Effect of polyvinylpyrrolidone (PVP) on the stability of Bi2Sr2CaCu2O8 (Bi-2212) in ethanol

Abstract

Suspension-based deposition methods, such as sedimentation and electrophoretic deposition, have been shown to synthesize quality Bi₂Sr₂CaCu₂O₈ (Bi-2212) thin films while being cheap and simple to set up. However, particles smaller than 1 µm destabilize and readily coagulate in suspensions. This study aims to stabilize Bi-2212 in ethanol using PVP. Bi-2212 was synthesized using the conventional solid-state reaction method and characterized using X-ray diffraction (XRD) and resistance-vs-temperature measurements. PVP was added in concentrations of 0 to 5 wt% to Bi-2212 suspensions in ethanol (0.042 wt% solid loading). Zeta potential, electrophoretic mobility, and average particle size were measured to characterize the suspension stability. It was shown through zeta potential and electrophoretic mobility measurements that the system undergoes more than one charge reversal as the concentration is varied. The particle size measurements after the charge reversals were smaller than the control, which indicates enhanced stability. The results are associated with the changing orientation of the adsorbed PVP as the competition for adsorption sites increases. In summary, 1.0 and 1.5 wt% PVP produced optimal suspensions with the smallest average particle sizes (276.3 and 279.5 nm) and largest zeta potential (+21.6 and +21.7 mV) and electrophoretic mobility (0.2835 and 0.2844 µm·cm/V·s).