Microstructural comparison between Nb- and Ta-systems in Li1+x-yM1-x-3yTix+4yO3 (M = Nb5+, Ta5+) solid solution with superstructure

We successfully synthesized Li1+x-yM1-x-3yTix+4yO3 solid solutions (M = Nb or Ta, LMT, 0.07 <= x <= 0.33, 0 <= y <= 0.175) that have a superstructure, using a conventional electric furnace. The synthesizing time depended on the Ti content, and annealing was repeated for 24-264 h until a homogeneous structure was formed by the insertion of periodical intergrowth layers. We characterized the LMT solid solutions, from micro-scale to nano-scale, using X-ray diffraction, a scanning electron microscope, and a transmission electron microscope. The period of the intergrowth layer was controlled by the Ti content. LNT's period of the intergrowth layer was narrower than that of LTT in the real lattice when the Ti content was the same. The narrowest interplanar distance (1.82 nm) of the intergrowth layer was formed in Li0.935Ta0.365 Ti0.810O3. The widest distance (14.3 nm) appeared in Li1.11Nb0.89Ti0.11O3, but no such wide period formed in the Ta-system. (C) 2014 Elsevier B.V. All rights reserved.