Defect structure and transport properties of Me6M2O11 (Me:Sr, Ba; M:Nb, Ta)-type phases

Abstract

Electrical conductivity and ion transfer numbers in complex oxides of Me6M2O11(Me:Sr, Ba; M: Nb, Ta) type and solid solutions based on them are investigated. The high mobility of oxygen ions is shown to be due to oxygen structural vacancies V ×S, and the decrease in ion conductivity in Me6M2O11–Me4M2O9 solid solutions is caused by the appearance of M Me…‐type substitutional defects and simultaneous filling of oxygen structural vacancies. The model of solid solution formation is corroborated by picnometric and vibrational spectroscopic methods. Self‐diffusion coefficients of cations in niobate ceramics Sr5Nb4O15, Sr2Nb2O7, SrNb2O6 and Ba0,4Sr0,6Nb2O6 monocrystals are measured. The proximity of Nb5+ and Me2+ ion mobilities is established and attributed to filling up of V Me″ by Nb5+ ions and Nb Me… and V Me5′ defect formation.

Interstitial Oxygen in Perovskite-Related Sr6–2xNb2+2xO11+3x

“…We may thus, conclude that the present conductivity is essentially ionic, at least, for the compound with x = 0.103. Previous studies also showed that the ionic contribution was found to dominate over the electronic contribution in the wide ranges of oxygen partial pressures for the compounds with x = 0.0667 and x = 0.2733 . Therefore, it is likely that the total conductivities measured in air for the compounds presented here were predominantly due to ionic.…”

“…A proper variation of composition in the B sublattice for given oxidation states of metal ions allows a variation of oxygen deficiency in the structures. It is the case for A II 4 (A II 2–2 x B V 2+2 x )O 11+3 x or A II 6–2 x B V 2+2 x O 11+3 x type structures, where A represents alkaline earth metals and B niobium or tantalum atoms. – Many of these compounds displayed predominant oxide ion conductivity at high temperatures, – as well as a proton conductivity at lower temperatures under wet atmospheres. – …”

Structure and electrical conductivity properties of K doped Sr1−xKx(Sr0.50Nb0.50)O2.75−δ complex perovskites

“…This may be due to the heterogeneous mixing of starting precursors. Based on the thermal analysis and previous literature data [25] all the K doped SSN samples are calcined at 1000°C for 2 h and checked for phase purity. .…”

“…Until now however, only a few materials have been proposed as electrolytes for SOFC, most of them are simple perovskites suitably doped to get the required property such as: Sr doped LaGaO 3 [9,10], (La,Sr)(Ga,Mg)O 3−δ [11], Ce 0.9 Gd 0.1 O 1.95 [12] and La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 2.8 [13]. Commonly used ceramic SOFC electrolytes are Scandium doped zirconia (SDZ), Gadolinium doped Ceria (GDC) and Bismuth Yttrium Oxide (BYO) [14] ) is a type of perovskite oxide reported to be good proton conductor with reasonable conductivity (∼10 −1 S cm −1 ) [25] and can be used as promising material for sensors and SOFCs [28].…”

“…In the present study, Sr 2+ is partially substituted by K + in the 1: 25 (SKSN100) for x=1 are synthesised by solid state reaction method. Their thermal, structural and morphological characteristics associated to the total conductivity and stability is investigated.…”