Aging effect on vanadium oxide hybrid nanotubes

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

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 V 4+ ions oxidize to V 5+  . 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 V 4+  /V 5+ relationship in the VO x NTs, which may contribute to explain the significant dispersion of data reported in the bibliography.