Vanadyl formate VO(HCOO)2·H2O as a precursor for preparing nanoscale vanadium sesquioxide V2O3

Abstract

Vanadyl formate monohydrate VO(HCOO)2·H2O has been synthesized by a facile two-stage method. The chemical and structural identity of the synthesized compound has been confirmed by X-ray diffraction, thermogravimetry, vibrational and absorption spectroscopy. It was established that during heating in water and ethylene glycol, VO(HCOO)2·H2O leads to vanadyl hydroxide VO(OH)2 and vanadyl glycolate VO(OCH2CH2O) being formed. When heated in air or in helium at 300 °C and higher, VO(HCOO)2·H2O transforms into vanadium pentoxide or sesquioxide, respectively. VO(HCOO)2·H2O was used as a precursor for the synthesis of nanoscale vanadium sesquioxide (with an average particle size of 50 nm), which is stable under the normal conditions and is characterized by a lower metal-insulator transition temperature than the microsized (bulk) compound. The effect of transition temperature reduction for nanoscale vanadium sesquioxide agrees with the lower value of its unit cell volume (V = 296.74 Å3) as compared with that for bulk V2O3 (297.7 Å3). The main factor affecting the V2O3 particle size is the annealing temperature of precursor in inert atmosphere.