Co-doping effects of Ba2+ and Ta5+ on the microstructure and ionic conductivity of garnet-type solid state electrolytes

A series of garnet-type electrolytes with the compositions of Li6.6+yLa3-yBayZr1.6Ta0.4O12 (0 <= y <= 0.08) and Li6.4+yLa3-yBayZr1.4Ta0.6O12 (0 <= y <= 0.08) were obtained through pressureless sintering method at 1230 degrees C for 1 h successfully. The microstructure and electr(0.4)O(12)performance of the electrolytes were characterized and the co-doping effects of Ba2+ and Ta5+ were investigated. The substantially promoted ionic conductivity was achieved by doping Ba2+ into the Li6.4La3Zr1.4Ta0.6O12 ceramic. Ba2+ dopant made the LLZTO electrolyte a higher Li+ concentration ascribed to the valence gap between Ba2+ and La3+. This facilitated the grain growth so that the electrolytes could be sintered densely in a relatively short sintering time. Meanwhile. The Li+ transportation channel would be enlarged due to the larger ion radius of Ba2+ compared to that of La3+. The higher Li+ concentration and the broader Li+ transportation channel contributed primarily to the improvement of the electrical performance of LLZTO electrolytes. The specimen with the constituent of Li6.46La2.94Ba0.06Zr1.4Ta0.6O12 exhibited the highest conductivity of 6.04 x 10(-4) S cm(-1) and the lowest activation energy of 0.27 eV. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

A series of garnet-type electrolytes with co-doping of Ba2+ and Ta5+ were successfully prepared through pressureless sintering method, resulting in significantly enhanced ionic conductivity attributed to the higher Li+ concentration and widened Li+ transportation channel. This improvement in electrical performance was achieved by facilitating grain growth and densification of the electrolytes.