Synthesis of Y_(0.2)Zr_xCe_(0.8-x)O_(1.9) Electrolytes From the Sol-Gel Method for Intermediate Temperature URSOFC Application

摘要

A series of Y_(0.2)Zr_xCe_(0.8-x)O_(1.9) compounds (0 ≤ x ≤ 0.6) had been prepared by the modified sol-gel method and characterized by powder X-ray diffraction, thermo-gravimetric analysis, four-probe resistivity, and Vickers's hardness studies. The gels from co-precipitation were treated with heated 1-octanol. All of the samples showed fluoride structure after calcined at 600℃. Sintering the powders of Y_(0.2)Ce_(0.8)O_(1.9) and Y_(0.2)Zr_(0.6)Ce_(0.2)O_(1.9) at 1300℃ gave the relative density of 95.8% and 99%, respectively. 99% relative density could be obtained for all samples after sintering at 1500℃. This study showed a much more improved result than that of the previous reports. The hardness was 13.7 GPa for the Y_(0.2)Zr_(0.6)Ce_(0.2)O_(1.9) pellet, which was twice greater than that for Y_(0.2)Ce_(0.8)O_(1.9) (7.1 GPa). Therefore, the mechanical properties could be improved by the addition of ZrO_2 to Y_(0.2)Zr_xCe_(0.8-x)O_(1.9). At 800℃, the electrical conductivity of Y_(0.2)Ce_(0.8)O_(1.9) and Y_(0.2)Zr_(0.6) Ce_(0.2)O_(1.9) were 3.3 × 10~(-2) S/cm and 5.5 × 10~(-3) S/cm, respectively. The conductivity was decreased by the addition of ZrO_2 to Y_(0.2)Ce_(0.8)O_(1.9). It showed that the conductivity and hardness of Y_(0.2)Zr_(0.2)Ce_(0.6)O_(1.9) were 1.2 × 10~(-2) S/cm and 9.6 GPa, respectively, at 800℃ and could be a better electrolyte candidate for "intermediate-temperature" unitized regenerative solid oxide fuel cells.