Ternary rare earth hexaboride-zirconium diboride eutectic composite material and preparation method thereof

Abstract

This invention provides a (La) 0.5 Ba 0.5 A method for preparing a B6[100]-ZrB2 eutectic composite material, and a cathode device comprising the same. In the eutectic composite material, La 0.5 B 0.5 The molar ratio of B6 to ZrB2 is 2.1:1, (La 0.5 Ba 0.5 ZrB6 is the matrix with a crystal orientation of [100]; ZrB2 is the reinforcing phase existing in the form of fibers. This eutectic composite material has high thermal emission properties and high strength and toughness.

Description

Technical Field

[0001] This invention relates to the field of rare earth boride hot cathode materials, specifically to a (La) boride hot cathode material with good mechanical properties and excellent thermal emission performance. 0.5 Ba 0.5 The preparation method of B6-ZrB2 eutectic composite material, and including the (La) 0.5 Ba 0.5 Cathode device of B6-ZrB2 eutectic composite material. Background Technology

[0002] LaB6, as an excellent thermionic emission source, has been widely used due to its high brightness, high melting point, low work function, low vapor pressure, and long lifetime. According to electronics theory, further improving the thermionic emission performance of LaB6 requires reducing its work function. Studying composite single crystals formed by surface doping is an effective way to reduce the work function of LaB6. Japanese scholar Futamoto systematically investigated the thermionic emission performance of ternary composite single crystals such as (LaSr)B6, (LaCe)B6, and (LaSm)B6 using the aluminum solvent method. Although this method introduced aluminum impurities, resulting in all composite single crystals having lower thermionic emission performance than LaB6 single crystals, he was the first to use the low work function alkaline earth metal Sr (strontium) to modulate the performance of LaB6. However, among the alkaline earth metals (Ca, Sr, Ba), Ba has the lowest work function. Australian scholars discovered that adding alkaline earth metal Ba to LaB6 forms (LaxBa... 1-x Polycrystalline B6 can effectively reduce the work function of materials. Compared with the aluminum solvent method, zone melting directional solidification technology has more advantages in preparing high-quality hexaboride single crystals. Ukrainian scholar Balakrishnan prepared high-purity rare earth hexaboride single crystals REB6 (RE = La, Ce, Pr, Nd) using induction zone melting directional solidification technology. However, there is currently no information on the preparation of (La... 0.5 Ba 0.5 Reports on B6 single crystals. In addition, La... 0.5 Ba 0.5 B6 is a ceramic material, and its hardness and brittleness make the hollowing process of the cathode very challenging. Summary of the Invention

[0003] Technical issues

[0004] To address the aforementioned problems in the prior art, the present invention provides a (La) material with high thermal emission performance and high toughness. 0.5 Ba 0.5 B6

[100] -ZrB2 eutectic composite material and its preparation method, (La 0.5 Ba 0.5The B6

[100] -ZrB2 eutectic composite material has high thermal radiation performance and excellent mechanical properties.

[0005] Technical solution

[0006] According to a first aspect of the invention, a (La) is provided 0.5 Ba 0.5 )B6

[100] -ZrB2 eutectic composite material, wherein La 0.5 B 0.5 The molar ratio of B6 to ZrB2 is 2.1:1, (La 0.5 Ba 0.5 ZrB6 is the matrix with a crystal orientation of

[100] ; ZrB2 is the reinforcing phase existing in the form of fibers.

[0007] Preferably, the (La) 0.5 Ba 0.5 The B6

[100] -ZrB2 eutectic composite material was tested at a temperature of 1873 K and a vacuum degree of 2.0 × 10⁻⁶. -5 The highest thermal emission current density measured under closed environmental conditions was 15 A / cm². 2 The above is preferred, 20A / cm. 2 The optimal value is 35A / cm. 2 above.

[0008] Preferably, the (La) 0.5 Ba 0.5 The Vickers hardness of the B6

[100] -ZrB2 eutectic composite material is above 18 GPa, preferably above 20 GPa; the fracture toughness is 3 MPa·m. 1 / 2 The above is preferred, 5MPa·m 1 / 2 The above. More preferably, the (La) 0.5 Ba 0.5 The Vickers hardness of the B6

[100] -ZrB2 eutectic composite material is 18-25 GPa, and the fracture toughness is 3-7 MPa·m. 1 / 2 .

[0009] According to a second aspect of the present invention, a method for preparing the (La) 0.5 Ba 0.5 A method for producing B6

[100] -ZrB2 eutectic composite materials includes the following steps:

[0010] 1) Preparation (La 0.5 Ba 0.5 B6-ZrB2 polycrystalline sample;

[0011] 2) The polycrystalline sample is cut into (La) using an electrical discharge wire cutting machine. 0.5 Ba 0.5The B6-ZrB2 polycrystalline sample was sanded smooth, cleaned, and dried.

[0012] 3) After cleaning (La) 0.5 Ba 0.5 The B6-ZrB2 polycrystalline rod is placed on the upper pull rod as the feeding rod, and the seed crystal LaB6

[100] is fixed on the lower pull rod as the feeding rod. The crystal growth experiment is carried out in a sealed high-purity quartz tube. First, high-purity argon gas is introduced into the tube to clean it. Then, the power is gradually increased to 12-15kW. The upper end of the feeding rod and the lower end of the feeding rod melt simultaneously and are fused together. After the molten zone stabilizes, the pulling system is then run to complete the crystal growth and obtain (LaB6-ZrB2) polycrystalline rod. 0.5 Ba 0.5 B6

[100] -ZrB2 eutectic composite material;

[0013] The crystal growth conditions are as follows: the pressure of flowing argon gas in the quartz tube is 2-3 MPa, the flow rate is 6-8 L / min, the upper and lower rods rotate in opposite directions at a speed of 10-30 rpm, and the growth rate of the upper and lower rods is 15-100 mm / h. Preferably, the growth rate of the upper rod is 20-40 mm / h, and the growth rate of the lower rod is 10-30 mm / h.

[0014] In the actual growth process, adjustments must be made according to the specific circumstances to match the gas flow rate, rotation speed, power, feed rate of the loading rod, and growth rate of the unloading rod, thereby ensuring stable crystal growth. Preferably, the growth rate of the loading rod is 30 mm / h, and the growth rate of the unloading rod is 20 mm / h.

[0015] Preferably, the (La) mentioned in step 1) 0.5 Ba 0.5 The B6-ZrB2 polycrystalline sample was prepared by the following steps:

[0016] 1-1) Lanthanum oxide, barium carbonate, boron carbide, and boron powder are mixed in a molar ratio of 1:2:4:9 and heated at 1400–1800 °C under a vacuum of 10. -2 La particles with a diameter of 10–50 μm were obtained by calcination in a vacuum resistance furnace at Pa. 0.5 Ba 0.5 B6 mixed powder;

[0017] 1-2) Ball mill the ZrB2 powder to a particle size of 10-50 μm; then ball mill the (La) powder to a particle size of 10-50 μm. 0.5 Ba 0.5 B6 powder and ZrB2 powder were mixed in a molar ratio of 2.1:1, with a ball-to-powder ratio of 10:1; then vacuum dried to obtain (La) 0.5 Ba 0.5B6-ZrB2 mixed powder;

[0018] 1-3) Take the (La) obtained in step 1-2) 0.5 Ba 0.5 B6-ZrB2 mixed powder was loaded into a graphite mold and pre-pressed to a pre-pressure of 2–10 MPa. The mold containing the powder was then placed into the furnace chamber of a spark plasma sintering furnace. A vacuum was evacuated to below 20 Pa, and an axial pressure of 40–60 MPa was applied. The heating rate was no more than 80 °C / min. The temperature was raised to 1700–1900 °C and held for 5–10 min. After completion, the sample was removed when the furnace temperature dropped below 50 °C to obtain (La) 0.5 Ba 0.5 )B6-ZrB2 polycrystalline sample.

[0019] Preferably, the cleaning conditions in step 2) are: ultrasonic cleaning in alcohol.

[0020] Preferably, the drying conditions in step 2) are: drying temperature of 50-150℃ and drying time of 8-24h.

[0021] Preferably, the purity of lanthanum oxide, barium carbonate, boron carbide, and boron powder is not less than 99.9%; the purity of the ZrB2 powder is not less than 99.9%.

[0022] According to a third aspect of the invention, a cathode device is provided, comprising the (La) method described in the invention. 0.5 Ba 0.5 B6

[100] -ZrB2 eutectic composite material.

[0023] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0024] (1) Preparation of (La) 0.5 Ba 0.5 B6

[100] -ZrB2 eutectic composite material has high thermal emission performance, which can meet the needs of future high-power and long-life devices;

[0025] (2) Preparation of (La 0.5 Ba 0.5 The B6

[100] -ZrB2 eutectic composite material has high strength and toughness, thus ensuring that the composite material will not be brittle during hollow processing, which greatly expands the application range of the material. Attached Figure Description

[0026] Figure 1 The product prepared according to Example 1 is (La 0.5 Ba 0.5 B6 single crystal as matrix (La) 0.5 Ba0.5 A photograph of the B6-ZrB2 composite material.

[0027] Figure 2 The product prepared according to Example 1 is (La 0.5 Ba 0.5 B6 single crystal as matrix (La) 0.5 Ba 0.5 The XRD pattern of the B6-ZrB2 composite material shows that the crystal has a (100) orientation.

[0028] Figure 3 The product prepared according to Example 1 is (La 0.5 Ba 0.5 B6 single crystal as matrix (La) 0.5 Ba 0.5 Microstructure of B6-ZrB2 composite material.

[0029] Figure 4 The product prepared according to Example 1 is (La 0.5 Ba 0.5 B6 single crystal as matrix (La) 0.5 Ba 0.5 The volt-ampere characteristic curves of the thermal emission properties of B6-ZrB2 composite material. Detailed Implementation

[0030] The present invention will now be described with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. Any modifications and improvements made without altering the inventive concept are within the scope of protection of the present invention.

[0031] The purity of the La2O3 powder and pure B powder in the examples below is not less than 99.9%; the purity of the ZrB2 powder is not less than 99.9%.

[0032] Example 1

[0033] (1) First, lanthanum oxide, barium carbonate, boron carbide, and boron powder are mixed in a molar ratio of 1:2:4:9, and then heated at 1400℃ under a vacuum of 10. -2 La particles with a diameter of 10–50 μm were obtained by calcination in a graphite crucible within a vacuum resistance furnace at Pa. 0.5 Ba 0.5 B6 mixed powder;

[0034] (2) Ball mill the ZrB2 powder to a particle size of 10–50 μm; then ball mill the (La) powder to a particle size of 10–50 μm. 0.5 Ba 0.5(La)B6 powder and ZrB2 powder were mixed in a molar ratio of 2.1:1 and a ball-to-powder ratio of 10:1; then vacuum dried at 100℃ for 12 hours to obtain (La) 0.5 Ba 0.5 B6-ZrB2 mixed powder;

[0035] (3) The obtained mixed powder was loaded into a graphite mold and pre-pressed to a pre-pressure of 8 MPa; then the graphite mold containing the powder was placed into the furnace cavity of a spark plasma sintering furnace, and a vacuum was drawn to a vacuum degree below 20 Pa and an axial pressure of 50 MPa was applied, with a heating rate not exceeding 80 °C / min; the temperature was raised to 1800 °C and held for 5 min; after completion, the sample was removed when the furnace temperature was cooled to below 50 °C to obtain (La 0.5 Ba 0.5 B6-ZrB2 polycrystalline sample;

[0036] (4) The polycrystalline sample was cut into rods with a diameter of 6 mm and a length of 40 mm using an electrical discharge wire cutter. The rods were then polished with sandpaper and ultrasonically cleaned in alcohol for 15 min. Finally, the samples were placed in a vacuum drying oven for drying at 100℃ for 12 h.

[0037] (5) The cleaned polycrystalline rod is placed on the upper pull rod as the feeding rod, and the seed crystal LaB6

[100] is fixed on the lower pull rod as the feeding rod. The crystal growth experiment is carried out in a sealed high-purity quartz tube. First, high-purity argon gas is introduced into the tube to clean it. Then, the power is gradually increased to 13.5kW. The upper end of the feeding rod and the lower end of the feeding rod melt at the same time and are fused together. After the molten zone is stable, the pulling system is then run to complete the crystal growth. During the crystal growth process, the pressure of the flowing argon gas in the quartz tube is 2MPa and the flow rate is 7L / min. The upper and lower feeding rods rotate in opposite directions at a speed of 20rpm. The growth rate of the feeding rod is 30mm / h and the growth rate of the feeding rod is 20mm / h.

[0038] Figure 1 The matrix prepared according to Example 1 is a single crystal (La). 0.5 Ba 0.5

[100] -ZrB2 eutectic composite material physical photos, from Figure 1 The material surface is smooth, with no trace of gas or impurities. The crystal diameter is Ф5mm and the length is 40mm.

[0039] Figure 2 The XRD pattern of this matrix shows no impurity peaks and the matrix is ​​

[100] oriented.

[0040] Figure 3 The microstructure of the composite material shows that only the matrix (La)0.5 Ba 0.5 )B6 and reinforcing phase ZrB2 fibers.

[0041] Figure 4 The figure shows the thermal emission volt-ampere characteristic curves, where the temperature is 1873 K and the vacuum degree is 2.0 × 10⁻⁶. -5 The composite material achieved a maximum thermal emission current density of 41.63 A / cm² under a closed environment with a voltage range of 2000–4000 V. 2 This is significantly higher than the 16.3 A / cm² of LaB6-ZrB2 eutectic composites reported in the literature. 2 This material was prepared using induction melting technology. Its mechanical properties were measured and calculated; its Vickers hardness was 23.43 GPa, and its fracture toughness was 6.21 MPa. 1 / 2 .

[0042] Example 2

[0043] (1) First, lanthanum oxide, barium carbonate, boron carbide, and boron powder are mixed in a molar ratio of 1:2:4:9, and then heated at 1600℃ under a vacuum of 10. -2 La particles with a diameter of 10–50 μm were obtained by calcination in a graphite crucible within a vacuum resistance furnace at Pa. 0.5 Ba 0.5 B6 mixed powder;

[0044] (2) Ball mill the ZrB2 powder to a particle size of 10–50 μm; then ball mill the (La) powder to a particle size of 10–50 μm. 0.5 Ba 0.5 (La)B6 powder and ZrB2 powder were mixed in a molar ratio of 2.1:1 and a ball-to-powder ratio of 10:1; then vacuum dried at 100℃ for 12 hours to obtain (La) 0.5 Ba 0.5 B6-ZrB2 mixed powder;

[0045] (3) The obtained mixed powder was loaded into a graphite mold and pre-pressed to a pre-pressure of 5 MPa; then the graphite mold containing the powder was placed into the furnace cavity of a spark plasma sintering furnace, and a vacuum was drawn to a vacuum degree below 20 Pa and an axial pressure of 40 MPa was applied, with a heating rate not exceeding 80 °C / min; the temperature was raised to 1700 °C and held for 5 min; after completion, the sample was removed when the furnace temperature was cooled to below 50 °C to obtain (La 0.5 Ba 0.5 B6-ZrB2 polycrystalline sample;

[0046] (4) The polycrystalline sample was cut into rods with a diameter of 6 mm and a length of 40 mm using an electrical discharge wire cutter. The rods were then polished with sandpaper and ultrasonically cleaned in alcohol for 15 min. Finally, the samples were placed in a vacuum drying oven for drying at 100℃ for 12 h.

[0047] (5) The cleaned polycrystalline rod is placed on the upper pull rod as the loading rod, and the seed crystal LaB6

[100] is fixed on the lower pull rod as the unloading rod. The crystal growth experiment is carried out in a sealed high-purity quartz tube. First, high-purity argon gas is introduced into the tube to clean it. Then, the power is gradually increased to 14.0kW. The upper end of the unloading rod and the lower end of the loading rod melt simultaneously and are welded. After the molten zone is stable, the pulling system is run to complete the crystal growth. During the crystal growth process, the pressure of the flowing argon gas in the quartz tube is 2MPa, the flow rate is 6L / min, the upper and lower rods rotate in opposite directions at a speed of 10rpm, the growth rate of the loading rod is 60mm / h, and the growth rate of the unloading rod is 50mm / h. Under these parameters, (La) 0.5 Ba 0.5

[100] -ZrB2 eutectic composite material at a temperature of 1873 K and a vacuum degree of 2.0 × 10⁻⁶ -5 The highest thermal emission current density at 2000–4000 V in a closed environment is 25.24 A / cm². 2 Its mechanical properties were measured and calculated; its Vickers hardness was 21.67 GPa, and its fracture toughness was 5.04 MPa. 1 / 2 .

[0048] Example 3

[0049] (1) First, lanthanum oxide, barium carbonate, boron carbide, and boron powder are mixed in a molar ratio of 1:2:4:9, and then heated at 1800℃ under a vacuum of 10. -2 La particles with a diameter of 10–50 μm were obtained by calcination in a graphite crucible within a vacuum resistance furnace at Pa. 0.5 Ba 0.5 B6 mixed powder;

[0050] (2) Ball mill the ZrB2 powder to a particle size of 10–50 μm; then ball mill the (La) powder to a particle size of 10–50 μm. 0.5 Ba 0.5 (La)B6 powder and ZrB2 powder were mixed in a molar ratio of 2.1:1 and a ball-to-powder ratio of 10:1; then vacuum dried at 100℃ for 12 hours to obtain (La) 0.5 Ba 0.5 B6-ZrB2 mixed powder;

[0051] (3) The obtained mixed powder was loaded into a graphite mold and pre-pressed to a pre-pressure of 2 MPa; then the graphite mold containing the powder was placed into the furnace cavity of a spark plasma sintering furnace, and a vacuum was drawn to a vacuum degree below 20 Pa and an axial pressure of 40 MPa was applied, with a heating rate not exceeding 80℃ / min; the temperature was raised to 1900℃ and held for 10 min; after completion, the sample was removed when the furnace temperature was cooled to below 50℃, and (La) was obtained. 0.5 Ba 0.5 B6-ZrB2 polycrystalline sample;

[0052] (4) The polycrystalline sample was cut into rods with a diameter of 6 mm and a length of 40 mm using an electrical discharge wire cutter. The rods were then polished with sandpaper and ultrasonically cleaned in alcohol for 15 min. Finally, the samples were placed in a vacuum drying oven for drying at 100℃ for 12 h.

[0053] (5) The cleaned polycrystalline rod is placed on the upper pull rod as the loading rod, and the seed crystal LaB6

[100] is fixed on the lower pull rod as the unloading rod. The crystal growth experiment is carried out in a sealed high-purity quartz tube. First, high-purity argon gas is introduced into the tube to clean it. Then, the power is gradually increased to 14.5kW. The upper end of the unloading rod and the lower end of the loading rod melt at the same time and are welded together. After the molten zone is stable, the pulling system is run to complete the crystal growth. During the crystal growth process, the pressure of the flowing argon gas in the quartz tube is 23MPa, the flow rate is 6L / min, the upper and lower rods rotate in opposite directions at a speed of 10rpm, the growth rate of the loading rod is 100mm / h, and the growth rate of the unloading rod is 30mm / h. Under these parameters, (La) 0.5 Ba 0.5

[100] -ZrB2 eutectic composite material at a temperature of 1873K, a voltage of 3000V, and a vacuum degree of 2.0×10⁻⁶ -5 The highest thermal emission current density of the composite material in a closed environment at Pa is 15.21 A / cm². 2 Its mechanical properties were measured and calculated; its Vickers hardness was 19.37 GPa, and its fracture toughness was 3.19 MPa·m. 1 / 2 .

[0054] The above are merely preferred embodiments of the present invention and are 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 protection scope of the present invention.

Claims

1. A kind of (La) 0.5 Ba 0.5 )B6[100]-ZrB2 eutectic composite material, wherein La 0.5 B 0.5 The molar ratio of B6 to ZrB2 is 2.1:1, (La 0.5 Ba 0.5 ZrB6 is the matrix with a crystal orientation of [100]; ZrB2 is the reinforcing phase existing in the form of fibers.

2. The (La) according to claim 1 0.5 Ba 0.5 B6[100]-ZrB2 eutectic composite material, wherein, The (La) 0.5 Ba 0.5 The B6[100]-ZrB2 eutectic composite material was tested at a temperature of 1873 K and a vacuum degree of 2.0 × 10⁻⁶. -5 The thermal emission current density measured under closed environmental conditions of Pa and voltages of 2000–4000 V is 15 A / cm². 2 above.

3. The (La) according to claim 2 0.5 Ba 0.5 B6[100]-ZrB2 eutectic composite material, wherein, The (La) 0.5 Ba 0.5 The B6[100]-ZrB2 eutectic composite material was tested at a temperature of 1873 K and a vacuum degree of 2.0 × 10⁻⁶. -5 The thermal emission current density measured under closed environmental conditions of Pa and voltages of 2000–4000 V is 20 A / cm². 2 above.

4. The (La) according to claim 2 0.5 Ba 0.5 B6[100]-ZrB2 eutectic composite material, wherein, The (La) 0.5 Ba 0.5 The B6[100]-ZrB2 eutectic composite material was tested at a temperature of 1873 K and a vacuum degree of 2.0 × 10⁻⁶. -5 The thermal emission current density measured under closed-environment conditions of 2000~4000V was 35A / cm². 2 above.

5. (La) according to any one of claims 1 to 4 0.5 Ba 0.5 B6[100]-ZrB2 eutectic composite material, wherein, The (La) 0.5 Ba 0.5 The Vickers hardness of the B6[100]-ZrB2 eutectic composite material is above 18 GPa; the fracture toughness is 3 MPa·m. 1 / 2 above.

6. The (La) according to claim 5 0.5 Ba 0.5 B6[100]-ZrB2 eutectic composite material, wherein, The (La) 0.5 Ba 0.5 The Vickers hardness of the B6[100]-ZrB2 eutectic composite material is above 20 GPa; And / or, the (La) 0.5 Ba 0.5 The fracture toughness of the B6[100]-ZrB2 eutectic composite material is 5 MPa·m. 1 / 2 above.

7. A method for preparing (La) according to any one of claims 1 to 6 0.5 Ba 0.5 A method for producing B6[100]-ZrB2 eutectic composite materials includes the following steps: 1) Preparation (La 0.5 Ba 0.5 B6-ZrB2 polycrystalline sample; 2) The polycrystalline sample is cut into (La) using an electrical discharge wire cutter. 0.5 Ba 0.5 The B6-ZrB2 polycrystalline sample was sanded smooth, cleaned, and dried. 3) After cleaning (La) 0.5 Ba 0.5 The B6-ZrB2 polycrystalline rod is placed on the upper pull rod as the feeding rod, and the seed crystal LaB6[100] is fixed on the lower pull rod as the feeding rod. The crystal growth experiment is carried out in a sealed high-purity quartz tube. First, high-purity argon gas is introduced into the tube to clean it. Then, the power is gradually increased to 12~15kW. The lower end of the feeding rod and the upper end of the feeding rod melt simultaneously and are fused together. After the molten zone stabilizes, the pulling system is then run to complete the crystal growth and obtain (LaB6-ZrB2) polycrystalline rod. 0.5 Ba 0.5 B6[100]-ZrB2 eutectic composite material; in, The crystal growth conditions are as follows: the pressure of flowing argon gas in the quartz tube is 2-3 MPa, the flow rate is 6-8 L / min, the upper and lower feed rods rotate in opposite directions at a speed of 10-30 rpm, and the growth rate of the upper and lower feed rods is 15-100 mm / h.

8. The preparation of the (La) according to claim 7 0.5 Ba 0.5 The method for producing B6[100]-ZrB2 eutectic composite materials, wherein, The growth rate of the feeding bar is 20~40 mm / h, and the growth rate of the unloading bar is 10~30 mm / h.

9. The preparation of the (La) according to claim 7 or 8 0.5 Ba 0.5 The method for producing B6[100]-ZrB2 eutectic composite materials, wherein, The growth rate of the feed bar is 30 mm / h, and the growth rate of the discharge bar is 20 mm / h.

10. The preparation of the (La) according to claim 7 or 8 0.5 Ba 0.5 The method for producing B6[100]-ZrB2 eutectic composite materials, wherein, The (La) mentioned in step 1) 0.5 Ba 0.5 The B6-ZrB2 polycrystalline sample was prepared by the following steps: 1-1) Lanthanum oxide, barium carbonate, boron carbide, and boron powder are mixed in a molar ratio of 1:2:4:9 and heated at 1400~1800℃ under a vacuum of 10. -2 La particles with a diameter of 10–50 μm were obtained by calcination in a vacuum resistance furnace under Pa conditions. 0.5 Ba 0.5 B6 powder; 1-2) Ball mill the ZrB2 powder to a particle size of 10-50 μm; then ball mill the (La) powder to a particle size of 10-50 μm. 0.5 Ba 0.5 B6 powder and ZrB2 powder were mixed in a molar ratio of 2.1:1, with a ball-to-powder ratio of 10:1; then vacuum dried to obtain (La) 0.5 Ba 0.5 B6-ZrB2 mixed powder; 1-3) Take the (La) obtained in step 1-2) 0.5 Ba 0.5 B6-ZrB2 mixed powder was loaded into a graphite mold and pre-pressed to a pre-pressure of 2–10 MPa. The graphite mold containing the powder was then placed into the furnace chamber of a spark plasma sintering furnace. A vacuum was evacuated to below 20 Pa, and an axial pressure of 40–60 MPa was applied. The heating rate was no more than 80 °C / min. The temperature was raised to 1700–1900 °C and held for 5–10 min. After completion, the sample was removed when the furnace temperature cooled to below 50 °C, yielding (La) 0.5 Ba 0.5 )B6-ZrB2 polycrystalline sample.

11. The preparation of the (La) according to claim 7 or 8 0.5 Ba 0.5 The method for producing B6[100]-ZrB2 eutectic composite materials, wherein, The cleaning conditions in step 2) are: ultrasonic cleaning in alcohol.

12. The preparation of the (La) according to claim 11 0.5 Ba 0.5 The method for producing B6[100]-ZrB2 eutectic composite materials, wherein, The drying conditions in step 2) are: drying temperature of 50~150℃ and drying time of 8~24h.

13. The preparation of the (La) according to claim 10 0.5 Ba 0.5 The method for producing B6[100]-ZrB2 eutectic composite materials, wherein, The purity of lanthanum oxide, barium carbonate, boron carbide, and boron powder is not less than 99.9%; the purity of the ZrB2 powder is not less than 99.9%.

14. A cathode device comprising (La) according to any one of claims 1 to 6. 0.5 Ba 0.5 B6[100]-ZrB2 eutectic composite material.

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