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Mg(1-x)Ca(x)B2 (0<x<0.07) series compounds and preparation method thereof

A compound and a series of technologies, applied in the field of Mg1-xCaxB2 compounds and their preparation, can solve the problems of difficult to obtain and form compounds

Inactive Publication Date: 2008-01-09
YANSHAN UNIV
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  • Abstract
  • Description
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Problems solved by technology

Due to Ca 2+ The radius of (0.99 Ȧ) is much larger than that of Mg 2+ radius (0.66 Ȧ) and CaB 2 The difficult formation of the compound makes Ca-doped MgB 2 Compounds are difficult to obtain under normal pressure

Method used

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  • Mg(1-x)Ca(x)B2 (0&lt;x&lt;0.07) series compounds and preparation method thereof

Examples

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Embodiment

[0011] Weigh 0.02g, 0.03g and 0.21g of Mg powder, Ca 3 B 2 N 4 Powder and B powder were thoroughly mixed and ground under Ar atmosphere. Prepress the mixed powder into a cylindrical sample 1 with a diameter of 8 mm and a thickness of 5 mm, and wrap it with tantalum foil 2. Since tantalum is an inert metal, it can be used to protect the sample and better isolate the sample from the outside world. Prevent sample contamination during high temperature and high pressure experiments. Put the sample 1 wrapped with tantalum foil into the pyrophyllite tube 5, seal the two ends with pyrophyllite sheets 4, and put them flush with the pyrophyllite tube 5, and put them into the graphite heating crucible 6 together. The pyrophyllite tube 5 and the pyrophyllite sheet 4 serve as pressure transmission medium and play the role of insulation and heat conduction. The graphite crucible 6 functions as a heating furnace. Put the loaded graphite crucible into the pyrophyllite block 3 containing ...

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Abstract

This invention relates to a group of series compounds (Mg1-xCaxB2, wherein 0<x<0.07). Its characteristics are: having the hexagonal structure same as that as MgB2, the lattice constants a and c values being monotone increased as the content of Ca being increased; and the superconducting transition temperature being monotone decreasing as the content of Ca being increased. The production procedures are: the raw materials Mg, B and Ca3B2N4 (as calcium source) are proportionally mixed, then pressed into sheets (1), being enclosed by tantalum sheets (2), then placed in graphite heating tubes (5) which being then placed in high pressure chamber, increasing the pressure to 4-5 GPa, then increasing the temperature to 1000-1200deg.C, keeping the same for 0.5-1hrs, lowing to room temperature, then decreasing the pressure to obtain the inventive product.

Description

technical field [0001] The invention relates to a superconducting material and a preparation method thereof, in particular to a Mg 1-x Ca x B 2 (0<x<0.07) compounds and methods for their preparation. Background technique [0002] Searching for superconductors with higher critical transition temperatures through chemical doping has always been the focus of attention. For MgB 2 Superconductors are no exception. Although MgB 2 has a simple crystal structure, but a large number of experiments have shown that in MgB 2 Doping with chemical elements is very difficult. The two experimentally successful cases are chemical doping in which Al replaces Mg sites and C replaces B sites, and the critical transition temperature Tc shows a downward trend. MgB 2 As a superconductor in the BCS theoretical framework, one of the main characteristics is its critical transition temperature T c Decreases linearly with increasing pressure. Therefore, the scientists predicted that the...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C04B35/58C04B35/645H01B12/00B01J3/06
CPCY02E40/64Y02E40/60
Inventor 田永君孙雅馨于栋利柳忠元徐波何巨龙
Owner YANSHAN UNIV
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