Differences in the thermal stability ofREBa2Cu3O7 − x (RE = Y, Nd) thin films investigated by high temperature in situ observation and melt-texturegrowth

Abstract

Following the increasing interest in the high thermal stability ofREBa2Cu3O7 − x (RE-123,RE = rare earth) thin films as seed materials, thermal stabilities of Y-123 and Nd-123 thin films wereinvestigated by two methods: high temperature in situ microscopy and the melt growthprocess. A monotonic dependence of thermal stability on RE solubility in the Ba–Cu–Oliquid was observed. The thermal stability of RE-123 films was found to strongly depend onthe melting growth process, which is predominated by the melting rate of the RE-123phase. Under the assumption of quasi-equilibrium, a simplified model of solutetransport was suggested. The correlation between the solute inflow and outflowindicates that the melting rate of RE-123 is proportional to the growth rate of theRE2BaCuO5 (RE-211) phase and the ratio of the concentration difference between the RE-211 growthfront and the RE-123 melting border. We conclude that an Nd-123 thin film is moreunstable than a Y-123 thin film because of the higher melting rate, resulting from a highergrowth rate of the RE-211 phase and a higher concentration difference ratio.