Conductivity and redox stability of new perovskite oxides SrFe0.7TM0.2Ti0.1O3-δ (TM = Mn, Fe, Co, Ni, Cu)

Peter I Cowin,Rong Lan,Christophe T.G Petit,Dongwei Du,Kui Xie,Huanting Wang,Shanwen Tao

doi:10.1016/j.ssi.2017.01.017

Abstract

New perovskite oxides SrFe0.7TM0.2Ti0.1O3-δ (TM=Mn, Fe, Co, Ni, Cu) were synthesised by sol-gel processes. Their redox stability and conductivity in both air and 5%H2/Ar were investigated in details. The cubic perovskite structure was also observed for all dopants with variation in the lattice parameters associated with different dopant environments and charge compensation mechanisms. Improvement of the electronic conductivity over SrFe0.9Ti0.1O3-δ was observed for all dopants in air, attributed to increasing charge carrier concentrations. Reduction in 5% H2/Ar exhibited minimal a material properties for SrFe0.7Cu0.2Ti0.1O3-δ, with a significant reduction in conductivity was observed for SrFe0.7Mn0.2Ti0.1O3-δ. All doped compounds exhibited a single phase cubic perovskite structure after reduction in 5%H2/Ar at 700°C with the exception of SrFe0.7Ni0.2Ti0.1O3-δ and SrFe0.7Co0.2Ti0.1O3-δ which displays secondary nickel and cobalt phases respectively upon reduction. SrFe0.7Cu0.2Ti0.1O3-δ is redox stable at a temperature below 700°C and highly conductive with conductivities around 10S cm−1 in both air and reducing atmosphere which are about five times higher than those of pure SrFe0.9Ti0.1O3-δ. In terms of conductivity and redox stability, it is a potential redox stable electrode material for reversible and symmetrical solid oxide fuel cells as well.

Highlights

Redox-stable and conductive oxide materials are very useful in application in anode materials for solid oxide fuel cells (SOFCs)
Cowin et al / Solid State Ionics 301 (2017) 99–105 conductivity in oxidising and reducing atmospheres elucidated in this paper in order to explore their potential as electrode materials for SOFCs
Whilst manganese doping improved the redox stability and conductivity in air, the reduction of the conductivity in 5% H2/Ar renders this compound unsuitable for use as an anode material for SOFCs

Summary

Introduction

Redox-stable and conductive oxide materials are very useful in application in anode materials for solid oxide fuel cells (SOFCs). The electrode materials for reversible and symmetric solid oxide fuel cells must be redox stable or redox reversible They should exhibit high electrical conductivity in both air and reducing atmosphere [9,10,11,12]. In the reported redox stable oxides, SrFe0.75Mo0.25O3-δ is an excellent material with electrical conductivity of 50 S cm-1 at 850 °C in dry 5 vol% H2/Ar [13]. This is slightly lower than those reported in the original report for Sr2Fe1.5Mo0.5O6-δ [14] different conductivity values were reported indicating the conductivity of the materials is very much related to the synthetic history [13]. Cowin et al / Solid State Ionics 301 (2017) 99–105 conductivity in oxidising and reducing atmospheres elucidated in this paper in order to explore their potential as electrode materials for SOFCs

Synthesis

Analytical procedures

Conductivity testing

Results and discussion

Conclusions