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A kind of preparation method of electronic compound c12a7:e single crystal

An electronic compound and single crystal technology, applied in the field of preparing C12A7:e-single crystal materials, can solve the problems of limiting practical application, reducing the purity of single crystals, reducing the emission current density, etc., and achieving the effects of large size, reduced energy consumption, and high quality

Inactive Publication Date: 2018-03-30
BEIJING UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] Currently, C12A7 is usually prepared by the pulling method: e - single crystal, but this method is easy to introduce impurity elements during the preparation process, which reduces the purity of the single crystal, thereby reducing the emission current density and limiting its practical application

Method used

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  • A kind of preparation method of electronic compound c12a7:e single crystal
  • A kind of preparation method of electronic compound c12a7:e single crystal
  • A kind of preparation method of electronic compound c12a7:e single crystal

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0033] 1) CaCO 3 Powder, Al 2 o 3 The powder is mixed evenly by mechanical ball milling at a molar ratio of 12:7, then loaded into a graphite mold, and placed in SPS for sintering. Sintering conditions: the total pressure in the cavity is lower than 8Pa; the heating rate is 60°C / min, and the holding temperature is 1000°C. The holding time is 15 minutes, and the furnace is cooled to room temperature to obtain CaO-Al 2 o 3 Enter step 2 after the polycrystalline rod);

[0034] 2) Sinter SPS to obtain CaO-Al with a diameter of 8mm 2 o 3 The polycrystalline rods are seed crystals and material rods, and the first zone melting is carried out in an optical zone melting furnace. Zone melting conditions: the equipment is evacuated to below 1Pa, and argon gas is injected at a gas flow rate of 0.2L / min to raise the air pressure to 0.5MPa. In order to make the melting zone more uniform, the seed crystal and the rod are rotated in reverse at a speed of 25rpm, the power of the furnace...

Embodiment 2

[0038] 1) CaCO 3 Powder, Al 2 o 3 The powder is mixed evenly by mechanical ball milling at a molar ratio of 12:7, then loaded into a graphite mold, placed in SPS for sintering, sintering conditions: the total pressure in the cavity is lower than 8Pa; the heating rate is 70°C / min, and the holding temperature is 1020°C. The holding time is 17 minutes, and the furnace is cooled to room temperature to obtain CaO-Al 2 o 3 Enter step 2 after the polycrystalline rod);

[0039] 2) Sinter SPS to obtain CaO-Al with a diameter of 10mm 2 o 3 Polycrystalline rods are used as seed crystals and material rods, and the first zone melting is carried out in an optical zone melting furnace. Zone melting conditions: the equipment is evacuated to below 1Pa, and argon gas is injected at a gas flow rate of 0.4L / min to raise the air pressure to 0.5MPa. In order to make the melting zone more uniform, the seed crystal and the rod are rotated in reverse at a speed of 25rpm, the power of the furnac...

Embodiment 3

[0043] 1) CaCO 3 Powder, Al 2 o 3 The powder is mixed evenly by mechanical ball milling at a molar ratio of 12:7, then loaded into a graphite mold, placed in SPS for sintering, sintering conditions: the total pressure in the cavity is lower than 8Pa; the heating rate is 80°C / min, and the holding temperature is 1030°C. The holding time is 20 minutes, and the furnace is cooled to room temperature to obtain CaO-Al 2 o 3 Enter step 2 after the polycrystalline rod);

[0044] 2) Sinter SPS to obtain CaO-Al with a diameter of 12mm 2 o 3 Polycrystalline rods are used as seed crystals and material rods, and the first zone melting is carried out in an optical zone melting furnace. Zone melting conditions: the equipment is evacuated to below 1Pa, and argon gas is injected at a gas flow rate of 0.6L / min to raise the air pressure to 0.5MPa. In order to make the melting zone more uniform, the seed crystal and the rod are rotated in reverse at a speed of 25rpm, the power of the furnac...

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Abstract

The invention relates to a preparation method of an electron compound C12A7:e<-> single crystal, and belongs to the technical field of cathode materials. The electron compound C12A7:e<-> attracts more attention due to low work function, but the study on the preparation technique and electron transmission of the single crystal of the electron compound C12A7:e<-> is little; the current preparation technology is complicated, the quality of the single crystal is poorer, and the large-scale application is difficult. The preparation method has the advantages that the large-size high-purity and high-quality C12A7:e<-> single crystal is prepared by SPS (spark plasma sintering), optical floating zone smelting and active matter reduction methods under the high-vacuum environment; by using CaCO3 (calcium carbonate) powder and Al2O3 (aluminum oxide) powder as initial raw materials, the prepared high-purity, high-quality and large-size C12A7:e<-> single crystal is in a cylinder shape with size of (phi8-15)mm*(20-30)mm; after proofing by testing results of a single-crystal diffractometer, the quality of the single crystal is good, the crystal twinning is avoided, and the carrier concentration at room temperature is 6.6*10<19>cm<-3>.

Description

technical field [0001] The invention belongs to the technical field of cathode electron emission materials, and in particular relates to a method for preparing C12A7:e by using an optical zone smelting method. - Methods for single crystal materials. Background technique [0002] C12A7 as 12CaO·7Al 2 o 3 The abbreviation of is in the form of porous ceramic crystals and belongs to the mayenite system. by Rankin and Wright in 1915 using CaO and Al 2 o 3 synthesized, and determined by Eitel and Bussem that CaO-Al 2 o 3 The molar ratio is 12:7, [Ca 24 al 28 o 64 ] 4+ +2O 2- to represent the chemical formula of a unit cell, the free O in C12A7 2- with the positively charged [Ca 24 al 28 o 64 ] 4+ The frames are loosely bound, which leads to free O in some cases 2- It is easy to migrate to other places and be easily replaced by other negative ions to generate various C12A7 derivatives. The common substitution ions are O - , H - , F - , Cl - ,OH - etc., and the...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C30B13/00C30B29/22
CPCC30B13/00C30B29/22
Inventor 张久兴江浩张忻刘燕琴刘洪亮
Owner BEIJING UNIV OF TECH
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