Quazi Arif Islam

Chemical Stability and Electrical Conductivity of Ba0.8Ce0.85-xZrxTb0.15O3-δ Proton Conductors with ZnO as Sintering Aid

ABSTRACT The chemical stability of Ba0.8Ce0.85-xZrxTb0.15O3-δ (0.1≤×≤0.5) has been studied in dry 5% H2/Ar, wet 5% H2/Ar and dry CO2 atmosphere at higher temperature. These materials are promising candidates for mixed ionic electronic conductor based H2 separation membr ane. The materials are prepared by combustion synthesis technique successively followed by calcination at 1100°C and sintering at 1550°C in air. The stabilization mechanism of sintered specimens in various atmospheres is explained with respect to the combined effect of zirconium oxide and zinc oxide as stabilizing agent and sintering aid respectively. Zr4+ introduction into Ce4+ site of doped bar ium cerate perovskite enhances the chemical stability of these materials, particularly for the composition with x>0.3. The stable sintered material is obtained with total electrical conductivity of 0.0189 S.cm−1 for the composition Ba0.8Ce0.35Zr0.5Tb0.15O3-δ in moist reducing atmosphere at 900°C. So, in the present work, we report a composition which shows excellent stability in pure CO2 atmosphere at high temperature without much compromising its ionic conductivity. GRAPHICAL ABSTRACT

Filter paper derived cross-linked interconnected BaBi0.2Co0.35Fe0.45O3−δ morphology with an enhanced oxygen permeation property

This study aims to investigate the effect of an engineered microstructure on the oxygen permeation property of a BaBi0.2Co0.35Fe0.45O3−δ (BBCF) type perovskite membrane. The interconnected multi-level cross-linked structure of the BBCF membrane has been synthesized by mimicking a common laboratory grade filter paper. The controlled calcination of the cellulose matrix results in a single phase BBCF structure when calcined at 950 °C in air. The average diameter of the interconnected BBCF fiber is about 1 μm as confirmed by FESEM. The electrical conductivity is measured to be ∼20 S cm−1 at 800 °C, higher than that of other conventionally prepared BBCF based membranes. The perovskite membrane derived by exo-templating of the filter papers cellulose fiber reveals an enhanced oxygen permeation flux of 0.98 ml min−1 cm−2 at 900 °C.

Low temperature synthesis of nanocrystalline scandia-stabilized zirconia by aqueous combustion method and its characterizations

Zirconia stabilized with 11 mol% scandia (11ScSZ) has been successfully synthesized by novel alanine-assisted soft chemical aqueous combustion method. The reaction kinetics during combustion synthesis has been studied in detail by analysing thermal behaviour of different metal–alanine complexes. A single phase 11ScSZ powder is achieved at significantly low calcination temperature of 500∘C. Field emission scanning electron micrograph reveals an agglomerated morphology with particle size ranging from 80 to 100 nm. The thermal expansion coefficient is found to be 11.03 × 10−6∘C−1 in the temperature range between room temperature and 1000∘C. Optical bandgap of 5.19 eV has been determined using UV–Vis spectroscopy and results are compared with the help of theoretical density of states. The total electrical conductivity of sintered pellet is found to be 7.3 × 10−3 S cm−1 at 700∘C as measured by impedance spectroscopy.