Study of the formation of bi2te4o11

Zs Szaller, L. Pöppl, Gy Lovas, I. Dódony

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The solid state reaction in a 1:4 mole ratio mixture of Bi2O3 and TeO2 and the polymorphic phase transition of Bi2Te4O11 have been investigated using differential scanning calorimetry (DSC), electron microprobe, X-ray powder diffraction (XPD), and selected area electron diffraction (SAED) analysis in the 25-730°C temperature range. Upon heating first a 8Bi2Te4O11 + 23TeO2 eutectic is formed, which melts at 598.9°C. In this melt the excess of Bi2O3 reacts further and the Bi2O3 + 4TeO2 = Bi2Te4O11 reaction takes place. The cubic modification is formed by fast crystallization of the Bi2Te4O11 melt. The structure of the cubic Bi2Te4O11 can be characterized by the lattice constant of a = 5.6397(5) Å and space group Fm3m. The main product of a slow cooling is the same cubic polymorph although a subordinate formation of the monoclinic phase is also observed. The β-Bi2Te4O11 cubic phase undergoes a monotropic transformation into the α-Bi2Te4O11 monoclinic modification at temperatures higher than 400°C. The cubic → monoclinic transition is the result of an ordering in one set of {111} planes and the orthogonality of the cubic phase in the [110] projection changes to monoclinic symmetry. The melting enthalpies of the cubic β-phase and the monoclinic α-phase are 35.9 ± 3.3 J/g and 84.3 ± 4.3 J/g respectively.

Original languageEnglish
Pages (from-to)251-261
Number of pages11
JournalJournal of Solid State Chemistry
Issue number2
Publication statusPublished - Feb 1 1996

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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