Modified strontium titanates: from defect chemistry to SOFC anodes

Abstract

Modified strontium titanates have received much attention recently for their potential as anode material in solid oxide fuel cells (SOFC). Their inherent redox stability and superior tolerance to sulphur poisoning and coking as compared to Ni based cermet anodes could improve durability of SOFC systems dramatically.Various substitution strategies can be deployed to optimise materials properties in these strontium titanates, such as electronic conductivity, electrocatalytic activity, chemical stability and sinterability, and thus mechanical strength. Substitution strategies not only cover choice and amount of substituent, but also perovskite defect chemistry, distinguishing between A-site deficiency (A 1Àx BO 3 ) and cationstoichiometry (ABO 3+d ). Literature suggests distinct differences in the materials properties between the latter two compositional approaches. After discussing the defect chemistry of modified strontium titanates, this paper reviews three different A-site deficient donor (La, Y, Nb) substituted strontium titanates for their electrical behaviour and fuel cell performance. Promising performances in both electrolyte as well as anode supported cell designs have been obtained, when using hydrogen as fuel.Performances are retained after numerous redox cycles. Long term stability in sulphur and carbon containing fuels still needs to be explored in greater detail.

An efficient gel-combustion synthesis of visible light emitting barium zirconate perovskite nanoceramics: Probing the photoluminescence of Sm 3+ and Eu 3+ doped BaZrO 3

“…Photoluminesence spectroscopy of Sm 3 þ doped BaZrO 3 A Sm 3 þ ion is a well known activator which gives bright photoluminescence in the visible and near infrared (NIR) region in various kinds of inorganic compounds. The emission bands observed for this particular ion are due to transitions between the energy levels in the 4f 5 to the f-f transitions are electronically forbidden and exhibit poor absorptivities in UV region. The high intensities of emission bands when excited with CTB are due to the intramolecular energy transfer (IMET) process, which occurs in the UV region.…”

“…This includes cheap solar cell [1], multiferroic material [2], energy harvesting device [3], photocatalysis [4], anode material in solid oxide fuel cell [5] etc. They can be tuned to different properties based on doping site i.e.…”

Synthesis, microstructural properties and chemical stability of 3DOM structures of Sr1−xYxTiO3

“…Strontium titanate is chemically stable [5]; however, doping of such materials often changes the chemical stability of perovskite [6], the comparative exposition test was performed to evaluate the chemical stability of Y-doped strontium titanate. Thermal analysis methods, especially combine with mass spectrometry, were found to be the proper tool for chemical stability evaluation in CO 2 -and H 2 O-enriched atmospheres [7][8][9].…”

Structural and electrical transport properties of Pr-doped SrTi0.93Co0.07O3-δ a novel SOEC fuel electrode materials

“…It can be stated, that the defect chemistry of donor and acceptor doped is studied for nearly fifty years [9,[18][19][20][21][22]. However, the compensation mechanisms are not established completely.…”

“…The counter hopping transport of oxygen ions via an oxygen vacancies and simultaneous electron hopping in the Ti 3+ − O 2− -Ti 4+ network due to the covalent overlapping of the Ti-3d and O-2p orbitals makes a STO ceramics a mixed ionic-electronic conductor (MIEC) [6][7][8]. Non-modified SrTiO 3 has insulating properties, but additional doping process or thermal treatment at low pO 2 conditions can change its electrical properties [9]. Its conductivity increases significantly at low oxygen partial pressure according to a change in the titanium valence from Ti 4+ to Ti 3+ .…”