Structure and electrical properties of oxygen-deficient hexagonal BaTiO3

D C Sinclair, Jan Skakle, F D Morrison, R I Smith, T P Beales

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Abstract

Rietveld refinements using neutron diffraction data have been used to determine the crystal structure of a series of oxygen-deficient barium titanate powders, (BaTi1-xTixO3-x/2)-Ti-IV-O-III (0 < x < 0.30). The powders were prepared by reduction of stoichiometric, tetragonal BaTiO3 in a vacuum furnace at temperatures above 1300 degrees C and under an oxygen partial pressure of 0.1 mbar. The 6H-BaTiO3 hexagonal perovskite structure is retained throughout and partial reduction of Ti-IV to Ti-III is accompanied by the formation of O(1) oxygen vacancies in the h-BaO3 layers which separate pairs of occupied face-sharing octahedra, Ti2O9. There is no evidence of O(2) vacancies associated with corner sharing TiO6 octahedra. The Ti(2) Ti(2) separation within face sharing dimers increases from 2.690(4) Angstrom for x = 0 to 2.7469(30) Angstrom for x = 0.30. BaTiO2.85 is a band-gap semiconductor at 300 K with a resistivity of ca. 1 Ohm cm and activation energy 0.16 eV. A switch in conduction mechanism to variable range hopping (VRH) of electrons between Ti-III and Ti-IV ions occurs on cooling below 240 K.

Original languageEnglish
Pages (from-to)1327-1331
Number of pages5
JournalJournal of Materials Chemistry
Volume9
Issue number6
Publication statusPublished - Jun 1999

Keywords

  • POWDER DIFFRACTION DATA
  • RIETVELD REFINEMENT
  • BARIUM-TITANATE
  • TRANSITIONS
  • CO

Cite this

Sinclair, D. C., Skakle, J., Morrison, F. D., Smith, R. I., & Beales, T. P. (1999). Structure and electrical properties of oxygen-deficient hexagonal BaTiO3. Journal of Materials Chemistry, 9(6), 1327-1331.