Synthesis, characterization and electronic properties of novel cubic phase
vanadium compounds

Victoria Soghomonian, Virginia Tech, Department of Physics, Blacksburg, VA 24061

Hydrothermal synthesis provides an alternative to solid state synthetic techniques.
The hydrothermal route is utilized for the synthesis of novel materials as well as for the
growth of single crystals ranging from zeolites to quartz. Hydrothermal syntheses are
carried out in aqueous conditions under autogenous pressure, and rely on the solubility
of reactants at the moderate temperatures used (generally up to 520 K). Thus, a wide
variety of starting materials may be used with various conditions of pressure and
temperature, yielding not only the thermodynamically stable products, but kinetically
stable ones as well. Furthermore, templating agents are judiciously used to guide
crystal formation.
Here we discuss several vanadium oxide compounds, their synthesis and
characterization, and their electronic properties. These compounds crystallize in cubic
space groups, and we have As or Ga substituting for a number of V centers and where F
substitutes for a number of O sites, sometimes leading to solid solutions. These
substitutions result from variations in reaction parameters, and attest the flexibility of
hydrothermal routes for the isolation of novel structures. These substitutions also
appear to influence the electronic properties of these compounds, and we present
variable temperature resistivity measurements. The room temperature resistivities of
these compounds range from 106 W cm to 108 W cm.
The cubic structures discussed here are constructed from different building blocks
ranging from weakly interacting V/As/O clusters to covalently bound 3-dimensional
V/As/O frameworks. We compare both the structure and electronic properties of these
compounds with their structural analogs where no substitution of the V or O sites are
present, and where P is substituted for the As site. We aim to correlate, within this set of
compounds, structural variations to electronic properties, as well as expand the
repertoire of new structures.

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