Molecular weight dependence of ethyl cellulose adsorption behavior on (La, Sr)(Ti, Fe)O3−δ particles in organic solvent pastes and their printing properties

Abstract

The perovskite oxide of La0.6Sr0.4Ti0.3Fe0.7O3−δ (LSTF) is the material used as a cathode for solid oxide fuel cells (SOFCs). Since the conductivity of a cathode formed via screen printing techniques depends on the conducting particle content in the film after sintering, the paste design is important to obtain the thick film with a high conductivity. The effects of the molecular weight of ethyl cellulose (EC) on the paste properties of the LSTF and the densities of printed thick films were investigated. EC as a binder was mixed with an organic solvent (diethylene glycol monobutyl ether acetate, BDGAC) and LSTF powder to prepare the paste. To understand the conformation of EC in the paste, the intrinsic viscosity ([η]), hydrodynamic radius (RH), and Mark–Houwink–Sakurada parameter (α) of EC in BDGAC were estimated. We also evaluated the conformation of EC on the LSTF particles by using the β parameter of Perkel and Ullman׳s equation for the adsorption of EC onto LSTF. We revealed that the conformation of EC was a train-loop-tail shape, close to a flat structure and affected the rheological properties and the film densities. The highest density of a sintered film was obtained with the paste using 3.0wt% EC with a molecular weight of 141,000.