High conductivity and chemical stability of BaCe1−x−yZrxYyO3−δ proton conductors prepared by a sol–gel method

Abstract

High-temperature proton conductors are promising as electrolytes for intermediate-temperature solid oxide fuel cells. Among them, BaCeO 3 -based materials have high proton conductivity but rather poor chemical stability. In contrast, barium zirconates are rather stable, but have poorly reproducible densities and conductivities. In this study, the investigation of BaCe 1ÀxÀy Zr x Y y O 3Àd solid solutions (x ¼ 0, 0.10, 0.20, 0.30, 0.40; y ¼ 0.15, 0.20) was undertaken, with the final aim of finding a composition having both high conductivity and good stability. The influence of the modified sol-gel Pechini synthetic approach on the powder morphology, and of a barium excess on the densification were demonstrated. Single-phase perovskite powders were prepared and high density pellets were obtained at temperatures lower than those commonly employed. Stability tests demonstrated that the Zr introduction into doped barium cerate greatly enhanced the chemical stability, particularly for Zr $ 20%. The proton conductivities, measured in a humidified H 2 /Ar atmosphere by impedance spectroscopy, were only slightly influenced by the Zr amount. Overall, BaCe 1ÀxÀy Zr x Y y O 3Àd solid solutions having Zr z 20-40% and Y z 15-20% showed good chemical stability and high conductivity.

Wet chemical synthesis and characterisation of Ba 0.5 Sr 0.5 Ce 0.6 Zr 0.2 Gd 0.1 Y 0.1 O 3−δ proton conductor

“…BSCZGY and BZ3C5YYb for comparison were heated up to 1200 ºC in pure CO2 with a flow rate of 40 ml/min, held isothermally for 30 minutes and then cooled down with the same rate of 3 o C/min. The heat treatment in CO2 up 1200 º C or a bit higher has already been reported by many in the literature [14,35,40,49,50]. Fig.…”

“…For a composition with same Zr ratio i.e. 20 mol%, BaCe0.65Zr0.20Y0.15O3 -δ, a densification of 93% was achieved after firing at 1400 ºC for 10 hours [40]. The same material i.e.…”

Processing and characterizations of a novel proton-conducting BaCe0.35Zr0.50Y0.15O3-δ electrolyte and its nickel-based anode composite for anode-supported IT-SOFC

“…These oxides show pure protonic conduction in wet hydrogen atmosphere, while they exhibit protonic, oxygen ionic and electronic mixed conduction under high oxygen partial pressure at elevated temperatures [6]. Major problem in case the of BaCe 1-xy Zr x YyO 3-d materials is the poor sinterability and they require very high temperature (i.e., above 1,700°C) for well sintering with pore free microstructure [8][9][10][11].…”

Conductivity studies of sol-gel prepared BaCe0.85−xZrxY0.15O3−δ solid electrolytes using impedance spectroscopy

“…Among various methods recently proposed to synthesize nano-crystalline powders, the modified Pechini method has the advantage to produce high purity and ultrafine powders. In previous investigations [6,18,19] we found that yttrium doped barium cerates (BaCe 1-y Y y O 3 with y = 0.1, 0.15, and 0.2) prepared by means of sol-gel route employing a barium excess gave high active nano-sized powders and sub-micrometric solid solutions. Sintering temperatures of 1,250°C for BaCeYO 3-d resulted in high densities.…”

“…The average particle sizes were about 0.1-0.3 micron. The preparation of specimens was similar to that in previous studies [6,18]. The resulting materials were characterized by various techniques.…”