Method for intercepting high-temperature phase of perovskite material

Abstract

The invention relates to a method for intercepting and capturing a high-temperature phase of a perovskite material, belongs to the technical field of perovskite materials, and is used for solving at least one of the problems that the high-temperature phase of the perovskite material cannot be intercepted and captured under a room-temperature condition and a high-temperature phase material cannot be reserved under the room-temperature condition in the prior art. A method for intercepting a high-temperature phase of a perovskite material comprises the following steps: pressing a room-temperature phase of the perovskite material into a cake-shaped sample, placing the cake-shaped sample in a high-pressure synthesis device, carrying out high-pressure heat treatment, quenching to room temperature, and finally reducing the pressure to normal pressure to obtain the high-temperature phase of the perovskite material. According to the method, the high-temperature phase of the perovskite material is prepared by adopting a method of combining high-pressure heat treatment with a quenching process, so that the high-temperature phase of the material is completely retained under a room-temperature condition, and the problem that the high-temperature phase material cannot be preserved under the room-temperature condition in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of perovskite materials, and in particular to a method for intercepting a high-temperature phase of a perovskite material. Background Art

[0002] The crystal structure of a material determines its physical properties, and the physical properties of a material determine its application areas and scope. Therefore, the same material with different microscopic crystal structures may have very different macroscopic properties. For example: graphite and diamond are two allotropes of carbon, but their crystal structures and macroscopic physical properties are significantly different. Among them, graphite belongs to the hexagonal system P63 / mmc (No.194) space group, and it presents an obvious layered structure at the microscopic level. The carbon atoms in the same layer form covalent bonds by sp2 hybridization. Each carbon atom is connected to three other carbon atoms. The six carbon atoms form a regular hexagonal ring on the same plane and stretch to form a lamellar structure. The distance between the layers is large, and they are mainly bonded by van der Waals forces. Because it has a small friction coefficient, the layers can slide between each other, so it is usually used as a lubricating material. The corresponding diamond belongs to the cubic crystal system Fd3m (No. 227) space group, in which each carbon atom forms a covalent bond with another 4 carbon atoms in the form of sp3 hybridization to form a regular tetrahedron. Due to the strong covalent bonds between CC, diamond has very high hardness and melting point. Its hardness is the highest among all substances in nature, so diamond is often used as a superhard material. Although diamond and graphite have the same chemical composition, their functional properties are completely different. The fundamental reason is that their crystal structures are different. From this, we can see that the microscopic crystal structure of the material determines its macroscopic physical properties and functional properties.

[0003] The crystal structure of a material usually changes with changes in external conditions such as temperature and pressure. For example, PbTiO 3 At room temperature, it belongs to the tetragonal phase P4mm (No.99) space group. In this structure, the positive charge center formed by Ti and Pb does not coincide with the negative charge center of O, resulting in an electric dipole moment, which produces an electric polarization intensity that is not equal to zero, making the crystal spontaneously polarized in the absence of an external electric field, thereby generating ferroelectricity. As the temperature rises, PbTiO 3 At about 490℃, a structural phase transition occurs, from a low-temperature tetragonal ferroelectric phase to a high-temperature cubic paraelectric phase, which belongs to the Pm-3m (No.221) space group. 3 It transforms from a high-temperature cubic paraelectric phase to a low-temperature tetragonal ferroelectric phase. 3 The structural phase transition induced by medium temperature is a reversible phase transition, and the high temperature phase of the material cannot usually be obtained at room temperature.

[0004] Like PbTiO3 Similarly, many materials have multiple high-temperature phases in addition to the room-temperature phase. Generally, the high-temperature phase is unstable at room temperature. However, the high-temperature phases of some materials have good physical properties. Since the higher phase transition temperature affects their use value, how to "intercept" the high-temperature phase of the material at room temperature and keep it at room temperature, then these high-temperature phases with good properties can be used at room temperature.

[0005] To this end, some methods of "intercepting" high-temperature phases have been developed accordingly. Commonly used methods include: (I) rapid cooling treatment, (II) adding chemical stabilizers, etc. The basic principle of rapid cooling treatment is to make the material undergo a crystal structure phase change at high temperature. Through rapid cooling, the high-temperature phase does not have time to transform into a low-temperature phase. By inhibiting the occurrence of phase change, the high-temperature phase is obtained at room temperature, avoiding the phase change that occurs during the natural cooling process. However, this method is not applicable to crystal structure phase changes with a faster phase change rate, so it has certain limitations. The basic principle of adding chemical stabilizers is to change the chemical composition of the material through element doping, thereby affecting its crystal structure and electronic structure, and ultimately leading to a change in the phase transition point, thereby retaining the high-temperature phase at room temperature. On the one hand, this method has very limited control over the phase transition point due to the limitation of the solid solubility of the doped elements. On the other hand, due to the introduction of other foreign elements, it may have an adverse effect on the physical and chemical properties of the material. Summary of the invention

[0006] In view of the above analysis, the present invention aims to provide a method for intercepting the high-temperature phase of perovskite materials, so as to solve at least one of the problems that the prior art cannot intercept the high-temperature phase of perovskite materials at room temperature and the high-temperature phase materials cannot be retained at room temperature.

[0007] In a first aspect, the present invention provides a method for intercepting a high-temperature phase of a perovskite material, comprising: pressing the room-temperature phase of the perovskite material into a round cake-shaped sample, placing it in a high-pressure synthesis device, performing high-pressure heat treatment, then quenching to room temperature, and finally reducing the pressure to normal pressure to obtain the high-temperature phase of the perovskite material.

[0008] Furthermore, the pressure P of the high-pressure heat treatment and the temperature T at which the captured perovskite material exists in a stable high-temperature phase satisfy the following relationship: P=4.73+0.055T, wherein P is in GPa and T is in °C.

[0009] Furthermore, the temperature of the high pressure heat treatment is 900-1200° C., and the treatment time is 0.5-1 h.

[0010] Furthermore, the quenching rate is 1000-2000°C / min.

[0011] Furthermore, the diameter of the round cake-shaped sample is 1-10 mm and the thickness is 1-10 mm.

[0012] Furthermore, the rate of reducing the pressure to normal pressure is 1-2 GPa / h.

[0013] Furthermore, the high-pressure synthesis device is a six-sided top press.

[0014] Furthermore, the perovskite material has at least one high-temperature phase in addition to the room-temperature phase.

[0015] Furthermore, the perovskite material is a B-site ordered perovskite material.

[0016] Furthermore, the general formula of the perovskite material is A 2 BB'O 6 , wherein A is Pb or Bi, B is at least one of Fe, Mn, Co or Ni, and B' is at least one of Mo, W, Ru or Re.

[0017] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0018] The present invention adopts a method of high-pressure heat treatment combined with a quenching process to prepare the high-temperature phase of the perovskite material, so that the high-temperature phase of the material is completely retained at room temperature, solving the problem in the prior art that the high-temperature phase material cannot be preserved at room temperature.

[0019] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0021] Figure 1 The room temperature phase α-Pb prepared in the present invention 2 MnMoO 6 Material testing XRD spectrum, fitted XRD spectrum and crystal structure diagram;

[0022] Figure 2 The α-Pb 2 MnMoO 6 The sample was tested for variable temperature X-ray diffraction patterns in the temperature range of 30-300°C;

[0023] Figure 3 β-Pb prepared in Example 1 of the present invention 2 MnMoO 6 XRD spectrum and β-Pb 2 MnMoO 6 High temperature phase contrast diagram;

[0024] Figure 4 β-Pb prepared in Example 1 of the present invention 2 MnMoO 6 Material testing XRD spectrum, fitted XRD spectrum and crystal structure diagram;

[0025] Figure 5 β-Pb prepared in Example 1-1 of the present invention 2 MnMoO 6 XRD spectrum of

[0026] Figure 6 β-Pb prepared in Example 1-2 of the present invention 2 MnMoO 6 XRD spectrum of

[0027] Figure 7 Pb prepared in Comparative Example 1 of the present invention 2 MnMoO 6 XRD spectrum of the main phase is α-Pb 2 MnMoO 6 ;

[0028] Figure 8 γ-Pb prepared in Example 2 of the present invention 2 MnMoO 6 XRD spectrum and high temperature phase contrast diagram of γ-PMMO;

[0029] Fig. 9 γ-Pb prepared in Example 2 of the present invention 2 MnMoO 6 Material testing XRD spectrum, fitted XRD spectrum and crystal structure diagram;

[0030] Fig.10 γ-Pb prepared in Example 2-1 of the present invention 2 MnMoO 6 XRD spectrum of

[0031] Fig.11 α-Pb prepared in Example 3 of the present invention 2 CoMoO 6 Material XRD spectrum, high temperature phase β-Pb 2 CoMoO 6XRD spectrum of the material and β-Pb intercepted by high pressure heat treatment 2 CoMoO 6 Material XRD spectrum;

[0032] Fig.12 Pb prepared in Comparative Example 2 of the present invention 2 CoMoO 6 XRD spectrum of the main phase is α-Pb 2 CoMoO 6 ;

[0033] Fig.13 α-Pb prepared in Example 4 of the present invention 2 NiMoO 6 Material XRD spectrum, high temperature phase β-Pb 2 NiMoO 6 XRD spectrum of the material and β-Pb intercepted by high pressure heat treatment 2 NiMoO 6 Material XRD spectrum;

[0034] Fig.14 Pb prepared in Comparative Example 3 of the present invention 2 NiMoO 6 XRD spectrum of the main phase is α-Pb 2 NiMoO 6 . DETAILED DESCRIPTION

[0035] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0036] A specific embodiment of the present invention discloses a method for intercepting a high-temperature phase of a perovskite material, comprising: pressing the room-temperature phase of the perovskite material into a round cake-shaped sample, placing it in a high-pressure synthesis device, performing high-pressure heat treatment, then quenching it to room temperature, and finally reducing the pressure to normal pressure to obtain the high-temperature phase of the perovskite material.

[0037] Compared with the prior art, the present invention adopts a method of high-pressure heat treatment combined with a quenching process to prepare the high-temperature phase of the perovskite material, so that the high-temperature phase of the material is completely retained at room temperature, solving the problem in the prior art that the high-temperature phase material cannot be preserved at room temperature.

[0038] Specifically, the pressure P of the high-pressure heat treatment and the temperature T at which the captured perovskite material exists in a stable high-temperature phase satisfy the following relationship: P=4.73+0.055T, wherein P is in GPa and T is in °C.

[0039] It should be noted that after a large number of experiments, the present invention has found that when the pressure P and the temperature T satisfy the above relationship, a high-temperature phase that is stable at room temperature can be obtained. The temperature T in the present invention refers to the temperature range within which the high-temperature phase of the perovskite material to be intercepted can exist stably. The temperature T is a range value.

[0040] Specifically, the temperature of the high pressure heat treatment is 900-1200°C, for example, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, and the treatment time is 0.5-1h, for example, 0.6h, 0.7h, 0.8h, 0.9h.

[0041] Specifically, the quenching rate is 1000-2000°C / min, for example, 1100°C / min, 1200°C / min, 1300°C / min, 1400°C / min, 1500°C / min, 1600°C / min, 1700°C / min, 1800°C / min, 1900°C / min. If the rate is too low, the high temperature phase will be transformed into the low temperature phase.

[0042] Specifically, the rate of reducing the pressure to normal pressure is 1-2 GPa / h, for example, 1.1 GPa / h, 1.2 GPa / h, 1.3 GPa / h, 1.4 GPa / h, 1.5 GPa / h, 1.6 GPa / h, 1.7 GPa / h, 1.8 GPa / h, 1.9 GPa / h.

[0043] Specifically, the perovskite material has at least one high-temperature phase in addition to a room temperature phase.

[0044] Specifically, the perovskite material is a B-site ordered perovskite material.

[0045] Specifically, the general formula of the perovskite material is A 2 BB'O 6 , wherein A is Pb or Bi, B is at least one of Fe, Mn, Co or Ni, and B' is at least one of Mo, W, Ru or Re.

[0046] Specifically, the diameter of the round cake-shaped sample is 1-10 mm, for example, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, and the thickness is 1-10 mm, for example, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm.

[0047] Specifically, the high pressure synthesis device is a six-sided top press.

[0048] The technical solution of the present invention is further explained below in conjunction with specific embodiments.

[0049] It should be noted that the room temperature phase perovskite material in Examples 1-2 of the present invention is Pb 2 MnMoO 6 , Pb 2 MnMoO 6 The preparation method can refer to the method of patent CN117550644A, and can also be prepared by other existing technologies; the specific preparation method is as follows:

[0050] (1) PbO, MnO and MoO 3 As raw materials, accurately weigh and mix according to a molar ratio of 2:1:1, and grind thoroughly to obtain powder;

[0051] (2) The powder is pressed into a round cake-shaped sample using a mold, and placed in a high-pressure synthesis device to perform a high-pressure and high-temperature synthesis experiment under the conditions of a pressure of 4 GPa and a temperature of 1000° C. The reaction time is 1 h;

[0052] (3) After the high-pressure experiment is completed, the product is taken out from the high-pressure synthesis device and tested for X-ray diffraction (XRD). The XRD spectrum is fitted to obtain the crystal structure as shown in Figure 1 As shown, it is confirmed that the obtained product Pb 2 MnMoO 6 , this material belongs to cubic system P2 1 3 space group is (No.198). It is defined as having cubic P2 at room temperature. 1 3 space group Pb 2 MnMoO 6 The material is α-phase Pb 2 MnMoO 6 , abbreviated as α-PMMO. The atomic position coordinates of α-PMMO obtained by crystal structure analysis are shown in Table 1. From Table 1, it can be seen that the lattice constant is: Unit cell volume: Theoretical density: 8.128g / cm 3 .

[0053] Table 1 Atomic position coordinates of the α-PMMO materials described

[0054]

[0055]

[0056] The α-PMMO sample was tested for variable temperature X-ray diffraction in the temperature range of 30-300°C, and the variable temperature XRD spectrum was obtained as follows: Figure 2As shown in the figure, it can be seen that the product α-PMMO undergoes a crystal structure phase transition at 60°C and 240°C as the temperature rises, which are recorded as β-PMMO and γ-PMMO respectively. It is also found through experiments that when the temperature drops to room temperature, the sample changes back to α-PMMO, confirming that the high-temperature phases of β-PMMO and γ-PMMO cannot be retained at room temperature.

[0057] from Figure 2 It can be seen that the temperature range in which α-PMMO exists stably is T<60℃, the temperature range in which β-PMMO exists stably is 60<T<240℃, and the temperature range in which γ-PMMO exists stably is T>240℃.

[0058] According to the formula P=4.73+0.055T, it can be calculated that if β-PMMO is desired, the pressure P required for high-pressure heat treatment needs to satisfy 8.03GPa<P<17.93GPa; if γ-PMMO is desired, the pressure P required for high-pressure heat treatment needs to satisfy P>17.93GPa.

[0059] Example 1

[0060] A method for intercepting a high-temperature phase of a perovskite material in the present embodiment includes: using a mold to press α-PMMO into a round cake-shaped sample with a diameter of 3 mm and a thickness of 3 mm, and placing it in a six-sided top press cavity for high-pressure heat treatment. Specifically, first increase the pressure to a target pressure of 9 GPa, then increase the temperature to a target temperature of 900°C, and heat treat for 0.5 h. After the heating is completed, cut off the heating power supply to quench the sample to room temperature at a rate of 1000°C / min, and finally reduce the pressure to normal pressure at a rate of 1 GPa / h; after the high-pressure heat treatment is completed, take the product out of the high-pressure synthesis device, test the X-ray diffraction, and obtain an XRD spectrum that is similar to the high-temperature phase of β-PMMO. Figure 3 As shown, it was confirmed that the obtained product was the β-PMMO.

[0061] The XRD spectrum is fitted and the high temperature phase β-PMMO crystal structure prepared in this embodiment is as follows Figure 4 As shown, the atomic position coordinates of β-PMMO obtained by crystal structure analysis are shown in Table 2.

[0062] Table 2 Atomic position coordinates of the β-PMMO materials described

[0063] Atomic Type Wyckoff Location Occupancy X Y Z Pb1 4h 1 0 0.1016 0.2434 Pb2 4h 1 0 0.6151 0.2236 Mn1 4g 1 0.25 0.8644 0.25 Mo1 4g 1 0.25 0.6326 0.75 O1 4f 1 0.2772 0.5 0 O2 4h 1 0.5 0.6234 0.6184 O3 4e 1 0.2274 0 0 O4 8i 1 0.2098 0.7495 0.9354 O5 4h 1 0 0.8749 0.2318

[0064] From the analysis of Table 2, it can be seen that the molecular formula of the β-PMMO material is Pb 2 MnMoO 6 . Space group: Pmna (NO.53), lattice constant: Primitive cell volume: Theoretical density: 8.114 g / cm 3 .

[0065] Example 1-1

[0066] The method of capturing the high-temperature phase of a perovskite material in this embodiment is the same as that in Embodiment 1, except that the pressure is first increased to a target pressure of 13 GPa.

[0067] The XRD spectrum of the product prepared in this example is as follows Figure 5 As shown, it is proved that β-PMMO was prepared in this example.

[0068] Example 1-2

[0069] The method of capturing the high-temperature phase of a perovskite material in this embodiment is the same as that in Embodiment 1, except that the pressure is first increased to a target pressure of 16 GPa.

[0070] The XRD spectrum of the product prepared in this example is as follows Figure 6 As shown, it is proved that β-PMMO was prepared in this example.

[0071] Comparative Example 1

[0072] A method for intercepting the high-temperature phase of a perovskite material in this comparative example is the same as that in Example 1, except that the pressure is first increased to a target pressure of 6 GPa.

[0073] The XRD spectrum of the product prepared in this comparative example is as follows Figure 7 As shown, the main product is α-PMMO, proving that β-PMMO is not obtained in this comparative example.

[0074] Example 2

[0075] A method for intercepting a high-temperature phase of a perovskite material in the present embodiment includes: using a mold to press α-PMMO into a round cake-shaped sample with a diameter of 2 mm and a thickness of 2 mm, and placing it in a six-sided top press of a high-pressure synthesis device for high-pressure heat treatment. Specifically, first increase the pressure to a target pressure of 18 GPa, then increase the temperature to a target temperature of 1000°C, and heat treat for 1 hour. After the heating is completed, cut off the heating power supply to quench the sample to room temperature at a rate of 1500°C / min, and finally reduce the pressure to normal pressure at a rate of 2 GPa / h; after the high-pressure heat treatment is completed, take the product out of the high-pressure synthesis device, test the X-ray diffraction, and obtain an XRD spectrum that is similar to the high-temperature phase of γ-PMMO. Figure 8 As shown, it was confirmed that the obtained product was the γ-PMMO.

[0076] The XRD spectrum is fitted and the high temperature phase β-PMMO crystal structure prepared in this embodiment is as follows Fig. 9As shown, the atomic position coordinates of β-PMMO obtained by crystal structure analysis are shown in Table 3.

[0077] Table 3 Atomic position coordinates of the γ-PMMO materials described

[0078] Atomic Type Wyckoff Location Occupancy X Y Z Pb 8c 1 0.25 0.25 0.25 Mn 4b 1 0.5 0.5 0.5 Mo 4a 1 0 0 0 O 24e 1 0.2466 0 0

[0079] From the analysis of Table 3, it can be seen that the molecular formula of the γ-PMMO material is Pb 2 MnMoO 6 . Space group: Fm-3m (NO.225), lattice constant: Primitive cell volume: Theoretical density: 8.164g / cm 3 .

[0080] Example 2-1

[0081] The method of capturing the high-temperature phase of a perovskite material in this embodiment is the same as that in Embodiment 1, except that the pressure is first increased to a target pressure of 20 GPa.

[0082] The XRD spectrum of the product prepared in this example is as follows Fig.10 As shown, it is proved that γ-PMMO was prepared in this example.

[0083] Example 3

[0084] The molecular formula of the perovskite material in this embodiment is Pb 2 CoMoO 6 , the Pb 2 CoMoO 6 It is prepared by the existing method (for example, see the literature Small 2024,20,2305219). In this embodiment, Pb 2 CoMoO 6 A specific preparation method is as follows:

[0085] (1) PbO, CoO and MoO 3 As raw materials, accurately weigh and mix according to a molar ratio of 2:1:1, and grind thoroughly to obtain powder;

[0086] (2) The powder is pressed into a round cake-shaped sample using a mold, and placed in a high-pressure synthesis device to perform a high-pressure and high-temperature synthesis experiment under the conditions of a pressure of 4 GPa and a temperature of 1000° C. The reaction time is 1 h;

[0087] (3) After the high-pressure experiment is completed, the product is taken out from the high-pressure synthesis device and tested for X-ray diffraction (XRD). The XRD spectrum is fitted to obtain the crystal structure as shown in Fig.11 As shown in (a), the obtained product Pb 2CoMoO 6 , the material belongs to the orthorhombic Pnma space group (No.62). Define Pb with orthorhombic Pnma space group at room temperature 2 CoMoO 6 The material is α-phase Pb 2 CoMoO 6 , abbreviated as α-PCMO.

[0088] (4) The α-PCMO sample was tested for variable temperature X-ray diffraction in the temperature range of 30-200°C. The sample underwent a structural phase transition at 127°C (see references Small 2024, 20, 2305219). The high-temperature phase after the phase transition was recorded as β-PCMO. The high-temperature phase had a cubic Fm-3m space group (NO.225), such as Fig.11 As shown in (b), it was found through experiments that when the temperature dropped to room temperature, the sample transformed back into α-PCMO, confirming that the β-PCMO high-temperature phase could not be retained at room temperature.

[0089] In this embodiment, the temperature T at which β-PCMO exists stably is greater than 127° C. According to the formula P=4.73+0.055T, it can be known that if β-PCMO is desired, PP>11.7 GPa.

[0090] A method for intercepting a high-temperature phase (β-PCMO) of a perovskite material in this embodiment includes: using a mold to press α-PCMO into a round cake-shaped sample with a diameter of 3 mm and a thickness of 3 mm, and placing it in a high-pressure synthesis device for high-pressure heat treatment. Specifically, first increase the pressure to a target pressure of 12 GPa, then increase the temperature to a target temperature of 1100°C, and heat treat for 0.5 h. After the heating is completed, cut off the heating power supply to quench the sample to room temperature at a rate of 1000°C / min, and finally reduce the pressure to normal pressure at a rate of 2 GPa / h; after the high-pressure heat treatment is completed, take the product out of the high-pressure synthesis device, test the X-ray diffraction, and obtain an XRD spectrum, such as Fig.11 As shown in (c).

[0091] contrast Fig.11 (b) and Fig.11 Middle (c), Fig.11 The high temperature phase shown in (b) cannot be retained at room temperature. Fig.11 The high-temperature phase β-PCMO shown in (c) can be retained at room temperature after high-pressure heat treatment and quenching.

[0092] Comparative Example 2

[0093] A method for intercepting a high-temperature phase (β-PCMO) of a perovskite material in this comparative example is the same as that in Example 3, except that the pressure is first increased to a target pressure of 8 GPa. The XRD spectrum of the product prepared in this comparative example is as follows: Fig.12 As shown, the main product is α-PCMO, proving that β-PCMO is not obtained in this comparative example.

[0094] Example 4

[0095] The molecular formula of the perovskite material in this embodiment is Pb 2 NiMoO 6 , the Pb 2 NiMoO 6 It is prepared by the existing method (for example, see the literature Chem. Mater. 2022, 34, 97-106). In this embodiment, Pb 2 NiMoO 6 A specific preparation method is as follows:

[0096] (1) PbO, NiO and MoO 3 As raw materials, accurately weigh and mix according to a molar ratio of 2:1:1, and grind thoroughly to obtain powder;

[0097] (2) The powder is pressed into a round cake-shaped sample using a mold, and placed in a high-pressure synthesis device to perform a high-pressure and high-temperature synthesis experiment under the conditions of a pressure of 4 GPa and a temperature of 1000° C. The reaction time is 1 h;

[0098] (3) After the high-pressure experiment is completed, the product is taken out from the high-pressure synthesis device and tested for X-ray diffraction (XRD). The XRD spectrum is fitted to obtain the crystal structure as shown in Fig.13 As shown in (a), the obtained product Pb 2 NiMoO 6 , the material belongs to the monoclinic Pc space group (No.7). Define Pb with monoclinic Pc space group at room temperature 2 NiMoO 6 The material is α-phase Pb 2 NiMoO 6 , abbreviated as α-PNMO.

[0099] (4) The α-PNMO sample was tested for variable temperature X-ray diffraction in the temperature range of 30-200°C. The sample underwent a structural phase transition at 130°C (see Chem. Mater. 2022, 34, 97-106). The high-temperature phase after the phase transition was recorded as β-PNMO. The high-temperature phase had a cubic Fm-3m space group (NO.225), such as Fig.13As shown in (b), it was found through experiments that when the temperature dropped to room temperature, the sample transformed back into α-PNMO, confirming that the β-PNMO high-temperature phase could not be retained at room temperature.

[0100] In this embodiment, the temperature at which β-PNMO exists stably is greater than 130° C. According to the formula P=4.73+0.055T, it can be known that if β-PNMO is to be obtained, P>11.9 GPa.

[0101] A method for intercepting a high-temperature phase (β-PNMO) of a perovskite material in this embodiment includes: using a mold to press α-PNMO into a round cake-shaped sample with a diameter of 3 mm and a thickness of 3 mm, and placing it in a high-pressure synthesis device for high-pressure heat treatment. Specifically, first increase the pressure to a target pressure of 12 GPa, then increase the temperature to a target temperature of 1100°C, and heat treat for 0.5 h. After the heating is completed, cut off the heating power supply to quench the sample to room temperature at a rate of 1000°C / min, and finally reduce the pressure to normal pressure at a rate of 1 GPa / h; after the high-pressure heat treatment is completed, take the product out of the high-pressure synthesis device, test the X-ray diffraction, and obtain an XRD spectrum, such as Fig.13 As shown in (c).

[0102] contrast Fig.13 (b) and Fig.13 Middle (c), Fig.13 The high temperature phase shown in (b) cannot be retained at room temperature. Fig.13 The high-temperature phase β-PNMO shown in (c) can be retained at room temperature after high-pressure heat treatment and quenching.

[0103] Comparative Example 3

[0104] A method for intercepting a high-temperature phase (β-PNMO) of a perovskite material in this comparative example is the same as that in Example 4, except that the pressure is first increased to a target pressure of 8 GPa. The XRD spectrum of the product prepared in this comparative example is as follows: Fig.14 As shown, the main product is α-PNMO, proving that β-PNMO is not obtained in this comparative example.

[0105] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for intercepting the high temperature phase of a perovskite material, characterized in that: include: The room temperature phase of the perovskite material is pressed into a round cake-shaped sample, placed in a high-pressure synthesis device, subjected to high-pressure heat treatment, and then quenched to room temperature. Finally, the pressure is reduced to normal pressure to obtain the high-temperature phase of the perovskite material.

2. A method for intercepting a high temperature phase of a perovskite material according to claim 1, characterized in that: The pressure P of the high-pressure heat treatment and the temperature T at which the captured perovskite material exists in a stable high-temperature phase satisfy the following relationship: P=4.73+0.055T, wherein P is in GPa and T is in °C.

3. The method for intercepting the high temperature phase of perovskite material according to claim 1, characterized in that: The temperature of the high pressure heat treatment is 900-1200° C., and the treatment time is 0.5-1h.

4. The method for intercepting the high temperature phase of perovskite material according to claim 1, characterized in that: The quenching rate is 1000-2000°C / min.

5. A method for intercepting a high temperature phase of a perovskite material according to any one of claims 1 to 4, characterized in that: The diameter of the round cake-shaped sample is 1-10 mm, and the thickness is 1-10 mm.

6. The method for intercepting the high temperature phase of perovskite material according to claim 1, characterized in that: The rate of reducing the pressure to normal pressure is 1-2 GPa / h.

7. A method for intercepting a high temperature phase of a perovskite material according to any one of claims 1 to 4, characterized in that: The high-pressure synthesis device is a six-sided top press.

8. A method for intercepting a high temperature phase of a perovskite material according to any one of claims 1 to 4, characterized in that: The perovskite material has at least one high-temperature phase in addition to a room-temperature phase.

9. A method for intercepting a high temperature phase of a perovskite material according to claim 8, characterized in that: The perovskite material is a B-site ordered perovskite material.

10. The method for intercepting the high temperature phase of perovskite material according to claim 8, characterized in that: The general formula of the perovskite material is A2BB'O6, wherein A is Pb or Bi, B is at least one of Fe, Mn, Co or Ni, and B' is at least one of Mo, W, Ru or Re.

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