Interfacial reactions between the Ba2YCu3O6+x superconductor and the CeO2 buffer layer employed in coated conductors have been modeled experimentally by investigating the kinetics of the reaction between Ba2YCu3O6+x and CeO2. At 810 C and pO2 = 100 Pa, the Ba2YCu3O6+x - CeO2 join within the BaO-Y2O3-CeO2-CuOx quaternary system is non-binary. At a mole ratio of Ba2YCu3O6+x : CeO2 = 40 : 60, a phase boundary was found to separate two four-phase regions. On the Ba2YCu3O6+x-rich side of the join, the four-phase region consists of Ba2YCu3O6+x, Ba(Ce1-zYz)O3-x, BaY2CuO5, and Cu2O; on the CeO2 rich side, the four phases were determined to be Ba(Ce1-zYz)O3-x, BaY2CuO5, Cu2O and CeO2. The Ba2YCu3O6+x /CeO2 reaction is limited by solid-state diffusion, and the reaction kinetics obeys the parabolic rule, x = Kt1/2 (where x is thickness of the reaction layer, t is time, and K is a constant related to the rate constant); K was determined to be 1.2 x 10 2 mm/min1/2 at 790 C and 3.6 x 10 2 mm/min1/2 at 830 C. The activation energy for the reaction was determined to be Eact = 2.44 x 105 J/mol using the Arrhenius Equation.
Citation: Journal of Electronic Materials
Pub Type: Journals
coated conductor, interfacial reaction of CeO<sub>2</sub>, kinetics of reaction, solid-state diffusion