Structural phase transition between γ-Ti3O5 and δ-Ti3O5 by breaking of a one-dimensionally conducting pathway

Kenji Tanaka, Tomomichi Nasu, Yasuto Miyamoto, Noriaki Ozaki, Shu Tanaka, Toshiaki Nagata, Fumiyoshi Hakoe, Marie Yoshikiyo, Kosuke Nakagawa, Yoshikazu Umeta, Kenta Imoto, Hiroko Tokoro, Asuka Namai, Shin Ichi Ohkoshi

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

The phase transition between gamma-trititanium-pentoxide (γ-Ti3O5) and delta-trititanium-pentoxide (δ-Ti3O5) was clarified from both experimental and theoretical viewpoints. With decreasing temperature, the monoclinic I2/c crystal structure of γ-Ti3O5 was found to switch to a monoclinic P2/a crystal structure of δ-Ti3O5 due to lowering of symmetry. Electrical conductivity (σ) measurement shows that γ-Ti3O5 behaves like a metallic conductor with a σ value of 4.7 S cm-1 at 320 K, while δ-Ti3O5 shows a semiconductive property with a σ value of 2.5 × 10-5 S cm-1 at 70 K. Optical measurement also supports that γ-Ti3O5 is a metallic conductor, while δ-Ti3O5 is a semiconductor with a band gap of 0.07 eV. First-principles calculations show that γ-Ti3O5 is a metallic conductor, and the energy state on the Fermi energy is composed of the 3d orbital of Ti and 2p orbital of O with one-dimensional linkage along the crystallographic c-axis. On the contrary, δ-Ti3O5 has a band gap, and the energy state around the Fermi energy is split into the valence band and the conduction band, which are assigned to the lower and upper Hubbard bands, respectively. Thus, the phase transition between γ-Ti3O5 and δ-Ti3O5 is caused by breaking of a one-dimensionally conducting pathway due to a Mott-Hubbard metal-insulator phase transition.

Original languageEnglish
Pages (from-to)653-657
Number of pages5
JournalCrystal Growth and Design
Volume15
Issue number2
DOIs
Publication statusPublished - 2015 Feb 4
Externally publishedYes

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Phase transitions
Fermi level
conduction
Electron energy levels
conductors
Energy gap
Crystal structure
Valence bands
Conduction bands
orbitals
crystal structure
energy
Metals
Switches
optical measurement
linkages
Semiconductor materials
conduction bands
switches
insulators

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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Structural phase transition between γ-Ti3O5 and δ-Ti3O5 by breaking of a one-dimensionally conducting pathway. / Tanaka, Kenji; Nasu, Tomomichi; Miyamoto, Yasuto; Ozaki, Noriaki; Tanaka, Shu; Nagata, Toshiaki; Hakoe, Fumiyoshi; Yoshikiyo, Marie; Nakagawa, Kosuke; Umeta, Yoshikazu; Imoto, Kenta; Tokoro, Hiroko; Namai, Asuka; Ohkoshi, Shin Ichi.

In: Crystal Growth and Design, Vol. 15, No. 2, 04.02.2015, p. 653-657.

Research output: Contribution to journalArticle

Tanaka, K, Nasu, T, Miyamoto, Y, Ozaki, N, Tanaka, S, Nagata, T, Hakoe, F, Yoshikiyo, M, Nakagawa, K, Umeta, Y, Imoto, K, Tokoro, H, Namai, A & Ohkoshi, SI 2015, 'Structural phase transition between γ-Ti3O5 and δ-Ti3O5 by breaking of a one-dimensionally conducting pathway', Crystal Growth and Design, vol. 15, no. 2, pp. 653-657. https://doi.org/10.1021/cg5013439
Tanaka, Kenji ; Nasu, Tomomichi ; Miyamoto, Yasuto ; Ozaki, Noriaki ; Tanaka, Shu ; Nagata, Toshiaki ; Hakoe, Fumiyoshi ; Yoshikiyo, Marie ; Nakagawa, Kosuke ; Umeta, Yoshikazu ; Imoto, Kenta ; Tokoro, Hiroko ; Namai, Asuka ; Ohkoshi, Shin Ichi. / Structural phase transition between γ-Ti3O5 and δ-Ti3O5 by breaking of a one-dimensionally conducting pathway. In: Crystal Growth and Design. 2015 ; Vol. 15, No. 2. pp. 653-657.
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abstract = "The phase transition between gamma-trititanium-pentoxide (γ-Ti3O5) and delta-trititanium-pentoxide (δ-Ti3O5) was clarified from both experimental and theoretical viewpoints. With decreasing temperature, the monoclinic I2/c crystal structure of γ-Ti3O5 was found to switch to a monoclinic P2/a crystal structure of δ-Ti3O5 due to lowering of symmetry. Electrical conductivity (σ) measurement shows that γ-Ti3O5 behaves like a metallic conductor with a σ value of 4.7 S cm-1 at 320 K, while δ-Ti3O5 shows a semiconductive property with a σ value of 2.5 × 10-5 S cm-1 at 70 K. Optical measurement also supports that γ-Ti3O5 is a metallic conductor, while δ-Ti3O5 is a semiconductor with a band gap of 0.07 eV. First-principles calculations show that γ-Ti3O5 is a metallic conductor, and the energy state on the Fermi energy is composed of the 3d orbital of Ti and 2p orbital of O with one-dimensional linkage along the crystallographic c-axis. On the contrary, δ-Ti3O5 has a band gap, and the energy state around the Fermi energy is split into the valence band and the conduction band, which are assigned to the lower and upper Hubbard bands, respectively. Thus, the phase transition between γ-Ti3O5 and δ-Ti3O5 is caused by breaking of a one-dimensionally conducting pathway due to a Mott-Hubbard metal-insulator phase transition.",
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AU - Ozaki, Noriaki

AU - Tanaka, Shu

AU - Nagata, Toshiaki

AU - Hakoe, Fumiyoshi

AU - Yoshikiyo, Marie

AU - Nakagawa, Kosuke

AU - Umeta, Yoshikazu

AU - Imoto, Kenta

AU - Tokoro, Hiroko

AU - Namai, Asuka

AU - Ohkoshi, Shin Ichi

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AB - The phase transition between gamma-trititanium-pentoxide (γ-Ti3O5) and delta-trititanium-pentoxide (δ-Ti3O5) was clarified from both experimental and theoretical viewpoints. With decreasing temperature, the monoclinic I2/c crystal structure of γ-Ti3O5 was found to switch to a monoclinic P2/a crystal structure of δ-Ti3O5 due to lowering of symmetry. Electrical conductivity (σ) measurement shows that γ-Ti3O5 behaves like a metallic conductor with a σ value of 4.7 S cm-1 at 320 K, while δ-Ti3O5 shows a semiconductive property with a σ value of 2.5 × 10-5 S cm-1 at 70 K. Optical measurement also supports that γ-Ti3O5 is a metallic conductor, while δ-Ti3O5 is a semiconductor with a band gap of 0.07 eV. First-principles calculations show that γ-Ti3O5 is a metallic conductor, and the energy state on the Fermi energy is composed of the 3d orbital of Ti and 2p orbital of O with one-dimensional linkage along the crystallographic c-axis. On the contrary, δ-Ti3O5 has a band gap, and the energy state around the Fermi energy is split into the valence band and the conduction band, which are assigned to the lower and upper Hubbard bands, respectively. Thus, the phase transition between γ-Ti3O5 and δ-Ti3O5 is caused by breaking of a one-dimensionally conducting pathway due to a Mott-Hubbard metal-insulator phase transition.

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