SK500412022A3 - Method of production of massive monocrystalline GdBCOAg superconductor - Google Patents

Abstract

The invention relates to a new concept of achieving the maximum size of the grown GdBCOAg massive monocrystalline superconductor, prepared by growth from fused superconductor components. According to the invention, by adding BaCeO3 in an amount of 0.75 to 3.02 wt.%. will reduce the volume fraction of the residual solidified melt compared to the equivalent addition of standard CeO2. This difference significantly increases the size of the prepared massive crystal.

Description

The field of technology

The invention belongs to the field of material physics and concerns high-temperature massive monocrystalline GdBa2Cu3O? superconductor with addition of silver (GdBCOAg).

Current state of the art

In the field of high-current electrical engineering, massive monocrystalline GdBCOAg superconductors are used in the form of superconducting permanent magnets for the construction of rotating electric machines, frictionless bearings, levitation transport devices, inertial energy reservoirs, devices for magnetic transport of drugs, wastewater treatment, and the like.

This system is particularly interesting because GdBCO-Ag-Pt bulk single crystal superconductors show the highest values of the trapped magnetic field (a record value of 17.6 T at 26 K [Durrell, J., Dennis, A. et.al., Supercond. Sci . Technol. 27 (2014) 082001] with reduced brittleness due to the addition of silver. A cheaper variant of this massive superconductor is to replace expensive platinum with cheaper cerium.

Currently, bulk single-crystal GdBCOAg superconductors are produced by growth from a molten mixture of superconductor components. By default, cerium is added in the form of cerium oxide CeO2. By reacting added CeO2 with GdBa2Cu3O7 superconductor:

2GdBa ₂ Cu ₃ O ₇ + 3CeO ₂ = 3BaCeO ₃ + Gd ₂ BaCuO ₅ + 5 CuO (1) the phase composition of the system changes and an excess of copper oxide CuO appears in the sample. The excess copper oxide is pushed by the growing crystal and thus increases its concentration in the melt from which the massive GdBa2Cu3O7 crystal grows. This process finally leads to the cessation of crystal growth and the residual melt solidifies around the perimeter of the grown crystal. The disadvantage of this solution is that the solidified melt has a different thermal expansion than the solid crystal and induces mechanical stresses at the crystal/solidified melt interface and can lead to cracks in the solid crystal.

Slovak patent application PP 137-2019 discloses a method of manufacturing a massive monocrystalline GdBCOAg superconductor by growth from a molten mixture of superconductor components, which contains at least 1.6 mass percent CeO2.

However, the addition of cerium in the form of CeO2 causes imperfect growth of the bulk GdBCOAg crystal, thereby degrading up to 20 percent of the expensive raw materials that remain as residual melt after the growth of the bulk crystal.

The aim of the invention is to reduce the amount of solidified residual melt after crystallization of a massive GdBCOAg crystal in air, thereby achieving a more efficient and cheaper production of massive GdBCOAg superconductors.

The essence of the invention

Surprisingly, it was found that the amount of residual melt after crystallization of a massive GdBCOAg crystal is significantly smaller if cerium is added in the form of double barium cerium oxide BaCeO3 compared to the addition of cerium in the form of an equivalent amount of cerium oxide CeO2.

The method of manufacturing a massive monocrystalline GdBCOAg superconductor according to the present invention includes the following steps:

a) homogenization of input raw materials in the form of powders in quantities:

- 60 to 80 wt. % GdBa2Cu3O7^, where δ is less than 0.5,

- 20 to 40 wt. % Gd2BaCuO5,

- 20 wt. % Ag ₂ O,

- 0.75 to 3.02% wt. BaCeO ₃ (prepared by the sol-gel method, with a particle size of around 100 nm), where wt. % AG2O and wt. % BaCeO3 are related to the sum of the weights of GdBa2Cu3O7^ and Gd2BaCuO5;

b) pressing the homogenized mixture with a uniaxial pressure of 3 to 5 MPa.

c) placement of a thin-film seed of the type NdBa2Cu3O7^ on the pressed mixture;

d) heating the pressed mixture to a temperature of min. 1,060 °C at a rate of 100 °C/h with an isothermal duration of 1 h, then cooling the mixture to a temperature of 1019-1015 °C at a rate of 100 °C/h, and further cooling the mixture to a temperature of 979-975 °C at a rate of 0.5 °C/ h, and further subsequent cooling of the mixture to room temperature in a closed, switched off furnace.

SK 50041-2022 A3

Delta (δ) is a stoichiometric coefficient. Where δ is less than 0.5, i.e. j. it is a superconducting phase with an orthorhombic structure.

The raw materials must be homogenized before processing. According to a preferred embodiment, the raw materials are homogenized in the following way: first they are mixed, for example in a powder mixer, then they are ground, for example in a friction mill, and then they are sieved, for example with a vibrating sieve. Mixing and grinding time is preferably 15 minutes (each separately).

According to a preferred embodiment, the mixture is pressed into tablets at a pressure of 3 to 5 MPa. The diameter of the tablets is preferably 20 mm. A manual hydraulic press can be used to produce tablets.

The addition of thin-film NdBa2Cu3O?-ô (Nd123) is essential in the process of growing a massive GdBa2Cu3O?δ (Gd123) crystal. To prepare massive Gd123 crystals, the TOP-SEEDED MELTGROWN (TSMG) process is used, in which the Gd123 crystal grows epitaxially from a thin-layer Nd123 seed, located in the center on the surface of the tablet. This thin film Nd123 seed represents a nucleation center where the crystal orientation of the Gd123 crystal coincides with the crystal orientation of the Nd123 seed.

The advantage of the addition of cerium in the form of BaCeO ₃ is that the growth of the massive GdBCOAg crystal is supported and a larger crystal is obtained from the same nominal weight of the weight. Another advantage of the proposed approach is that a smaller amount of solidified residual melt will lead to a reduction of dilatational thermal stresses at the crystal/solidified melt interface, thereby reducing the risk of cracking during cooling from the bulk crystal growth temperature.

Overview of Figures in the Drawings Figure 1 is a macro-photograph of a bulk GdBCOAg crystal with an addition of 0.75 wt%. BaCeO3, in Figure 2 is a macro-photograph of a massive GdBCOAg crystal with an addition of 1.89 wt.%. BaCeO3 and in Figure 3 is a macro-photograph of a massive GdBCOAg crystal with an addition of 3.02 wt.%. BaCeO3.

Figure 4 shows a macro-photograph of a massive GdBCOAg crystal with an addition of 0.4 wt.%. CeO2, in Figure 5 is a macro-photograph of a massive GdBCOAg crystal with the addition of 1.0 wt.%. CeO ₂ , in Figure 6 is a macro-photograph of a massive GdBCOAg crystal with an addition of 1.6 wt.%. CeO ₂ ,

Examples of implementation of the invention

Example 1

Commercial powders were used in the amounts of:

% wt. GdBa2Cu3O ₂ ^, (Solvay, purity 99.9%, predominant fraction 30 μm) % wt. Gd2BaCuO5, (Toshima, purity 99.9%, predominant fraction 1 - 2 μm) % wt. Ag2O, (Chempur, purity 99%)

0.75% wt. BaCeO3, (0.32% wt. Ce) where % wt. AG2O and % wt. BaCeO3 are related to the sum of the weights of GdBa2Cu3O7^ and Gd2BaCuO5.

which represents:

14.188 g of GdBa2^O7^;

5.812 g of Gd2BaCuO5;

g Ag2O, a

0.151 g of BaCeO3

After weighing, the input powders were mixed together for 15 minutes in a powder mixer, ground in a friction mill for 15 minutes and sieved with a vibrating sieve. The thus homogenized input powders were pressed using a manual hydraulic press at a pressure of 4 MPa into cylindrical tablets with a diameter of 20 mm.

The compressed tablet was placed on an Al ₂ O ₃ substrate together with a thin-film Nd123 seed located in the center on the surface of the tablet. In the case of the Nd123 seed, it is a thin 700 nm layer of NdBa ₂ Cu ₃ O ₇ ^ deposited on a MgO substrate with (buffer layer) a damping 20 nm layer of YBa2Cu3O7^. MgO and ZrO2 pads were used as interlayers to prevent contamination of the sample from the Al2O3 pad. GdBCOAg bulk single-crystal superconductors were prepared in air at normal atmospheric pressure in an electric circular resistance furnace using a slow-cooling time-temperature regime consisting of the following steps: the compressed tablet was heated to a maximum temperature of Tmax = 1060 °C, at a rate of 100 ° C/hs with an isothermal duration of 1 h, followed by rapid cooling to a temperature of 1019-1015 °C at a rate of 100 °C/h, after slow cooling at a rate of 0.5 °C/h to a temperature of 979-975 °C followed by cooling

SK 50041-2022 A3 in the oven to room temperature.

A massive GdBCOAg crystal produced according to Example 1 is shown in Fig. 1.

Example 2

The same commercial powders were used in amounts of:

% wt. Gdl^CihO?^ % wt. Gd2BaCuO5 % wt. Ag2O

1.89% wt. BaCeO3 (0.81 wt% Ce) which represents:

12.161 g of GdBa2Cu3Oy^;

7.749 g of Gd ₂ BaCuO ₅ ;

g Ag2O, a

0.378 g of BaCeO3

After weighing, the input powders were mixed together for 15 minutes in a powder mixer, ground in a friction mill for 15 minutes and sieved with a vibrating sieve. The thus homogenized input powders were pressed using a manual hydraulic press at a pressure of 4 MPa into cylindrical tablets with a diameter of 20 mm.

The pressed tablet was placed on an Al2O3 substrate together with a thin-film seed of type Nd123 located in the center on the surface of the tablet. To prevent sample contamination from the Al2O3 mat, MgO and ZrO ₂ mats were used as interlayers. GdBCOAg bulk single crystal superconductors were prepared in air at normal atmospheric pressure in an electric circular resistance furnace using a slow cooling time-temperature regime consisting of the following steps: the compressed tablet was heated to a maximum temperature of Tmax = 1060 °C, at a rate of 100 °C/ hs with an isothermal duration of 1 h, followed by rapid cooling to a temperature of 1,019-1,015 °C at a rate of 100 °C/h, after slow cooling at a rate of 0.5 °C/h to a temperature of 979-975 °C, followed by cooling in a furnace to room temperature temperature.

A massive GdBCOAg crystal produced according to Example 2 is shown in Fig. 2.

Example 3

The same commercial powders were used in amounts of:

% wt. GdBa2Cu3O7^ % wt. Gd2BaCuO5 % wt. Ag2O

3.02% wt. BaCeO ₃ (1.30 wt% Ce) which represents:

16.214 g of GdBa2Cu3O7^;

3.874 g of Gd2BaCuO5;

g Ag2O, a

0.605 g of BaCeO3

After weighing, the input powders were mixed together for 15 minutes in a powder mixer, ground in a friction mill for 15 minutes and sieved with a vibrating sieve. The thus homogenized input powders were pressed using a manual hydraulic press at a pressure of 4 MPa into cylindrical tablets with a diameter of 20 mm.

The pressed tablet was placed on an Al2O3 substrate together with a thin-film seed of type Nd123 located in the center on the surface of the tablet. To prevent sample contamination from the Al2O3 mat, MgO and ZrO2 mats were used as interlayers. GdBCOAg bulk single-crystal superconductors were prepared in air at normal atmospheric pressure in an electric circular resistance furnace using a slow-cooling time-temperature regime consisting of the following steps: the compressed tablet was heated to a maximum temperature of T _max = 1060 °C, at a rate of 100 °C /hs with an isothermal duration of 1 h, followed by rapid cooling to a temperature of 1,019 to 1,015 °C at a rate of 100 °C/h, after slow cooling at a rate of 0.5 °C/h to a temperature of 979-975 °C, followed by cooling in a furnace to room temperature.

A massive GdBCOAg crystal produced according to Example 3 is shown in Fig. 3.

Comparative examples 4 - 6

SK 50041-2022 A3

Example 4

The same commercial powders were used in amounts of:

% wt. Gdl^CihO?^ % wt. Gd2BaCuO5 % wt. Ag ₂ O

0.4% wt. CeO2 (0.32 wt% Ce), which represents:

14.188 g of GdBa2Cu3O7^;

5.812 g of Gd2BaCuO5;

g Ag2O, a

0.08 g of CeO2

After weighing, the input powders were mixed together for 15 minutes in a powder mixer, ground in a friction mill for 15 minutes and sieved with a vibrating sieve. The thus homogenized input powders were pressed using a manual hydraulic press at a pressure of 4 MPa into cylindrical tablets with a diameter of 20 mm.

The pressed tablet was placed on an Al2O3 substrate together with a thin-film seed of type Nd123 located in the center on the surface of the tablet. To prevent sample contamination from the Al2O3 mat, MgO and ZrO2 mats were used as interlayers. GdBCOAg bulk single crystal superconductors were prepared in air at normal atmospheric pressure in an electric circular resistance furnace using a time-temperature slow-cooling regime consisting of the following steps: the compressed tablet was heated to a maximum temperature of T _max = 1060 °C at a rate of 100 °C /hs with an isothermal duration of 1 h, followed by rapid cooling to a temperature of 1,019-1,015 °C at a rate of 100 °C/h, after slow cooling at a rate of 0.5 °C/h to a temperature of 979-975 °C, followed by cooling in a furnace to room temperature.

A massive GdBCOAg crystal produced according to Example 4 is shown in Fig. 4.

Example 5

The same commercial powders were used in amounts of:

% wt. GdBa2Cu3O7^ % wt. Gd2BaCuO5 % wt. Ag2O

1.0% wt. CeO2 (0.81 wt% Ce), which represents:

12.161 g of GdBa2Cu3O7^;

7.749 g of Gd ₂ BaCuO ₅ ;

g Ag2O, a

0.2 g of CeO2

After weighing, the input powders were mixed together for 15 minutes in a powder mixer, ground in a friction mill for 15 minutes and sieved with a vibrating sieve. The thus homogenized input powders were pressed using a manual hydraulic press into cylindrical tablets with a diameter of 20 mm.

The pressed tablet was placed on an Al2O3 substrate together with a thin-film seed of type Nd123 located in the center on the surface of the tablet. To prevent sample contamination from the Al2O3 mat, MgO and ZrO ₂ mats were used as interlayers. GdBCOAg bulk single crystal superconductors were prepared in air at normal atmospheric pressure in an electric circular resistance furnace using a slow cooling time-temperature regime consisting of the following steps: the compressed tablet was heated to a maximum temperature of Tmax = 1060 °C, at a rate of 100 °C/ hs with an isothermal duration of 1 h, followed by rapid cooling to a temperature of 1,019-1,015 °C at a rate of 100 °C/h, after slow cooling at a rate of 0.5 °C/h to a temperature of 979-975 °C, followed by cooling in a furnace to room temperature temperature.

A massive GdBCOAg crystal produced according to Example 5 is shown in Fig. 5.

Example 6

The same commercial powders were used in amounts of:

% wt. GdBa2Cu3O7^ % wt. Gd2BaCuO5 % wt. Ag2O

1.6% wt. CeO2 (1.30 wt% Ce).

SK 50041-2022 A3 which represents:

16.214 g of Gd^CusOy-c;

3.874 g of Gd2BaCuO5;

g Ag2O, a

0.32 g of CeO2

After weighing, the input powders were mixed together for 15 minutes in a powder mixer, ground in a friction mill for 15 minutes and sieved with a vibrating sieve. The thus homogenized input powders were pressed using a manual hydraulic press into cylindrical tablets with a diameter of 20 mm.

The compressed tablet was placed on an ALO3 pad together with a thin-film seed of type Nd123 located in the center on the surface of the tablet. In order to avoid contamination of the sample from the ALO3 pad, MgO and ZrO2 pads were used as interlayers. GdBCOAg bulk single crystal superconductors were prepared in air at normal atmospheric pressure in an electric circular resistance furnace using a slow cooling time-temperature regime consisting of the following steps: the compressed tablet was heated to a maximum temperature of T _max = 1060 °C at a rate of 100 °C /hs with an isothermal duration of 1 h, followed by rapid cooling to a temperature of 1,019 to 1,015 °C at a rate of 100 °C/h, after slow cooling at a rate of 0.5 °C/h to a temperature of 979-975 °C, followed by cooling in a furnace to room temperature.

A massive GdBCOAg crystal produced according to Example 6 is shown in Fig. 6.

Table 1 shows the resulting amounts of the residual melt that remained after the production of the massive single-crystal GdBCOAg superconductor by the method indicated in Examples 1 to 6.

Table 1:

Examples Ce equivalent [wt%] CeO2 [wt%] BaCeO3 [wt%] Residual solidified melt [% vol.] Example 1 0.32 0 0.75 9.8 Example 2 0.81 0 1.89 8,9 Example 3 1.30 0 3.02 8,9 Comparative example 4 0.32 0.4 0 13.0 Comparative example 5 0.81 1.0 0 22.1 Comparative example 6 1.30 1.6 0 24.6

It is clear from Table 1 that the volume fraction of the residual solidified melt is 8.9% by volume. with a BaCeO ₃ content of 3.02% by weight, while in the case of a superconductor prepared by the same technology, under the same conditions with the addition of 1.6% by weight. CeO2 (the addition represents an equivalent amount of cerium as with the addition of 3.02 wt.% BaCeO3) the volume fraction of the residual solidified melt is 24.6 vol.%. This difference contributes significantly to the size of the prepared massive superconductor crystal.

Industrial applicability

The invention can be used in the production of massive monocrystalline superconductors by the method of crystal growth from a molten mixture of superconductor components.

Claims (1)

The method for the production of a massive monocrystalline GdBCOAg superconductor, characterized by the fact that it includes the following steps: a) homogenization of the input raw materials in the form of powders in amounts: 60 to 80 wt. % 5 GdBa2Cu3O7- ₆ , where δ is less than 0.5; 20 to 40 wt. % Gd2BaCuOs; 20 wt. % Ag2O; 0.75 to 3.02 wt.% BaCeO ₃ ; where material % AG ₂ O and wt. % BaCeO ₃ are related to the sum of the weights of GdBa ₂ Cu ₃ O ₇ ^ and Gd2BaCuO5; b) pressing the homogenized mixture with a uniaxial pressure of 3 to 5 MPa; c) placement of a thin-film seed of the type NdBa2Cu3O7^ on the pressed mixture; d) heating the pressed mixture with the seed to a minimum temperature. 1060 °C at a rate of 100 °C/h with an isothermal duration of 1 h, followed by cooling the mixture to a temperature of 1019 to 1015 °C at a rate of 100 °C/h, and subsequent cooling of the mixture to a temperature of 979 to 975 °C at a rate of 0.5 °C/h, and subsequent cooling of the mixture to room temperature in a closed, switched off furnace.