Abstract Body

Bi₂Sr₂Ca₂Cu₃O_y (Bi-2223) is a highly regarded material in the field of superconductors for its high critical temperature (Tc ~110K), which allows it to operate under liquid nitrogen cooling (~77K). This study investigates aerosol deposition (AD) as a potential technique for fabricating Bi-2223 thin films with properties comparable to those produced by traditional methods like pulsed laser deposition (PLD) and sputtering. The potential to create dense, high-quality superconducting films at room temperature with shorter processing times offers significant advantages for large-scale applications. Additionally, AD's flexibility allows for the direct deposition of superconducting films on various substrates, including heat-sensitive ones, broadening the potential applications of Bi-2223 films in advanced technologies.

Bi(Pb)-2223 bulk materials were synthesized with a composition of Bi_1.75Pb_0.35Sr_1.9Ca_2.1Cu₃O_z using powder oxides as starting materials. After mixing, the samples were uniaxially pressed into pellets and underwent a series of heat treatments. This process resulted in a highly pure Bi-2223 phase with minimal impurities. X-ray diffraction (XRD) patterns confirmed the successful formation of the Bi-2223 phase, with no secondary phases. The synthesized bulk material exhibited a Tc of approximately 107K.

To prepare the bulk material for AD, the bulk material was wet milled using a planetary ball mill to produce fine particles with a mean diameter of 0.49μm. The size of the particles was essential for effective aerosolization and facilitating the thin film formation. The milled powder was then dried under vacuum for two hours at 200oC to remove residual solvents and moisture. The chamber is then placed in the system and aerosolized using N₂ gas at a rate of 10L/min. The deposition of Bi(Pb)-2223 films was carried out on an annealed silver substrate with a substate temperature of 200°C at a scan rate of 105μm/s for 10 scans.

The resulting films, approximately 64μm thick, retained the crystalline structure of the Bi-2223 precursor but showed partial amorphization. Post-deposition annealing at 845°C for 8 hours, followed by 820°C for 12 hours, was crucial in re-establishing crystalline order, enhancing c-axis orientation, and improving the films' superconducting properties. XRD analysis confirmed a highly oriented Bi-2223 phase after annealing, while resistance-temperature (R-T) measurements showed a superconducting transition with a Tc of 103K, indicating the successful formation of superconducting pathways predominantly composed of the Bi-2223 phase.

The presentation will further discuss data on the effects of varying bulk compositional ratios and deposition parameters on subsequent thin film formation via AD.

Figure 1. XRD pattern of aerosol-deposited Bi(Pb)-2223 films before and after annealing
Figure 2. R-T graph of annealed Bi(Pb)-2223 films

Keywords: Bi-2223, aerosol deposition, thin film