Synthesis and Characterization of MgB_2 Thin Films Prepared by 2.4 Mhz Ultrasonic Spray Pyrolysis System

摘要

Nano-sized B and Mg powders have been successfully deposited onto single crystal MgO(100) and Al_2O_3(001) substrates using 2.4 MHz ultrasonic spray pyrolysis system and an appropriate solution to obtain thin films of MgB_2 superconductors. After an in-situ heating process, ～600-1000 nm thick superconductor films were obtained. The microstructure, electrical, and magnetic properties were characterized by means of particle size analyzer, XRD, SEM-EDX, R-T, and M-H analysis. The effect of particle concentration in the solution, spraying time, and heating temperature on the quality of the MgB_2 films were discussed. The best T_c and T_(zero) results were obtained to be 39.5 and 37.4 K, respectively, for the film deposited on the Al_2O_3(001) substrates. Magnetic properties of the MgB_2 films were investigated at 3 different temperatures and up to 5 T. Symmetric hysteresis loops for all temperature and field cases were obtained and maximum J_c~(mag) value was calculated to be 4.0 × 10~6 A cm~(-2) at 10 K for 0 T for the film deposited on the Al_2O_3(001) substrates. The results obtained were found to be highly dependant on the particle concentration in the solution, heating temperature of substrates and carrier gas flow rate during spraying.