Oxygen vacancies doping effect on the electrical and magnetic behavior of Ba5-xLaxNb4-xTixO15

J.M. DE PAOLI; R.D. SÁNCHEZ; R.E. CARBONIO

JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS

Elsevier

Año: 2007 vol. 68 p. 124 - 130

0022-3697

We report electric and magnetic properties of oxygen deficient Ba5xLaxNb4xTixO15d phases, which have been prepared by solidstate reaction method followed by a controlled reduction process under hydrogen atmosphere. The extra electrons added by the formation of the oxygen vacancies (d) introduce localized spins and the magnetic susceptibility can be described by a temperatureindependent contribution and a Curie–Weiss term associated to the Ti3+ ion formation. Besides, the experimental resistivity (r) data of these four reduced compounds are well described in a wide temperature range with the equation r = AT exp(BT^1/4), which suggests the presence of small polarons in the system. Although, all samples present electrical insulating behavior, the electrical resistivity decreases four orders of magnitude for intermediate x values. We interpreted this fact as a consequence of the mix between the localized bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap.