Aging effect on vanadium oxide hybrid nanotubes

SALETA, MARTÍN E; TOBIA, DINA; FIGUEROA, SANTIAGO J A; LOPEZ, CARLOS A; GRANADA, MARA; SÁNCHEZ, RODOLFO D; MALTA, MARCOS; TORRESI, ROBERTO M

JOURNAL OF PHYSICS CONDENSED MATTER

IOP PUBLISHING LTD

Lugar: Londres; Año: 2019 vol. 31

0953-8984

Vanadium oxides present a rich magnetic phase diagram depending on the oxidation state of the V ions. In particular the vanadium oxide nanotubes (VO x NTs) present several promising perspectives for different technological applications for which it is essential to know the oxidation state of V ions, as well as to evaluate the stability with the aging time of the tubes. In this work we present a systematic study of the time evolution of the magnetic properties of VO x NTs. For this complete characterization, we used electron spin resonance (ESR) and dc-susceptibility techniques, which were supplemented with TEM microscopy and XANES. We observed that for aging in normal environmental conditions of pressure, temperature and humidity, the V4+ ions oxidize to V5+ . Although the multiwall tubular structure is maintained, this oxidation process produces a marked change in the magnetic properties. We conclude that the aging of the samples affects the V4+ /V5+ relationship in the VO x NTs, which may contribute to explain the significant dispersion of data reported in the bibliography.