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We present the high-pressure synthesis and crystal structure of a novel titanium hydride complex, BaCa2Ti2H14, with 9-fold coordination. It comprises a unique dinuclear [Ti2H14]6– complex that cons...

We have successfully synthesized a hyperkagome antiferromagnet ${\mathrm{Zn}}_{2}{\mathrm{Mn}}_{3}{\mathrm{O}}_{8}$ by a topochemical method, where ${\mathrm{Mn}}^{4+}$ ions with $S=3/2$ spins form a three-dimensional (3D) corner-sharing triangle network. Magnetic susceptibility and heat capacity measurements revealed an antiferromagnetic transition at ${T}_{\mathrm{N}}=5.8\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. Although no evidence was found for any structural distortion accompanying the transition, the low-temperature magnetic heat capacity showed a nearly ${T}^{2}$ dependence, suggesting the realization of a 2D magnonlike excitation in the 3D hyperkagome lattice.

The discovery of new extended structures has often led to the development of new fields in chemistry and physics. However, the numerous combinations of metals (or cations) to yield new materials ha...

Single crystals of the lithium-ion conductor Li10GeP2S12 have been successfully grown by the self-flux method and are studied by means of X-ray diffraction and impedance spectroscopy. The weak anis...

We report the synthesis, crystal structure, and magnetic properties of two new quantum antiferromagnets A3ReO5Cl2 (A = Sr and Ba). The crystal structure is isostructural with the mineral pinalite Pb3WO5Cl2, in which the Re6+ ion is square-pyramidally coordinated by five oxide atoms, and forms an anisotropic triangular lattice (ATL) made of S = 1/2 spins. The magnetic interactions J and J' in the ATL are estimated from magnetic susceptibilities to be 19.5 (44.9) and 9.2 (19.3) K, respectively, with J'/J = 0.47 (0.43) for A = Ba (Sr). For each compound, heat capacity at low temperatures shows a large T-linear component with no signature of long-range magnetic order above 2 K, which suggests a gapless spin liquid state of one-dimensional character of the J chains in spite of the significantly large J' couplings. This is a consequence of one-dimensionalization by geometrical frustration in the ATL magnet; a similar phenomenon has been observed in two compounds with slightly smaller J'/J values: Cs2CuCl4 (J'/J = 0.3) and the related compound Ca3ReO5Cl2 (0.32). Our findings demonstrate that 5d mixed-anion compounds provide a unique opportunity to explore novel quantum magnetism., Comment: 24 pages, 7 figures, 2 Tables

For the Fukushima decommissioning, the distribution of boron species in the fuel debris must be determined to assess the risk of recriticality, the debris hardness and thus complicate its successful retrieval. As a result, the relocation behavior of boron carbide (B4C) control rod materials has attracted significant attention. In this work, the influence of the thickness of its stainless steel (SS) clad on the initial relocation behavior of the control rod was investigated. In particular, the initial relocation behavior of the B4C control rod materials was dynamically visualized using a technique previously developed by the authors. To simulate the control rod, a type-304 SS tube filled with B4C powder containing particles with sizes of approximately 20–30 µm was heated to a temperature exceeding its eutectic point (1473 K). The three relocation modes of the obtained eutectic melt corresponded to film formation, droplet formation without collapse and droplet formation with collapse.

We investigated topochemical anion exchange reactions for a ScIII-substituted SrTiIVO3 perovskite, Sr(Ti1–yScy)O3–y/2□y/2 (y ≤ 0.1), using CaH2. It was found that the initial introduction of a small amount of anion vacancies (y/2) is crucial to enhance the anion (H–/O2–) exchangeability. For example, hydride reduction of Sr(Ti0.95Sc0.05)O2.975 yielded the oxyhydride SrTi0.95Sc0.05O2.56H0.41 in which the hydride concentration is increased by 33% with respect to pristine SrTiO3 (leading to SrTiO2.76H0.24). This observation highlights the importance of anion vacancies to improve anion (H–/O2–) diffusion, which is a well-known strategy for improving oxide anion conductivity, and suggests that such a vacancy-assisted reaction could be applied to other anion exchange reactions (e.g., F–/O2– and N3–/O2–) to extend the solubility range.

Single crystals are indispensable for understanding the fundamental properties of materials, although obtaining them are often challenging. To investigate the magnetic properties of a kagome-lattice antiferromagnet, we have performed a topochemical crystal transformation from a copper mineral volborthite with a distorted kagome lattice into another copper mineral vesignieite with an almost perfect kagome lattice. A millimeter-sized crystal of vesignieite, which is difficult to prepare via direct chemical reactions, has been successfully obtained. Magnetization measurements on the crystals reveal a unique magnetic order with weak-ferromagnetic moments lying within the kagome plane and successive anomalies in the magnetization curve, which would give important information on the magnetic order of the kagome-lattice antiferromagnet. The present results demonstrate a novel route via the topochemical crystal transformation in preparing a hard-to-obtain crystal.

We investigate the low temperature anion exchange behavior of hydride and oxide in perovskite oxynitrides. CaH 2 reduction of (Sr 1– x La x )Ti(O 3 –x N x ) (0 x ≤ 1) resulted in the selective anion exchange of hydride for oxide rather than nitride, yielding the oxyhydride-nitride (Sr 1– x La x )Ti(O 3 –x–y H y N x ). However, the exchange of hydride is drastically suppressed with increasing nitrogen content and is completely impeded when the nitride content reaches 10% of the anionic site. This implies that the N 3– anions in the oxide lattice play a crucial role in lowering diffusion of O 2– (and H – ). The present study indicates the necessity to consider kinetic aspects when manipulating anion compositions, in particular in a mixed anion system with a small amount of anion vacancies.

Layered materials embrace rich intercalation reactions to accommodate high concentrations of foreign species within their structures, and find many applications spanning from energy storage, ion exchange to secondary batteries. Light alkali metals are generally most easily intercalated due to their light mass, high charge/volume ratio and in many cases strong reducing properties. An evolving area of materials chemistry, however, is to capture metals selectively, which is of technological and environmental significance but rather unexplored. Here we show that the layered telluride T[2]PTe[2] (T=Ti, Zr) displays exclusive insertion of transition metals (for example, Cd, Zn) as opposed to alkali cations, with tetrahedral coordination preference to tellurium. Interestingly, the intercalation reactions proceed in solid state and at surprisingly low temperatures (for example, 80 °C for cadmium in Ti[2]PTe[2]). The current method of controlling selectivity provides opportunities in the search for new materials for various applications that used to be possible only in a liquid., 重金属を固体中で選択的に吸収する材料の発見 : 電子機器からの新たな金属回収法などの開発に期待. 京都大学プレスリリース. 2016-12-20.

An osmium chloride with the chemical formula of OsxCl3 (x = 0.81) was synthesized and its crystal structure and thermodynamic properties were investigated. OsxCl3 crystallizes in a layered CdCl2-type structure with the triangular lattice partially occupied by Os ions on average. However, on microscopic length scales, the triangular lattice is composed of nano-domains with a honeycomb arrangement of Os ions, as observed by electron microscopy and Raman scattering experiments. Magnetization and heat capacity measurements revealed an absence of magnetic long-range order down to 0.08 K, while a broad peak in heat capacity at 0.15 K may indicate a short-range order in the local honeycomb lattice. OsxCl3 may exhibit certain aspects of the Kitaev spin liquid that are expected for a perfect honeycomb lattice of osmium trichloride., Comment: 11 pages, 8 figures

We show anion intercalation reaction to ternary palladate Bi2PdO4 (P4/ncc) with one-dimensional (1D) channels comprised of Bi3+ ions. By low-temperature treatment with XeF2, fluoride anions are inserted in the 1D pores (4b site), giving Bi2PdO4Fx (x ​

International audience; Layered perovskite titanium oxyhydrides have been prepared by low-temperature topochemical CaH reduction from Ruddlesden-Popper Sr Ti O phases ( n = 1, 2) and structurally characterized by combined synchrotron X-ray and neutron diffraction data refinements. In the single-layered SrTiOD material, hydride anions are statistically disordered with oxides on the apical site only, as opposed to known transition-metal oxyhydrides exhibiting a preferred occupation of the equatorial site. This unprecedented site selectivity of H has been reproduced by periodic DFT+ U calculations, emphasizing for the hydride defect a difference in formation energy of 0.24 eV between equatorial and apical sites. In terms of electronic structure, the model system SrTiOH is found to be slightly metallic and the released electron remains mostly delocalized over several Ti atoms. On the other hand, hydride anions in the double-layered SrTiOH material show a clear preference for the bridging apical site within the perovskite slabs, as confirmed by DFT calculations on the SrTiOH model system. Finally, the influence of the B-site chemical nature on the hydride site selectivity for early 3d transition metals is theoretically explored in the single-layered system by substituting vanadium for titanium. The V electronic polaron is suggested to play a role in stabilizing H on the equatorial site in SrVOH for x = 0.125.

We have studied electronic properties of perovskite oxyhydrides ATiO3–xHx (A = Ba, Sr). Epitaxial thin films of ATiO3–xHx with various hydride compositions, up to x = 0.58 for Ba and x = 0.45 for Sr, are prepared by the low-temperature CaH2 reduction of the corresponding oxide films deposited on (LaAlO3)0.3(SrAl0.5Ta0.5O3)0.7 (LSAT) substrates by pulsed laser deposition. Resistivity measurements for A = Sr show a metallic phase over a wide range of H– composition, implying a substantial stabilization of H 1s orbitals that should be distributed over O 2p orbitals. On the other hand, for A = Ba, a semiconducting behavior is seen up to ∼5–8% of H– substitution. Interestingly, a similar contrasting behavior is observed in a Nb-substituted BaTiO3 and SrTiO3, which suggests that a local cation–off centering in lightly doped Ba films creates in-gap states in the band structure (as opposed to the Sr films), hindering the electron transport.

The hydride reduction of a tetragonal layered perovskite LaSrCoO4 is known to yield orthorhombic LaSrCoO3H0.7 with a complete hydride/oxide order within the ab plane. In this study, epitaxial thin films of LaSrCoO4 with a-axis and c-axis orientations have been deposited on (100) and (001) LaSrAlO4 (LSAO) substrates, respectively, and allowed to react with hydride to convert into oxyhydrides. X-ray diffraction, secondary ion mass spectroscopy and thermal desorption spectroscopy experiments indicate that both films are topochemically reduced and can integrate hydride ions with a chemical composition close to that obtained for the powder. A significant reduction in the a-axis was observed for the a-axis oriented LaSrCoO3H0.7 film, indicating hydride/oxide order, as previously reported. In contrast, the c-axis oriented LaSrCoO3H0.7 film remains tetragonal, suggesting hydride/oxide disorder. These results demonstrate that strain engineering can lead to new materials with designed anion arrangement in mixed anion materials.

An oxygen-stoichiometric, B-site-ordered perovskite Ca2Fe1.1Mn0.9O6 (CFMO) with alternate stacking of Fe and Mn layers was obtained through topochemical oxidation of the corresponding brownmillerite phase under high pressure in the presence of KClO4. The structure crystallizes in the P21/m space group with a doubling of the cell along all three crystallographic axes. Mossbauer spectroscopy, susceptibility, and resistivity measurements suggest ferromagnetic interactions between Fe4+(d4) and Mn4+(d3) along [001] through a double-exchange mechanism, a situation similar to half-doped manganese perovskite oxides. Upon cooling, CFMO exhibits a ferrimagnetic transition below Tc = 90 K, likely accompanied by a charge disproportionation of the iron site, 2Fe4+ → Fe3+ + Fe5+. A reasonably good magnetoresistivity of 27 % was observed below Tc.

A novel cubic perovskite MnCu$_3$V$_4$O$_{12}$ has been synthesized at a high pressure and high temperature of 12 GPa and 1373 K. This compound crystallizes in the A-site-ordered perovskite structure (space group Im3̅) with lattice constant a = 7.26684(10) Å at room temperature. The most notable feature of this compound lies in the fact that the Mn2+ ion is surrounded by 12 equidistant oxide ions to form a regular icosahedron; the situation of Mn2+ is unprecedented for the crystal chemistry of an oxide. An anomalously large atomic displacement parameter Uiso= 0.0222(8) Å$^2$ is found for Mn$^{2+}$ at room temperature, indicating that the thermal oscillation of the small Mn$^{2+}$ ion in a large icosahedron is fairly active. Magnetic susceptibility and electric resistivity measurements reveal that 3d electrons of Mn$^{2+}$ ions are mainly localized, while 3d electrons in Cu$^{2+}$ and V$^{4+}$ ions are delocalized and contribute to the metallic conduction.

In this report, we demonstrate a novel synthesis method to obtain reduced titanium oxides with monolithic shape and with a well-defined hierarchically porous structure from the titanium-based network bridged with ethylenediamine. The hierarchically porous monoliths are fabricated by the nonhydrolytic sol–gel reaction accompanied by phase separation. This method allows a low-temperature crystallization into Ti4O7 and Ti3O5 at 800 and 900 °C, respectively, with N-doped carbon. These reduced titanium oxides are well-doped with N atoms even under argon atmosphere without NH3, which accounts for the low-temperature reduction. The resultant monolithic materials possess controllable macropores and high specific surface area together with excellent electric conductivity up to 230 S cm–1, indicating promise as a conductive substrate that can substitute carbon electrodes.

Ten types of neutral charge transfer (CT) complexes of coronene (electron donor; D) were obtained with various electron acceptors (A). In addition to the reported 7,7,8,8-tetracyanoquinodimethane (TCNQ) complex of 1:1 stoichiometry with a DA-type alternating π column, TCNQ also afforded a 3:1 complex, in which a face-to-face dimer of parallel coronenes (Cor-As) is sandwiched between TCNQs to construct a DDA-type alternating π column flanked by another coronene (Cor-B). Whereas solid-state (2)H NMR spectra of the 1:1 TCNQ complex formed with deuterated coronene confirmed the single in-plane 6-fold flipping motion of the coronenes, two unsynchronized motions were confirmed for the 3:1 TCNQ complex, which is consistent with a crystallographic study. Neutral [Ni(mnt)2] (mnt: maleonitriledithiolate) as an electron acceptor afforded a 5:2 complex with a DDA-type alternating π column flanked by another coronene, similar to the 3:1 TCNQ complex. The fact that the Cor-As in the [Ni(mnt)2] complex arrange in a non-parallel fashion must cause the fast in-plane rotation of Cor-A relative to that of Cor-B. This is in sharp contrast to the 3:1 TCNQ complex, in which the dimer of parallel Cor-As shows inter-column interactions with neighboring Cor-As. The solid-state (1)H NMR signal of the [Ni(mnt)2] complex suddenly broadens at temperatures below approximately 60 K, indicating that the in-plane rotation of the coronenes undergoes down to approximately 60 K; the rotational rate reaches the gigahertz regime at room temperature. Rotational barriers of these CT complexes, as estimated from variable-temperature spin-lattice relaxation time (T1) experiments, are significantly lower than that of pristine coronene. The investigated structure-property relationships indicate that the complexation not only facilitates the molecular rotation of coronenes but also provides a new solid-state rotor system that involves unsynchronized plural rotators.

A series of copper(II) solvatochromic complexes [Cu(acac)(N^N)(ligand)]BPh4 (acac = acetylacetonato; N^N = 1,10-phenanthoroline (1), 2,2′-bipyridyl (2); ligand = HMPA, pyridine, DMSO, DMF, MeOH, acetone, and MeCN) have been synthesized and their coordination geometries were crystallographically investigated. The solvent-coordinated cations, adopting a five-coordinate square-pyramidal structure, formed head-to-tail dimers via π⋯π interactions. Solid-state absorption studies revealed that their d–d transition energies are correlated with the donor number of the axial ligands. A linear correlation was found between the d–d transition energies and the Cu–O (axial ligands) distances in the solid-state, revealing the role of the coordination environment on the d–d transition energies in the copper(II) solvatochromic complexes.

In oxides, the substitution of non-oxide anions (F(-),S(2-),N(3-) and so on) for oxide introduces many properties, but the least commonly encountered substitution is where the hydride anion (H(-)) replaces oxygen to form an oxyhydride. Only a handful of oxyhydrides have been reported, mainly with electropositive main group elements or as layered cobalt oxides with unusually low oxidation states. Here, we present an oxyhydride of the perhaps most well-known perovskite, BaTiO(3), as an O(2-)/H(-) solid solution with hydride concentrations up to 20% of the anion sites. BaTiO(3-x)H(x) is electronically conducting, and stable in air and water at ambient conditions. Furthermore, the hydride species is exchangeable with hydrogen gas at 400 °C. Such an exchange implies diffusion of hydride, and interesting diffusion mechanisms specific to hydrogen may be at play. Moreover, such a labile anion in an oxide framework should be useful in further expanding the mixed-anion chemistry of the solid state.

We investigated superconducting (SC) properties of two layered titanium oxypnictides BaTi 2 Sb 2 O ( T c = 1.2 K) and BaTi 2 Bi 2 O ( T c = 4.6 K) being located in distinct SC phases in BaTi 2 (Sb 1− x Bi x ) 2 O by means of magnetic field dependence of electrical resistivities and magnetic susceptibilies. The SC parameter H c2 (0) and ξ 0 for BaTi 2 Sb 2 O are determined to be 1.32 T and 158 A. For BaTi 2 Bi 2 O, we obtained H c1 (0) = 0.006 T, H c2 (0) = 1.70 T, λ 0 = 2900 A, ξ 0 = 139 A, and κ = 20.8. The density of states (DOS) for BaTi 2 Bi 2 O at the Fermi level (4.79 states/eV/f.u.) is smaller than that for BaTi 2 Sb 2 O (5.7 states/eV/f.u.). The DOS change by the Bi-for-Sb substitution is in accordance with theoretical calculations but it cannot explain the enhanced T c .

The titanium oxypnictide superconductor is studied by resistivity, magnetization and heat capacity measurements down to 0.5 K on the powder samples of all proportional solid solution BaTi2(Sb1–x Bi x )2O. An unusual electronic phase diagram as a function of x is obtained, in which a double superconducting dome with peaks at T c = 3.6 and ~4 K appears across an intervening range with lower T cs of ~1 K at 0.35 ≤ x ≤ 0.55. Moreover, a sudden jump in T c is observed at x c between 0.55 and 0.60. These facts suggest unconventional mechanisms of the superconductivity of the titanium oxypnictides.

Single crystals of the new compound KCuMoO4(OH) are hydrothermally synthesized from aqueous solutions of Cu(NO3)2 and K2MoO4 (autoclave, 433 K followed by slow heating to 493 K in 240 h).

A new spin-1/2 quasi-one-dimensional antiferromagnet KCuMoO_4(OH) is prepared by the hydrothermal method. The crystal structures of KCuMoO_4(OH) and the already-known Na-analogue, NaCuMoO_4(OH), are isotypic, comprising chains of Cu^{2+} ions in edge-sharing CuO_4(OH)_2 octahedra. Despite the structural similarity, their magnetic properties are quite different because of the different arrangements of d_{x2-y2} orbitals carrying spins. For NaCuMoO_4(OH), d_{x2-y2} orbitals are linked by superexchange couplings via two bridging oxide ions, which gives a ferromagnetic nearest-neighbor interaction J_1 of -51 K and an antiferromagnetic next-nearest-neighbor interaction J_2 of 36 K in the chain. In contrast, a staggered d_{x2-y2} orbital arrangement in KCuMoO_4(OH) results in superexchange couplings via only one bridging oxide ion, which makes J_1 antiferromagnetic as large as 238 K and J_2 negligible. This comparison between the two isotypic compounds demonstrates an important role of orbital arrangements in determining the magnetic properties of cuprates., Comment: 7 pages, 5 figures published to Inorg. Chem. (2015)

In 2012, a novel superconductor BaTi2Sb2O was found in the layered titanium pnictide oxides ATi2Pn2O. A related superconductor BaTi2Bi2O was subsequently discovered in 2013. The structure of these materials consists of alternate stacking of superconducting Ti2Pn2O layers and Ba blocking layers, which is somewhat similar to high-Tc cuprates since the Ti2Pn2O layer contains an anti-CuO2-type Ti2O square lattice. In addition to the structural similarity to the well-known high-Tc superconductors, BaTi2Pn2O shows unique physical properties: two superconducting domes appear in the electronic phase diagram for solid solutions of BaTi2(Sb1‒xBix)2O and a unique density-wave instability which coexists with superconductivity. In this short review, the early studies of titanium pnictide oxides, the discovery of novel superconductors BaTi2Pn2O, and recent progress are summarized.

The oxygen-stoichiometric, B-site-ordered perovskite Ca2Fe1.1Mn0.9O6 with alternate stacking of Fe and Mn layers is prepared by reaction of Ca2Fe1.1Mn0.9O5 with KClO4 in a molar ratio of 1:0.5 (gold foil, 4 GPa, 550 °C, 45 min).

The title compound is obtained from stoichiometric amounts of the elements (evacuated silica tube, 900 °C, 40 h; quenching).

MnCu3V4O12 is prepared by high pressure solid state reaction of MnO, CuO, and VO2 (Pt capsule in high-pressure cell, 12 GPa, 1373 K, 20 min).

The oxyhydride solid solutions (Ca,Sr)TiO(3-x)H(x) and (Sr,Ba)TiO(3-x)H(x) have been prepared by reducing the corresponding ATiO(3) oxides with calcium hydride. Under the reaction conditions examined, a hydride content of x = 0.1-0.3 was obtained for all compositions. Compared to our previous result with BaTiO(3-x)H(x), the larger particle size in this study (20-30 μm vs 170 nm) resulted in a somewhat lower hydride amount despite prolonged reaction times. We examined changes in cell volume, octahedral tilt angle, and site occupancy of different anion sites after conversion to oxyhydrides; it appears that these oxyhydrides fit the geometrical descriptions typical for regular ABO(3) perovskites quite well. The hydrogen release temperature, previously shown to be indicative of the hydride exchange temperature, however, does not scale linearly with the A-site composition, indicating a potential effect of chemical randomness.

Epitaxial thin films of titanium perovskite oxyhydride ATiO(3-x)H(x) (A = Ba, Sr, Ca) were prepared by CaH(2) reduction of epitaxial ATiO(3) thin films deposited on a (LaAlO(3))(0.3)(SrAl(0.5)Ta(0.5)O(3))(0.7) substrate. Secondary ion mass spectroscopy detected a substantial amount and uniform distribution of hydride within the film. SrTiO(3)/LSAT thin film hydridized at 530 °C for 1 day had hydride concentration of 4.0 × 10(21) atoms/cm(3) (i.e., SrTiO(2.75)H(0.25)). The electric resistivity of all the ATiO(3-x)H(x) films exhibited metallic (positive) temperature dependence, as opposed to negative as in BaTiO(3-x)H(x) powder, revealing that ATiO(3-x)H(x) are intrinsically metallic, with high conductivity of 10(2)-10(4) S/cm. Treatment with D(2) gas results in hydride/deuteride exchange of the films; these films should be valuable in further studies on hydride diffusion kinetics. Combined with the materials' inherent high electronic conductivity, new mixed electron/hydride ion conductors may also be possible.

Critical heat flux enhancement by the electrohydrodynamic (EHD) effect has been analyzed quantitatively based on the increased frequency of liquid-vapor interface oscillations around the edge of the bubble. The majority of heat transfer occurs when the liquid film thickness becomes less than 50 μ m, which only occurs once per period. The main mechanism of heat flux enhancement induced by the EHD effect would be a result of an increase in surface tension due to the effect of electric lines of force. By representing the terms of the forces for a change in curvature and the surface tension resulting from the electric lines of force, the equation of the liquid-vapor instability was obtained and analyzed. Experimentally it has been shown that as the applied voltage increased, the periodic time interval of the thickness change was shortened. This effect reduces the potential for dryout of the liquid film by making the minimum thickness time period shorter. By measuring the pressure oscillation on the boiling surface, the change of the thin liquid film thickness and the dynamic shape of bubbles, the relationship among the pressure, the liquid film thickness and the bubble shape was clarified. Consequently, this model successfully explains the relationship between the applied voltage and the enhancement of the critical heat flux.Copyright © 2004 by ASME

Magnetic susceptibility and specific heat measurements have been performed on two-dimensional spin systems (M2+Cl)LaNb2O7 (M = Mn (S = 5/2), Cr (S = 2), Co (S = 3/2)), prepared via a topotactic ion-exchange reaction. All three compounds establish antiferromagnetic order at TN = 53 K, 61 K and 52 K, respectively for M = Mn, Co, Cr. Together with TN = 78 K for M = Fe (S = 2), this result indicates that the TN is not simply scaled by the magnitude of spin. In particular, the presence of strong spin-orbit interactions is suggested for (CoCl)LaNb2O7.

The change in the spatial distribution of oxygen ions after an initial voltage application called the forming process was investigated for oxide resistance switching devices by secondary ion mass spectrometry mapping. To track the motion of oxygen ions, tracer 18O ions were implanted in a planar Pt/CuO/Pt device. We found clear evidence for the oxygen reduction in the conductive bridge structure formed between two electrodes. In addition, the oxygen ions in the bridge structure drift to the anode, implying the oxygen diffusion (migration) induced by high electric field and/or current density. We discuss those results in terms of a filament model.