CHARACTERIZATION OF Yb-DOPED Ba(Ce,Zr)O3 NANOPOWDERS PREPARED BY PECHINI METHOD

Abstract

Ceramic compounds of Ba(Ce_1-xZr_x)_0.95Yb_0.05O_2.975; x=0.20, 0.30, 0.40, 0.50 and 0.60 were successfully prepared by a Pechini method using metal-nitrate salts as starting materials. The samples were characterized by XRD, particle analyzer, SEM and impedance spectroscopy (IS). It was found that annealing temperature of 1400 to 1450 ^oC is sufficient to produce pure perovskite-like phase with a single structure. Particles size distribution and scanning electron micrographs revealed that the size of the loose powder particles was in nanosize range (50-200 nm). The increase in Zr content reduced the size of the loose powders and they tend to form agglomerates. Sintered at T ≥ 1400 ^oC, samples with x=0.20, 0.30 and 0.40 showed density ≥ 93% of the theoretical. The samples formed clear and compact grains with submicron sizes. On the other hand, samples with x=0.5 and 0.6 exhibited low relative density (< 80%) with smaller grains size. This observation might be due to the agglomerates effect. Proton conductivities of the Ba(Ce_1-xZr_x)_0.95Yb_0.05O_2.975; x=0.20, 0.30 and 0.40 were measured by impedance spectroscopy between 200 to 800 ^oC in wet hydrogen. The results showed that the grain semicircle was observed only at T ≤ 250 ^oC. This phenomenon limits the grain resistance (Rg) data and it was found that the Rg data points deviated from the linearity of Arrhenius behaviour. Thus, only total conduction was discussed in this study.