Reduced $J_{\mathrm{c}}$ Anisotropy and Enhanced In-Field Performance of Thick BaHfO3-Doped $\text{YBa}_{2}\text{Cu}_{3}\text{O}_{7-\delta}$ Films on ABAD-YSZ Templates

Pure and 6 mol% BaHfO
₃
(BHO)-doped
$\text{YBa}_{2}\text{Cu}_{3}\text{O}_{7-\delta}$
(YBCO) films with a film thickness of around 1
$\mu\text{m}$
were prepared on CeO
₂
-buffered ABAD-YSZ templates by pulsed laser deposition. The self-field
$J_{\mathrm{c}}$
at 77 K reaches 1.1 MA/cm
²
in the doped sample compared with 2.5 MA/cm
²
in pure YBCO. Above a magnetic field of 2.2 T along
$B\|c$
,
$J_{\mathrm{c}}$
of the BHO-doped sample exceeds the
$J_{\mathrm{c}}$
of the undoped film. The maximum pinning force density
$(F_{\mathrm{P},\max})$
reaches a value of around 3 GN/cm
²
for both samples, but
$B(F_{\mathrm{P},\max})$
increases from 1.4 T (pure) to a value of 2.9 T (BHO:YBCO). The
$J_{\mathrm{c}}$
anisotropy curves of the doped sample show a large and broad peak at
$B\|c$
and a strongly reduced anisotropy at all temperatures and fields compared with the pure sample. A complex defect structure with YBa
₂
Cu
₄
O
₈
intergrowths, Y
₂
O
₃
precipitates, and BHO nanocolumns with a fan-shaped structure is observed by transmission electron microscopy investigations, which can explain the measured
$J_{\mathrm{c}}(B,\theta)$
behavior.