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Structure and Dielectric Properties of Lead Pyrochlores
Author(s) -
Ubic Rick,
Reaney Ian M.
Publication year - 2002
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2002.tb00483.x
Subject(s) - pyrochlore , dielectric , materials science , phase (matter) , diffraction , microwave , crystallography , trigonal crystal system , solid solution , mineralogy , scanning electron microscope , analytical chemistry (journal) , crystal structure , optics , chemistry , composite material , metallurgy , optoelectronics , physics , organic chemistry , chromatography , quantum mechanics
This work investigates the structure and stability of the pyrochlore solid solution Pb n Nb 2 O 5+ 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 Ta 5+ for Nb 5+ 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.