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Title: XPS and ionic conductivity studies on Li2O-Al2O3-(TiO2 or GeO2)-P2O5 glass-ceramics
Authors: Chowdari, B.V.R. 
Subba Rao, G.V. 
Lee, G.Y.H.
Issue Date: 2-Nov-2000
Citation: Chowdari, B.V.R., Subba Rao, G.V., Lee, G.Y.H. (2000-11-02). XPS and ionic conductivity studies on Li2O-Al2O3-(TiO2 or GeO2)-P2O5 glass-ceramics. Solid State Ionics 136-137 : 1067-1075. ScholarBank@NUS Repository.
Abstract: Lithium ion conducting glass-ceramics composed of the crystalline conducting phase LiM2(PO4)3 (M = Ti and Ge) in which the M4+ ions are partially substituted by Al3+ ions (Li-analogue of NASICON) have been synthesized by heat-treatment of Li2O-Al2O3-MO2-P2O5 (M = Ti and Ge) glasses. The as-prepared and annealed glasses and glass-ceramics have been characterized by XRD, DSC, XPS and conductivity techniques. The glass transition temperature, Tg of the annealed glasses was found to be 601 °C and 474 °C for the M = Ti and Ge glass systems whereas the crystallization temperature, Tc of the annealed glasses are 644 °C and 578 °C respectively. XPS studies show that the O 1s 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 deconvoluted 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 character. The glass-ceramics show fast ion conduction (σ303 K = 6.53×10-4 (M = Ti) and 3.99×10-4 S cm-1 (M = Ge)) and low Ea value (0.31 eV). These σ values are slightly higher than the corresponding crystalline Li1+xM2-xAlxP3O12 (M = Ti and Ge) phases and four to five orders of magnitude higher than the respective glassy phases. Plausible explanation for the enhancement of σ in glass-ceramics is given. It is suggested that the M = Ge glass-ceramics can be used as a solid electrolyte in the all-solid state Li-ion rechargeable battery.
Source Title: Solid State Ionics
ISSN: 01672738
DOI: 10.1016/S0167-2738(00)00500-2
Appears in Collections:Staff Publications

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