Multifunctional rare earth borate material, preparation method, single crystal growth method and application

Abstract

The invention relates to a multifunctional rare earth borate material, a preparation method, a single crystal growth method and application, and belongs to the technical field of rare earth borate functional materials. The chemical formula of the material is K5Mg3Pr3 (BO3) 6, the material is crystallized in a trigonal system, the space group is P31c, and the cell parameters are as follows: a = b = 9.0140 (2), c = 13.0557 (5), alpha = beta = 90 degrees, and gamma = 120 degrees. Pr ions in the K5Mg3Pr3 (BO3) 6 compound are bridged through O ions on a BO3 group to form a two-dimensional triangular lattice, the ultraviolet absorption cutoff wavelength is 255 nm, the band gap is 4.87 eV, and it is indicated that the compound is an ultraviolet band nonlinear optical material. The material ingeniously combines the characteristics of magnetic rare earth ions Pr and BO3 elements, so that the material has optical response and two-dimensional spin blocking quantum magnetism at the same time.

Description

Technical Field

[0001] This invention belongs to the field of rare earth borate functional materials technology, and more specifically, relates to a multifunctional rare earth borate material, its preparation and single crystal growth method and application. Background Technology

[0002] In the cutting-edge field of materials science, the application prospects of bifunctional materials are receiving increasing attention. These materials aim to integrate two or more superior physical properties into a single system, thereby achieving device miniaturization and functional integration, which is crucial for the development of next-generation optoelectronic and information storage technologies. Under this trend, rare-earth borate systems exhibit unique value. Rare-earth elements are hailed as a "treasure trove of optical materials" due to their abundant electronic transitions (4f-5d and 4f-4f), while materials containing borate groups possess wide optical band gaps and high laser damage thresholds, making them ideal for constructing ultraviolet nonlinear optical crystals. Meanwhile, in the field of magnetism, two-dimensional frustrated magnetic materials, due to the spin frustration formed by the geometric arrangement of magnetic ions in triangular and cage-like lattices, result in competing spin interactions, making it impossible to simultaneously satisfy all minimum energy requirements. This makes them ideal carriers for exploring novel quantum states such as quantum spin liquids. Summary of the Invention

[0003] This invention provides a multifunctional rare-earth borate material, its preparation method, single crystal growth method, and applications. The compound is trigonal with space group [missing information]. P 31 c The unit cell parameters are a = b = 9.0140(2) Å, c = 13.0557(5) Å, α = β = 90°, γ = 120°; its basic structure consists of along ab Two-dimensional [Mg2Pr3(BO3)3] extending infinitely in a plane. ∞ It consists of layers, with adjacent layers connected by along c The BO3 groups are axially oriented and connected, with K ions distributed in adjacent [Mg2Pr3(BO3)3]. ∞ The layers maintain charge balance. The compounds in this invention simultaneously exhibit nonlinear optical response and spin-frustrated quantum magnetism.

[0004] According to a first aspect of the present invention, a compound with the chemical formula K5Mg3Pr3(BO3)6 is provided, the compound having a trigonal crystal system and a space group of P 31c, cell parameters are a = b = 9.0140(2) Å,c = 13.0557(5) Å, α = β = 90°, γ = 120°.

[0005] According to another aspect of the present invention, a method for preparing the compound is provided, comprising the following steps: (1) Mix potassium carbonate, magnesium oxide, boric acid and praseodymium oxide in a molar ratio of 1.25:1:(2.5~3):(0.1~0.75); (2) The mixture obtained in step (1) is sintered at 600~830℃ for 48~72 h to obtain the compound.

[0006] Preferably, the process further includes grinding the product obtained in step (2) into powder, soaking it in water, and then filtering and drying it.

[0007] According to another aspect of the present invention, a method for preparing the compound is provided, characterized by comprising the following steps: (1) Mix potassium carbonate, magnesium oxide, boric acid, praseodymium oxide and alkali metal fluoride in a molar ratio of 4:2:(8~10):(0.3~0.6):5; (2) The mixture obtained in step (1) is sintered at 700~800℃ for 48~72 h, and then cooled at a rate of 1℃ / h~20℃ / h to obtain the single crystal state of the compound.

[0008] Preferably, the process includes soaking the product obtained in step (2) in water, washing it, and then drying it.

[0009] Preferably, the alkali metal fluoride is potassium fluoride, rubidium fluoride, or cesium fluoride.

[0010] According to another aspect of the invention, the application of said compound as a low-dimensional quantum magnetic material is provided.

[0011] According to another aspect of the invention, the compound is provided for use as a nonlinear optical material.

[0012] According to another aspect of the invention, the application of said compound as a ferroelectric material is provided.

[0013] According to another aspect of the invention, the application of said compound as a piezoelectric material is provided.

[0014] In summary, compared with the prior art, the above-described technical solutions conceived by this invention mainly possess the following technical advantages: (1) This invention combines the rare earth magnetic ion Pr with the BO3 motif having a planar triangular structure. The chemical formula of the compound is K5Mg3Pr3(BO3)6. This compound belongs to the trigonal crystal system and has a space group of 6. P 31 c The unit cell parameters are a = b = 9.0140(2)Å, c = 13.0557(5) Å, α = β = 90°, γ = 120°. Its basic structure consists of along ab Two-dimensional [Mg2Pr3(BO3)3] extending infinitely in a plane. ∞ Layers are formed, and these layers are further connected along c The BO3 groups are axially oriented and connected, with K ions distributed in adjacent [Mg2Pr3(BO3)3]. ∞ To maintain charge balance between layers, the compounds in this invention simultaneously possess optical response and two-dimensional spin-frustrated quantum magnetism.

[0015] (2) The compound of the present invention can be used as a low-dimensional quantum magnetic material. In the compound, Pr ions are connected by single O ions on the BO3 group to form a two-dimensional triangular lattice. The magnetic susceptibility shows that the compound has strong magnetic anisotropy and the magnetic interaction is antiferromagnetic. The specific heat data shows that it does not reach long-range magnetic order even at a low temperature of 0.5K, indicating that the compound is a quasi-two-dimensional spin frustrated quantum magnetic material.

[0016] (3) The compound of the present invention can be used as a nonlinear optical material. The powder frequency doubling coefficient of the compound is about 1.6 times that of the commercial nonlinear optical crystal KDP. The ultraviolet diffuse reflectance spectrum shows that the ultraviolet absorption cutoff wavelength of the material is 255nm and the band gap is 4.87eV, indicating that the compound is a nonlinear optical material in the ultraviolet band.

[0017] (4) The compound of the present invention crystallizes in P 31 c (No. 159) The trigonal polar point group, with its non-centrosymmetric polar structure, results in linear stress-electric displacement coupling, giving it a piezoelectric response. Simultaneously, its structure possesses an inherent polar axis, enabling spontaneous polarization. The reversibility of this spontaneous polarization endows the compound with ferroelectric properties—under an applied electric field, atoms can undergo reversible displacement along the polar axis, achieving polarization reversal and exhibiting a typical hysteresis loop. Furthermore, the coupling between polarization and magnetic moment generates a magnetoelectric coupling effect. The synergistic effect of these three factors makes the compound of this invention potentially valuable for applications in piezoelectric sensing, ferroelectric storage, and magnetoelectric coupling. Attached Figure Description

[0018] Figure 1 These are crystal photographs of K5Mg3Pr3(BO3)6 of the present invention; wherein, (a) is a crystal image obtained in Example 4; (b) is a crystal image obtained in Example 5; (c) is a crystal image obtained in Example 6; and (d) is a crystal image obtained in Example 7.

[0019] Figure 2 This is a schematic diagram of the crystal structure of K5Mg3Pr3(BO3)6 of the present invention; wherein, (a) is a three-dimensional structural diagram of K5Mg3Pr3(BO3)6; (b) is a schematic diagram of Pr ions in... ab (c) Topological structure diagram of Pr ions.

[0020] Figure 3 These are X-ray diffraction comparison diagrams of the polycrystalline powder of K5Mg3Pr3(BO3)6 of the present invention; (a) is an X-ray diffraction comparison diagram of the powder obtained in Example 1; (b) is an X-ray diffraction comparison diagram of the powder obtained in Example 2; and (c) is an X-ray diffraction comparison diagram of the powder obtained in Example 3.

[0021] Figure 4 This is the UV-Vis diffuse reflectance spectrum of K5Mg3Pr3(BO3)6 of the present invention; wherein, the inset shows the direct band gap of K5Mg3Pr3(BO3)6.

[0022] Figure 5 These are the harmonics test results of K5Mg3Pr3(BO3)6 of the present invention; wherein, (a) the second harmonic signal diagram of K5Mg3Pr3(BO3)6 and standard sample KDP; (b) the phase matching diagram of K5Mg3Pr3(BO3)6 and standard sample KDP.

[0023] Figure 6 This is the magnetic data result of K5Mg3Pr3(BO3)6 of the present invention; wherein, (a) K5Mg3Pr3(BO3)6 powder and magnetic field along c direction or ab magnetic susceptibility of a plane χ - T Figure; (b) K5Mg3Pr3(BO3)6 powder and magnetic field along c direction or ab planar χ 1 - T Figure; (c) K5Mg3Pr3(BO3)6 powder and magnetic field along c direction or ab planar M - H picture.

[0024] Figure 7These are the specific heat data for K5Mg3Pr3(BO3)6 of the present invention; wherein, the inset shows the specific heat data at extremely low temperatures of 0.5-10K. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0026] This invention provides a compound with the chemical formula K5Mg3Pr3(BO3)6, which belongs to the trigonal crystal system and has a space group of P 31 c The unit cell parameters are a = b = 9.0140(2) Å, c = 13.0557(5) Å, α = β = 90°, γ = 120°. Its basic structure consists of along ab Two-dimensional [Mg2Pr3(BO3)3] extending infinitely in a plane. ∞ Layers are formed, and these layers are further connected along c The BO3 groups are axially oriented and connected, with K ions distributed in adjacent [Mg2Pr3(BO3)3]. ∞ To maintain charge balance between layers.

[0027] In the K5Mg3Pr3(BO3)6 compound of this invention, Pr ions are bridged by O ions on the BO3 groups to form a two-dimensional triangular lattice. Magnetic susceptibility shows that the compound has strong magnetic anisotropy, and antiferromagnetic interactions between magnetic ions are dominant. Specific heat data shows that long-range magnetic order is not achieved even at 0.5 K, indicating that the compound is a quasi-two-dimensional magnetoresistive material.

[0028] The powder overtone coefficient of the K5Mg3Pr3(BO3)6 compound of this invention is about 1.6 times that of the commercial nonlinear optical crystal KDP. The ultraviolet diffuse reflectance spectrum shows that the ultraviolet absorption cutoff wavelength of this material is 255 nm and the band gap is 4.87 eV, indicating that the compound is a nonlinear optical material in the ultraviolet band.

[0029] This invention also provides a method for preparing the K5Mg3Pr3(BO3)6 compound, which involves synthesizing K5Mg3Pr3(BO3)6 powder samples using a high-temperature solid-state method and growing K5Mg3Pr3(BO3)6 single-crystal samples using the Flux method. The specific steps are as follows: (1) Synthesis of powder samples Step 1: First, mix potassium carbonate, magnesium oxide, boric acid and praseodymium oxide in a molar ratio of 1.25:1:(2.5~3):(0.1~0.75) and grind them evenly.

[0030] Step 2: Grind and press the product from Step 1 into tablets again, place them in an alumina crucible, and sinter them in a muffle furnace at 600~830℃ for 72 hours.

[0031] Step 3: Grind the product obtained in Step 2 into powder, soak it in hot water for 3-5 hours to wash away the impurities generated in the reaction, and filter it to obtain a pure phase powder sample.

[0032] Furthermore, praseodymium borate magnetic impurities are prone to appear during the synthesis process. Therefore, the proportion of praseodymium oxide should be reduced as much as possible to avoid interference from praseodymium borate magnetic impurities in magnetic testing.

[0033] (2) Single crystal samples grown by the Flux method Step 1: First, mix potassium carbonate, magnesium oxide, boric acid, praseodymium oxide and alkali metal fluoride in a molar ratio of 4:2:(8~10):(0.3~0.6):5 and grind them evenly.

[0034] Step 2: Place the powder ground in Step 1 into an alumina crucible and sinter at 700~800℃ for 72h, then slowly cool it down to 25℃ at a rate of 1℃ / h~20℃ / h.

[0035] Step 3: Soak the product from Step 2 in hot water for 3-5 hours, and then ultrasonically clean it to obtain a green crystal sample.

[0036] Furthermore, the alkali metal mentioned in step one is selected from potassium fluoride, rubidium fluoride, or cesium fluoride.

[0037] Furthermore, in step one, boric acid serves both as a reactant and as a flux together with alkali metal fluorides.

[0038] The following are specific examples.

[0039] Example 1: Preparation of K5Mg3Pr3(BO3)6 powder sample K5Mg3Pr3(BO3)6 powder samples were synthesized using a high-temperature solid-state method. The specific operation steps are as follows: (1) First, mix potassium carbonate, magnesium oxide, boric acid and praseodymium oxide in a molar ratio of 1.25:1:3:0.25 and grind them evenly. Then, press the mixture into tablets and place them in an alumina crucible. (2) Place the crucible in a muffle furnace and heat it to 350°C for 10 hours; (3) Grind the product obtained in step (2) again, compress it into tablets, and place it in an alumina crucible; (4) Place the crucible back into the muffle furnace and sinter at 600°C for 72 hours; (5) Grind the obtained product into powder, soak it in hot water for 3 hours to wash away the impurities generated in the reaction, and filter it to obtain a pure phase powder sample.

[0040] Example 2: Preparation of K5Mg3Pr3(BO3)6 powder sample K5Mg3Pr3(BO3)6 powder samples were synthesized using a high-temperature solid-state method. The specific operation steps are as follows: (1) First, mix potassium carbonate, magnesium oxide, boric acid and praseodymium oxide in a molar ratio of 1.25:1:3:0.75 and grind them evenly. Then, press the mixture into tablets and place them in an alumina crucible. (2) Place the crucible in a muffle furnace and heat it to 350°C for 10 hours; (3) Grind the product obtained in step (2) again, compress it into tablets, and place it in an alumina crucible; (4) Place the crucible back into the muffle furnace and sinter at 830°C for 48 hours; (5) Grind the obtained product into powder, soak it in hot water for 3 hours to wash away the impurities generated in the reaction, and filter it to obtain a pure phase powder sample.

[0041] Example 3: Preparation of K5Mg3Pr3(BO3)6 powder sample K5Mg3Pr3(BO3)6 powder samples were synthesized using a high-temperature solid-state method. The specific operation steps are as follows: (1) First, mix potassium carbonate, magnesium oxide, boric acid and praseodymium oxide in a molar ratio of 1.25:1:2.5:0.1 and grind them evenly. Then, press the mixture into tablets and place them in an alumina crucible. (2) Place the crucible in a muffle furnace and heat it to 350°C for 10 hours; (3) Grind the product obtained in step (2) again, compress it into tablets, and place it in an alumina crucible; (4) Place the crucible back into the muffle furnace and sinter at 780°C for 72 hours; (5) Grind the obtained product into powder, soak it in hot water for 3 hours to wash away the impurities generated in the reaction, and filter it to obtain a pure phase powder sample.

[0042] Example 4: Preparation of K5Mg3Pr3(BO3)6 single crystal sample K5Mg3Pr3(BO3)6 single crystal samples were synthesized using the Flux method. The specific operation steps are as follows: (1) First, mix potassium carbonate, magnesium oxide, boric acid, praseodymium oxide and potassium fluoride in a molar ratio of 4:2:10:0.6:5 ​​and grind them evenly, wherein boric acid and potassium fluoride are used as co-fluxes; (2) The uniformly ground powder sample is placed into an alumina crucible and sintered at 800℃ for 72h, then reduced to 700℃ at 1℃ / h, then reduced to 400℃ at 3℃ / h, and then reduced to room temperature at 20℃ / h. (3) After sintering, the product is soaked in hot water for 3 hours, and after washing, a green blocky crystal sample that has agglomerated together is obtained, which is the target product, such as Figure 1 As shown in (a) of the diagram.

[0043] Example 5: Preparation of K5Mg3Pr3(BO3)6 single crystal sample K5Mg3Pr3(BO3)6 single crystal samples were synthesized using the Flux method. The specific operation steps are as follows: (1) First, mix potassium carbonate, magnesium oxide, boric acid, praseodymium oxide and rubidium fluoride in a molar ratio of 4:2:8:0.3:5 and grind them evenly, wherein boric acid and rubidium fluoride are used as co-fluxes; (2) The uniformly ground powder sample is placed into an alumina crucible and sintered at 700℃ for 48h. Then, the temperature is lowered to 600℃ at 1℃ / h, then to 400℃ at 3℃ / h, and finally to room temperature at 20℃ / h. A large number of hexagonal prism-shaped green crystals grow in the crucible, which is the target product. Figure 1 As shown in (b) of the diagram.

[0044] Example 6: Preparation of K5Mg3Pr3(BO3)6 single crystal sample K5Mg3Pr3(BO3)6 single crystal samples were synthesized using the Flux method. The specific operation steps are as follows: (1) First, mix potassium carbonate, magnesium oxide, boric acid, praseodymium oxide and cesium fluoride in a molar ratio of 4:2:8:0.3:5 and grind them evenly, wherein boric acid and cesium fluoride are used as co-fluxes; (2) The uniformly ground powder sample is placed into an alumina crucible and sintered at 700℃ for 48h. Then, the temperature is lowered to 600℃ at 1℃ / h, then to 400℃ at 3℃ / h, and finally to room temperature at 20℃ / h. A large number of hexagonal prism-shaped green crystals grow in the crucible, which is the target product. Figure 1 As shown in (c) in the figure.

[0045] Example 7: Preparation of K5Mg3Pr3(BO3)6 single crystal sample K5Mg3Pr3(BO3)6 single crystal samples were synthesized using the Flux method. The specific operation steps are as follows: (1) First, mix potassium carbonate, magnesium oxide, boric acid, praseodymium oxide and potassium fluoride in a molar ratio of 4:2:8:0.3:5 and grind them evenly, wherein boric acid and potassium fluoride are used as co-fluxes; (2) The uniformly ground powder sample is placed into an alumina crucible and sintered at 700℃ for 48h, then reduced to 600℃ at 1℃ / h, then reduced to 400℃ at 3℃ / h, and then reduced to room temperature at 20℃ / h. (3) After sintering, the product is soaked in hot water for 3 hours and ultrasonically cleaned to obtain hexagonal prism-shaped green crystals with relatively complete morphology and large size, which is the target product. The largest crystal size reaches 1 mm. Figure 1 As shown in (d) in the figure.

[0046] Structural analysis of K5Mg3Pr3(BO3)6 sample The crystal structure was analyzed using single-crystal X-ray diffraction, and the purity of the powder samples was determined using powder X-ray diffraction. Single-crystal X-ray diffraction experiments were conducted at 180 K using an XtaLAB PRO 007HF diffractometer equipped with a Mo target Kα beam (λ = 0.71073 Å), and data were acquired using CrysAlisPro and refined using the SHELXL crystallography program with full-matrix least squares method. Powder X-ray diffraction (XRD) data were obtained using a Rigaku SmartLab SE powder X-ray diffractometer with a Cu target Kα beam (λ = 0.71073 Å). λ Collected at 1.54184 Å, with a measurement range of 2. θ = 10°~120°.

[0047] Single-crystal X-ray diffraction results showed that the K5Mg3Pr3(BO3)6 crystal obtained in Example 4 belongs to the trigonal crystal system with space group 6. P 31 c The unit cell parameters are a = b = 9.0140(2) Å, c = 13.0557(5) Å, α = β = 90°, γ = 120°. Structural analysis reveals that its basic structure consists of along... ab Two-dimensional [Mg2Pr3(BO3)3] extending infinitely in a plane. ∞ Layers are formed, and these layers are further connected along c The BO3 groups are axially oriented and connected, with K ions distributed in adjacent [Mg2Pr3(BO3)3]. ∞ To maintain charge balance between layers, such as Figure 2As shown in (a) above. In this case, Pr ions are bridged by O ions on the BO3 groups to form a two-dimensional triangular lattice, as shown in (a). Figure 2 As shown in (b), the triangular lattice layer formed by Pr ions along... c Axial arrangement as follows Figure 2 As shown in (c) in the figure.

[0048] Powder X-ray diffraction results showed that the main phase of the powder sample obtained in Example 1 was a mixture of Pr(BO3), PrO2 and K5Mg3Pr3(BO3)6, such as Figure 3 As shown in (a); the powder sample obtained in Example 2 was a mixture of K3Pr3(BO3)4 and K5Mg3Pr3(BO3)6. Figure 3 As shown in (b) of the diagram; the diffraction pattern of the powder sample obtained in Example 3 is consistent with the simulated pattern obtained by analyzing the structure of K5Mg3Pr3(BO3)6 single crystal in Example 2, indicating that the powder sample is a pure phase, as shown in (b). Figure 3 As shown in (c) in the figure.

[0049] Ultraviolet diffuse reflectance spectroscopy test The ultraviolet diffuse reflectance spectra in the range of 200–2400 nm were collected using the powder sample from Example 3 on a Shimadzu UV-3600 spectrophotometer. Due to Pr 3+ 4 f 2 Electron from ground state 3 The H4 transition to the excited state leads to characteristic absorption peaks in the visible region of the ultraviolet spectrum at 445–483 nm and 590 nm, which is the main reason for the green color of the crystals. Simultaneously, three absorption peaks also appear in the near-infrared region at 1402 nm, 1524 nm, and 1915 nm, as shown in the results. Figure 4 As shown. The compound has a UV absorption cutoff edge of 255 nm and a direct band gap of 4.87 eV, as... Figure 4 As shown in the illustration.

[0050] Frequency multiplier test The powder sample from Example 3 and the standard KDP were ground and sieved to obtain different particle sizes, ranging from 25 to 45 μm, 45 to 62 μm, 62 to 75 μm, 75 to 109 μm, 109 to 150 μm, and 150 to 212 μm. The second harmonic signals of the powder sample from Example 1 and the standard KDP were collected using a test method based on the Kurtz-Perry powder harmonic effect. By observing the dependence of the harmonic signal on the sample particle size, it was determined that the sample could achieve phase matching, such as... Figure 5As shown in (a) above. Furthermore, by comparing the second harmonic intensity with that of the standard KDP, the intensity of the sample's harmonic signal is found to be 1.6 times that of KDP, as shown below. Figure 5 As shown in (b) of the diagram.

[0051] Magnetic test Powder magnetism was tested on the powder sample of Example 3 using a superconducting quantum interference device (SQUID), and magnetic anisotropy was tested on the crystal sample of Example 7. The dependence of magnetic susceptibility on temperature was investigated in the temperature range of 2–300 K under an applied magnetic field of 0.1 T. χ - T Tests were conducted, with ZFC being zero-field cooling and FC being field-cooled. At 2K temperature, Dependence of magnetization on field in the 7 ~ 7T magnetic field range M - H Tests were conducted. The results showed that, down to 2K, no significant long-range magnetic order was observed, and the applied magnetic field... H Parallel to crystal c The magnetic susceptibility of the axis is approximately parallel to that of the crystal. ab Six times the size of the plane indicates c The axis is the easy magnetization direction, and the powder data is the average result of the two, falling between the two, such as Figure 6 As shown in (a) of the diagram. Through the analysis of... χ The reciprocal of the equation and its dependence on temperature χ 1 - T By performing Curie-Weiss fitting, the Weiss constants of the powder and crystal along different directions were obtained. θ and effective magnetic moment μ eff ,like Figure 6 As shown in (b) of the figure, the black solid line represents the Curiewes fitting result. Table 1 shows the results of powder and crystal fitting at high and low temperatures. θ Value and μ eff , at low temperature θ The values ​​are all negative, indicating that the antiferromagnetic interaction between the magnetic ions in the compound is dominant. (Observation) M - H Data reveals external magnetic field H Parallel to crystal c The magnetization of the axis is much greater than that of the axis parallel to the crystal. ab plane, and χ - T The results are consistent, indicating that the compound K5Mg3Pr3(BO3)6 has strong magnetic anisotropy, such as... Figure 6 As shown in (c) in the figure.

[0052] Table 1. Magnetic data of compound K5Mg3Pr3(BO3)6

[0053] Specific heat test The powder sample from Example 7 was ground and pressed into sheets for testing. Specific heat was measured using a physical property measurement system (PPMS) within the temperature range of 0.5–50 K. Data were obtained between 0.5 and 10 K using helium-3 cooling. The specific heat data showed no significant phase transition within the 0.5–50 K range. Figure 7 As shown, the inset shows the specific heat data at extremely low temperatures of 0.5 ~ 10 K. This indicates that the compound does not exhibit long-range magnetic order down to 0.5 K.

[0054] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A compound with the chemical formula K5Mg3Pr3(BO3)6, characterized in that, This compound has a trigonal crystal system and a space group of . P 31c, cell parameters are a = b = 9.0140(2) Å, c = 13.0557(5) Å, α = β = 90°, γ = 120°.

2. The method for preparing the compound according to claim 1, characterized in that, Includes the following steps: (1) Mix potassium carbonate, magnesium oxide, boric acid and praseodymium oxide in a molar ratio of 1.25:1:(2.5~3):(0.1~0.75); (2) The mixture obtained in step (1) is sintered at 600~830℃ for 48~72 h to obtain the compound.

3. The method for preparing the compound according to claim 2, characterized in that, It also includes grinding the product obtained in step (2) into powder, soaking it in water, and then filtering and drying it.

4. The method for preparing the compound according to claim 1, characterized in that, Includes the following steps: (1) Mix potassium carbonate, magnesium oxide, boric acid, praseodymium oxide and alkali metal fluoride in a molar ratio of 4:2:(8~10):(0.3~0.6):5; (2) The mixture obtained in step (1) is sintered at 700~800℃ for 48~72 h, and then cooled at a rate of 1℃ / h~20℃ / h to obtain the single crystal state of the compound.

5. The method for preparing the compound according to claim 4, characterized in that, This includes soaking the product obtained in step (2) in water, washing it, and then drying it.

6. The method for preparing the compound according to claim 4 or 5, characterized in that, The alkali metal fluoride is potassium fluoride, rubidium fluoride, or cesium fluoride.

7. The application of the compound as described in claim 1 as a low-dimensional quantum magnetic material.

8. The application of the compound as a nonlinear optical material as claimed in claim 1.

9. The application of the compound as described in claim 1 as a ferroelectric material.

10. The application of the compound as a piezoelectric material as claimed in claim 1.

Images