阅读说明：本技术 一种纳米复合钇钡铜氧超导块材生长过程中阻止顶部籽晶移动的方法 (Method for preventing top seed crystal from moving in growth process of nano composite yttrium barium copper oxide superconducting block ) 是由 李国政 吴杰 董磊 于 2021-10-25 设计创作，主要内容包括：本发明公开了一种纳米复合钇钡铜氧超导块材生长过程中阻止顶部籽晶移动的方法。通过在模具的垫片上粘贴一小块粗糙塑料圆片,压块后可得到带有顶部圆坑的固相块,而且圆坑具有粗糙的底面,可有效阻止其内薄膜籽晶的移动。该操作非常简单,但能有效解决薄膜籽晶在热处理过程中移动的问题,降低了实验的不可控性,提高了稳定性和成品率。本发明可推广到Nd、Sm、Gd等其他系列超导块材的制备工艺中,也可推广到传统熔化生长方法中。(The invention discloses a method for preventing top seed crystals from moving in the growth process of a nano composite yttrium barium copper oxide superconducting block. A small rough plastic wafer is adhered to a gasket of the die, a solid phase block with a top round pit can be obtained after briquetting, and the round pit has a rough bottom surface, so that the movement of the inner film seed crystal can be effectively prevented. The operation is very simple, but the problem that the film seed crystal moves in the heat treatment process can be effectively solved, the uncontrollable property of the experiment is reduced, and the stability and the yield are improved. The method can be popularized to the preparation process of Nd, Sm, Gd and other series superconducting blocks, and can also be popularized to the traditional melting growth method.)

1. A method for preventing top seed crystal from moving in the growth process of a nano composite yttrium barium copper oxide superconducting block is characterized by comprising the following steps:

(1) preparing solid phase powder:

mixing BaCO₃The mol ratio of powder to CuO powder is 1: 1, and preparing BaCuO by a solid phase reaction method₂Pulverizing; then Y with a particle size of 50-200 nm₂O₃Nano powder and BaCuO₂The mol ratio of powder to CuO powder is 1: 1.15: 0.1, adding 1 wt% of CeO with the particle size of 15-30 nm₂Nanometer powder, mixing well to obtain solid phase powder;

(2) preparing liquid phase powder:

yb of₂O₃Powder with BaCuO₂The mol ratio of powder to CuO powder is 1: 10: 6 as liquid phase powder;

(3) pressing a briquette:

firstly, sticking a rough plastic sheet with the diameter of 6mm and the thickness of 0.2mm at the central position of a gasket of a cylindrical split mold, then putting solid-phase powder into the cylindrical split mold, then putting the gasket, ensuring that one surface with the plastic sheet faces downwards, then putting a compression bar, then pressing and molding by using a tablet press under the pressure of 200MPa, and obtaining a solid-phase block with a top circular pit after demolding; taking liquid phase powder, putting the liquid phase powder into a cylindrical split mold, and pressing the liquid phase powder into a liquid phase block by a tablet press under the pressure of 50 MPa; then take Yb₂O₃Placing the powder into a cylindrical split mold, and pressing into slices with thickness of about 2mm as supporting blocks under 50MPa with a tablet press(ii) a Wherein the mass ratio of the solid phase powder to the liquid phase powder is 1: 3, the diameter of the die for pressing the liquid phase block and the supporting block is 10mm larger than that of the die for pressing the solid phase block;

(4) assembling a billet:

the supporting block, the liquid phase block and the solid phase block are coaxially arranged on the Al from bottom to top in sequence₂O₃On the circular pad, 5 equal-height MgO single crystal grains are spaced; for the solid phase block, ensuring that one surface with a round pit faces upwards, and then putting a piece of NdBCO/YBCO/MgO film seed crystal with the size of 2mm multiplied by 2mm into the round pit;

(5) high-temperature heat treatment:

putting the assembled briquettes into a pit furnace, heating to 900 ℃ at the heating rate of 180 ℃ per hour, and preserving heat for 10 hours; then heating to 1045-1105 ℃ at a heating rate of 60 ℃ per hour, and preserving heat for 1 hour; then cooling to 1005 ℃ at a cooling rate of 60 ℃ per hour, then slowly cooling to 975 ℃ at a cooling rate of 0.2-0.33 ℃ per hour, and furnace cooling to room temperature to obtain an YBCO single domain block;

(6) oxygen permeation treatment:

and (3) putting the yttrium barium copper oxide single domain block material into a quartz tube furnace, and slowly cooling for 200 hours in a temperature region of 450-400 ℃ in a flowing oxygen atmosphere to obtain the yttrium barium copper oxide superconducting block material.

2. The use of the method of claim 1 for preventing top seed crystal movement during the growth of a nanocomposite yttrium barium copper oxide superconductor bulk for improving the growth stability of a sample and the yield of a single domain sample.

Technical Field

The invention belongs to the technical field of high-temperature copper oxide superconducting materials, and particularly relates to a method for preventing top seed crystals from moving in the growth process of a nano composite yttrium barium copper oxide superconducting block.

Background

The single domain yttrium barium copper oxide (Y-Ba-Cu-O, YBCO for short) high temperature superconducting block material which is guided to grow by utilizing the top seed crystal has strong magnetic flux pinning capability and can keep high critical current density (J) under high field_c) One of the hot spots in the research field of international high and new technology materials and high and new technology applications is. The top seed crystal assisted melting growth (Melt growth) and infiltration growth (infiltration growth) processes are two of the most mainstream methods for preparing single-domain yttrium barium copper oxide bulk materials.

Neodymium barium copper oxide (Nd-Ba-Cu-O, NdBCO for short) small grains and NdBCO films are two of the most commonly used seed materials at present. Among them, the NdBCO thin film has higher melting point and thermal stability, can guide the growth of YBCO more stably, and is receiving more and more attention. However, due to the characteristics of thin film and smooth film surface, the NdBCO film often moves on the top of the sample and deviates from the center position during the heat treatment, which reduces the stability of the experiment. Although pressing the NdBCO film into the ingot (i.e., the embedded seed mode) is effective in preventing seed movement, it often initiates growth of the film substrate (usually MgO) to guide the sample laterally, resulting in a multi-domain sample that ultimately results in a lower yield of single-domain samples. Therefore, it is necessary to invent a new method to prevent the movement of the thin film seed crystal during the heat treatment of the sample, and to improve the stability of the process and the yield of the single domain sample.

Disclosure of Invention

The invention aims to provide a method for preventing top seed crystals from moving in the growth process of a nano composite yttrium barium copper oxide superconducting block.

The technical scheme adopted for solving the technical problems comprises the following steps:

(1) preparing solid phase powder:

mixing BaCO₃The mol ratio of powder to CuO powder is 1: 1, and preparing BaCuO by a solid phase reaction method₂Pulverizing; then Y is put₂O₃Nano powder (particle size 50-200 nm) and BaCuO₂The mol ratio of powder to CuO powder is 1: 1.15: 0.1 while adding 1% by weight of CeO₂Uniformly mixing nano powder (with the particle size of 15-30 nm) to obtain solid phase powder;

(2) preparing liquid phase powder:

yb of₂O₃Powder with BaCuO₂The mol ratio of powder to CuO powder is 1: 10: 6 as liquid phase powder;

(3) pressing a briquette:

firstly, sticking a rough plastic sheet with the diameter of 6mm and the thickness of 0.2mm at the central position of a gasket of a cylindrical split mold, then putting solid-phase powder into the cylindrical split mold, then putting the gasket, ensuring that one surface with the plastic sheet faces downwards, then putting a compression bar, then pressing and molding by using a tablet press under the pressure of 200MPa, and obtaining a solid-phase block with a top circular pit after demolding; taking liquid phase powder, putting the liquid phase powder into a cylindrical split mold, and pressing the liquid phase powder into a liquid phase block by a tablet press under the pressure of 50 MPa; then take Yb₂O₃Putting the powder into a cylindrical split mold, and pressing into a sheet with the thickness of about 2mm by a tablet press under the pressure of 50MPa to be used as a supporting block; wherein the mass ratio of the solid phase powder to the liquid phase powder is 1: 3, the diameter of the die for pressing the liquid phase block and the supporting block is 10mm larger than that of the die for pressing the solid phase block;

(4) assembling a billet:

the supporting block, the liquid phase block and the solid phase block are coaxially arranged on the Al from bottom to top in sequence₂O₃On the circular pad, 5 equal-height MgO single crystal grains are spaced; for the solid phase block, ensuring that one surface with a round pit faces upwards, and then putting a piece of NdBCO/YBCO/MgO film seed crystal with the size of 2mm multiplied by 2mm into the round pit;

the NdBCO/YBCO/MgO film seed crystal used in the steps is provided by Ceraco ceramic coating GmbH company;

(5) high-temperature heat treatment:

putting the assembled briquettes into a pit furnace, heating to 900 ℃ at the heating rate of 180 ℃ per hour, and preserving heat for 10 hours; then heating to 1045-1105 ℃ at a heating rate of 60 ℃ per hour, and preserving heat for 1 hour; then cooling to 1005 ℃ at a cooling rate of 60 ℃ per hour, then slowly cooling to 975 ℃ at a cooling rate of 0.2-0.33 ℃ per hour, and furnace cooling to room temperature to obtain an YBCO single domain block;

(6) oxygen permeation treatment:

and (3) putting the yttrium barium copper oxide single domain block material into a quartz tube furnace, and slowly cooling for 200 hours in a temperature region of 450-400 ℃ in a flowing oxygen atmosphere to obtain the yttrium barium copper oxide superconducting block material.

The invention further discloses an application of the method for preventing the top seed crystal from moving in the growth process of the nano composite yttrium barium copper oxide superconducting bulk material in the aspects of improving the growth stability of a sample and the yield of a single-domain sample. The experimental results show that: after the film seed crystal is placed in the round pit with the rough bottom surface, the position of the film seed crystal can not move during heat treatment and is always positioned at the central position of the upper surface of the sample, so that the epitaxial growth of the sample from the center to the periphery is ensured, and the side surface of the film seed crystal can not contact with the sample, thereby avoiding the nucleation of the substrate of the film by guiding the sample from the side surface, ensuring that only the bottom surface of the seed crystal guides the growth of the sample, and finally improving the growth stability of the sample and the yield of the single-domain sample.

Compared with the prior art, the method for preventing the top seed crystal from moving in the growth process of the nano composite yttrium barium copper oxide superconducting block disclosed by the invention has the positive effects that:

according to the invention, a small rough plastic wafer is adhered to the gasket of the die, and the solid phase block with the top round pit can be obtained after briquetting, and the round pit has a rough bottom surface, so that the movement of the inner film seed crystal can be effectively prevented. The operation is very simple, but the problem that the film seed crystal moves in the heat treatment process can be effectively solved, the uncontrollable property of the experiment is reduced, and the stability and the yield are improved. The method can be popularized to the preparation process of Nd, Sm, Gd and other series superconducting blocks, and can also be popularized to the traditional melting growth method.

Drawings

FIG. 1 is a view of the nano-Y used in example 1₂O₃A micro-topography of;

FIG. 2 shows the nano-CeO used in example 1₂A micro-topography of;

FIG. 3 is a schematic view of the method of pressing a solid block with a top round pit by a split mold in example 1;

FIG. 4 is a schematic view of the assembly of a thin film seed crystal and a precursor ingot in example 1;

FIG. 5 is a surface topography of a nanocomposite yttrium barium copper oxide superconducting bulk prepared in example 1;

FIG. 6 is a magnetic levitation force curve of the nanocomposite yttrium barium copper oxide superconducting bulk prepared in example 1.

FIG. 7 is a microscopic structure view of the nanocomposite yttrium barium copper oxide superconducting bulk prepared in example 1.

Detailed Description

The present invention will be described in further detail with reference to the following drawings and examples, but the present invention is not limited to these examples. In which the nano-Y is used₂O₃CeO, CeO nanoparticles₂、Yb₂O₃、BaCO₃And CuO chemical starting materials are commercially available. The NdBCO/YBCO/MgO thin film seed crystal used is supplied by Ceraco ceramic coating GmbH company.

Example 1

(1) Preparing solid phase powder:

213.8131g of BaCO are taken₃Mixing powder 86.1869g CuO powder uniformly to obtain BaCO₃The mol ratio of the powder to the CuO powder is 1: 1, preparing BaCuO by a solid-phase reaction method₂And (3) pulverizing. Get 45.0210g Y₂O₃Nanometer powder (particle size of 50-200 nm) 53.3931g BaCuO₂The powders were mixed with 1.5859g of CuO powder, and 1g of CeO was added₂Nanometer powder (with the particle size of 15-30 nm) is evenly mixed, namely Y₂O₃Nano powder and BaCuO₂The mol ratio of the powder to the CuO powder is 1: 1.15: 0.1, while adding 1% by weight of CeO₂Nano powder as solid phase powder. Y is₂O₃The micro-morphology of the nano-powder is shown in figure 1; CeO (CeO)₂The micro-morphology of the nanopowder is shown in FIG. 2.

(2) Preparing liquid phase powder:

18.4721g Yb was sampled₂O₃Powder 109.1563g BaCuO₂The powder 22.3716g CuO powder is mixed evenly, namely Yb₂O₃Powder with BaCuO₂The mol ratio of the powder to the CuO powder is 1: 10: 6, as liquid phase powder.

(3) Pressing a briquette:

firstly, sticking a rough plastic sheet with the diameter of 6mm and the thickness of 0.2mm at the central position of a gasket of a cylindrical split mold (the diameter of 16 mm), then putting 5g of solid-phase powder into the cylindrical split mold (the diameter of 16 mm), then putting the gasket, ensuring that one surface with the plastic sheet faces downwards, then putting a compression bar, then pressing and molding by using a tablet press under the pressure of 200MPa, and obtaining a solid-phase block with a top round pit after demolding, wherein the process is shown in figure 3; taking 15g of liquid phase powder, putting the powder into a cylindrical split mold (with the diameter of 26 mm), and pressing the powder into a liquid phase block by a tablet press under the pressure of 50 MPa; then 3g Yb was sampled₂O₃The powder was placed in a cylindrical split die (diameter 26 mm) and pressed into a sheet having a thickness of about 2mm as a support block by a tablet press under a pressure of 50 MPa. Namely, the mass ratio of the solid phase powder to the liquid phase powder is 1: and 3, the diameter of the die for pressing the liquid phase block and the supporting block is 10mm larger than that of the die for pressing the solid phase block.

(4) Assembling a billet:

the supporting block, the liquid phase block and the solid phase block are coaxially arranged on the Al from bottom to top in sequence₂O₃On the circular pad, 5 equal-height MgO single crystal grains are spaced; for the solid phase block, the side with the round pit is ensured to face upwards, and then a piece of NdBCO/YBCO/MgO film seed crystal with the size of about 2mm multiplied by 2mm is put into the round pit, as shown in figure 4.

(5) High-temperature heat treatment:

putting the assembled briquettes into a pit furnace, heating to 900 ℃ at the heating rate of 180 ℃ per hour, and preserving heat for 10 hours; then the temperature is raised to 1045 ℃ at the rate of 60 ℃ per hour, and the temperature is kept for 1 hour; then the temperature is reduced to 1005 ℃ at the cooling rate of 60 ℃ per hour, and then is slowly cooled to 975 ℃ at the cooling rate of 0.33 ℃ per hour, and the temperature is cooled to room temperature along with the furnace, so as to obtain the YBCO single domain bulk.

(6) Oxygen permeation treatment:

and (3) putting the yttrium barium copper oxide single domain bulk into a quartz tube furnace, and slowly cooling for 200 hours in a temperature region of 450-400 ℃ in a flowing oxygen atmosphere to obtain the nano composite yttrium barium copper oxide superconducting bulk.

Prepared seed crystal from thin film in top round pitThe surface appearance of the grown nanocomposite yttrium barium copper oxide superconducting block is photographed by a camera, and the picture is shown in fig. 5. As can be seen from the figure, the film seed crystal is still positioned in the circular pit, the position of the film seed crystal does not move, the four diameters of the surface of the final sample are clear, the spontaneous nucleation phenomenon does not occur, and the film seed crystal successfully grows into a single-domain sample with the diameter of the single-domain sampledAbout 17.5 mm.

The magnetic suspension force performance of the prepared nano composite yttrium barium copper oxide superconducting block is tested at the liquid nitrogen temperature by applying a three-dimensional magnetic field and magnetic force testing device, and the result is shown in figure 6. As can be seen from the figure, the maximum magnetic levitation force of the sample is 63.63N, and the sample shows excellent superconducting performance.

The next small wafer was cleaved at the edge of the nanocomposite yttrium barium copper oxide superconducting bulk, and microstructure analysis was performed using a scanning electron microscope, the result of which is shown in fig. 7. As can be seen, in YBa₂Cu₃O_7−xA plurality of nano-scale Y are dispersed in the superconducting matrix₂BaCuO₅The particle size of the particles ranges from dozens of nanometers to hundreds of nanometers, which shows that the magnetic flux pinning centers on the nanometer scale are successfully introduced into the yttrium barium copper oxide superconducting bulk material.

Example 2

In the step (3) of blank block pressing, firstly, a rough plastic sheet with the diameter of 6mm and the thickness of 0.2mm is stuck at the central position of a gasket of a cylindrical split mold (with the diameter of 26 mm), then 10g of solid phase powder is put into the cylindrical split mold (with the diameter of 26 mm), then the gasket is put in, the side with the plastic sheet is ensured to be downward, then a compression bar is put in, then a tablet press is used for pressing and forming under the pressure of 200MPa, and a solid phase block with a top circular pit is obtained after demoulding; taking 30g of liquid phase powder, putting the powder into a cylindrical split mold (the diameter is 36 mm), and pressing the powder into a liquid phase block by a tablet press under the pressure of 50 MPa; then take 6g Yb₂O₃The powder was placed in a cylindrical split die (diameter 36 mm) and pressed into a sheet having a thickness of about 2mm as a support block by a tablet press under a pressure of 50 MPa. Namely, the mass ratio of the solid phase powder to the liquid phase powder is 1: and 3, the diameter of the die for pressing the liquid phase block and the supporting block is 10mm larger than that of the die for pressing the solid phase block.

In the high-temperature heat treatment step (5), the assembled compact is put into a shaft furnace, the temperature is raised to 900 ℃ at the temperature rise rate of 180 ℃ per hour, and the temperature is preserved for 10 hours; then heating to 1105 ℃ at the heating rate of 60 ℃ per hour, and preserving heat for 1 hour; then the temperature is reduced to 1005 ℃ at the cooling rate of 60 ℃ per hour, and then is slowly cooled to 975 ℃ at the cooling rate of 0.2 ℃ per hour, and the temperature is cooled to room temperature along with the furnace, so as to obtain the yttrium barium copper oxide single domain bulk.

The other steps are the same as the example 1, and the yttrium barium copper oxide superconducting bulk material is prepared.