Synthesis and physical properties of the hollandite‐type titanium oxide KxTi8O16

Muraoka, Yuji; Noami, Kengo; Wakita, Takanori; Hirai, Masaaki; Yokoya, Takayoshi; Kayo, Yukako; Matsuki, Takayuki; Tamenori, Y.

doi:10.1002/pssc.201000383

Cited by 8 publications

(8 citation statements)

References 14 publications

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“…The obtained saturated magnetization, to the best of our knowledge, showed the highest value among all Ti‐based oxides reported previously (e.g., hollandite‐type titanium oxide,13a–b, 16 Co‐doped, V‐doped, and Cr‐doped titanium oxides17). In comparison with non‐doped titanium oxides with a hollandite crystal structure,13a–b, 16 the saturated magnetization was increased 1,000 times by partially substituting Fe atoms for Ti atoms in the hollandite crystal structure. This magnetization is sufficient for magnetic attraction by a commercial magnet (Figure S6, see the Supporting Information).…”

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confidence: 48%

“…In this communication, we prepare mesoporous monocrystalline hollandite‐type Ti–Fe oxide (K x Ti y Fe 8− y O 16 ) through sophisticated crystal transformation from Prussian Blue analogue, which is a representative coordination polymer with a face‐centered cubic (fcc) crystal structure 12. Hollandite‐type compounds (A x B 8 O 16 ) are currently very attractive materials, which have potential in applications such as ferromagnetic materials,13a, b battery electrodes,13c and immobilization substances for radioactive elements 13d. Here, the successful incorporation of Fe atoms in the highly crystallized hollandite‐type compounds caused room‐temperature ferromagnetic property with high saturated magnetization.…”

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confidence: 99%

“…In general, a hollandite‐type polycrystalline K x Ti 8 O 16 sample is prepared by a solid‐state reaction under complex synthetic conditions. For example, a mixture of K 2 CO 3 and R‐type TiO 2 is pressed into a pellet, and then calcined at 1050 °C for 10 hours under an atmosphere of hydrogen and argon 13a–b. As shown in Figure 3, the similarity of the the skeleton in both TPBA and K 0.8 Ti 4.3 Fe 3.7 O 16 can reduce the consumption of energy for rearrangement of the Fe and Ti atoms.…”

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Sophisticated Crystal Transformation of a Coordination Polymer into Mesoporous Monocrystalline Ti–Fe‐Based Oxide with Room‐Temperature Ferromagnetic Behavior

Belik

Sukegawa

et al. 2011

Chemistry An Asian Journal

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Since the discovery of mesoporous silica in the 1990s, [1,2] a significant increase in research focusing on the synthesis of mesoporous/mesostructured materials has been observed over the past two decades. Owing to their high surface area, mesoporous materials have played important roles in catalysis, separation, and biomedicine. [3] In almost all the cases, however, as-prepared mesoporous materials possess amorphous walls (or poorly crystallized walls). Mesoporous materials with highly crystallized walls exhibit superior mechanical, thermal, and hydrothermal stability, which are very advantageous for the practical use of mesoporous materials. Furthermore, the crystallized frameworks are expected to show novel solid-state properties (such as rapid electronic transfer and unique magnetic property), which are not attainable by amorphous walls. For instance, it was reported that mesoporous monocrystalline TiO 2 presented superior photocatalytic activity in comparison to that of mesoporous amorphous and polycrystalline TiO 2 . [4] However, it is really difficult to obtain mesoporous crystalline materials, especially mesoporous monocrystalline materials. Recently, many efforts have been made for preparation of mesoporous crystalline materials. In general, during the framework crystallization, framework shrinkage is hard to avoid, which can cause collapse of the mesoporous structure. Kondo and Domen et al. have reported single-crystal particles of mixed transition metal oxide with a wormhole mesoporous structure by controlled two-step calcination. [5] Fine control of the calcination temperature is effective for successful crystallization with the retention of mesoporosity. Hard-templating strategy is another way; [6] this approach is widely applicable to the preparation of metal oxides, which are difficult to synthesize by conventional surfactant-templating pathways. Many kinds of mesoporous crystalline metal oxides (e.g., CoO, [7] Co 3 O 4 , [8] Mn 3 O 4 , [9] NiO, [10] a-Fe 2 O 3 , g-Fe 2 O 3 , Fe 3 O 4 [11]) have been prepared by using hard templates such as mesoporous silicas (e.g., SBA-15 and KIT-6) or mesoporous carbon. [7][8][9][10][11] This hard-templating strategy, however, involves several steps: 1) selection and formation of the original mesoporous silica templates, 2) filling the target precursors into mesopores, 3) converting the precursors into solids, and 4) removing the original templates.Therefore, it is a great challenge to develop a facile approach to obtain mesoporous monocrystalline materials. In this communication, we prepare mesoporous monocrystalline hollandite-type Ti-Fe oxide (K x Ti y Fe 8Ày O 16 ) through sophisticated crystal transformation from Prussian Blue analogue, which is a representative coordination polymer with a face-centered cubic (fcc) crystal structure. [12] Hollandite-type compounds (A x B 8 O 16 ) are currently very attractive materials, which have potential in applications such as ferromagnetic materials, [13a, b] battery electrodes, [13c] and immobilization substances f...

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confidence: 99%

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confidence: 99%

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Sophisticated Crystal Transformation of a Coordination Polymer into Mesoporous Monocrystalline Ti–Fe‐Based Oxide with Room‐Temperature Ferromagnetic Behavior

Belik

Sukegawa

et al. 2011

Chemistry An Asian Journal

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“…For instance, the spinel-type LiTi 2 O 4 exhibits superconductivity with critical temperatures as high as T c = 13.7 K. 3 The rutile-type Na 0.25 TiO 2 shows a magnetic transition at T c = 430 K followed by a metal−insulator transition at T p = 630 K. 4 Furthermore, magnetization measurements of hollandite-type K 1.46 Ti 8 O 16 revealed a small spontaneous magnetization at room temperature which suggests the appearance of weak ferromagnetism. 5 These oxides generally show a great deal of alkali-metal nonstoichiometry, leading to diversity in electronic/magnetic properties as a function of the alkali-metal content. For instance, the Li 1+x Ti 2−x O 4 (x = 0− 1/3) solid solution shows distinct electric behaviors at the terminal compositions: LiTi 2 O 4 (x = 0) is a superconductor, while Li 4 Ti 5 O 12 (x = 1/3) is an electrical insulator.…”

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confidence: 99%

High-Temperature Electrochemical Crystal Growth of Hollandite-Type Cs_xTi₈O₁₆ with Controlled Electronic Properties

Chiba

Saito

Hagiwara

et al. 2017

Crystal Growth & Design

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Electrochemical crystal growth of hollandite-type Cs x Ti8O16 was examined employing high-temperature electrolysis of a molten mixture consisting of TiO2 and Cs2MoO4 with constant applied voltages. The resultant needle-like crystals showed obviously distinct appearances, either optical transparency or metallic luster, depending on the applied voltage. While the transparent crystals were electrical insulators, the metallic luster crystals were moderately conductive, with ρ–T curves being fitted with the one-dimensional (1D) VRH model, suggesting that the compound is a 1D metal involving carrier localization.

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“…The hollandite-type TiO 2 and the similar hollandite-type K x Ti 8 O 16 compounds are shown in Figures 1a and 1b. 10,11 A mixed valence of the titanium ions (as Ti 4+ and Ti 3+ cations) occupy the tunnel and preserve the charge balance. 12 Owing to the unique microporous structure, the cations can be easily inserted into and extracted from the tunnel while the overall original structure remains intact.…”

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Electrochemical Synthesis of Potassium Titanate Nanowires in Molten Salts with Good Li⁺-Intercalation Performance

Huang

Zhou

Wang

et al. 2017

J. Electrochem. Soc.

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The novel material K 1.35 Ti 8 O 16 @C was successfully fabricated via an effective, controllable, and cost-effective electrochemical synthetic method and further evaluated as an anode material for lithium-ion batteries (LIBs). This material delivered high reversible capacities of ∼320 mAh g -1 at 50 mA g -1 and excellent long-term cycle stability (135 mAh g -1 after 2000 cycles at 1 A g -1 ) owing to the high electronic conductivity and fast reversible electrochemical Li-intercalation/extraction behavior of the nanowire structure of K 1.35 Lithium ion batteries (LIBs) are promising electrochemical power sources owing to their high output voltage, energy density, and long calendar life.1 In order to enhance their capacity and power density, several new candidates such as transition metal oxides, 2 alloy-based materials, 3 and sulfides 4 have been explored as next-generation anode materials for commercial LIBs. Among the currently used anodes for LIBs, TiO 2 is the most prevalent owing to its low cost, environmentalfriendliness, structural stability, and better insertion kinetics.5 However, the large polarization at high charge/discharge rates because of the sluggish Li + diffusion and poor electron transport impedes the practical application of TiO 2 in LIBs. 6,7 Hollandites are very well known mainly because of the performance of α-MnO.8 However, the ability to accept lithium ions via an intercalation reaction of this compound is too high to be considered as a suitable candidate for anode material. 9 As one of polymorphs of titanium dioxide, hollandite-type TiO 2 is composed of edge-shared TiO 6 -octahedral units interlinked as a one-dimensional tunnel structure. The hollandite-type TiO 2 and the similar hollandite-type K cations) occupy the tunnel and preserve the charge balance. 12 Owing to the unique microporous structure, the cations can be easily inserted into and extracted from the tunnel while the overall original structure remains intact.The electrochemical synthetic method is a simple, fast, and controllable preparation route which can be used to obtain different metal oxides with different valence states. 13,14 In this work, the electrochemical synthesis of K 1.35 Ti 8 O 16 via electrolysis of solid TiO 2 in molten KCl salt has been described. To the best of our knowledge, this is the first report in literature to develop this synthetic technique. The structure and morphology of the as-prepared K 1.35 Ti 8 O 16 was studied. Furthermore, it was applied as an anode material of LIBs and showed excellent performance in Li + storage. ExperimentalSynthesis of the TiO 2 @C precursor.-The TiO 2 @C composite was prepared by a facile hydrothermal method, as schematically illustrated in Figures 2a-2c. TiCl 4 (1 mL) was dissolved in 80 mL of ethylene glycol by continuous stirring until the solution was clear. Ammonium hydroxide (2 mL, 25%) was then added into the solution and the mixture was stirred for 10 min. This solution was transferred into a 100 mL Teflon-lined stainless steel autoclave and kept in the ov...

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Synthesis and physical properties of the hollandite‐type titanium oxide K_xTi₈O₁₆

Cited by 8 publications

References 14 publications

Sophisticated Crystal Transformation of a Coordination Polymer into Mesoporous Monocrystalline Ti–Fe‐Based Oxide with Room‐Temperature Ferromagnetic Behavior

Sophisticated Crystal Transformation of a Coordination Polymer into Mesoporous Monocrystalline Ti–Fe‐Based Oxide with Room‐Temperature Ferromagnetic Behavior

High-Temperature Electrochemical Crystal Growth of Hollandite-Type Cs_xTi₈O₁₆ with Controlled Electronic Properties

Electrochemical Synthesis of Potassium Titanate Nanowires in Molten Salts with Good Li⁺-Intercalation Performance

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Synthesis and physical properties of the hollandite‐type titanium oxide KxTi8O16

Cited by 8 publications

References 14 publications

Sophisticated Crystal Transformation of a Coordination Polymer into Mesoporous Monocrystalline Ti–Fe‐Based Oxide with Room‐Temperature Ferromagnetic Behavior

Sophisticated Crystal Transformation of a Coordination Polymer into Mesoporous Monocrystalline Ti–Fe‐Based Oxide with Room‐Temperature Ferromagnetic Behavior

High-Temperature Electrochemical Crystal Growth of Hollandite-Type CsxTi8O16 with Controlled Electronic Properties

Electrochemical Synthesis of Potassium Titanate Nanowires in Molten Salts with Good Li+-Intercalation Performance

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Synthesis and physical properties of the hollandite‐type titanium oxide K_xTi₈O₁₆

High-Temperature Electrochemical Crystal Growth of Hollandite-Type Cs_xTi₈O₁₆ with Controlled Electronic Properties

Electrochemical Synthesis of Potassium Titanate Nanowires in Molten Salts with Good Li⁺-Intercalation Performance