Growth rate of YBCO-Ag superconducting single grains

International Cryogenic Materials Conference 2017

Congreve, J.V.J.^1 ; Shi, Y.H.^1 ; Dennis, A.R.^1 ; Durrell, J.H.^1 ; Cardwell, D.A.^1

Department of Engineering, University of Cambridge, Cambridge, 1PZ, United Kingdom^1

关键词: Brittle ceramic materials;    Bulk superconductors;    Continuous cooling;    Isothermal holding;    Processing variables;    Related variables;    Superconducting properties;    Top-seeded melt growths;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/279/1/012027/pdf
DOI  :  10.1088/1757-899X/279/1/012027

来源: IOP

【 摘 要 】

The large scale use of (RE)Ba2Cu3O7bulk superconductors, where RE=Y, Gd, Sm, is, in part, limited by the relatively poor mechanical properties of these inherently brittle ceramic materials. It is reported that alloying of (RE)Ba2Cu3O7with silver enables a significant improvement in the mechanical strength of bulk, single grain samples without any detrimental effect on their superconducting properties. However, due to the complexity and number of inter-related variables involved in the top seeded melt growth (TSMG) process, the growth of large single grains is difficult and the addition of silver makes it even more difficult to achieve successful growth reliably. The key processing variables in the TSMG process include the times and temperatures of the stages within the heating profile, which can be derived from the growth rate during the growth process. To date, the growth rate of the YBa2Cu3O7-Ag system has not been reported in detail and it is this lacuna that we have sought to address. In this work we measure the growth rate of the YBCO-Ag system using a method based on continuous cooling and isothermal holding (CCIH). We have determined the growth rate by measuring the side length of the crystallised region for a number of samples for specified isothermal hold temperatures and periods. This has enabled the growth rate to be modelled and from this an optimized heating profile for the successful growth of YBCO-Ag single grains to be derived.