Development of HoBCO thin film for SN transition type fault current limiter

The authors have developed large-area Ho/sub 1/Ba/sub 2/Cu/sub 3/O/sub x/ (HoBCO) thin films on sapphire (Al/sub 2/O/sub 3/) single crystal substrates for SN transition type fault current limiter. Two types of pulsed laser deposition (PLD) method, the rotation PLD method and the two-dimensional (2-D) scanning PLD method, have been used for preparing uniform large-area thin films. Using the rotation PLD method, 3cm /spl times/ 7cm size HoBCO thin films were successfully prepared. 3cm /spl times/ 7cm HoBCO thin films showed excellent crystal growth and high uniformity of film thickness and critical temperature (T/sub c/). Critical current densities (J/sub c/) were 1.9/spl sim/2.0 MA/cm/sup 2/ at 77 K. Using the 2-D scanning PLD method, 3cm /spl times/ 10cm size HoBCO thin films have also been developed. 3cm /spl times/ 10cm HoBCO thin films showed high uniformity of film thickness and high J/sub c/ over 3.0 MA/cm/sup 2/ at 77 K.