The qualitative change in decomposition ofc-oriented Sm-123 films due to a minor change in substitution ofa-oriented grains

Abstract

Decomposition of SmBa2Cu3Ox (Sm-123) films deposited on MgO substrates was in situ observed by high-temperature optical microscopy. The films were detected to be predominantly c-axis oriented, with highly fourfold symmetry. It was observed that a minor change in the a-axis-oriented grains percentage had a strong effect on the thermal stability of the films and the melting mode. In the case of nearly 1% of a-oriented grains, the decomposition temperature of the SmBCO film was above the peritectic temperature (Tp), showing a high thermal stability. The peritectic product of the Sm2BaCuO5 (Sm-211) phase exhibited the preferential orientation of [0 0 1] parallel to [1 1 0] of the Sm-123 matrix. On the other hand, when substitution of a-axis-oriented grains increased up to 3% or more, the decomposition temperature of the Sm-123 film dropped below Tp. Interestingly, in the latter case, the Sm-211 phase had an epitaxial relation with Sm-123 as Sm-211[0 0 1]//Sm-123 [1 0 0] or Sm-211[0 0 1]//Sm-123[0 1 0], distinctly different from that mentioned above. In this paper the melting behaviour and its mechanisms, together with the epitaxial orientation of Sm-211 grains in Sm-123 thin films, are studied in detail by means of the interface-energy analysis.

Growth condition related orientation transition for YBa2Cu3O7−δ films on NdGaO3 substrate

“…On the one hand, according to the nucleation approach, the stability of grains depends mainly on the surface energy and the interface energy. For the YBCO system, because of the lower surface energy and better lattice match with the (110) NGO substrate [19,[23][24][25], the c-oriented film is more stable as compared to the a-oriented one. To be specific, the energy well of c-phase is deeper than that of a-phase.…”

YBCO-buffered NdBCO film with higher thermal stability in seeding REBCO growth

“…7,12,13 It is evident that the NdBCO/YBCO/MgO thin film possesses a higher superheating upper limit. More importantly, using a higher T max in the MT process is of great assistance in growing large-size and high-performance REBCO bulks.…”

“…Table 1 , 1090 °C 11 and 1098~1100 °C 7,12,13 (the difference in the upper-limit temperature is due to different furnace conditions or temperature criterion) respectively, which are in a rising trend corresponding to the increasing T p for YBCO, SmBCO and NdBCO. What is more, the film structure affects the T max significantly, as the T max for…”

Peritectic melting of thin films, superheating and applications in growth of REBCO superconductors

“…Therefore, it is necessary to study the thermal stability of the c-axis oriented REBCO thin films with various concentrations of a-axis oriented grains. Cheng et al have performed an in-situ research on the out-of-plane effect on the thermal stability as well as melting behaviors of the thin film [36].…”

“…Optical micrographs showing the melting process of the films A and B: (a-c) for film A at 1100°C just achieved, at 1100°C after 3 min, and at 1130°C after 5 min, respectively. (e-f) for film B at 1041°C just achieved, at 1050°C just achieved, and at 1065°C after 3 min, respectively [36]. preferential orientation with respect to h1 0 0i of the MgO substrate, i.e., Sm211h0 0 1i//Sm123h1 10i// MgOh1 10i, denoted as 45°Sm211.…”