In situ HTXRD formation of magnesium titanates

Tamir Tuval, Jacob Zabicky, Francesc Gispert-Guirado, Giora Kimmel, Elena Goncharov, Roni Z. Shneck

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

Coprecipitated xerogel precursors of nanocrystalline magnesium titanates, with a Mg:Ti stoichiometric ratio of 2:1, were subjected to thermal treatment in air at constant temperature, from 100 to 1300°C, using a hot-stage X-ray powder diffractometer. The phase sequences, the kinetics of phase evolution and crystallite size were studied during the first hour of the process at different temperatures. Until 500°C no diffraction peaks were observed. Between 550 and 800°C the structure was a mixture of two cubic nanocrystalline coherent structures: qandilite-like and periclase-like forms. At 900 and 1000°C, after 15 minutes, geikielite and periclase appear in small amounts but the qandilite-like phase remains predominant; at 1100°C and above, qandilite is formed again as a single phase. The diffraction lines were substantially broadened for all crystalline phases formed at low temperatures, becoming sharper with increasing temperature and time. The phase evolution is interpreted as a consequence of the decrease in the surface area to volume ratio with increasing temperature and time, thus decreasing the significance of the surface energy. Linear thermal expansion coefficients were derived for qandilite.

Original languageEnglish
Pages (from-to)4367-4374
Number of pages8
JournalJournal of the American Ceramic Society
Volume101
Issue number9
DOIs
StatePublished - 1 Sep 2018

Keywords

  • geikielite
  • high-temperature X-ray diffraction
  • nanocrystalline magnesium titanates
  • periclase
  • phase transformations
  • qandilite
  • sol–gel synthesis
  • thermal expansion coefficients

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