Influence of sintering aids and excess Lithium on the conductivity of perovskite-type Li3/8Sr7/16Zr1/4Nb3/4O3 solid electrolyte

Perovskite-structured Li3/8Sr7/16Zr1/4Nb3/4O3 solid-state Lithium-conductors were prepared by conventional solid-state reaction method. Influence of sintering aids (Al2O3, B2O3) and excess Lithium on structure and electrical properties of Li3/8Sr7/16Zr1/4Nb3/4O3 (LSNZ) has been investigated. Their crystal structure and microstructure were characterized by X-ray diffraction analysis and scanning electron microscope, respectively. The conductivity and electronic conductivity were evaluated by AC-impedance spectra and potentiostatic polarization experiment. All sintered compounds are cubic perovskite structure. Optimal amount of excess Li2CO3 was chosen as 20 wt% because of the total conductivity of LSNZ-20% was as high as 1.6×10−5 S cm−1 at 30 °C and 1.1×10−4 S cm−1 at 100 °C, respectively. Electronic conductivity of LSNZ-20% is 2.93×10−8 S cm−1, nearly 3 orders of magnitude lower than ionic conductivity. The density of solid electrolytes appears to be increased by the addition of sintering aids. The addition of B2O3 leads to a considerable increase of the total conductivity and the enhancement of conductivity is attributed to the decrease of grain-boundary resistance. Among these compounds, LSNZ-1 wt%B2O3 has lower activation energy of 0.34 eV and the highest conductivity of 1.98×10−5 S cm−1 at 30 °C.