On the Electrical Properties of Synthetic Manganocolumbite MnNb2O6-
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- 作者：Flaviano Garcí ; a-Alvarado ; Alodia Orera ; Jesú ; s Canales-Vá ; zquez ; John T. S. Irvine
- 刊名：Chemistry of Materials
- 出版年：2006
- 出版时间：August 8, 2006
- 年：2006
- 卷：18
- 期：16
- 页码：3827 - 3834
- 全文大小：624K
- 年卷期：v.18,no.16(August 8, 2006)
- ISSN：1520-5002
文摘
A manganocolumbite with nominal composition MnNb2O6 has been prepared under air in order tocharacterize its electrical behavior. Although powder X-ray diffraction indicates the presence of a singlephase, electrical and microscopic characterization reveals two different bulk responses. The origin ofthese two bulk elements seems to relate to the presence of two compositions with slight excess of eithermanganese or niobium. These are stabilized instead of MnNb2O6, indicating the instability of the nominalcomposition. However, these variations of composition are not large enough to be detected by our structuralcharacterization methods, although the effect is easily detected by impedance spectroscopy and fromparticle shape in scanning electron microscopy (SEM). Under reducing conditions, monophasic sampleswith Nb/Mn ratio close to 2 are obtained. From magnetic measurements the main magnetic contributionis determined to be from Mn2+ in all cases. The oxygen deficiency of reduced MnNb2O6-
was only justdeterminable by thermogravimetry, indicating that ~ 0.02. On annealing at 1150 
C in 5% H2, a decreasein unit cell volume of 0.22%, an increase in electrical conductivity of 4 orders of magnitude, and theappearance of a Pauli contribution also indicate a small degree of Nb reduction.
was only justdeterminable by thermogravimetry, indicating that ~ 0.02. On annealing at 1150 C in 5% H2, a decreasein unit cell volume of 0.22%, an increase in electrical conductivity of 4 orders of magnitude, and theappearance of a Pauli contribution also indicate a small degree of Nb reduction.