Low-temperature chemical synthesis of lanthanum monoaluminate


Taspinar E., Tas A.

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, vol.80, no.1, pp.133-141, 1997 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 80 Issue: 1
  • Publication Date: 1997
  • Doi Number: 10.1111/j.1151-2916.1997.tb02801.x
  • Title of Journal : JOURNAL OF THE AMERICAN CERAMIC SOCIETY
  • Page Numbers: pp.133-141

Abstract

One of the promising candidates for ferroelectric substrate materials, lanthanum monoaluminate (LaAlO3), was successfully synthesized by two separate chemical powder preparation techniques: (i) homogeneous precipitation from aqueous solutions containing urea (CH4N2O) in the presence of nitrate salts, and (ii) self-propagating combustion synthesis from aqueous solutions containing CH4N2O and the respective nitrate salts of lanthanum and aluminum. The submicrometer, spherical-like particles of the precursors were completely converted to pure LaAlO3 at 850 degrees C in the homogeneous precipitation route, and the same conversion temperature was observed to be 750 degrees C, which becomes the lowest temperature ever reported for the powder synthesis of a pure LaAlO3 phase. The materials were characterized by powder X-ray diffractometry, simultaneous thermogravimetric/differential thermal analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Structural refinements by Rietveld analysis showed that LaAlO3 was isostructural with BaTbO3 and had the space group R-3c, in contrast to the previously assumed space group of R-3m for this phase. The atomic positions in the structure of LaAlO3 were refined and presented for the first time, with respect to the present space group.