Synthesis and Structural Analysis of Li_1+x-yM_1-x-3yTi_x+4yO₃ (M : Ta, Nb) Solid Solutions with Superstructure

Abstract

In the ternary Li₂O-M₂O₅-TiO₂ （M＝Ta, Nb） system, a superstructure is formed in the chemical formula of Li_1+x-yM_1-x-3yTi_x+4yO₃ (0.06<x<0.33, 0<y<0.175), which is the so-called M-phase. In the Ta-system, the superstructure was found to form with higher Ti content (0.06<x<0.2, 0.05<y<0.175). In this paper, we focus on the difference between Ta and Nb ions in the formation of a superstructure in the quaternary system Li_1+x (Ta_1-zNb_z)_1-xTi_xO₃ (0.11<x<0.33, 0<z<1.0). The structural change is observed through the grain morphology, X-ray diffraction pattern, and transmission electron microscope image. The results show that the period of the intergrowth layer in the superstructure could be controlled with the Ti content and Ta/Nb ratio.