A large-size nickel silicate single crystal and preparation method thereof

Abstract

The present invention belongs to the technical field of single crystal growth, and specifically relates to a large-sized nickel silicate single crystal and a preparation method thereof. The preparation method comprises: uniformly mixing NiO and K2MoO4, then adding quartz powder, and then placing the mixture in a quartz tube for vacuum sealing, and then preparing the single crystal by a flux method. The Ni2SiO4 single crystal obtained by the present invention is in the form of a long strip, olive green, excellent in color, large in size, high in purity, and low in preparation temperature. It can be completed by using a quartz tube, has a simple process, and is low in cost.

Description

Technical Field

[0001] The invention belongs to the technical field of single crystal growth, and in particular relates to a large-size nickel silicate single crystal and a preparation method thereof. Background Art

[0002] At low temperatures, the quantum effect of low-dimensional magnetic materials is enhanced, and the competition between quantum fluctuations and thermal fluctuations will present a variety of quantum phenomena, such as spin disorder and spin liquid. Studying the physics behind these strange phenomena is of great significance for the research and development of next-generation spin devices and electronic components, and is one of the frontier hotspots in the current research fields of materials science and condensed matter physics.

[0003] Ni2SiO4 has a magnetic Ni bond due to its anion bridge 2+ The ions form a low-dimensional chain structure, which can be used to study the unknown physics of low-dimensional magnetic systems. 2+ The special ion occupancy makes it present a unique olive green color. It can not only stably color and match colors in different environments, but also has good high-temperature stability, and has great potential applications in high-temperature fields. In addition, Ni2SiO4 can undergo conversion reactions during the lithiation and delithiation process, has good cycle stability, excellent charge and discharge rate, and greater capacity, and is a promising lithium-ion battery anode material. At the same time, the material has a high density (up to 4.91g / cm 3 ) enables it to maintain a higher volumetric capacity, storing more charge in the same volume compared to graphite.

[0004] At present, the preparation of Ni2SiO4 is mainly concentrated in the field of powder and microcrystals. For example, Hadri et al. (Journal of European Ceramic Society 39 (2019) 5442-5456) disclosed the sol-gel synthesis of Ni2SiO4 and its comparative study on the color properties of related nickel-doped forsterite green pigments, and Shuzhen Yang et al. (Journal of Alloys and Compounds 785 (2019) 80-88) disclosed the preparation and characterization of high-performance lithium-ion battery positive electrode materials nickel orthosilicate nanosheets. The microcrystals synthesized in the above literature are relatively small, mostly at the micron scale, and their application in industrial fields such as single crystal neutron scattering, single crystal magnetization measurement physical property research, specific heat research, and large-size silicon wafers is limited. In addition, Miyuko Ozima (Journal of Crystal Growth 33 (1976) 193-195) synthesized nickel olivine single crystals by the flux method and obtained millimeter-sized single crystals, but the single crystals contained impurities that were difficult to remove and the single crystal quality was poor. In addition, the reaction temperature in this document was high and a platinum crucible was required, which resulted in high production costs. Summary of the invention

[0005] In view of the shortcomings of the existing methods, the present invention provides a nickel silicate single crystal and a preparation method thereof. The obtained nickel silicate single crystal has large size, high purity, low preparation cost and simple operation.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] A method for preparing a large-size nickel silicate single crystal comprises the following steps:

[0008] NiO and K2MoO4 are mixed evenly, and then quartz powder is added. Subsequently, the mixture is placed in a quartz tube and vacuum-sealed, and a single crystal is prepared by a flux method.

[0009] Preferably, the reaction conditions of the flux method are: keeping at 1000°C-1300°C for 15-24 hours, then slowly cooling to 600°C-800°C at a rate of 0.5°C-3°C / hour, and then naturally cooling to room temperature.

[0010] Preferably, the molar ratio of NiO to K2MoO4 is 1:2-6.

[0011] Preferably, the molar ratio of NiO to quartz powder is 1:0.4-0.8.

[0012] Preferably, the vacuum degree of the quartz tube after sealing is ≥-0.1 MPa.

[0013] Preferably, the wall thickness of the quartz tube is 1.5 mm-4 mm.

[0014] A large-sized nickel silicate single crystal prepared by the above preparation method.

[0015] The positive beneficial effects of the present invention are:

[0016] 1. In the present invention, NiO and K2MoO4 are mixed as precursors, and K2MoO4 is used as a flux. + Ion ratio Li + The ion size is large and impurities are not easily formed. The obtained Ni2SiO4 single crystal has high purity. The quartz tube is used as both a reaction container and a reaction raw material. It can be sealed to prevent the solvent from volatilizing at high temperature, and can participate in the reaction to make the single crystal grow faster. The Ni2SiO4 single crystal obtained by the present invention is a long strip plate, olive green, excellent in color, large in size, and can be used in more experiments and device scenarios. It is inert to air and alcohol, soluble in acid, high in purity, excellent in quality, and can be used as an optical element. It also has low-dimensional magnetism and has good application value prospects in the field of quantum magnetism. In addition, the high-purity single crystal of the present invention can be ground into microcrystals of different sizes for high-temperature coloring and lithium battery anode materials, with a wide range of applications.

[0017] 2. When the reaction temperature of the flux method of the present invention is reduced, a small amount of single crystals will be produced or almost no crystals will be obtained. When the reaction temperature is too high, the reactants will seriously corrode the quartz tube, and even cause leakage and pollution of the furnace, and the single crystal yield and quality are low. The preparation method of Ni2SiO4 single crystal of the present invention has a suitable temperature, which is lower than the temperature of the prior art. It can be completed using a quartz tube, and the process is simple and the cost is low. When the amount of K2MoO4 used in the present invention is reduced, the size of the single crystal obtained is small. When the amount of K2MoO4 used in the present invention is increased, the corrosion of the quartz tube is serious. The amount of each raw material used in the present invention is appropriate. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the morphology structure of the Ni2SiO4 single crystal according to Example 1 of the present invention;

[0019] Figure 2 Schematic diagram of the unit cell structure of the Ni2SiO4 single crystal of Example 1 of the present invention;

[0020] Figure 3 The X-ray energy spectrum (EDS) of the Ni2SiO4 single crystal of Example 1 of the present invention;

[0021] Figure 4 The X-ray diffraction pattern of the powder of the Ni2SiO4 single crystal after grinding in Example 1 of the present invention;

[0022] Figure 5 is the X-ray diffraction pattern of the ab plane of the Ni2SiO4 single crystal of Example 1 of the present invention;

[0023] Figure 6 The magnetic susceptibility curve of the Ni2SiO4 single crystal in Example 1 of the present invention in the temperature range of 300K-2K and the magnetic field along the a, b and c axes;

[0024] Figure 7 The specific heat curve of the Ni2SiO4 single crystal of Example 1 of the present invention at a temperature of 70K-2K under zero field;

[0025] Figure 8 is a magnetization curve of the Ni2SiO4 single crystal in the a-axis direction of Example 1 of the present invention when the temperature is 1.7K;

[0026] Fig. 9 This is a schematic diagram of the morphology structure of the Ni2SiO4 single crystal according to Example 2 of the present invention;

[0027] Fig.10 This is a schematic diagram of the morphology structure of a Ni2SiO4 single crystal according to Example 3 of the present invention;

[0028] Fig.11This is a schematic diagram of the morphology structure of the Ni2SiO4 single crystal according to Example 4 of the present invention;

[0029] Fig.12 This is a schematic diagram of the morphology and structure of a Ni2SiO4 single crystal according to Example 5 of the present invention;

[0030] Fig.13 This is a schematic diagram of the Ni2SiO4 single crystal morphology structure of Example 6 of the present invention. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with some specific embodiments.

[0032] Example 1

[0033] A method for preparing a large-size nickel silicate single crystal comprises the following steps:

[0034] NiO and K2MoO4 were mixed evenly, the molar ratio of NiO to K2MoO4 was 1:6, and then quartz powder was added, the molar ratio of NiO to quartz powder was 1:0.5, and then the mixture was placed in a quartz tube and vacuum sealed, the vacuum degree was -0.1MPa, the wall thickness of the quartz tube was 1.5mm, and then placed in a muffle furnace at 1000℃ for 15 hours, and then slowly cooled to 700℃ at a rate of 1℃ / hour, and then naturally cooled to room temperature to obtain the single crystal test results. Figure 1-8 .

[0035] Figure 1 This is a schematic diagram of the morphology and structure of the Ni2SiO4 single crystal in this embodiment. Each grid represents 1mm. It is a long strip plate, olive green, with excellent color, and has a size of 6*1*0.2mm, which is large.

[0036] Figure 2 The schematic diagram of the unit cell structure of the Ni2SiO4 single crystal in this embodiment is shown in FIG. 2+ The ions form a quasi-one-dimensional magnetic chain structure, which can be used as a candidate model for studying low-dimensional magnetism.

[0037] Figure 3 The X-ray energy spectrum (EDS) of the single crystal of this example shows that the atomic ratio of Ni, Si and O is close to 2:1:4, indicating that the obtained single crystal is high-purity Ni2SiO4.

[0038] Figure 4 This is the powder X-ray diffraction pattern of the single crystal of this example after grinding. The measurement results correspond well with the standard peak position of Ni2SiO4, indicating that the single crystal is pure phase Ni2SiO4.

[0039] Figure 5This is the X-ray diffraction spectrum of the ab plane of the Ni2SiO4 single crystal in this embodiment. It can be seen from the figure that the diffraction peak perpendicular to the ab plane of the single crystal is

[002] , which proves that it is the c-axis.

[0040] Figure 6 This is the magnetic susceptibility curve of the Ni2SiO4 single crystal in the temperature range of 300K-2K, and the magnetic field along the a, b and c axes. Figure 6 It can be seen that the magnetic susceptibility in the three directions of a, b and c axes increases with decreasing temperature, and an obvious antiferromagnetic peak appears near 29.5K, indicating that the material enters the antiferromagnetic state. As the temperature further decreases to 2K, the magnetic susceptibility of H / a is the lowest, showing the magnetic easy axis characteristics, and the magnetic susceptibility of H / / b is the highest, showing the hard axis characteristics. The different magnetic susceptibilities in the three directions indicate that the material has magnetic anisotropy and has different physical and chemical properties along different crystal axes, which improves its application value.

[0041] Figure 7 The specific heat curve of the Ni2SiO4 single crystal in this embodiment under zero field at a temperature of 70K-2K is shown in FIG. Figure 7 It can be seen that the specific heat curve shows a specific heat peak near 30K, indicating that the material undergoes an antiferromagnetic phase transition at 30K, proving that the material is an antiferromagnet at low temperatures.

[0042] Figure 8 This is the magnetization curve of the Ni2SiO4 single crystal in the a-axis direction of this embodiment when the temperature is 1.7K. The measurement results show that the single crystal undergoes three magnetic phase transitions at magnetic fields of 15T, 18T and 32.5T, indicating that the material has rich anomalous magnetic effects.

[0043] Example 2

[0044] A method for preparing a large-size nickel silicate single crystal comprises the following steps:

[0045] NiO and K2MoO4 are mixed evenly, the molar ratio of NiO to K2MoO4 is 1:3, and then quartz powder is added, the molar ratio of NiO to quartz powder is 1:0.5, and then the mixture is placed in a quartz tube and vacuum-sealed, the vacuum degree is -0.08MPa, the wall thickness of the quartz tube is 1.5mm, and then placed in a muffle furnace at 1000℃ for 15 hours, and then slowly cooled to 700℃ at a rate of 1℃ / hour, and then naturally cooled to room temperature, that is, see Fig. 9 .

[0046] Fig. 9 This is a schematic diagram of the morphology and structure of the Ni2SiO4 single crystal in this embodiment. Each grid represents 1mm. It is a long strip-shaped plate, olive green in color, with excellent color, and a size of 3*1*0.2mm, which is large.

[0047] Example 3

[0048] A method for preparing a large-size nickel silicate single crystal comprises the following steps:

[0049] NiO and K2MoO4 are mixed evenly, wherein the molar ratio of NiO to K2MoO4 is 1:5, and then quartz powder is added, wherein the molar ratio of NiO to quartz powder is 1:0.5, and then the mixture is placed in a quartz tube and vacuum-sealed, the vacuum degree is -0.1MPa, and the wall thickness of the quartz tube is 1.5mm, and then placed in a muffle furnace at 1000℃ for 15 hours, and then slowly cooled to 700℃ at a rate of 1℃ / hour, and then naturally cooled to room temperature, that is, see Fig.10 .

[0050] Fig.10 This is a schematic diagram of the morphology and structure of the Ni2SiO4 single crystal in this embodiment. Each grid represents 1mm. It is a long strip-shaped plate, olive green in color, with excellent color, and a size of 4*1.3*0.2mm, which is large.

[0051] Example 4

[0052] A method for preparing a large-size nickel silicate single crystal comprises the following steps:

[0053] NiO and K2MoO4 are mixed evenly, wherein the molar ratio of NiO to K2MoO4 is 1:4, and then quartz powder is added, wherein the molar ratio of NiO to quartz powder is 1:0.5, and then the mixture is placed in a quartz tube and vacuum-sealed, the vacuum degree is -0.05MPa, and the wall thickness of the quartz tube is 1.5mm, and then placed in a muffle furnace at 1000℃ for 15 hours, and then slowly cooled to 700℃ at a rate of 1℃ / hour, and then naturally cooled to room temperature, that is, see Fig.11 .

[0054] Fig.11 This is a schematic diagram of the morphology and structure of the Ni2SiO4 single crystal in this embodiment. Each grid represents 1mm. It is a long strip-shaped plate, olive green in color, with excellent color, and a size of 3.5*0.8*0.2mm, which is large.

[0055] Example 5

[0056] A method for preparing a large-size nickel silicate single crystal comprises the following steps:

[0057] NiO and K2MoO4 are mixed evenly, the molar ratio of NiO to K2MoO4 is 1:2, and then quartz powder is added, the molar ratio of NiO to quartz powder is 1:0.8, and then the mixture is placed in a quartz tube and vacuum-sealed, the vacuum degree is -0.08MPa, the wall thickness of the quartz tube is 1.5mm, and then placed in a muffle furnace at 1300℃ for 15 hours, and then slowly cooled to 600℃ at a rate of 2℃ / hour, and then naturally cooled to room temperature, that is, see Fig.12 .

[0058] Fig.12 This is a schematic diagram of the morphology and structure of the Ni2SiO4 single crystal in this embodiment. Each grid represents 1mm. It is a long strip-shaped plate, olive green in color, with excellent color, and a size of 1.6*1*0.2mm, which is large.

[0059] Example 6

[0060] A method for preparing a large-size nickel silicate single crystal comprises the following steps:

[0061] NiO and K2MoO4 are mixed evenly, the molar ratio of NiO to K2MoO4 is 1:6, and then quartz powder is added, the molar ratio of NiO to quartz powder is 1:0.4, and then the mixture is placed in a quartz tube and vacuum-sealed, the vacuum degree is -0.08MPa, the wall thickness of the quartz tube is 2mm, and the quartz tube wall is too thick to be easily sealed, and then placed in a muffle furnace at 1200℃ for 24 hours, and then slowly cooled to 800℃ at a rate of 0.5℃ / hour, and then naturally cooled to room temperature, that is, see Fig.13 .

[0062] Fig.13 This is a schematic diagram of the morphology and structure of the Ni2SiO4 single crystal in this embodiment. Each grid represents 1 mm. It is a long strip-shaped plate, olive green in color, with excellent color, and a size of 4.2*1*0.2, which is large.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in the field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing large-size nickel silicate single crystals, characterized in that: The steps include: NiO and K2MoO4 are mixed evenly, and then quartz powder is added, and then the mixture is placed in a quartz tube and sealed in vacuum, and a single crystal is prepared by a flux method; The reaction conditions of the flux method are: keeping at 1000°C-1300°C for 15-24 hours, then slowly cooling to 600°C-800°C at a rate of 0.5°C-3°C / hour, and then naturally cooling to room temperature; The molar ratio of NiO to K2MoO4 is 1:2-6; The molar ratio of NiO to quartz powder is 1:0.4-0.

8.

2. The method for preparing large-size nickel silicate single crystal according to claim 1, characterized in that: The vacuum degree of the quartz tube after sealing is ≥-0.1MPa.

3. The method for preparing large-size nickel silicate single crystal according to claim 1, characterized in that: The wall thickness of the quartz tube is 1.5 mm to 4 mm.

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