Structural analysis of Al and Si substituted lithium germanium phosphate glass-ceramics using neutron and X-ray diffraction

Abstract Li 2 O-Al 2 O 3 -GeO 2 -P 2 O 5 (LAGP) glass ceramics (GC) has potential for use as solid state electrolyte in Li-ion rechargeable batteries with better safety and thermal stability. In this work LAGP glass-ceramics with nominal composition of Li 1.5 Al 0.5 Ge 1.5 P 2.9 Si 0.1 O 12 , have been prepared and structural studies have been carried out to understand the effect of Al 3+ and Si 4+ substitution in place of Ge 4+ and P 5+ . Glass was prepared using melt quenching technique and converted into glass-ceramics by controlled heat treatment. We observed that the entire glass has changed in to crystalline form. Phase formation was confirmed using XRD (X-ray diffraction) and ND (Neutron diffraction). Rietveld refinement analysis was used for structural analysis using both ND and XRD data. Analysis showed better refinement in ND and the nuclear density information of two different positions of Li + ion (M1&M2) was revealed from Fourier maps using ND data. This helps to predict the pathway of Li diffusion in the structural units and optimize the conductivity of material. Results showed expansion of c-axis and reduction of a-axis with substitution of Al 3+ in place of Ge +4 . Bottleneck for Li + ion conduction found to increase making an easier path for conduction. The study was further correlated from the recorded local structural data using X-ray photoelectron spectroscopy and Raman Spectroscopy.