Li ion conduction of perovskite Li0.375Sr0.4375Ti0.25Ta0.75O3 and related compounds

In this work, perovskite-structured Li0.375Sr0.4375M0.25N0.75O3 (M=Ti, Sn, N=Nb, Ta) solid electrolytes were synthesized by conventional solid state reaction method. Phase compositions, fractured morphologies and conductivities of these compounds were investigated by X-ray diffraction, scanning electron microscope and AC-impedance spectroscopy, respectively. X-ray diffraction analysis confirms that all of Li0.375Sr0.4375M0.25N0.75O3 (M=Ti, Sn, N=Nb, Ta) ceramics present perovskite structure. Pure Li0.375Sr0.4375Ti0.25Ta0.75O3 and Li0.375Sr0.4375Sn0.25Ta0.75O3 perovskite ceramics were obtained. But impurities were detected in Li0.375Sr0.4375Ti0.25Nb0.75O3 and Li0.375Sr0.4375Sn0.25Nb0.75O3. Among all investigated compounds, Li0.375Sr0.4375Ti0.25Ta0.75O3 shows the highest total ionic conductivity of 2.60 × 10−4 S cm−1 at room temperature and the lowest activation energy of 0.347 eV. Conductivities of Li0.375Sr0.4375Sn0.25Ta0.75O3 and Li0.375Sr0.4375Sn0.25Nb0.75O3 were 4.4 × 10−5 S cm−1 and 1.82 × 10−6 S cm−1, respectively. Their conductivities were much lower than Li0.375Sr0.4375Ti0.25Ta0.75O3 and Li0.375Sr0.4375Ti0.25Nb0.75O3.