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A novel route to enhance the sinterability and its effect on microstructure, conductivity and chemical stability of BaCe<inf>0.4</inf>Zr<inf>0.4</inf>Y<inf>0.2</inf>O<inf>3-δ</inf> proton conductors
Date Issued
01-09-2018
Author(s)
Reddy, G. Srinivas
Indian Institute of Technology, Madras
Abstract
BaCeO3 based perovskites exhibit highest protonic conductivity in their class but suffer from low chemical stability. Addition of more stable BaZrO3 to BaCeO3 has been explored to obtain a good combination of conductivity and chemical stability. BaZrO3, however, is unfavourable towards densification due to its poor sinterability. In this study, a two-step sintering process and Zn addition have been explored vis-à-vis conventional sintering to obtain dense Y-doped BaCeO3-BaZrO3 solid solution (BaCe0.4Zr0.4Y0.2O3-δ) at comparatively lower temperatures. The conventional single-step sintering at 1450 °C for different sintering times (5, 10, 15 h) could not provide a dense sample. The two-step sintering process (1550 °C-5 min, 1450 °C-15 h), on the other hand, yielded a relative density of 95%. Addition of 4 mol.% Zn resulted in high sintered density (97%) at 1300 °C though it was not effective at 1200 °C due to insufficient shrinkage (densification). Zn addition also improved the chemical stability against CO2. The grain size of the sintered samples decreased with decreasing sintering temperature and or time. As a result the specific grain boundary conductivity decreased with decreasing sintering time. The overall conductivity was higher in the two-step processed sample compared to the Zn-doped sample.
Volume
216