A method for producing magnesium niobate

Abstract

The application provides a preparation method of magnesium niobate, comprising the following steps: uniformly mixing MgO and Nb2O5 by wet ball milling, drying to obtain mixed powder; performing water quenching after the mixed powder is heated to 1500-1700 DEG C for 1-3 h to obtain solid particles with core-shell structure inclusions; heating the solid particles to 1000-1200 DEG C, and keeping the temperature to obtain the magnesium niobate. The solid particles with core-shell structure inclusions are formed by the water quenching process, and then the MN obtained by rapid heating sintering has high purity and high stability, the Mg 2+ 、Nb 5+ Two components are high in uniformity and large in reactivity, which is beneficial to the full mixing with PbO and TiO2 to form a liquid phase at high temperature, the single nature and uniformity of the PMNT crystal growth raw material formed are better, and then the single perovskite structure, high purity and excellent piezoelectric performance of the PMNT single crystal are helpful to obtain, and the yield is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of piezoelectric materials, in particular to a preparation method of magnesium niobate. BACKGROUND

[0002] Lead magnesium niobate-lead titanate (PMNT) is a typical perovskite ferroelectric material, which has excellent piezoelectric properties. Its piezoelectric constant d 33 is 4-5 times that of PZT ceramic, so it has a wide application prospect in the fields of medical ultrasonic imaging, sonar, underwater acoustic transducer, etc. However, in order to obtain high-quality PMNT single crystals, high-purity crystal growth raw materials are required.

[0003] Currently, the PMNT raw material is mainly synthesized by a two-step method: first, magnesium niobate (MN) precursor is synthesized by solid-phase reaction of niobium pentoxide (Nb2O5) and magnesium oxide (MgO); then, titanium oxide (TiO2) and lead oxide (PbO) are reacted to obtain PMNT growth raw materials. However, in the preparation process of MN precursor, there is a problem of incomplete reaction of MgO and Nb2O5, which makes free niobium easily appear in MN, thereby causing residual Nb2O5 and PbO to react to generate Pb2Nb2O7 second phase (pyrochlore phase). The coexistence of pyrochlore phase and main crystal perovskite phase will seriously reduce the piezoelectric properties of PMNT single crystals and hinder the full use of material performance. Therefore, finding a method to synthesize high-purity magnesium niobate is the key to improving the purity of crystal growth raw materials. SUMMARY

[0004] The purpose of the present application is to provide a preparation method of magnesium niobate, which can improve the purity and stability of the prepared magnesium niobate. The specific technical solutions are as follows:

[0005] The first aspect of the present application provides a preparation method of magnesium niobate, comprising the following steps:

[0006] (1) uniformly mixing MgO and Nb2O5 by wet ball milling, drying to obtain mixed powder;

[0007] (2) heating the mixed powder to 1500-1700℃ for 1-3h and then water quenching to obtain solid particles of core-shell structure inclusions;

[0008] (3) heating the solid particles to 1000-1200℃ and keeping the temperature to obtain the magnesium niobate.

[0009] In some embodiments of the present application, the molar ratio of MgO to Nb2O5 is 1:1.

[0010] In some embodiments of the present application, the Dv50 particle size of MgO is 50-100nm.

[0011] In some embodiments of the present application, the Dv50 particle size of the Nb2O5 is 2-15 μm.

[0012] In some embodiments of the present application, the mass ratio of the grinding ball, the material, and the ball milling medium used in the wet ball milling is 1:(0.9-1.1):(1.2-1.8).

[0013] In some embodiments of the present application, the material of the ball milling tank used in the wet ball milling is polyurethane.

[0014] In some embodiments of the present application, the ball milling medium used in the wet ball milling is anhydrous ethanol.

[0015] In some embodiments of the present application, the grinding ball used in the wet ball milling is an alumina ball.

[0016] In some embodiments of the present application, the rotation speed of the wet ball milling is 100-200 r / min, and the time of the wet ball milling is 20-30 h.

[0017] In some embodiments of the present application, the heating rate for heating to 1000-1200℃ is 5-10℃ / min.

[0018] In some embodiments of the present application, the time of the heat preservation is 25-35 min.

[0019] In some embodiments of the present application, the Dv50 particle size of the solid particles is 0.5-2 mm.

[0020] In some embodiments of the present application, the temperature of the drying is 90-110℃.

[0021] The second aspect of the present application provides a preparation method of a raw material for growing lead magnesium niobate-lead titanate (PMNT), comprising the preparation method of the magnesium niobate described in the first aspect of the present application.

[0022] The beneficial effects of the present application are:

[0023] The wet ball milling is used in the present application, which can make the obtained slurry more uniform; the core-shell structure of the cladding body is formed through the water quenching process, i.e., the Nb2O5 uniformly wraps the outside of the MgO, so that the contact area of the two is larger and the binding force is stronger; in the subsequent rapid heating and sintering process, the solid phase reaction between the core and the shell of the solid particles can be more complete, and the obtained magnesium niobate (MgNb2O6, MN) has high purity and high stability, and the Mg 2+ , Nb 5+The two components are high in uniformity and reactivity, and are beneficial to the full mixing with PbO and TiO2 to form a liquid phase at high temperature, and the uniformity of the lead magnesium niobate-lead titanate (PMNT) crystal growth raw material is better, which is conducive to obtaining a PMNT single crystal with a single perovskite structure, high purity, excellent piezoelectric performance, and high yield.

[0024] Of course, practicing any of the products or methods of the present application does not necessarily require achieving all of the above advantages simultaneously. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other embodiments can also be obtained by those skilled in the art based on these drawings.

[0026] Figure 1 Structure diagram of the solid particles of the core-shell structure encapsulated body prepared in the present application;

[0027] Figure 2 X-ray diffraction spectrum of the magnesium niobate product prepared in Example 1;

[0028] Figure 3 X-ray diffraction spectrum of the magnesium niobate product prepared in Comparative Example 4. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. All other embodiments obtained by those skilled in the art based on the present application are within the scope of protection of the present application.

[0030] The first aspect of the present application provides a preparation method of magnesium niobate, characterized in that it comprises the following steps:

[0031] (1) uniformly mixing MgO and Nb2O5 by wet ball milling, drying to obtain a mixed powder;

[0032] (2) water quenching after heating the mixed powder to 1500-1700℃ for 1-3h to obtain solid particles of core-shell structure encapsulated body;

[0033] (3) heating the solid particles to 1000-1200℃ and keeping the temperature to obtain the magnesium niobate.

[0034] The preparation method of the magnesium niobate provided in the application does not have the problem of incomplete reaction of MgO and Nb2O5, and free niobium does not appear in the prepared magnesium niobate, so that the second phase Pb2Nb2O7 (pyrochlore phase) is not generated in the subsequent reaction process of Nb2O5 and PbO.

[0035] The wet ball milling is adopted in the application, so that the obtained slurry is more uniform; the core-shell structure of the obtained Nb2O5 is uniformly wrapped outside the MgO (a structural schematic diagram is shown in Figure 1 The contact area of the two is larger, and the binding force is stronger; in the subsequent rapid temperature rising sintering process, the solid phase reaction between the core and the shell of the solid particles is more complete, and the obtained magnesium niobate (MgNb2O6, MN) has no free niobium, high purity, and high stability; the Mg 2+ , Nb 5+ The two components are uniform, and have high reactivity, which is beneficial to the full mixing with PbO and TiO2 to form a liquid phase at high temperature, and the obtained lead magnesium niobate-lead titanate (PMNT) crystal growth raw material is single and uniform, which is further conducive to obtaining a single perovskite structure, high purity, and excellent piezoelectric performance of the PMNT single crystal, and improving the yield.

[0036] In some embodiments of the application, the initial raw materials MgO and Nb2O5 are high-purity reagents with a purity of greater than 99.99%. When the purity of the initial raw materials MgO and Nb2O5 is in the above range, the influence of impurities on the purity of magnesium niobate can be avoided, and the quality of the magnesium niobate is improved.

[0037] The initial raw material MgO used in the application is preferably nanoscale high-activity MgO, and the Nb2O5 is preferably micron-sized Nb2O5.

[0038] The application does not have special restrictions on the specific operation method and device for heating the mixed powder to 1500-1700°C for 1-3h, as long as the purpose of the application can be achieved, for example: the mixed powder is placed in a crucible, and then placed in a high-temperature melting furnace, and heated to 1500-1700°C for 1-3h.

[0039] In the application, the heating to 1500-1700°C for 1-3h is carried out at a constant heating rate, and the temperature before heating is room temperature. When the heating time and the temperature after heating of the mixed powder are controlled in the above range, the MgO and Nb2O5 can fully form a core-shell structure of the wrapped body, and the obtained magnesium niobate has higher purity and greater reactivity after rapid temperature rising sintering.

[0040] The room temperature in the application refers to the indoor temperature, which is generally about 25°C.

[0041] The specific operation method of water quenching is not particularly limited in the present application, as long as the purpose of the present application can be achieved, for example: the mixed powder is rapidly discharged from the high-temperature melting device after high-temperature treatment, flows into room temperature water, is water quenched, and solid particles are obtained.

[0042] The specific operation method and device for heating the solid particles to 1000-1200℃ are not particularly limited in the present application, as long as the purpose of the present application can be achieved, for example: the solid particles are placed into a high-temperature electric furnace and heated from room temperature to 1000-1200℃.

[0043] In some embodiments of the present application, the molar ratio of MgO to Nb2O5 is 1:1. When the molar ratio of MgO to Nb2O5 is controlled to the above ratio, the problem of incomplete reaction of MgO and Nb2O5 can be better avoided.

[0044] In some embodiments of the present application, the Dv50 particle size of MgO is 50-100 nm. When the Dv50 particle size of MgO is controlled to the above range, the slurry obtained by grinding can be more uniform, so that the reaction in the subsequent process is more sufficient, and the purity of the generated magnesium niobate is higher.

[0045] In some embodiments of the present application, the Dv50 particle size of Nb2O5 is 2-15 μm. When the Dv50 particle size of Nb2O5 is controlled to the above range, the mixed powder obtained by grinding can be more uniform, so that the reaction in the subsequent process is more sufficient, and the purity of the generated magnesium niobate is higher.

[0046] In some embodiments of the present application, the mass ratio of grinding balls, materials, and ball milling medium used in the wet ball milling is 1:(0.9-1.1):(1.2-1.8). When the mass ratio of grinding balls, materials, and ball milling medium is controlled to the above range, the mixing of MgO and Nb2O5 can be more uniform, so that the reaction in the subsequent process is more sufficient, and the purity of the generated magnesium niobate is higher.

[0047] In some embodiments of the present application, the material of the ball milling tank used in the wet ball milling is polyurethane. The present application selects polyurethane as the material of the ball milling tank, which can make the slurry obtained by grinding more uniform, and can better avoid the introduction of new impurities.

[0048] In some embodiments of the present application, the ball milling medium used in the wet ball milling is anhydrous ethanol. The present application selects anhydrous ethanol as the ball milling medium, which can make the slurry obtained by grinding more uniform, so that the reaction in the subsequent process is more sufficient, and the purity of the generated magnesium niobate is higher.

[0049] In some embodiments of this application, the wet ball milling uses alumina balls. Choosing alumina balls as the grinding balls in this application results in a more uniform slurry, leading to a more complete reaction in subsequent processes and producing magnesium niobate with higher purity.

[0050] In some embodiments of this application, the rotation speed of the wet ball mill is 100-200 r / min, and the wet ball milling time is 20-30 h. When the rotation speed and time of the wet ball mill are controlled within the above range, MgO and Nb2O5 can be mixed more uniformly, resulting in a more complete reaction in subsequent processes and higher purity magnesium niobate.

[0051] In some embodiments of this application, the drying temperature is 90-110°C. When the drying temperature is controlled within the above range, the slurry after wet ball milling can be dried more thoroughly. This application does not have a particular limitation on the drying time, as long as the purpose of this application can be achieved, for example, 20-30 hours.

[0052] In some embodiments of this application, the heating rate to 1000-1200℃ is 5-10℃ / min. The solid particles in this application are at room temperature before heating. When the heating rate of the solid particles in the core-shell structure is controlled within the above range, rapid heating and sintering can be achieved, resulting in a more complete solid-phase reaction between the core and shell parts of the solid particles and a higher purity magnesium niobate.

[0053] In some embodiments of this application, the heat preservation time is 25-35 minutes. When the heat preservation time is controlled within the above range, the solid-phase reaction between the core and shell of the solid particles can be more complete, resulting in higher purity magnesium niobate.

[0054] In some embodiments of this application, the Dv50 particle size of the solid particles is 0.5-2 mm. When the Dv50 particle size of the generated solid particles is within the above range, the reactivity is greater, enabling them to react better with titanium oxide and lead oxide, thereby obtaining a PMNT growth raw material with better uniformity and homogeneity.

[0055] The second aspect of this application provides a method for preparing raw materials for PMNT growth, which includes the method for preparing magnesium niobate as described in the first aspect of this application.

[0056] Magnesium niobate obtained from the first aspect of this application can be reacted with titanium oxide (TiO2) and lead oxide (PbO) to obtain raw materials for PMNT growth.

[0057] Example

[0058] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0059] The MgO and Nb2O5 used in the following examples and comparative examples are high-purity reagents with a purity of 99.99%. Among them, MgO is nano-sized highly active MgO, Nb2O5 is micron-sized Nb2O5, and the Dv50 particle size is 10.5 μm.

[0060] X-ray diffraction pattern testing:

[0061] The prepared magnesium niobate was tested using an X-ray powder diffractometer (model Bruker D8 Advance) (Cu Kα), with a scanning range of 2θ: 10°-80°, a scanning rate of 6° / min, and a test temperature of 20±5℃.

[0062] Example 1

[0063] MgO (Dv50 particle size of 50nm) and Nb2O5 with a molar ratio of 1:1 were weighed and wet-milled in a ball mill at a speed of 150r / min for 24h to obtain a slurry; then the slurry was dried at 100℃ for 24h to obtain a mixed powder; wherein, the ball milling jar material used in the wet ball milling was polyurethane, the ball milling media was anhydrous ethanol, and the grinding balls were alumina balls; the mass ratio of grinding balls, material and ball milling media was 1:1:1.5.

[0064] The dried mixed powder was placed in a crucible and then placed in a high-temperature melting furnace. The temperature was raised from room temperature to 1600°C over 120 minutes. The powder was then quickly released from the bottom of the furnace and flowed into room temperature water for water quenching to obtain solid particles with a Dv50 particle size of 1.5 mm.

[0065] The solid particles were placed in a high-temperature electric furnace and heated from room temperature to 1100°C at a heating rate of 8°C / min, and held at that temperature for 30 min to obtain the magnesium niobate.

[0066] Examples 2-4

[0067] Except for adjusting the preparation parameters as shown in Table 1, the rest is the same as in Example 1.

[0068] Comparative Examples 1-3

[0069] Except for adjusting the preparation parameters as shown in Table 1, the rest is the same as in Example 1.

[0070] Table 1. Preparation parameters and product information for Examples 1-4 and Comparative Examples 1-3.

[0071]

[0072] The X-ray diffraction pattern of the magnesium niobate product obtained in Example 1 is shown below. Figure 2 As shown, from Figure 2 As can be seen from the results, the magnesium niobate product prepared in Example 1 has a single crystal phase, indicating that the magnesium niobate prepared by the method of this application has high crystal phase purity and is free of impurities; this is beneficial for further obtaining high-purity PMNT single crystals with excellent piezoelectric properties.

[0073] As can be seen from Table 1, the mass ratio of grinding balls, materials, and grinding media in Examples 1-4, the rotation speed and time of wet ball milling, the heating process of the mixed powder, and the Dv50 particle size of the raw material MgO were all controlled within the range of this application. The resulting magnesium niobate products all had a single phase and no residual niobium pentoxide (Nb2O5).

[0074] In Comparative Example 1, the heating process of the mixed powder and the Dv50 particle size of MgO were not controlled within the range of this application, resulting in a small amount of niobium pentoxide (Nb2O5) remaining in the prepared magnesium niobate product. When used as a raw material for subsequent reactions, the residual Nb2O5 may react with PbO to form pyrochlore phase during the subsequent reaction process, resulting in low crystal phase purity of the raw material for PMNT single crystal growth, which in turn affects the performance of the obtained PMNT single crystal.

[0075] In Comparative Example 2, the mass ratio of grinding balls, materials, and grinding media, the heating process of the mixed powder, and the Dv50 particle size of MgO were not controlled within the scope of this application. In Comparative Example 3, the rotation speed, heating process, and Dv50 particle size of MgO in the wet ball mill were not controlled within the scope of this application. As a result, trace amounts of niobium pentoxide (Nb2O5) remained in the prepared magnesium niobate product. When used as a raw material for subsequent reactions, the residual Nb2O5 may react with PbO to form a pyrochlore phase during the subsequent reaction process. This results in low crystal phase purity of the raw material for PMNT single crystal growth, which in turn affects the performance of the obtained PMNT single crystal.

[0076] Comparative Example 4

[0077] MgO and Nb₂O₅ in a molar ratio of 1:1 were weighed and wet-milled in a ball mill at 150 r / min for 24 h to obtain a slurry. The ball mill jar was made of polyurethane, the grinding media was anhydrous ethanol, and the grinding balls were alumina balls. The mass ratio of grinding balls, material, and grinding media was 1:1:1.5. The slurry was dried and placed in a corundum crucible, sealed, and placed in a box furnace. The furnace was then heated from room temperature to 1000℃ over 360 min, then to 1200℃ over 120 min, and held at that temperature for 360 min. The temperature was then lowered to 300℃ over 240 min, and then to room temperature over 120 min to obtain magnesium niobate.

[0078] The X-ray diffraction pattern of the obtained magnesium niobate product is as follows: Figure 3 As shown, from Figure 3 As can be seen from the data, the magnesium niobate product prepared in Comparative Example 4 contains not only magnesium niobate but also residual niobium pentoxide (Nb2O5). This indicates that when the magnesium niobate product prepared using the traditional synthesis method provided in Comparative Example 4 is used as a raw material for subsequent reactions, some residual Nb2O5 may react with PbO to form pyrochlore phase during the subsequent reaction process. This results in low crystal phase purity of the raw material for PMNT single crystal growth, which in turn affects the performance of the obtained PMNT single crystal.

[0079] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing magnesium niobate, characterized in that, Includes the following steps: (1) Mix MgO and Nb2O5 evenly by wet ball milling, and dry to obtain mixed powder; (2) The mixed powder is heated to 1500-1700℃ for 1-3 hours and then water-quenched to obtain solid particles with a core-shell structure; (3) Heat the solid particles to 1000-1200℃ and keep them at that temperature to obtain the magnesium niobate.

2. The preparation method according to claim 1, characterized in that, The MgO has a Dv50 particle size of 50-100 nm.

3. The preparation method according to claim 1, characterized in that, The Dv50 particle size of the Nb2O5 is 2-15 μm.

4. The preparation method according to claim 1, characterized in that, The mass ratio of grinding balls, materials, and grinding media used in the wet ball milling is 1:(0.9-1.1):(1.2-1.8).

5. The preparation method according to claim 1, characterized in that, The wet ball milling speed is 100-200 r / min, and the wet ball milling time is 20-30 h.

6. The preparation method according to claim 1, characterized in that, The heating rate to 1000-1200℃ is 5-10℃ / min.

7. The preparation method according to claim 1, characterized in that, The heat preservation time is 25-35 minutes.

8. The preparation method according to claim 1, characterized in that, The solid particles have a Dv50 particle size of 0.5-2 mm.

9. The preparation method according to any one of claims 1-8, characterized in that, The drying temperature is 90-110℃.

10. A method for preparing raw materials for PMNT growth, characterized in that, A method for preparing magnesium niobate comprising any one of claims 1-9.

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