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Effect of Powder Purity and Second Phases on the Dielectric Properties of Lead Magnesium Niobate Ceramics
Author(s) -
Chen Jie,
Gorton Andrew,
Chan Helen M.,
Harmer Martin P.
Publication year - 1986
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.1151-2916.1986.tb07396.x
Subject(s) - pyrochlore , materials science , microstructure , dielectric , impurity , ceramic , magnesium , phase boundary , mineralogy , phase (matter) , analytical chemistry (journal) , grain boundary , solid solution , metallurgy , chemistry , chromatography , optoelectronics , organic chemistry
The dielectric properties of lead magnesium niobate ceramics have been studied as a function of powder purity and microstructure. Starting powder purity was shown to have d pronounced effect on the resultant dielectric properties. Values of K max as high as 20 000 were obtained using starting powders of exceptionally high purity (99.999%), despite the formation of a pyrochlore phase. The pyrochlore phase formed as large isolated grains in the microstructure. It was found to be a cubic‐type pyrochlore with a composition of Pb 2 Nb 1.75 Mg 0.25 O 6.62 . Much lower dielectric constants were obtained with samples of lower reagent‐grade purity. This was partially explained by the presence of an intergranular second phase. Other factors such as lattice impurities and grain‐boundary chemistry were also argued to be important.