Phase evolution and morphology of nanocrystalline BaCe<inf>0.9</inf>Er<inf>0.1</inf>O<inf>3-δ</inf> proton conducting oxide synthesised by a novel modified solution combustion route

Pure BaCeO3 and 10 mol% Er2O3 doped BaCeO3 (BCE) was synthesised by a novel modified solution combustion synthesis (MCS) route wherein the pH of the precursor solution was varied and the phase formation and morphology were compared with those obtained in conventional solution combustion synthesis (SCS). X-ray diffraction (XRD) studies confirmed the presence of the undesirable BaCO3 phase in the calcined powders prepared using SCS route whereas the powders synthesised with the modified (MCS) route exhibited a single perovskite phase after calcination. Variation in the pH of the precursor solution resulted in a morphology change from a mix of irregular and globular at pH 4 to more spherical at pH 6 and 8. Fourier transform infrared spectroscopy (FT-IR) studies revealed that calcination time has more pronounced effect on phase formation than calcination temperature. A calcination time of 10 h at 1000°C resulted in negligible amount of BaCO3. Such prolonged calcination treatment resulted in substantial grain growth in the SCS sample while the MCS samples were still in the nanocrystalline form. Absence of the ceria peak (464 cm-1) in the Raman spectra confirmed the presence of a single perovskite BaCeO3 phase in the sintered pellets as well.