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Impact on the TS-MTG single domain YBCO superconducting bulk properties of doped nanoparticles

Author: GaoPing
Tutor: ChaoZuoXu
School: Shaanxi Normal University
Course: Condensed Matter Physics
Keywords: single domain YBCO superconductor melt texture growth Y2Ba4CuBiOx nanoparticle Bi2O3 doped levitation force
CLC: TM26
Type: Master's thesis
Year: 2011
Downloads: 44
Quote: 1
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Abstract

In the last twenty years, the High-temperature YBCO superconductor material has made considerable progress and it has been used in many fields. The top seeded melt texture growth (TSMTG) technique is one of the most important methods. In order to achieve superconductors with large and high quality, today, scientists are mainly using nanometer-materials doping to improve properties of YBCO superconductor through introducing more magnetic flux pinning centers.In this paper, we prepared YBCO bulk superconductor with different addition of Y2Ba4CuBiOy (YBi2411)by TSMTG on the basis of successful preparation of YBi2411 powder. Meanwhile, the top surface morphology, levitation force and microstructure were analyzed; Secondly, We successfully prepared the YBCO bulk superconductor doped with Bi2O3, then the surface morphology, levitation force and microstructure were investigated. Besides, the influence of the temperature parameters on the properties and morphology of YBCO superconductors have also been studied.Firstly, YBi2411 powder were prepared by solid-state sintering, and its general synthesis temperature range (nearly 950℃) was found; Then, the newly prepared powders were carlined at five different temperature of 950℃、960℃、970℃、980℃and 990℃, respectively; Thirdly, it was found that pure powder of YBi2411 could be synthesized at 980℃through XRD analysis..For the YBi2411 doped YBCO bulk superconductor, we studied the morphology and the magnetic force. It indicated that up to the whole size of the single domain YBCO bulks can be fabricated when YBi2411 addition x<8wt%; When x>8wt%, the single domain area is reduced and random nucleations are difficult to be depressed, When the doping ratio reaches 20wt%, it appears no crystal growth morphology. Besides, the levitation forces present first increases and then decreases along with the increasing of additions. The largest levitation force of the sample can be obtained with x=8wt%, because there is a reasonable ration among the superconducting phase, Y211 and YBi2411 phases.It is found that namometer YBi2411 particles (φ100nm-200nm) uniformly scattered in Y123 matrix, and nanoparticles increased caused the formed Y2411/Y123 interface area increased, which caused the increasing of magnetic flux pinning centers, so maglev performance improved. The levitation force is decreasing with the increases of YBi2411 addition because reduction of the superconducting volume in the samples.Bi2O3 doped single domain YBCO bulk superconductors have been fabricated and investigated based on the precursors of Y123:Y211:=1:0.4. Up to the whole size of the single domain YBCO bulks can be fabricated when Bi2O3 addition is less than 1.5wt%; there is only a little square around seed with the doping ratio of 2wt%; When Bi2O3 doping ratio exceeds to 2wt%, it appears no crystal growth morphology. It is found that the levitation forces present first increases and then decreases along with the increasing of Bi2O3 additions. The largest levitation force of the sample can be obtained with doping ratio of 1.5wt%. The SEM analysis shows that YBi2411 nanoparticles can also be formed with Bi2O3 doped, but present uneven distribution. Nano-YBi2411 particles which provide effective magnetic flux pinning centers are formed when Bi2O3 doping ratio below 1.5wt%. The levitation force increases with the increasing Bi2O3, but the YBi2411 particles are coarsening when the Bi2O3 addition exceeds to 1.5wt%, and result in a decreasing of levitation force. The influence of the temperature parameters on morphology of YBCO superconductors have also been studied.It is found that the optimal Tmax is 1040℃, the suitable growth temperature window is 1023℃～980℃.

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