Abstract
In this study, the Ho-substituted BaZrO3 electrolyte ceramics (BaZr1-xHoxO3-δ, 0.05 ≤ x ≤ 0.20) were synthesized through a low-cost flash pyrolysis process followed by conventional sintering. The effects of Ho-substitution in BaZrO3 studied in terms of the structural phase relationship, microstructure and electrical conductivity to substantiate augmented total electrical conductivity for intermediate temperature solid oxide fuel cells (IT-SOFCs). The Rietveld refined X-ray diffraction (XRD) patterns revealed that pure phase with Pmbar{3}m space group symmetry of cubic crystal system as originated in all samples sintered at 1600 °C for 8 h. The Raman spectroscopic investigations also approved that Ho incorporation in BaZrO3 ceramics. Field Emission Scanning Microscopic (FESEM) study informed a mixture of fine and coarse grains in the fracture surface of Ho-substituted BaZrO3 sintered samples. The relative density and average grain size of samples were observed to decrease as per the addition of Ho-substitution in BaZrO3 ceramics. The electrical conductivity study was accomplished by Electrical Impedance Spectroscopy (EIS) under 3% humidified O2 atmosphere from 300 to 800 °C. Furthermore, the total electrical conductivity of BaZr0.8Ho0.2O3-δ ceramic was found to be 5.8 × 10−3S-cm−1 at 600 °C under 3% humidified atmosphere, which may be a promising electrolyte for IT-SOFCs.
Highlights
The proton conductive oxide ceramics have fascinated worldwide attention due to widespread applications in intermediate temperature solid oxide fuel cells (IT-SOFCs), hydrogen separation and electrolysis of steam, etc
The highly pure and Ho-substituted BaZrO3 nano-sized powders were synthesized through a flash pyrolysis process and followed by conventional sintering
The Rietveld refined X-ray diffraction (XRD) pattern approves that all Ho-substituted BaZrO3 samples sintered at 1600 °C revealing Pm3m space group of cubic crystal system
Summary
The proton conductive oxide ceramics have fascinated worldwide attention due to widespread applications in intermediate temperature solid oxide fuel cells (IT-SOFCs), hydrogen separation and electrolysis of steam, etc In this context, the rare-earth cerates and zirconates with the perovskite-type A(II)B(IV)O3 crystallographic structure are the two foremost families of proton-conducting oxides for electrochemical applications[1,2,3,4]. The rare-earth cerates and zirconates with the perovskite-type A(II)B(IV)O3 crystallographic structure are the two foremost families of proton-conducting oxides for electrochemical applications[1,2,3,4] In these categories of oxide materials, oxygen vacancies are increased by replacement of tetravalent cation B(IV) by trivalent cation M(III) as given in the Eq (1) using Kröger-Vink notation. We adopted Ho as a single substituent for BaZrO3 ceramics to explore the influence of Ho3+ on the electrical properties of BaZrO3 ceramics for operative SOFC applications
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