Local cationic ordering behavior in Ba(Mg1/3Nb2/3)O3 ceramics

We have studied the effect of sintering temperature and time on cationic ordering in BaMg1/3Nb2/3O3 (BMN) microwave dielectric ceramics using transmission electron microscopy. Energy-dispersive spectroscopy was used to analyze the local chemical compositions. It is revealed that according to the sintering conditions the BMN ceramics show diverse local cationic ordering behavior, such as the development of domain twinning and ‘core-shell’-structured grains and the formation of local disordered domains, although generally having 1:2 cation ordering structure. The disordered structure is formed in Mg-excess regions. Such local chemical variation seems to be caused by the formation of BaNb2O6 second phase in the neighboring grain boundary. Microwave dielectric properties of the ceramics will also be discussed in relation to the structural variation.