Control of YBCO growth at the compact substrate interface by bottom seeding and Yb2O3 coating in seeded melt-growth processed YBCO oxides using a MgOsubstrate

Effects of a seeding technique and surface coating with Yb2O3 powder on the growth of YBCO grains at the compact/substrate (a MgO single crystal) inte rfaces were studied. Zn a single top-seeded sample without Yb2O3 coating, s everal YBCO grains nucleated at the compact/substrate interface. In a doubl e seeded (top and bottom) sample without Yb2O3 coating, YBCO grains nucleat ed both at the bottom seed and MgO substrate competitively, resulting in pa rtial texturing of YBCO grains at the bottom. Applying a double seeding tec hnique with Yb2O3 coating both at the compact/MgO interface and sample surf aces inhibited the undesirable subsidiary YBCO nucleation at both the surfa ces and interfaces, resulting in the growth of a single YBCO grain. As a re sult of the suppression of subsidiary Y123 nucleation, a magnetic levitatio n force of the sample bottom was improved significantly. (C) 1999 Elsevier Science B.V. All rights reserved.