Preparation of Tazheranite Powders by Solid Phase Reaction and Conductivity of Sintered Bodies

Abstract

Ca_0.20Zr_0.80-xTi_xO_y composition (x=0.04-0.25) powders, whose phases were the tazheranite (x=0.04-0.10) and the calzirtite (x=0.20) of single phases, were prepared at 1300°C for 10h by the solid phase reaction. The range of the tazheranite composition was broadened up to x=0.15 by firing them at 1500°C for 4-10h. The conductivity of the sintered bodies, fabricated at 1500°C for 4h in x=0.04-0.15 and 10h in x=0.20, was measured at 400°-900°C using the complex impedance method in the air. The activation energies of the conductivity were 120-130kJ/mol, thus it is presumed that the mechanism of electric conduction was dominated by an oxygen ion conduction in the range of these temperatures. In the case of x=0.04-0.15 composition samples, the resistance of grain decreased with an increase of x, while that of grain boundary increased. With regard to the calzirtite (x=0.20) composition sintered body, it is made ascertained that the specific resistance took a figure up one place. The results have suggested that the elevation of conductivity is due to the increase of dissolved TiO₂ amount, the valence deviation of Ti, the change of grain size and the segregation of a trace amount of calzirtite phase at the grain boundaries of the tazheranite of single phase.