PUMA
Istituto dei materiali per l'elettronica ed il magnetismo     
Calestani D., Licci F., Kopnin E., Calestani G., Gauzzi A., Bolzoni F., Besagni T., Boffa V., Marezio M. Preparation and characterization of powders and crystals of V(n-x)Ti(x)O(2n-1) Magneli oxides. In: Crystal Research and Technology, vol. 40 (10-11) pp. 1067 - 1071. Wiley, 2005.
 
 
Abstract
(English)
Vn-xTixO2n-1 Magnéli phases have been synthesized under vacuum in powder form (n=4, 0≤x≤0.4) andcrystals (n = 4 and 5, x = 0.5 and 1.4, respectively), grown by chemical vapour transport in closed ampoules. TeCl4 and NH4Cl were used as transporting agents. Needle-shaped crystals as long as 200-300 micrometers or 2-3 mm were obtained when in presence of NH4Cl or TeCl4, respectively. The powder and crystal structures were examined by X-ray diffraction and the transport and magnetic characteristics were measured.. The powders resulted to be single-phase and the relevant composition was assumed to be equal to the nominal one. The overall stoichiometry of compounds, n, was determined from single crystal X-ray diffraction data. The Ti content, x, was deduced from the elementary cell volume, by applying the Végard law. Crystals were mainly untwinned and of good quality. The elementary cell of both, powders and crystals, was triclinic (P-1) and did not change with doping. DC electrical resistivity of the crystals was measured in a four-points (van der Pauw) configuration. DC magnetic susceptibility of the powders was measured in a SQUID magnetometer. The Ti doping was found to progressively smooth and finally to suppress the magnetic transitions occurring in the V4O7. The metal-insulator transitions observed in V4O7 and V5O9, at around 235 and 125 K respectively, were not observed in the doped crystals, thus indicating some significant change of the electronic structure of the V oxides.
URL: http://www.crystalresearch.com/crt/ab40/1067_a.pdf
DOI: DOI 10.1002/crat.200410488
Subject vanadium and titanium oxides
Magnéli phases
CVD crystal growth
I-V characterization
SQUID magnetic susceptibility
metal-insulator transition
81.15.Gh Chemical vapor deposition
81.10.Bk Growth from vapor
81.05.Je Ceramics and refractories
71.30.+h Metal-insulator transitions and other electronic transitions
64.70.Kb


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