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

The authors have developed large-area Ho₁Ba₂Cu₃O_x (HoBCO) thin films on sapphire (Al₂O₃) 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 × 7cm size HoBCO thin films were successfully prepared. 3cm × 7cm HoBCO thin films showed excellent crystal growth and high uniformity of film thickness and critical temperature (T_c). Critical current densities (J_c) were 1.9∼2.0 MA/cm² at 77 K. Using the 2-D scanning PLD method, 3cm × 10cm size HoBCO thin films have also been developed. 3cm × 10cm HoBCO thin films showed high uniformity of film thickness and high J_c over 3.0 MA/cm² at 77 K.