Ordering structure of barium magnesium niobate ceramic with A-site substitution

The ordering behaviour of Ba(Mg1/3Nb2/3)O3 ceramics (BMN) substituted by La3+, Na+, K+ was investigated using X-ray powder diffraction and transmission electron microscopy. The 1:2 ordered structure of BMN can be transformed to 1:1 ordered structure by substituting a small amount of La cation ion into the A-site. Moreover, the degree of ordering was increased with La content in the compound, and reached almost unity at [La] = 50 mol%. When the La ion in (Ba1−xLax)(Mg(1+x)/3Nb(2−x)/3)O3 (BLMN) was substituted by Na or K ions, the 1:1 ordered structure of BLMN was transformed into the 1:2 ordered structure. The degree of 1:2 ordering was influenced by the sintering temperature and the size difference between the A and B site ions.