High $J_{rm c}$ ${hbox {GdBa}}_{2}{hbox {Cu}}_{3}{hbox {O}}_{7-delta}$ Coated Conductors on ${hbox {CeO}}_{2}$-Buffered IBAD MgO Template Fabricated by Pulsed Laser Deposition

摘要

High quality ${hbox {GdBa}}_{2}{hbox {Cu}}_{3}{hbox {O}}_{7-delta}$ (GdBCO) coated conductors (CCs) were successfully fabricated on ${hbox {CeO}}_{2}$-buffered IBAD MgO template by pulsed laser deposition (PLD). With the same energy density of 2 J/cm$^{2}$, laser frequency of 8 Hz, and oxygen pressure of 300 mTorr, both target-to-substrate distance $(D_{rm ts})$ and substrate temperature $(T_{rm s})$ were systematically varied from 5.5 to 4.0 cm at $T_{rm s}$ of 780 $^{circ}{hbox {C}}$ and from 760 to 820 $^{circ}{hbox {C}}$ at $D_{rm ts}$ of 4.5 cm, respectively, to investigate their effects on the grain alignment, microstructure, and superconducting properties of GdBCO films. Biaxially aligned GdBCO films without $a$-axis oriented GdBCO grains could be deposited at $T_{rm s}$ higher than 780 $^{circ}{hbox {C}}$ and $D_{rm ts}$ shorter than 5.0 cm. At $T_{rm s}$ of 760 $^{circ}{hbox {C}}$, a small amount of $a$-axis oriented and 45$^{circ}$ misaligned GdBCO grains was formed. The in-plane textures of GdBCO films were gradually improved when $D_{rm ts}$ decreased, while those were first improved with increasing $T_{rm s}$ up to 800 $^{circ}{hbox {C}}$ and then degraded at 820 $^{circ}{hbox {C}}$. The highest critical current density $(J_{rm c})$ of 3.9 ${rm MA/cm}^{2}$ and critical current $(I_{rm c})$ of 195 A/cm-width (77 K, self-field) were achieved from the 500 nm GdBCO film deposited at 800$^{circ}{hbox {C}}$ with $D_{rm ts}$ of 4.5 cm . The $J_{rm c}$ values of GdBCO films were found to be sensitive to the in-plane texture and also to the presence of $a$ -axis oriented grains and 45$^{circ}$ misaligned grains.