Journal article
Conductivity and water uptake of Sr4(Sr2Nb2)O11·nH2O and Sr4(Sr2Ta2)O11·nH2O
Department of Chemistry, University of Oslo, Centre for Materials Science and Nanotechnology, FERMiO, Gaustadalleen 21, NO-0349 Oslo, Norway
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.
| Language: | English |
|---|---|
| Year: | 2009 |
| Pages: | 1151-1156 |
| ISSN: | 18727689 and 01672738 |
| Types: | Journal article |
| DOI: | 10.1016/j.ssi.2009.05.021 |
