Development of HoBCO tapes fabricated by ISD process

Ho₁Ba₂Cu₃O_x (HoBCO) tapes by using pulsed laser deposition (PLD) have been developed on flexible Ni-alloy substrates. Inclined substrate deposition (ISD) was developed to introduce in-plane alignment for buffer layers. YSZ was deposited by PLD combined with ISD as a buffer layer on Ni-alloy tape. The advantage of ISD is a high growth rate due to the self in-plane alignment without any other assistance. This was demonstrated by using a CeO₂ buffer layer. A CeO₂ buffer layer shows high growth rates of 1 - 2 μm/min. As for the growth rate of HoBCO, 4 μm/min. was confirmed. Scale-up of the PLD system for making a long tape was performed. In this system, a 200 W-KrF excimer laser over 100 h continuous operation, a large deposition chamber including long ramp heater and three 10-in target system, and a reel to reel tape transfer system up to several hundred meters were introduced and combined. The continuous sputtering system for silver layer and O₂ annealing system were also introduced. By using these systems, a 50 m CeO₂ buffer was continuously deposited on a Ni-alloy tape. The deposition tape speed was 0.75 m/h, thickness was 2 μm, and full-width at half-maximum was 23° in average. By depositing HoBCO on a part of this CeO₂/Ni-alloy tape, Ic = 29 A/cm-width and Jc = 0.27 MA/cm² were demonstrated.