Preparation of Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) feedstocks with different thermoplastic binders and their use in the production of thin tubular membranes by extrusion

This work presents the effects of processing on the shape stability of different ceramic-polymer compounds (feedstocks) to obtain, by extrusion, thin tubular Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) perovskite membranes with a diameter of 10 mm and wall thickness of <300 μm. The influence on the polymer degradation during compounding and the processability to achieve geometrically stable thin wall tubes after debinding were analyzed. The ceramic-polymer composite was evaluated with a torque rheometer and capillary rheometer using Arrhenius plots (temperature–viscosity relationship) to investigate the activation energy of viscous flow (Ef). The shape stability, e.g. roundness and straightness, of the extruded tubes before and after the debinding step was investigated for the different binder systems. The feedstock based on 52 vol% BSCF powder and a polymeric mixture of 80 wt% polystyrene (PS) and 20 wt% polyethylene glycol (PEG) demonstrated reproducible processing behavior and sufficient shape stability after debinding. The tubes fabricated with this feedstock showed good longitudinal shrinkage (2.86%) and roundness (ΔDmax−min/Dmax<1.62%), absence of defects, suitable straightness and a homogeneous microstructure.