10 -5 Pa. Place the sealed quartz tube in a muffle furnace, heat it to 1200 °C at a rate of 5 °C / min, and hold for 10 h. After natural cooling, obtain black crude Sr2CrReO6 powder.

[0034] Step 3. Grind the crude Sr2CrReO6 powder obtained in Step 2 evenly, transfer it to an alumina crucible, place it in a tube furnace, heat it to 1150 °C at a rate of 5 °C / min in an argon atmosphere, hold for 12 h, and then let it cool naturally. Then, heat it to 1150 °C at a rate of 5 °C / min in an argon atmosphere again, hold for 12 h, and after natural cooling, obtain high-purity Sr2CrReO6 powder.

[0035] As Figure 2 shown, where (a), (b), and (c) are the XRD patterns of Sr2CrReO6 powder before heat treatment, after the first heat treatment, and after the second heat treatment, respectively. It can be seen that with the increase in the number of heat treatment times, the purity of the product gradually improves. After two heat treatments, only a very weak Re peak can be detected in the XRD.

[0036] Example 2

[0037] In this example, use the high-purity Sr2CrReO6 powder prepared in Example 1 to prepare Sr2CrReO6 ceramics:

[0038] After grinding the high-purity Sr2CrReO6 powder prepared in Example 1 evenly, seal it in a graphite mold with an inner hole diameter of 13 mm. Under a pressure of 40 MPa, heat it to 800 °C at a rate of 100 °C / min and hold for 10 min. After natural cooling, obtain a dense Sr2CrReO6 ceramic sample. Figure 3 is the refined diagram of this ceramic sample. A very good fitting result can be obtained using the cubic Fm3m space group, and the refined result shows that AS is 13.5%. The high-temperature field-cooled-zero-field-cooled curve is as Figure 4As shown, its T is determined according to the Curie-Weiss law C to be 613 K. The corresponding hysteresis loop at 2 K is as Figure 5 shown, and M S is 0.84 μB / f.u., which has application prospects in the field of spintronic materials.

[0039] As mentioned above, the above are only some specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those familiar with the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. Preparation method of high-purity double perovskite oxide Sr2CrReO6, characterized in that: Specifically, it includes the following steps: Step 1: Using SrCO3 and Re2O7 as raw materials, in a glove box under argon protection, mix them evenly in a molar ratio of 1:4 and then transfer to an alumina crucible. Conduct a heating reaction in a muffle furnace, and after cooling, obtain the intermediate product Sr2ReO 5.5 ; Step 2: Weigh Sr2ReO with a molar ratio of 6:1:4 5.5 , Cr2O3, and Cr are mixed and ground evenly in an argon-protected glove box, and then transferred to a crucible, the crucible is placed in a quartz tube and vacuum-sealed, the sealed quartz tube is placed in a muffle furnace for heating and reaction, and crude Sr2CrReO6 powder is obtained after cooling; Step 3: Grind the as-prepared Sr2CrReO6 powder obtained in Step 2 evenly and transfer it to a crucible. Place the crucible in a tubular furnace and conduct multiple heat treatments under an argon atmosphere to reduce residual impurity phases and obtain high-purity Sr2CrReO6 powder.

2. The preparation method of the high-purity double perovskite oxide Sr2CrReO6 as described in claim 1, wherein: In Step 1, set the heating rate of the heating reaction to 5 °C / min, the reaction temperature to 1000 °C, and the holding time to 2 h.

3. The preparation method of the high-purity double perovskite oxide Sr2CrReO6 as claimed in claim 1, characterized in that: The pressure of the vacuum-sealed tube is less than 5×10 -5 Pa.

4. The preparation method of high-purity double perovskite oxide Sr2CrReO6 according to claim 1, characterized in that: The heating rate for heating the sealed quartz tube is 5 °C / min, the reaction temperature is 1200 °C, and the holding time is 10 h.

5. The preparation method of the high-purity double perovskite oxide Sr2CrReO6 according to claim 1, characterized in that: In Step 3, set the heating rate of the heat treatment to 5 °C / min, the reaction temperature to 1150 °C, and the holding time to 12 h.

6. The preparation method of the high-purity double perovskite oxide Sr2CrReO6 according to claim 1, characterized in that: The cooling method is natural cooling.

7. A method for preparing high-purity Sr2CrReO6 ceramics, characterized in that: Seal the high-purity double perovskite oxide Sr2CrReO6 powder prepared as described in any one of Claims 1 to 5 into a graphite mold and perform spark plasma sintering under high temperature and high pressure. After cooling, a dense ceramic sample is obtained.

8. The preparation method of a high-purity Sr2CrReO6 ceramic according to claim 7, characterized in that: Set the spark plasma sintering to be carried out at 800 °C and 40 MPa.

9. The preparation method of a high-purity Sr2CrReO6 ceramic according to claim 7, characterized in that: Set the heating rate to 100 °C / min and the holding time to 10 min.

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