Lead doped calcium niobate–tantalate pyrochlores: phase structure and dielectric properties

Authors: Merry, J. C.; Leach, A. C.; Ubic, R.

Source: British Ceramic Transactions, Volume 101, Number 4, August 2002 , pp. 143-145(3)

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Abstract:

The microwave properties of lead pyroniobates have been shown to be influenced by their crystal structures. The incorporation of PbO rich layers as the concentration of Pb increases enables these materials to attain high Q_f but this is offset by poor ?_r and ?_f performance. Isovalent doping of Ta⁵⁺ ions on the niobium sites can reduce ?_f. In a similar previous study, calcium niobate-tantalate with zero ?_f was derived but both ?_r and Q_f were lower than for the lead pyroniobates. The present work aims to build on these findings by preparing pyrochlore ceramics simultaneously doped on both A and B sites, to give minimal ?_f values and enhanced quality factors for medium permittivity applications. A single phase composition of (Ca_1·4Pb_0·6) (Nb_0·5Ta_1·5) O₇ was prepared by mixing precalcined batches of Ca₂(Nb_0·5Ta_1·5) O₇ and Pb₂(Nb_0·5Ta_1·5) O₇ in the appropriate ratio. Pellets were sintered to high densities and their dielectric properties tested. Preliminary data suggest that compositions with greater lead content and higher A/B cation ratio should be pursued.

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Document Type: Research Article

DOI: http://dx.doi.org/10.1179/096797802225003389

Publication date: 2002-08-01

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