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Method to improve current transport in YBCO accross high angle grain boundaries by diffusing Ca into the YBCO from a Ca-containing buffer

IP.com Disclosure Number: IPCOM000019659D
Publication Date: 2003-Sep-24
Document File: 1 page(s) / 53K

Publishing Venue

The IP.com Prior Art Database

Related People

Suresh Annavarapu: INVENTOR [+2]

Abstract

The general purpose of this approach is to improve current transport across high angle grain boundaries in YBCO films grown for use in high-temperature superconductors. Typically, the critical current of YBCO films grown on biaxially textured substrates (RABiTS or IBAD or similar) is limited by the presence of high angle grain boundaries i.e. boundaries separating grains misoriented by greater than 5°.

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Method to improve current transport in YBCO across high angle grain boundaries by diffusing Ca into the YBCO from a Ca-containing buffer

     The general purpose of this approach is to improve current transport across high angle grain boundaries in YBCO films grown for use in high-temperature superconductors. Typically, the critical current of YBCO films grown on biaxially textured substrates (RABiTS or IBAD or similar) is limited by the presence of high angle grain boundaries i.e. boundaries separating grains misoriented by greater than 5°.

This approach involves the use of Ca-containing barrier such as CaO-stabilized ZrO2 or CaO-doped MgO or CaO doped SrTiO3. The advantage of using a CaO-doped barrier is that the layer in contact with YBCO viz. CeO2 will not initially contain any Ca so that YBCO can be nucleated without Ca contamination, and that Ca can penetrate the YBCO grain boundaries only after diffusing through the CeO2 layer. A review of CeO2-CaO phase diagram indicates a terminal solid solution of cubic CeO2 up to 8 mol% of CaO at 1200C, so that Ca should be able to diffuse through the CeO2 layer without destabilizing it. In the case of CaO-doped MgO, it has been documented in literature that Ca segregates preferentially to (100) surfaces in MgO on annealing at about 900C, so that 20% of the surface is composed of Ca ions. This should provide a strong driving force diffusion of Ca into and through the cap layer (CeO2 or SrTiO3). During YBCO processing, the s...