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Ordering‐Induced Microstructures and Microwave Dielectric Properties of the Ba(Mg 1/3 Nb 2/3 )O 3 –BaZrO 3 System
Author(s) -
Akbas Mehmet A.,
Davies Peter K.
Publication year - 1998
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.1151-2916.1998.tb02388.x
Subject(s) - microstructure , materials science , transmission electron microscopy , dielectric , niobium , crystallography , phase (matter) , analytical chemistry (journal) , perovskite (structure) , sintering , grain size , chemistry , nanotechnology , metallurgy , optoelectronics , organic chemistry , chromatography
The structures of compositions across the Ba(Mg 1/3 Nb 2/3 )‐O 3 ‐BaZrO 3 (BMN–BZ) system have been examined using X‐ray diffractometry and transmission electron microscopy, and their dielectric properties have been characterized in the microwave range. Although pure BMN adopts a 1:2 ordered structure, of space group Pm 1, additions of 5–15 mol% BZ stabilize a cubic ( Fm m ), 1:1 ordered phase with a doubled perovskite repeat. At higher levels of substitution (>25 mol% BZ), the B‐site cations are disordered. After normal sintering, the niobates in the 1:1 phase field are comprised of nanometer‐sized ordered domains that are dispersed in a disordered matrix. However, by reducing the cooling rate to 10°C/h, a fully ordered microstructure is formed with domain sizes >100 nm in size. The structure of the 1:1 phases has been interpreted using a “random‐layer” model, in which one site is occupied by niobium, and the second is occupied by a random distribution of the remaining cations. The addition of small concentrations of BZ produces a 100% improvement in the dielectric‐loss properties of BMN, and a Q · f value of 82000 is obtained for a 5 mol% substitution.