Structure and conductivity of perovskite Li0.355La0.35Sr0.3Ti0.995M0.005O3 (M = Al, Co and In) ceramics

Perovskite-type solid electrolyte Li(0.355)La(0.35)St(0.3)Ti(0.995)M(0.005)O(3) (LLSTM, M = Al, Co and In) ceramics were prepared via a conventional solid phase reaction method. The conductivities and microstructure of LLSTM samples were systematically investigated by scanning electron microscopy (SEM), Raman spectroscope, XRD, X-ray photoelectron spectroscopy (XPS) and AC impedance spectroscope. All samples exhibited a cubic perovskite structure, meanwhile, lattice parameter increased when the larger B-site ions were substituted compared to Ti4+ and vice versa. It was found that the shift of characteristic peaks of Ti4+ from Raman and XPS spectra are connected to their different bond strength as the cation substitutions with different ionic radii. The ionic conductivity decreased with increasing the radii of B-site ions due to the change of interatomic bond strength. Besides, lattice parameter changed companying with a Ti(M)-O octahedron distortion and bottle sizes difference also have an influence on conductivity. It was shown that all samples at room temperature have sigma(t), at a magnitude of 10(-5)S/cm and sigma(e) at 10(-11) S/cm, indicating that the LLSTM samples are good lithium conductors. The findings would deepen the understanding of the relations among B-site cation substitution, ionic conduction and microstructure in perovskite ionic conductors.