Dielectric and structural characteristics in barium lanthanum magnesium niobate

The dielectric properties and their related microstructural characteristics in solid solutions of (1-x)Ba(Mg_1/3Nb_2/3)O₃ (BMN)-xLa(Mg_2/3Nb_1/3)O₃ (LMN) (BLMN) were investigated by measuring the relative permittivity (ε_r), Q value, and temperature coefficient of resonator frequency (τ_f), and by observing the microstructure using transmission electron microscopy. The trend of variation of the temperature coefficient of the dielectric permittivity (τ_ε) was the same for our solid solutions as that reported by Reaney et al. When the tolerance factor (t) was >1.01 in BLMN with composition x = 0 to 1.0, where the tilting of oxygen octahedra was not involved, the components of the microstructure included a disordered and transition phase as well 1:1 and 1:2 ordered phases. In the region where 1.01<t<0.96 with x = 0.2 to 0.7, the 1:1 order, the disorder, and the phase due to the antiphase tilting of oxygen octahedra were present. Finally, in the region where t<0.96 with x = 0.7 to 1.0, the microstructure of BLMN was the same as that of the pure LMN, including the 1:1 order and the antiphase, inphase tilting of oxygen octahedra, and the antiparallel shift of A-site cations.