Synthesis and structural characterization of perovskite type proton conducting BaZr 1− xIn xO 3− δ (0.0 ≤ x ≤ 0.75)

Abstract

Solid state sintering has been used to prepare the cubic perovskite structured compounds BaZr 1− x In x O 3− δ (0.0 ≤ x ≤ 0.75). Analysis of X-ray powder diffraction (XRPD) data reveals that the unit cell parameter, a, increases linearly with an increased Indium concentration. XRPD data was also used to demonstrate the completion of sample hydration, which was reached when the materials showed a set of single-phase Bragg-peaks. Dynamic thermogravimetric analysis (TGA) data showed that approx. 89% of the total number of available oxygen vacancies can be filled in BaZr 1− x In x O 3− δ for x = 0.50, and that the maximum water uptake occurs below 300 °C. Rietveld analysis of the room temperature neutron powder diffraction (NPD) data confirmed the average cubic symmetry (space group Pm-3m), and an expansion of the unit cell parameter after the hydration reaction. The strong O–H stretch band, 2500–3500 cm − 1 , in the infrared absorbance spectrum clearly manifests the presence of protons in the hydrated material. Proton conductivity of hydrated BaZr 1− x In x O 3− δ , x = 0.75 was investigated during heating and cooling cycles under dry argon atmosphere. The total conductivity during the heating cycle was nearly two orders of magnitude greater than that of cooling cycle at 300 °C, whilst these values were similar at higher temperatures i.e. T > 600 °C.