Key Microstructural Features of MOD ${\rm YBa}_{2}{\rm Cu}_{3}{\rm O}_{{7}-\partial}$ Films on Textured Nickel Substrates

Key features of the microstructure in high critical current density (
J_C
) MOD Y
₁
Ba
₂
Cu
₃
O
_y
(YBCO) films on biaxially-textured nickel substrates with intervening buffer layers are presented. 0.8
mu
m thick MOD YBCO films on the 4cm wide RABiTS templates have 77K, self-field
J_C
and
I_C
values exceeding 3 MA/cm
²
and 250A/cm-width, respectively. MOD YBCO films have a laminar grain structure with a high density of YBa
₂
Cu
₄
O
_y
(Y124) intergrowths, which give rise to an enhanced peak in angular anisotropy measurements of
J_C
when the applied field is parallel to the ab planes of the YBCO films. Other key aspects of MOD YBCO films related to the laminar growth mode and layered microstructure are grain boundary overgrowth, grain boundary meandering, colony microstructures, incoherent precipitates of Y
₂
O
₃
and Y
₂
Cu
₂
O
₅
, and phase separations.