Doping strategies to optimise the oxide ion conductivity in apatite-type ionic conductors

A Najib, J E H Sansom, J R Tolchard, P R Slater, M S Islam

Research output: Contribution to journalArticle

97 Citations (Scopus)

Abstract

The apatite-type phases, La9.33+x(Si/Ge)(6)O26+ 3x/2, have recently been attracting considerable interest as potential electrolytes for solid oxide fuel cells. In this paper we report results from a range of doping studies in the Si based systems, aimed at determining the key features required for the optimisation of the conductivities. Systems examined have included alkaline earth doping on the rare earth site, and P, B, Ga, V doping on the Si site. By suitable doping strategies, factors such as the level of cation vacancies and oxygen excess have been investigated. The results show that the oxide ion conductivities of these apatite systems are maximised by the incorporation of either oxygen excess or cation vacancies, with the former producing the best oxide ion conductors. In terms of samples containing cation vacancies, conductivities are enhanced by doping lower valent ions, Ga, B, on the Si site. The presence of higher valent ions on these sites, e.g P, appears to inhibit the incorporation of excess oxygen within the channels, and so limits the maximum conductivity that can be obtained. Overall the results suggest that the tetrahedral sites play a key role in the conduction properties of these materials, supporting recent modelling studies, which have suggested that these tetrahedra aid in the motion of the oxide ions down the conduction channels by co-operative displacements.
Original languageEnglish
Pages (from-to)3106-3109
Number of pages4
JournalDalton Transactions
Issue number19
DOIs
Publication statusPublished - 2004

Fingerprint

Apatites
Oxides
Doping (additives)
Ions
Vacancies
Cations
Oxygen
Solid oxide fuel cells (SOFC)
Rare earths
Electrolytes
Earth (planet)

Cite this

Doping strategies to optimise the oxide ion conductivity in apatite-type ionic conductors. / Najib, A; Sansom, J E H; Tolchard, J R; Slater, P R; Islam, M S.

In: Dalton Transactions, No. 19, 2004, p. 3106-3109.

Research output: Contribution to journalArticle

Najib, A ; Sansom, J E H ; Tolchard, J R ; Slater, P R ; Islam, M S. / Doping strategies to optimise the oxide ion conductivity in apatite-type ionic conductors. In: Dalton Transactions. 2004 ; No. 19. pp. 3106-3109.
@article{2633817c7fac4621998084e79ab5c7e8,
title = "Doping strategies to optimise the oxide ion conductivity in apatite-type ionic conductors",
abstract = "The apatite-type phases, La9.33+x(Si/Ge)(6)O26+ 3x/2, have recently been attracting considerable interest as potential electrolytes for solid oxide fuel cells. In this paper we report results from a range of doping studies in the Si based systems, aimed at determining the key features required for the optimisation of the conductivities. Systems examined have included alkaline earth doping on the rare earth site, and P, B, Ga, V doping on the Si site. By suitable doping strategies, factors such as the level of cation vacancies and oxygen excess have been investigated. The results show that the oxide ion conductivities of these apatite systems are maximised by the incorporation of either oxygen excess or cation vacancies, with the former producing the best oxide ion conductors. In terms of samples containing cation vacancies, conductivities are enhanced by doping lower valent ions, Ga, B, on the Si site. The presence of higher valent ions on these sites, e.g P, appears to inhibit the incorporation of excess oxygen within the channels, and so limits the maximum conductivity that can be obtained. Overall the results suggest that the tetrahedral sites play a key role in the conduction properties of these materials, supporting recent modelling studies, which have suggested that these tetrahedra aid in the motion of the oxide ions down the conduction channels by co-operative displacements.",
author = "A Najib and Sansom, {J E H} and Tolchard, {J R} and Slater, {P R} and Islam, {M S}",
note = "ID number: ISI:000224862600021",
year = "2004",
doi = "10.1039/b401273a",
language = "English",
pages = "3106--3109",
journal = "Dalton Transactions",
issn = "1477-9226",
publisher = "Royal Society of Chemistry",
number = "19",

}

TY - JOUR

T1 - Doping strategies to optimise the oxide ion conductivity in apatite-type ionic conductors

AU - Najib, A

AU - Sansom, J E H

AU - Tolchard, J R

AU - Slater, P R

AU - Islam, M S

N1 - ID number: ISI:000224862600021

PY - 2004

Y1 - 2004

N2 - The apatite-type phases, La9.33+x(Si/Ge)(6)O26+ 3x/2, have recently been attracting considerable interest as potential electrolytes for solid oxide fuel cells. In this paper we report results from a range of doping studies in the Si based systems, aimed at determining the key features required for the optimisation of the conductivities. Systems examined have included alkaline earth doping on the rare earth site, and P, B, Ga, V doping on the Si site. By suitable doping strategies, factors such as the level of cation vacancies and oxygen excess have been investigated. The results show that the oxide ion conductivities of these apatite systems are maximised by the incorporation of either oxygen excess or cation vacancies, with the former producing the best oxide ion conductors. In terms of samples containing cation vacancies, conductivities are enhanced by doping lower valent ions, Ga, B, on the Si site. The presence of higher valent ions on these sites, e.g P, appears to inhibit the incorporation of excess oxygen within the channels, and so limits the maximum conductivity that can be obtained. Overall the results suggest that the tetrahedral sites play a key role in the conduction properties of these materials, supporting recent modelling studies, which have suggested that these tetrahedra aid in the motion of the oxide ions down the conduction channels by co-operative displacements.

AB - The apatite-type phases, La9.33+x(Si/Ge)(6)O26+ 3x/2, have recently been attracting considerable interest as potential electrolytes for solid oxide fuel cells. In this paper we report results from a range of doping studies in the Si based systems, aimed at determining the key features required for the optimisation of the conductivities. Systems examined have included alkaline earth doping on the rare earth site, and P, B, Ga, V doping on the Si site. By suitable doping strategies, factors such as the level of cation vacancies and oxygen excess have been investigated. The results show that the oxide ion conductivities of these apatite systems are maximised by the incorporation of either oxygen excess or cation vacancies, with the former producing the best oxide ion conductors. In terms of samples containing cation vacancies, conductivities are enhanced by doping lower valent ions, Ga, B, on the Si site. The presence of higher valent ions on these sites, e.g P, appears to inhibit the incorporation of excess oxygen within the channels, and so limits the maximum conductivity that can be obtained. Overall the results suggest that the tetrahedral sites play a key role in the conduction properties of these materials, supporting recent modelling studies, which have suggested that these tetrahedra aid in the motion of the oxide ions down the conduction channels by co-operative displacements.

U2 - 10.1039/b401273a

DO - 10.1039/b401273a

M3 - Article

SP - 3106

EP - 3109

JO - Dalton Transactions

JF - Dalton Transactions

SN - 1477-9226

IS - 19

ER -