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Phase Transformations of Superionic PbSnF4 Above Ambient Temperature: X-Ray Diffraction Versus Temperature
Published online by Cambridge University Press: 10 February 2011
Abstract
PbSnF4 is the highest performance fluoride ion conductor. A fast amperometric response oxygen sensor based on PbSnF4 has been constructed and tested. A long life device with time independent response and reliable performance requires the materials used for its construction be stable over the life time of the device in the operating conditions. Since ionic conductivity is thermally activated, possible use at high temperature can be envisaged. Therefore, it is of prime importance to know in details the behavior of the material versus time in the expected temperature range of use and of storage. PbSnF4 can be prepared by many methods that we have investigated, and each method gives a material that is different from the others in one way or another (symmetry, strain, particle rendomization, particle dimensions, temperature range of stability). In addition, we have shown that several phase transitions take place versus temperature or when some other treatments are applied. Many of these transitions are very sluggish, and therefore give a false impression of stability, when the phases are actually metastable, and thus changes take place slowly over time. We have studied the stability of tetragonal α-PbSnF4 and o-PbSnF4 by use of X-ray diffraction, in the most probable conditions of use (ambient temperature to 200°C in air). Changes were found to take place, which should be taken into account in the design of devices and when establishing their optimum temperature of use and storage.
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- Copyright © Materials Research Society 1999
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