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

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

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 expðB=TÞ1=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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. 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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. these four reduced compounds are well described in a wide temperature range with the equation r  AT expðB=TÞ1=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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. 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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. 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 expðB=TÞ1=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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. 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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. these four reduced compounds are well described in a wide temperature range with the equation r  AT expðB=TÞ1=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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. 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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. 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 expðB=TÞ1=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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. 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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. these four reduced compounds are well described in a wide temperature range with the equation r  AT expðB=TÞ1=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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. 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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. 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 expðB=TÞ1=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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. 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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. these four reduced compounds are well described in a wide temperature range with the equation r  AT expðB=TÞ1=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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. 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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. 5xLaxNb4xTixO15d 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 expðB=TÞ1=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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. 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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. these four reduced compounds are well described in a wide temperature range with the equation r  AT expðB=TÞ1=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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. 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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. 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 expðB=TÞ1=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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. 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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. these four reduced compounds are well described in a wide temperature range with the equation r  AT expðB=TÞ1=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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. 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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. 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 expðB=TÞ1=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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. 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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. these four reduced compounds are well described in a wide temperature range with the equation r  AT expðB=TÞ1=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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. 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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. 3+ 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 expðB=TÞ1=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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. 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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. r  AT expðB=TÞ1=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. bands of the Nb and Ti ions, which favors the promotion of carriers due to reduction of the band gap. 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.