Lithium ion conducting glass-ceramics composed of the crystalline conductin
g phase LiM2(PO4)(3) (M = Ti and Ge) in which the M4+ ions are partially su
bstituted by Al3+ ions (Li-analogue of NASICON) have been synthesized by he
at-treatment of Li2O-Al2O3-MO2-P2O5 (M = Ti and Ce) glasses. The as-prepare
d and annealed glasses and glass-ceramics have been characterized by XRD, D
SC, XPS and conductivity techniques. The glass transition temperature, Tg O
f the annealed glasses was found to be 601 degreesC and 474 degreesC for th
e M = Ti and Ge glass systems whereas the crystallization temperature, T-c
of the annealed glasses are 644 degreesC and 578 degreesC respectively. XPS
studies show that the O Is spectra for all the glasses and glass-ceramics
could be deconvoluted into two peaks corresponding to the non-bridging (NBO
) and bridging oxygen (BO) atoms. The binding energies (BE) of Li, Ti, Ge,
Al and P have also been listed. In the Li2O-Al2O3-TiO2-P2O5 system, the dec
onvoluted Ti 2p XPS spectra indicate the existence of two oxidation states
of titanium, 3 + and 4 +. The Ti 2p and Ge 3d core levels are characterized
by high BEs, suggesting that Ti4+-O and Ge4+-O bonds are highly ionic in c
haracter. The glass-ceramics show fast ion conduction (sigma (303 K) = 6.53
x 10(-4) (M = Ti) and 3.99 x 10(-4) S cm(-1) (M=Ge)) and low E-a value (0.
31 eV). These sigma values are slightly higher than the corresponding cryst
alline Li1+xM2-xAlxP3O12 (M = Ti and Ge) phases and four to five orders of
magnitude higher than the respective glassy phases. Plausible explanation f
or the enhancement of sigma in glass-ceramics is given. It is suggested tha
t the M = Ge glass-ceramics can be used as a solid electrolyte in the all-s
olid stare Li-ion rechargeable battery. (C) 2000 Elsevier Science B.V. All
rights reserved.