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Crystal Symmetry of BaTiO 3 Grains in X7R Multilayer Ceramic Capacitors
Author(s) -
Lee HwanWen,
Chu Mike S. H.,
Lu HongYang
Publication year - 2011
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.1551-2916.2010.04232.x
Subject(s) - tetragonal crystal system , materials science , ceramic capacitor , barium titanate , acceptor , grain boundary , crystal (programming language) , shell (structure) , vacancy defect , single crystal , dopant , ceramic , crystallography , mineralogy , microstructure , condensed matter physics , crystal structure , doping , composite material , chemistry , capacitor , physics , optoelectronics , quantum mechanics , voltage , computer science , programming language
Convergent beam electron diffraction combined with conventional transmission electron microscopy is used to determine the crystal symmetry, and with energy‐dispersive spectrometry (EDS) the microchemistry of BaTiO 3 grains in (CaO+MgO)‐codoped, EIA‐X7R multilayer ceramic capacitors (MLCCs). The point group symmetries of the core–shell grain and the shell grain in MLCCs are analyzed following the procedures reported by Buxton and colleagues. It is found that the point group symmetry of the core region from the type‐I and type‐II core–shell grains are tetragonal ( T ) 4 mm and rhombohedral ( R ) 3 m , respectively, with that of the shell region and the shell grain is the cubic ( C ) m 3 m . The dependence of the C ‐, T ‐, and R ‐phases on the oxygen vacancy concentration generated by acceptor dopants, sintered in low oxygen partial pressure ( p O 2 ), is discussed.