Large magnetoresistances and non-Ohmic conductivity in EuWO1+xN2−x

Kusmartseva, Anna F.; Oró‐Solé, Judith; Bea, Ana M.; Fuertes, Amparo; Attfield, J. Paul

doi:10.1063/1.3180813

Cited by 27 publications

(27 citation statements)

References 12 publications

(14 reference statements)

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“…Anion order in oxynitrides is expected to have a strong influence on physical properties 26 The flow rate of ammonia was 180 cm 3 min −1 . Syntheses of EuNbO 2 N, EuTaO 2 N and EuWON 2 are described elsewhere 6,7,25 . Nitrogen contents were determined by combustion analysis using a Carlo Erba instrument.…”

Section: The Combination Of the Cis-coordination Of Each M Cation By mentioning

confidence: 99%

Anion order in perovskite oxynitrides

et al. 2010

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Transition-metal oxynitrides with perovskite-type structures are an emerging class of materials with optical, photocatalytic, dielectric and magnetoresistive properties that may be sensitive to oxide-nitride order, but the anion-ordering principles were unclear. Here we report an investigation of the representative compounds SrMO(2)N (M = Nb, Ta) using neutron and electron diffraction. This revealed a robust 1O/2(O(0.5)N(0.5)) partial anion order (up to at least 750 °C in the apparently cubic high-temperature phases) that directs the rotations of MO(4)N(2) octahedra in the room-temperature superstructure. The anion distribution is consistent with local cis-ordering of the two nitrides in each octahedron driven by covalency, which results in disordered zigzag M-N chains in planes within the perovskite lattice. Local structures for the full range of oxynitride perovskites are predicted and a future challenge is to tune properties by controlling the order and dimensionality of the anion chains and networks.

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Section: The Combination Of the Cis-coordination Of Each M Cation By mentioning

confidence: 99%

Anion order in perovskite oxynitrides

et al. 2010

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“…3)5) dielectrics, 6)8) colossal magnetoresistance, 9), 10) etc. The functionalities relevant to above applications stem primarily from the coexistence of nitrogen and oxygen atoms within the anion sublattice.…”

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confidence: 99%

Constant-wavelength neutron diffraction study of cubic perovskites BaTaO2N and BaNbO2N

Kim

Lee

2011

J. Ceram. Soc. Japan

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Local structural disorder of perovskite oxynitrides BaTaO 2 N and BaNbO 2 N is investigated by constant-wavelength neutron powder diffraction measurements at 300 and 6 K. Temperature-dependent diffraction line-broadening analyses together with the Rietveld refinements confirm that both perovskites retain average structures of simple cubic symmetry down to 6 K. While the Ta and Nb atoms in the above oxynitrides have remarkably large displacement parameters, indicative of pronounced octahedral distortions, the rigidity of Ba sublattice seems to suppress the cooperative propagation of long-range octahedral tilting.©2011 The Ceramic Society of Japan. All rights reserved.Key-words : Oxynitrides, Perovskites, Atomic displacement parameters, Neutron diffraction, Rietveld refinement [Received January 24, 2011; Accepted March 6, 2011] The perovskite-type oxynitrides emerged recently as a promising material class for developing pigments, 1),2) photocatalysts,3)5) dielectrics, 6)8) colossal magnetoresistance, 9),10) etc. The functionalities relevant to above applications stem primarily from the coexistence of nitrogen and oxygen atoms within the anion sublattice. Nitrogen being more polarizable and less electronegative than oxygen, the oxynitride-type compounds generally have narrower band gaps and more covalent metal-anion bonds, compared with the analogous oxides. Such modifications in the electronic structure and the bonding nature have immediate impacts on the range of optical absorption and dielectric behaviors. 6)Besides the above described electronic effects, the mixed anion composition in oxynitrides presents intriguing structural subjects: anion ordering and local structural disorder. These two phenomena occur contrariwise to each other. That is, a complete O/N ordering in oxynitrides corresponds to an absence of local structural disorder, whereas a statistical O/N distribution means a substantial disruption of the lattice periodicity. Particularly the primitive cubic perovskites BaTaO 2 N and BaNbO 2 N are regarded to have purely random O/N arrangements in the anion sublattice, and hence to be typical examples in which the local and average structural descriptions largely deviate. In fact, while the conventional diffraction studies using X-ray 6) and neutron 11) radiations invariably indicated an average structure of Pm 3m symmetry for BaTaO 2 N and BaNbO 2 N, the zone-axis electron diffraction (ED), 12) extended X-ray absorption fine structure (EXAFS), 13) and pair-distribution-function (PDF) 14) analyses for BaTaO 2 N revealed evidences supporting short-range structural distortions around Ta atoms. On the one hand, above inconsistency reflects the sensitivity of the latter local probes to shortrange structural phenomena, but on the other hand, it raises a question: Would there be no local information retrievable from the bulk diffraction analysis of the above oxynitride perovskites? At this point it can be mentioned that the previous neutron powder diffraction (NPD) study of BaTaO 2 N and BaNbO 2 N, conducte...

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“…In particular, the partial replacement of oxide (O 2À ) by nitride (N 3À ), fluoride (F À ) or sulfide (S 2À ) proved to be effective means of modifying the crystal structure, electronic structure and bonding nature of existing oxide-based materials [8][9][10][11][12]. The resulting oxynitrides, oxyfluorides and oxysulfides exhibited promising properties applicable to pigments [13,14], photocatalysts [15][16][17], phosphors [18,19], dielectrics [20,21], and colossal magneto-resistance [22,23].…”

Section: Introductionmentioning

confidence: 99%

Ionic conductivity of Dion-Jacobson type oxide LiLaTa2O7 and oxynitride LiLaTa2O6.15N0.57 measured by impedance spectroscopy

Kim

2015

Ceramics International

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Large magnetoresistances and non-Ohmic conductivity in EuWO1+xN2−x

Cited by 27 publications

References 12 publications

Anion order in perovskite oxynitrides

Anion order in perovskite oxynitrides

Constant-wavelength neutron diffraction study of cubic perovskites BaTaO2N and BaNbO2N

Ionic conductivity of Dion-Jacobson type oxide LiLaTa2O7 and oxynitride LiLaTa2O6.15N0.57 measured by impedance spectroscopy

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