Structure and Dielectric Properties of Lead Pyrochlores |
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Authors: | Rick Ubic Ian M. Reaney |
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Affiliation: | Department of Materials, Queen Mary, University of London, London E1 4NS, United Kingdom;Department of Engineering Materials, The University of Sheffield, Sheffield S1 3JD, United Kingdom |
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Abstract: | This work investigates the structure and stability of the pyrochlore solid solution Pb n Nb2O5+ n using a combination of high-resolution electron microscopy and electron diffraction. The microwave dielectric properties of the series 1.5 ≤ n ≤3.0 have been established, and the effect of the substitution of Ta5+ for Nb5+ on dielectric properties has also been investigated for n = 1.5 and 2.0. Single-phase cubic pyrochlore was obtained for n = 1.5. Compositions for which n > 1.5 showed discreet PbO-rich layers on {111}cubic planes between alternating slabs of pyrochlore, similar in appearance to Ruddlesden–Popper phases. The occurrence of these layers results in a lowering of the overall symmetry to trigonal, and their presence was found to have a profound effect on the microwave dielectric properties. |
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Keywords: | structure dielectric materials/properties pyrochlore |
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