Effects of High-Pressure Sintering on Critical Current Density in (Ba,K)Fe2As2 PIT Wires

The effects of high-pressure sintering on the critical current density J
_c
in superconducting wires of (Ba
_0.6
K
_0.4
)Fe
₂
As
₂
and (Sr
_0.6
K
_0.4
)Fe
₂
As
₂
fabricated by the powder-in-tube technique were studied. The high-pressure sintering was conducted using the hot isostatic pressing (HIP) technique in a pressure up to 120 MPa. Local measurements on the magnetic induction distribution of the wire core in the critical state using magnetooptical imaging demonstrate that a uniform shielding current is flowing and intergranular couplings are very strong. Self-field J
_c
up to 1 × 10
⁵
A/cm
²
is achieved in wires processed at 120 MPa and 700°C. A systematic measurement of J
_c
in HIP-processed (Ba
_0.6
K
_0.4
)Fe
₂
As
₂
wires demonstrates that J
_c
increases steadily with the pressure during the high-pressure sintering. On the other hand, the obtained J
_c
depends sensitively on the temperature during the high-pressure sintering, and the duration of the high-pressure sintering also affects the value of J
_c
.