Effect of preparation and impurities on the size and shape of the crystallites and on the crystal symmetry of superionic PbSnF{sub}4

摘要

The highest performance fluoride ion conductor, PbSnF{sub}4, has been applied for the fabrication of an ambient temperature amperometric oxygen sensor, where it is used in the polycrystalline form. However, the structure of this material is highly anisotropic, thus one could expect polycrystalline samples to give a performance strongly dependent on crystallite direction. We have shown that the tin electronic structure has a very strong influence on the local structure, which determines the preferred direction of crystal growth, which is itself responsible for the crystal shape. This, in turn, determines the direction of preferred orientation which can dramatically alter the properties relative to a randomly oriented sample. The effect of minor impurities on the size of the crystallites and on the crystalline symmetry has been studied.