A microcontact impedance study on NASICON-type Li1+xAlxTi2-x(PO4)(3) (0 <= x <= 0.5) single crystals

作者：Rettenwander D^*; Welzl A; Pristat S; Tietz F; Taibl S; Redhammer G J; Fleig J

来源：Journal of Materials Chemistry A, 2016, 4(4): 1506-1513.

DOI：10.1039/c5ta08545d

We successfully demonstrated the applicability of microcontact impedance spectroscopy (MC IS) on Li+ conducting solid electrolytes and measured the Li+bulk conductivity (sigma(b)) of LiTi2(PO4)(3) (LTP) and Li1+xAlxTi2-x(PO4)(3) (LATP) single crystals independent of microstructural effects (e.g., grain boundaries, pores, and density). The crystals had a size of about 100 mu m in each direction and crystallized with NASICON-type structure (R (3) over barc). Finite element calculations were performed to validate the impedance data analysis. A strong increase in sigma(b) in the order of three magnitudes (3.16 x 10(-6) to 1.73 x 10(-3) S cm(-1)) was found after incorporating 0.1 mol Al3+ per formula unit into LTP. Moreover, since the crystal structural changes are almost linear in the LATP system up to x = 0.5, the increase of sigma(b) is most probably related to additional Li+ sites at the M-3 (36f) position. The additional Li+ leads to a displacement of Li+ occupying the M-1 (6b) sites towards the nearest-neighboring M-3 position, and therefore opens the fast-conducting pathway within the NASICON structure. A significant change in sigma(b) was also observed as the Al3+ content further increased (x = 0.1 to 0.5). The highest sigma(b) value of 5.63 x 10(-3) S cm(-1) was obtained for samples with x = 0.4.

• 出版日期2016