Barium Non‐Stoichiometry Role on the Properties of Ba_1+xCe_0.65Zr_0.20Y_0.15O_3–δ Proton Conductors for IT‐SOFCs

Abstract

Proton conducting perovskite oxides have been widely investigated because of their potential as electrolytes for intermediate temperature solid oxide fuel cells. Among them, BaCeO3‐ based materials exhibit good proton conductivity under a humidified hydrogen‐containing atmosphere, but rather poor chemical stability in CO2 atmosphere. The substitution with Zr for Ce improves the chemical stability but reduces proton conductivity due to difficulties in fabricating dense materials. In the present work, single phase nanostructured powders of Ba1+xCe0.65Zr0.20Y0.15O3–δ (x = 0, 0.05, 0.10) solid solutions have been prepared by a modified sol–gel Pechini method with the final aim of evaluating the role of barium on their chemical and electrical properties. A significant influence of barium excess on the preparation and on properties of these materials has been demonstrated. In fact, density measurements evidenced that a 5 or 10 mol% nominal barium excess sensibly favoured the sintering process. Impedance analyses of sintered pellets confirmed the necessity of barium excess in order to avoid the lowering of proton conductivity, which has been evidenced for samples having stoichiometric barium content. Moreover, an unforeseen increase in chemical stability in CO2‐containing atmosphere with the growth of the barium excess was detected by thermogravimetric analyses.

Synthesis of acceptor‐doped Ba‐Ce‐Zr‐O perovskites

“…Therefore, the values of activation energy reported in the literature vary from sample to sample and depend on the sample preparation technology. In case of the barium cerate it is between 0.22 eV [24] and 0.61 eV [14] for intra-grain conductivity, about 0.9 eV for intergrain conductivity [14]. It means that the conduction process is dominated by inter-granular transport.…”

“…The nonstoichiometric amount of barium has been applied in order to avoid baria evaporation occuring at high temperature [13]. Moreover, it favours the sintering process and obtaining single-phase samples [14].…”

Influence of Microwave‐Assisted Pechini Method on La0.80Sr0.20Ga0.83Mg0.17O3–δ Ionic Conductivity

“…The collected data were fitted by means of a complex non-linear least square fitting using ZView™ software (ScribnerAssociates) based on an equivalent circuit made of three (RQ) sub-circuits, where R, a resistor, and Q, a constant phase element, are in parallel to one another, as described in ref. [26]. Total ionic conductivities were determined with the lower frequency intercept of grain boundary arc for each temperature.…”

A Study on Sintering Behavior and Conductivity for NiO-doped BaZr0.85Y0.15O3-δ

“…또한 고온에서 하소(calcination) 및 소결을 진행하면 Barium(Ba) 증발현상에 의해 Barium Oxide 형태로 변형되어 grain boundaries 에 서 proton의 이동을 방해하게 된다 11) . 따라서 소결 후 전도도가 낮아지는 문제점을 보완하기 위해서 5-10 mol% Barium을 초과 투입해야 된다 12,13) . Barison …”