Performance and capacity fade of V2O5–lithium polymer batteries at a moderate–low temperature

Characterization of V2O3 Nanoscale Thin Films Prepared by DC Magnetron Sputtering Technique

Vanadium sesquioxide V2O3, a transition metal oxide, is an important metal transition insulator due to its potential applications in novel electronic and memory devices. V2O3 thin films of thickness around 230 nm were grown on Si/SiO2/Ti/Pt substrates at deposition temperature of 723 K in a controlled Ar:O2 atmosphere of 35:2.5 sccm employing Direct Current (DC) magnetron sputtering. X-ray diffraction studies confirmed single phase of the material stabilized in corundum rhombohedral R3¯C phase. X-ray photoelectron spectroscopic results revealed chemical oxidation states are of V3+ and O2− and have nearly stochiometric elemental compositions in the films. Magnetization studies down to 10 K predicts a canted antiferromagnetic transition around 55 K. Out of 7 expected Raman active modes (2A1g + 5Eg), two A1g Raman active modes at 242 and 500 cm−1 were observed at ambient R3¯C phase. Temperature dependent Raman spectroscopic studies carried out from 80 to 300 K identified a monoclinic to rhombohedral phase transition at ~143 K.

Synthesis and characterization of metastable transition metal oxides and oxide nitrides

New routes to vanadium sesquioxide and tantalum oxide nitride (γ- and δ-phase) are presented. Phase pure V2O3 with bixbyite-type structure, a metastable polymorph, was obtained from vanadium fluoride hydrates at ~750 K. It crystallizes in the cubic crystal system in space group I a 3 ¯ $Ia\bar 3$ with lattice parameter a=939.30(5) pm. The catalytical properties of the corresponding oxide nitride phases and their oxidation and reduction solid-state kinetics were investigated. The preparation of γ-TaON as a phase pure sample can be realized by ammonolysis of X-ray amorphous tantalum oxide precursors at 1073 K. This metastable tantalum oxide nitride crystallizes in the monoclinic VO2(B)-type structure in space group C2/m. The same precursors can be used to synthesize the δ-modification with an anatase-type structure at 1023 K. It crystallizes in the tetragonal crystal system in space group I41/amd. A maximum yield of 82 m % could be obtained. The fundamental band gaps of the synthesized and of other metastable TaON polymorphs were calculated from first principles using the GW method. The present results are compared to experimental data and to previous calculations at hybrid DFT level.

Synthesis and Electrical Transport of Single-Crystal NH4V3O8 Nanobelts

Monoclinic NH(4)V(3)O(8) single-crystalline nanobelts with widths of 80-180 nm, thicknesses of 50-100 nm, and lengths up to tens of micrometers have been synthesized at large scale in an ammonium metavanadate solution by a templates/catalysts-free route. Such nanobelts grow along the direction of [010]. The individual NH(4)V(3)O(8) nanobelt exhibits nonlinear, symmetric current/voltage (I/V) characteristics, with a conductivity of 0.1-1 S/cm at room temperature and a dielectric constant of approximately 130. The dominant conduction mechanism is based on small polaron hopping due to ohmic mechanism at low electric field below 249 V/cm due to Schottky emission at medium electric field between 249 and 600 V/cm and due to the Poole-Frenkel emission mechanism at high field above 600 V/cm.