Study of structure and conductivity of Li3/8Sr7/16-3x/2LaxZr1/4Nb3/4O3 solid electrolytes

Abstract Li 3/8 Sr 7/16-3x/2 La x Zr 1/4 Nb 3/4 O 3 (x = 0, 0.05, 0.10, 0.15, 0.20) were synthesized using the conventional solid-state reaction method. In order to increase the vacancy concentration, La 3+ was doped on the Sr 2+ site. Crystal structures of doped samples were characterized by X-ray diffraction. Except, perovskite-type Li 3/8 Sr 7/16-3x/2 La x Zr 1/4 Nb 3/4 O 3 (x = 0, 0.05, 0.10, 0.15) samples were fabricated by heat treatment at 1250 °C, 1275 °C, 1275 °C and 1275 °C, respectively, for 15 h. Lattice sizes decreased with the increase of doping amounts because of the smaller ion radius of La 3+ compared to that of Sr 2+ . Ionic conductivities of the samples were measured by AC impedance spectroscopy. The results showed that the ionic conductivity increases at first and then decreases with raising doping amounts and sintering temperatures. So the optimized composition Li 3/8 Sr 7/16-3x/2 La x Zr 1/4 Nb 3/4 O 3 (x = 0.05) sintered at 1275 °C was selected with the highest total conductivity of 3.33 × 10 −5 S cm −1 at 30 °C and an activation energy of 0.27 eV. Additionally, potentiostatic polarization test was used to evaluate the electronic conductivity. The optimal composition Li 3/8 Sr 7/16-3x/2 La x Zr 1/4 Nb 3/4 O 3 (x = 0.05) as a possible Li-ion conducting solid electrolyte has an electronic conductivity of only 8.39 × 10 −9 S cm −1 .