A sulfide perovskite with antiferromagnetic properties and a preparation method thereof

Abstract

The present invention relates to the field of magnetic perovskite materials. Sulfide perovskites have advantages such as high stability and good carrier transport characteristics. By appropriate doping or alloying with magnetic ions, they can become dilute magnetic semiconductors, showing both semiconductor and magnetic characteristics. However, doping and alloying are prone to problems such as phase separation. To solve the above problems, the present invention discloses a sulfide perovskite material with antiferromagnetic properties and its preparation method, including the following steps: weighing raw materials HfS2 and EuS in a molar ratio of 1:1; grinding, mixing, and pressing the above raw materials into flakes; carrying out a solid-state reaction on the above flake mixture in a CS2 protection atmosphere at 1300 °C for 6 hours to obtain a single pure-phase EuHfS3 sulfide perovskite material. This material exhibits good crystallinity, unique antiferromagnetic characteristics, and high conductivity, and can be widely applied in magnetic storage and spintronic devices.

Description

Technical Field

[0001] The present invention relates to the field of magnetic perovskite materials, and in particular to a sulfide perovskite with antiferromagnetic properties and a preparation method thereof. Background Art

[0002] Materials with both magnetic and semiconductor properties have important and extensive applications in magnetic storage devices, magnetic sensors, spintronics, and thermoelectric fields. Diluted magnetic semiconductors can simultaneously achieve magnetic and semiconductor properties by introducing magnetic metal ions into semiconductors. However, the introduction of magnetic metal ions often requires doping or alloying, which can lead to phase separation and thus deteriorate the material properties. Therefore, obtaining a pure-phase material with both magnetic and semiconductor characteristics has important scientific significance and application value.

[0003] Sulfide perovskite materials are mainly represented by IIA-IVB-S3, where IIA refers to Ca, Sr, Ba; and IVB refers to Ti, Zr, Hf. This material system has high stability, good carrier transport characteristics, and unique advantages such as environmental friendliness and high crust abundance of its constituent elements, and is an excellent semiconductor material. However, its elements are non-magnetic elements. In this patent, the A-site magnetic cation Eu is introduced, fully combining the semiconductor advantages of sulfide perovskite and the magnetic characteristics of Eu ions to form a single pure-phase EuHfS3 compound material.

[0004] This patent uses a simple solid-phase reaction method to simultaneously obtain EuHfS3 wafers and powder materials, which is an efficient and feasible technical solution. Summary of the Invention

[0005] The purpose of the present invention is to obtain a highly crystalline, pure-phase, magnetic semiconductor material EuHfS3, and thus a preparation method based on solid-phase reaction is proposed.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A preparation method of a sulfide perovskite EuHfS3 with antiferromagnetic properties, comprising the following steps:

[0008] S1. Weigh EuS and HfS2 powders in a molar ratio of 1:1;

[0009] S2. Grind, mix, and tablet the above powders;

[0010] S3. Place the above sheet material in a tube furnace and sinter at 1300 °C for 6 hours under a CS2 protection atmosphere;

[0011] S4. Obtain EuHfS3 sheet material and further grind to obtain EuHfS3 powder material;

[0012] In step S1, EuS and HfS2 are screened through a molecular vibration sieve before weighing to obtain fine powder particles with a particle size below 50 microns;

[0013] In step S2, grinding is carried out in a mortar for 30 minutes; a tablet press is used to press the raw materials with a pressure of 6 tons, cold pressing. The tablet press mold is circular with a diameter of 10 mm and a pressure holding time of 3 minutes. After pressure relief, a raw material wafer is obtained;

[0014] In step S3, the wafer obtained in step S2 is placed in a tube furnace, pumped to a base vacuum using a mechanical pump, and CS2 is introduced for protection. The tube furnace is set to heat up to 1300 °C and hold the temperature. The base vacuum should be lower than 0.1 Pa, and the pressure inside the furnace is 30 Pa after introducing CS2;

[0015] In step S4, grinding is carried out in a mortar for 30 minutes;

[0016] Preferably, in step S2, the thickness of the wafer is 2 - 5 mm;

[0017] Preferably, in step S3, the flow rate of CS2 is 30 SCCM;

[0018] Preferably, in step S4, fine powder particles can be obtained through an ultrasonic vibration sieve;

[0019] The present invention provides a preparation method of a sulfide perovskite EuHfS3 with antiferromagnetic properties. The beneficial effects and scientific principles of the present invention are as follows:

[0020] 1. The reaction equation is EuS + HfS2 = EuHfS3, achieving 100% utilization of the raw materials, meeting the requirements of green environmental protection, and not generating any waste;

[0021] 2. The product EuHfS3 combines the excellent semiconductor characteristics of sulfide perovskite and the unique magnetism of Eu ions;

[0022] 3. The required raw materials can be conveniently purchased in the commercial market, and the required tube furnace is also a common industrial product on the market;

[0023] 4. Avoid using common means such as doping and alloying to obtain a single-phase magnetic semiconductor material;

[0024] 5. The elements involved are non-toxic and environmentally friendly; Description of the Drawings

[0025] Figure 1 is a flow chart of the preparation method of the sulfide perovskite EuHfS3 with antiferromagnetic properties described in the present invention;

[0026] Figure 2 It is the XRD pattern of the EuHfS3 powder prepared in Example 1 of the present invention;

[0027] Figure 3 They are the physical pictures of the EuS and HfS2 raw materials involved in Example 1 of the present invention, as well as the physical pictures of the EuHfS3 wafers and powders;

[0028] Figure 4 It is the scanning electron microscope image of the EuHfS3 powder prepared in Example 1 of the present invention;

[0029] Figure 5 It is the transmission electron microscope image of the EuHfS3 powder prepared in Example 1 of the present invention;

[0030] Figure 6 It is the integrating sphere diffuse reflectance absorption spectrum of the EuHfS3 powder prepared in Example 1 of the present invention;

[0031] Figure 7 It is the resistivity graph of the EuHfS3 powder prepared in Example 1 of the present invention under different pressure conditions;

[0032] Figure 8 It is the variation of the magnetic susceptibility of the EuHfS3 powder prepared in Example 1 of the present invention with temperature;

[0033] Figure 9 It is the variation of the reciprocal of the magnetic susceptibility of the EuHfS3 powder prepared in Example 1 of the present invention with temperature and its linear fitting relationship;

[0034] Figure 10 The variation of the magnetic moment of the EuHfS3 powder prepared in Example 1 of the present invention with the external magnetic field at different temperatures; Detailed implementation manners

[0035] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0036] Example 1

[0037] Step S1. Screen the EuS and HfS2 powders with fine particles through a molecular sieve. The particle size is less than 50 microns. Weigh the EuS and HfS2 powders with a molar ratio of 1:1, and the total mass of the powders is 1 gram.

[0038] Step S2. Grind the above powder for 30 minutes to mix it evenly. Use a tablet press to press the raw materials. The pressure is 6 tons, and it is cold-pressed. The tablet press mold is circular with a diameter of 10 mm, and the pressure holding time is 3 minutes. After pressure relief, a raw material wafer is obtained. After testing, the thickness of the wafer is 2 mm;

[0039] Step S3. Put the wafer obtained in Step S2 into a tube furnace. Use a mechanical pump to pump it to the base vacuum. Introduce CS2 for protection, and set the flow rate to 30 SCCM. Set the tube furnace to heat up to 1300 °C and hold the temperature. The base vacuum should be lower than 0.1 Pa, and the pressure in the furnace after introducing CS2 is 30 Pa; Put the above sheet material into the tube furnace and sinter it at 1300 °C for 6 hours under the protection atmosphere of CS2;

[0040] S4. Obtain EuHfS3 sheet material, grind it to obtain EuHfS3 powder material, and further obtain fine powder particles through an ultrasonic vibrating sieve;

[0041] Figure 1 It is the flow chart of the preparation method of the sulfide perovskite EuHfS3 with antiferromagnetic properties described in the present invention;

[0042] Figure 2 It is the XRD pattern of the EuHfS3 powder prepared in Example 1 of the present invention. It can be seen that the positions of the experimental observation peaks match well with the theoretical simulation positions, indicating that the EuHfS3 powder has good crystallinity and is a single phase;

[0043] Figure 3 It is the physical diagram of the EuS and HfS2 raw materials involved in Example 1 of the present invention, as well as the physical diagrams of the EuHfS3 wafer and powder, indicating the successful preparation of the EuHfS3 wafer and powder, which are shown as delicate powders;

[0044] Figure 4 It is the scanning electron microscope image of the EuHfS3 powder prepared in Example 1 of the present invention. It can be seen that its particle size is in the micron level, indicating that its particle size meets the requirements;

[0045] Figure 5 It is the transmission electron microscope image of the EuHfS3 powder prepared in Example 1 of the present invention, and its lattice spacing and The corresponding crystal planes are (001) and (110);

[0046] Figure 6 It is the integrating sphere diffuse reflectance absorption spectrum of the EuHfS3 powder prepared in Example 1 of the present invention, indicating that its absorption band edge is located at about 800 nm, and the corresponding band gap is 1.6 eV, which meets the semiconductor characteristics;

[0047] Figure 7It is the resistivity graph of the EuHfS3 powder prepared in Example 1 of the present invention under different pressure conditions. As the pressure increases, the resistivity stabilizes in the range of 1 - 2 ohm·centimeter, which conforms to the semiconductor resistance value and has high conductivity;

[0048] Figure 8 It is the change of the magnetic susceptibility of the EuHfS3 powder prepared in Example 1 of the present invention with temperature. It can be seen that when the thermodynamic temperature is 3 Kelvin, the magnetic susceptibility significantly shows an inflection point of decreasing with the decrease of temperature, fully proving that this material is an antiferromagnetic material;

[0049] Figure 9 It is the change of the reciprocal of the magnetic susceptibility of the EuHfS3 powder prepared in Example 1 of the present invention with temperature and its linear fitting relationship. The Curie - Weiss constant fitted is 8.33, and further the effective magnetic moment of Eu ions is deduced to be 8.16μ B and is in agreement with the theoretical data of 7.94μ B ;

[0050] Figure 10 The change of the magnetic moment of the EuHfS3 powder prepared in Example 1 of the present invention with the external magnetic field at different temperatures. At low temperatures, the magnetic moment gradually increases, which belongs to typical magnetic characteristics.

[0051] Example 2

[0052] The steps of Example 2 are basically the same as those of Example 1. The difference is that in step S1, the raw materials are not sieved.

[0053] The results show that the prepared particles are relatively coarse, with a particle size reaching 100 - 200 microns, but it is still a pure phase of EuHfS3, and there is no obvious change in the semiconductor performance and magnetic performance, indicating that the method of this patent has universality.

[0054] Comparative Example

[0055] The steps of the comparative example are basically the same as those of Example 1. The difference is that in step S3, the reaction temperature is reduced to 1200 °C.

[0056] The results show that there are impurities such as raw materials in the reaction product, and it no longer belongs to the pure phase of EuHfS3. This comparative result shows that the method of this patent is an optimized method.

[0057] The present invention provides a preparation method of a highly crystalline, pure-phase, magnetic semiconductor material EuHfS3. The required raw materials such as EuS and HfS2 are common sulfide powders and can be conveniently purchased in the commercial market. The preparation reaction belongs to a simple solid-phase reaction method, with simple operation and easy to popularize. The obtained EuHfS3 has an elemental chemical composition that meets expectations and exhibits good semiconductor characteristics and antiferromagnetic properties. By introducing Eu elements, semiconductor performance and antiferromagnetic phenomena can be simultaneously achieved in sulfide perovskites, and it is promising to be applied in fields such as semiconductor devices, magnetic storage, magnetic detectors, spintronic devices, and thermoelectricity.

[0058] As mentioned above, the above is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention should not be limited thereto. Any person skilled in the art within the technical scope described in the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered within the protection scope of the present invention.

Claims

1. A method for preparing an antiferromagnetic sulfide perovskite EuHfS3 material, characterized in that: The following steps are involved: S1. Weigh EuS and HfS2 powders in a molar ratio of 1:1; S2. Grinding, mixing and tableting the above powder; S3. The sheet material was placed in a tubular furnace and fired at 1300 ° C for 6 hours under a CS2 protective atmosphere; S4. Obtaining EuHfS3 flake material, further grinding to obtain EuHfS3 powder material; It is characterized in that, in step S1, EuS and HfS2 are screened by a molecular vibration screen before being weighed to obtain fine powder particles with a particle size of less than 50 microns; Characterized in that, in step S2, grinding is performed in a mortar for 30 minutes; It is characterized in that in step S2, the raw material is tableted using a tablet press, the pressure is 6 tons, cold pressing, the tablet pressing mold is round, the diameter is 10 mm, the pressure holding time is 3 minutes, and the raw material disc is obtained after the pressure is released; It is characterized in that in step S3, the wafer obtained in step S2 is placed in a tube furnace, pumped to a background vacuum using a mechanical pump, CS2 is introduced for protection, the tube furnace is set to heat up to 1300° C. and keep warm, the background vacuum should be lower than 0.1 Pa, and the pressure in the furnace is 30 Pa after CS2 is introduced; It is characterized in that, in step S4, grinding is performed using a mortar, and the grinding time is 30 minutes.

2. The EuHfS3 material prepared by the method for preparing an antiferromagnetic sulfide perovskite EuHfS3 material as claimed in claim 1.

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