Growth of Highly Epitaxial YBa2Cu3O(7-δ) Films from a Simple Propionate-Based Solution

Intensive investigations have been conducted to develop epitaxial oxide thin films with superior electromagnetic performance by low-cost chemical solution deposition routes. In this paper, a novel propionate-based precursor solution without involving any other additive was proposed and employed to grow superconducting YBa2Cu3O(7-δ) (YBCO) films on LaAlO3 (LAO) single crystals. The precursor solutions are stable with a long shelf life of up to several months. Since the primary compositions are propionates after evaporating the solvent, the toxic reagents and evolved gases during solution synthesis and heat treatment can be eliminated completely. In this process, rapid pyrolysis and high conversation rate can also be achieved during growth of YBCO films in comparison with the conventional trifluoroacetate metal organic deposition routes. Remarkably, a 210 nm YBCO film exhibits high superconducting performance with a Jc value of 3.7 MA/cm(2) at 77 K, self-field. Nucleation and growth behaviors in the chemical solution process have also been studied. It is revealed that the amount of liquid phase (Ba-Cu-O) is sufficient through the entire thickness within a very short time at high growth temperatures, which results in pronounced densification and fast conversion of the YBCO phase.

Thermodynamic Simulation of MOCVD YBa2Cu3O7−x Thin Film Deposition

Chemical Vapour Deposition of YBa2Cu3O7−x superconductors using organometallic precursor materials involves the formation of a great variety of condensed phases (oxides, carbonates, hydroxides, carbides, hydrides) and a complex gas phase. Therefore, the possibility of calculating the stability ranges of the different phases susceptible of being deposited and the influence of the main experimental parameters (precursor partial pressure, oxygen partial pressure, total pressure, temperature) is very attractive. Recently, some initial attempts have been published, but the authors did not have sufficiently complete and reliable thermodynamic data on the species involved in the process. These results will be discussed. Furthermore, a homogeneous and complete set of data for the whole system will be presented, and the reactions of the deposition process will be simulated on the basis of this data set. The most important results will be compared to the previous calculations and to recent experimental work.

High Tc ceramic superconductors: introduction, background, and challenges to the electron microscopist

This introductory article reviews the recent developments in high Tc superconducting ceramics. Particular emphasis is given to the structural and chemical aspects of these compounds that may be of interest to the electron microscopist. Included are some of the contributions made by electron microscopy techniques over the last 10 months. The applications of electron microscopy to solving practical problems associated with these exciting new materials are also discussed.