INFLUENCE OF PORE FORMERS ON ELECTRICAL PROPERTIES OF CaTi_0.9Fe_0.1O_3-δ PEROVSKITE-TYPE CERAMICS

Porous CaTi_0.9Fe_0.1O_3-δ (CTF) perovskites were synthesized by the standard solid state method at different sintering temperatures with carbon black (CB), corn starch (CS) and potato starch (PS) as pore-forming agents. The ceramic samples of porosity between 9% and 42% with 5 - 40 μm pore sizes, were obtained by a 6 h sintering at either 1130° C or 1200° C of precursor powder prepared at 1470° C. X-ray diffraction analysis proved the existence of orthorhombic single-phase perovskites crystalline structure. Electrical conductivity at 800° C was between 1.42×10^-2 S cm^-1 and 1.86×10^-3 Scm^-1. The conductivity markedly depended on the sample porosity. It should be noted that 30% of porosity, resulted in reduction of conductivity by less than one order of magnitude. Activation energy of conductivity varied between 0.41 and 0.56 eV. Cornstarch has been chosen as the most suitable pore-forming agent for obtaining the cathode of good properties. The best amount of the cornstarch has been proposed as between 5 and 10%.