TY - JOUR
T1 - Extensive lithium disorder in Li1.5Fe0.5Ti1.5(PO4)3 Nasicon by neutron diffraction, and the Li1+xFexTi2-x(PO4)3 phase diagram
AU - Catti, Michele
AU - Comotti, Angiolina
AU - Di Blas, Silvia
AU - Ibberson, Richard M.
PY - 2004
Y1 - 2004
N2 - Phases with 0 < x ≤ 1.5 were synthesized within the system Li1+xFexTi2-x(PO4)3, of interest for applications as high Li+ mobility material. By powder X-ray diffractometry, three modifications were found to be stable for x ≤ 0.6 (Nasicon-type R3-c), 0.6 < x < 1.1 (orthorhombic Pbca), and x ≥ 1.1 (orthorhombic Pbna). The compound Li1.5Fe0.5Ti1.5(PO4)3 was employed for a detailed structural investigation by high resolution powder neutron diffraction (HRPD time-of-flight diffractometer, ISIS spallation source, UK) at 298 and 673 K. Using Rietveld and Fourier difference techniques, lithium atoms were located and the two structures refined to wRp = 0.053 and 0.035, respectively. Lithium was found to be highly disordered, and distributed in similar amounts between the M1 and M2 cavities of the Nasicon framework, unlike what is usually observed in lithium Nasicon phases. A particularly large ion mobility should thus be expected. The configuration of Li sites within the M1 hollow is strongly affected on heating, so as to displace lithium towards the periphery of the cavity. The effects on the mobility pathways of Li+ ions are analyzed and discussed.
AB - Phases with 0 < x ≤ 1.5 were synthesized within the system Li1+xFexTi2-x(PO4)3, of interest for applications as high Li+ mobility material. By powder X-ray diffractometry, three modifications were found to be stable for x ≤ 0.6 (Nasicon-type R3-c), 0.6 < x < 1.1 (orthorhombic Pbca), and x ≥ 1.1 (orthorhombic Pbna). The compound Li1.5Fe0.5Ti1.5(PO4)3 was employed for a detailed structural investigation by high resolution powder neutron diffraction (HRPD time-of-flight diffractometer, ISIS spallation source, UK) at 298 and 673 K. Using Rietveld and Fourier difference techniques, lithium atoms were located and the two structures refined to wRp = 0.053 and 0.035, respectively. Lithium was found to be highly disordered, and distributed in similar amounts between the M1 and M2 cavities of the Nasicon framework, unlike what is usually observed in lithium Nasicon phases. A particularly large ion mobility should thus be expected. The configuration of Li sites within the M1 hollow is strongly affected on heating, so as to displace lithium towards the periphery of the cavity. The effects on the mobility pathways of Li+ ions are analyzed and discussed.
UR - http://www.scopus.com/inward/record.url?scp=1642326587&partnerID=8YFLogxK
U2 - 10.1039/b312865b
DO - 10.1039/b312865b
M3 - Article
AN - SCOPUS:1642326587
SN - 0959-9428
SP - 835
EP - 839
JO - Journal of Materials Chemistry
JF - Journal of Materials Chemistry
ER -
