Effects of ethyl cellulose polymers on rheological properties of (La,Sr)(Ti,Fe)O3-terpineol pastes for screen printing

Ethyl cellulose (EC) was mixed with terpineol and conductive ceramic La0.6Sr0.4Ti0.3Fe0.7O3−δ to prepare pastes with different EC content. Viscosity of the vehicles was found to increase with EC content, and the intrinsic viscosity, hydrodynamic radius, and effective sphere of EC in terpineol were estimated to be 0.07 L/g, 78.8 nm, and 0.06 L/g, respectively. For a ceramic paste of 70 wt% powder and vehicle, shear thinning properties were observed for pastes of 0 and 1 wt% EC. For EC contents above 3 wt%, the pastes become Newtonian-like behavior and EC was considered to act effectively as a dispersant. Screen printing of the pastes was carried out. The relative densities of the sintered films were as low as 51.7% for the 0 wt% EC paste, but increased to 67.6% for the 3 wt% EC paste. The high density observed for the 3 wt% EC paste was due to particles being well dispersed, which was also expected from the rheological results.