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We found that the grain size of V2O5 thin films produced by pulsed laser ablation strongly influences their optical characteristics. The decrease in the optical band gap associated with a change in spectral transmittance of the pulsed laser deposited V2O5 films are mainly due to structure evolution from amorphous to crystalline state and size evolution and distribution characteristics of the grains as a function of increasing growth temperature. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A novel material, namely, Fe-containing lithium-metal triphosphate (LiM2P3O10; MFe), has been synthesized by wet-chemical method. The phase shows the monoclinic structure (P21/m≡C 2 2 h ). The crystal chemistry and chemical structural characteristics have been analyzed by X-ray-diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). Surface chemical composition, valence state, and chemical bonding and local structure analysis have been performed by X-ray photoelectron (XPS) and Raman scattering (RS) spectroscopy. EDS and HAADF-STEM indicate the chemical homogeneity and purity of LiFe2P3O10 samples. Both XPS and RS experiments show the existence of an amorphous carbon deposit at the surface of the LiFe2P3O10 particles. Comparison between XPS results for LiFePO4 olivine and LiFe2P3O10 revealed the change in the binding energy of Fe(II) ions. Studies of the local structure characterized by Raman scattering show the evolution of the chemical bonding with the increased number of interconnected PO4 oxo-anionic groups. The electrochemical characteristics of LiFe2P3O10 demonstrate their applicability in lithium batteries.

Vanadium pentoxide films were prepared by pulsed laser deposition (PLD) and their surface structure evolution in relation to the growth temperature and as a function of lithium intercalation was studied. The deposition was made onto various substrate materials over a wide substrate temperature range of 30-500• C, keeping the oxygen partial pressure at 100 mTorr. The surface properties of V 2 O 5 films were studied by Raman scattering spectroscopy in order to understand the effect of substrate temperature on the structure and growth behavior. The results indicated that the structure of PLD V 2 O 5 films is highly dependent on the growth temperature. The Raman spectra provide additional insight into the nature of the structural changes of lithiated films, showing the appearance of the d-and g-phases of Li x V 2 O 5 .

The structural characteristics of lithium nickel phosphate (LiNiPO4) prepared by solid-state chemical reaction have been studied in detail using the analytical electron microscopy and Raman spectroscopy measurements. The high-resolution transmission electron microscopy and selected area electron diffraction measurements indicate that the grown LiNiPO4 is well-crystallized in olivine structure without any indication of crystallographic defects such as dislocations or misfits. The energy-dispersive X-ray spectrometry coupled with the elemental compositional mapping using high-angle angular dark field scanning electron microscopy confirms the chemical quality of the grown LiNiPO4 in terms of homogeneity and uniform elemental distribution characteristics. The local structure and chemical bonding between NiO6 octahedral and (PO4)3- tetrahedral groups probed by Raman spectroscopy also indicate the high-quality of LiNiPO4. Structural analysis of the delithiated Li0.09NiPO4 phase indicates lattice contraction and distortion upon lithium extraction. A detailed analysis and comparison of the pristine and delithiated phases is also reported.

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