Conductivity and water uptake of Sr4(Sr2Nb2)O11·nH2O and Sr4(Sr2Ta2)O11·nH2O

Niina Jalarvo; Camilla Haavik; Camilla Kongshaug; Poul Norby; Truls Norby

doi:10.1016/j.ssi.2009.05.021

Conductivity and water uptake of Sr₄(Sr₂Nb₂)O₁₁·nH₂O and Sr₄(Sr₂Ta₂)O₁₁·nH₂O

Niina Jalarvo, Camilla Haavik, Camilla Kongshaug, Poul Norby, Truls Norby

Research output: Contribution to journal › Article › peer-review

33 Scopus citations

Abstract

The hydrated oxygen deficient complex perovskite-related materials Sr₄(Sr₂Nb₂)O₁₁·nH₂O and Sr₄(Sr₂Ta₂)O₁₁·nH₂O were studied at high water vapour pressures over a large temperature range by electrical conductivity measurements, thermogravimetry (TG), and X-ray powder diffraction (XRPD). In humid atmospheres both materials are known to exhibit protonic conductivity below dehydration temperatures, with peak-shaped maxima at about 500 °C. In this work we show that the peaks expand to plateaus of high conductivity from 500 to 700 °C at a water vapour pressure of 1 atm. However, in situ synchrotron XRPD of Sr₄(Sr₂Nb₂)O₁₁·nH₂O as a function of temperature shows that these observations are in fact coincident with melting and dehydration of a secondary phase Sr(OH)₂. The stability of Sr₄(Sr₂Nb₂)O₁₁·nH₂O and Sr₄(Sr₂Ta₂)O₁₁·nH₂O in humid atmospheres is thus insufficient, causing decomposition into perovskites with lower Sr content and SrO/Sr(OH)₂ secondary phases. This, in turn, rationalizes the observation of peaks and plateaus in the conductivity of these materials.

Original language	English
Pages (from-to)	1151-1156
Number of pages	6
Journal	Solid State Ionics
Volume	180
Issue number	20-22
DOIs	https://doi.org/10.1016/j.ssi.2009.05.021
State	Published - Aug 17 2009
Externally published	Yes

Funding

The authors would like to thank Dr. Egil Bakken at SINTEF for the help with the TG measurements. This work is supported by the FRINAT project 171157/V30 “Hydrogen in oxides (HYDROX)” of the Research Council of Norway.

Funders	Funder number
Norges Forskningsråd

Keywords

Complex perovskite
Electrical conductivity
Proton conductor
Scanning electron microscopy
Sr(SrNb)O·nHO
Sr(SrTa)O·nHO
Thermogravimetry
X-ray powder diffraction

Access to Document

10.1016/j.ssi.2009.05.021

Cite this

@article{f84a5815ad04447bb889ecc7939e5968,

title = "Conductivity and water uptake of Sr4(Sr2Nb2)O11·nH2O and Sr4(Sr2Ta2)O11·nH2O",

abstract = "The hydrated oxygen deficient complex perovskite-related materials Sr4(Sr2Nb2)O11·nH2O and Sr4(Sr2Ta2)O11·nH2O were studied at high water vapour pressures over a large temperature range by electrical conductivity measurements, thermogravimetry (TG), and X-ray powder diffraction (XRPD). In humid atmospheres both materials are known to exhibit protonic conductivity below dehydration temperatures, with peak-shaped maxima at about 500 °C. In this work we show that the peaks expand to plateaus of high conductivity from 500 to 700 °C at a water vapour pressure of 1 atm. However, in situ synchrotron XRPD of Sr4(Sr2Nb2)O11·nH2O as a function of temperature shows that these observations are in fact coincident with melting and dehydration of a secondary phase Sr(OH)2. The stability of Sr4(Sr2Nb2)O11·nH2O and Sr4(Sr2Ta2)O11·nH2O in humid atmospheres is thus insufficient, causing decomposition into perovskites with lower Sr content and SrO/Sr(OH)2 secondary phases. This, in turn, rationalizes the observation of peaks and plateaus in the conductivity of these materials.",

keywords = "Complex perovskite, Electrical conductivity, Proton conductor, Scanning electron microscopy, Sr(SrNb)O·nHO, Sr(SrTa)O·nHO, Thermogravimetry, X-ray powder diffraction",

author = "Niina Jalarvo and Camilla Haavik and Camilla Kongshaug and Poul Norby and Truls Norby",

year = "2009",

month = aug,

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doi = "10.1016/j.ssi.2009.05.021",

language = "English",

volume = "180",

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journal = "Solid State Ionics",

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T1 - Conductivity and water uptake of Sr4(Sr2Nb2)O11·nH2O and Sr4(Sr2Ta2)O11·nH2O

AU - Jalarvo, Niina

AU - Haavik, Camilla

AU - Kongshaug, Camilla

AU - Norby, Poul

AU - Norby, Truls

PY - 2009/8/17

Y1 - 2009/8/17

N2 - The hydrated oxygen deficient complex perovskite-related materials Sr4(Sr2Nb2)O11·nH2O and Sr4(Sr2Ta2)O11·nH2O were studied at high water vapour pressures over a large temperature range by electrical conductivity measurements, thermogravimetry (TG), and X-ray powder diffraction (XRPD). In humid atmospheres both materials are known to exhibit protonic conductivity below dehydration temperatures, with peak-shaped maxima at about 500 °C. In this work we show that the peaks expand to plateaus of high conductivity from 500 to 700 °C at a water vapour pressure of 1 atm. However, in situ synchrotron XRPD of Sr4(Sr2Nb2)O11·nH2O as a function of temperature shows that these observations are in fact coincident with melting and dehydration of a secondary phase Sr(OH)2. The stability of Sr4(Sr2Nb2)O11·nH2O and Sr4(Sr2Ta2)O11·nH2O in humid atmospheres is thus insufficient, causing decomposition into perovskites with lower Sr content and SrO/Sr(OH)2 secondary phases. This, in turn, rationalizes the observation of peaks and plateaus in the conductivity of these materials.

AB - The hydrated oxygen deficient complex perovskite-related materials Sr4(Sr2Nb2)O11·nH2O and Sr4(Sr2Ta2)O11·nH2O were studied at high water vapour pressures over a large temperature range by electrical conductivity measurements, thermogravimetry (TG), and X-ray powder diffraction (XRPD). In humid atmospheres both materials are known to exhibit protonic conductivity below dehydration temperatures, with peak-shaped maxima at about 500 °C. In this work we show that the peaks expand to plateaus of high conductivity from 500 to 700 °C at a water vapour pressure of 1 atm. However, in situ synchrotron XRPD of Sr4(Sr2Nb2)O11·nH2O as a function of temperature shows that these observations are in fact coincident with melting and dehydration of a secondary phase Sr(OH)2. The stability of Sr4(Sr2Nb2)O11·nH2O and Sr4(Sr2Ta2)O11·nH2O in humid atmospheres is thus insufficient, causing decomposition into perovskites with lower Sr content and SrO/Sr(OH)2 secondary phases. This, in turn, rationalizes the observation of peaks and plateaus in the conductivity of these materials.

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KW - Electrical conductivity

KW - Proton conductor

KW - Scanning electron microscopy

KW - Sr(SrNb)O·nHO

KW - Sr(SrTa)O·nHO

KW - Thermogravimetry

KW - X-ray powder diffraction

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