Discommensurate structure in [(Ca0.90Sr0.10) 2CoO3]0.61CoO2

Kunio Yubuta, Xiangyang Huang, Yuzuru Miyazaki, Tsuyoshi Kajitani

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

The crystal structure of partly Sr-substituted Co-121, i.e., "Ca 3Co4Co9", single crystal is studied by means of the electron diffraction measurements and high-resolution transmission electron microscopy (HREM). The crystal structure consists of two interpenetrating subsystems of a CoO2 sheet and a distorted three-layered (Ca,Sr)2CoO3 rock-salt (RS)-type block layers, which belong to a triclinic system. Both subsystems have common a-, c-axes and α-, β-, γ-angle with a = 4.8267(1)Å, c = 10.9214(3)Å, α = 90.916(2)°, β = 98.291(5)̊, and γ = 89.957(3)°. On the other hand, the crystal structure is modulated parallel to the b-axis, along which the CoO2 sheet has b1 = 2.8346(1)A° and the (Ca,Sr)2CoO3 RS-type block layer has b2 = 4.6391(2)Å, respectively. On the basis of the b 1/b2 ratio and analyzed chemical compositions, the structure analogue is formulated as [(Ca0.90Sr0.10) 2CoO3]0.61CoO2. In electron diffraction patterns, there are many new satellite reflections, namely 0101, 0202, 0204, and 0103, which are not present in the end member Co-121, i.e., (Ca2CoO3)0.620CoO2. Because of the new superlattice reflections, the crystal structure of the Sr-doped compound is different from the end member. HREM images were taken with the incident electron beam parallel to the [0010] and [1000] directions. The basic crystal structure of the present system consists of 5-CoO2 and 3-RS subcells with b = 14Å being connected discommensuratedly parallel to the a- and b-axes. Systematic introduction of stacking faults parallel to the a-b plane is also noticed.

Original languageEnglish
Article number064604
Journaljournal of the physical society of japan
Volume77
Issue number6
DOIs
Publication statusPublished - 2008 Jun 1

Keywords

  • Electron diffraction
  • High-resolution image
  • Misfit-layered structure
  • Thermoelectric compound

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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