Aluminum Titanate (Al2TiO5) ceramics: complementary Al and Ti K - XAS studies

LEANDRO ANDRINI; MATÍAS R. GAUNA; NICOLÁS M. RENDTORFF; M. AGUSTINA VIOLINI; REQUEJO, FÉLIX G.; RAMIRO MOREIRA TOJA; M. SUSANA CONCONI

Campinas

Otro; Annual Users Meeting LNLS/CNPEM; 2016

LNLS

Aluminum  titanate  (Al2TiO5)  ceramics  are  excellent  thermal  shock-resistant  materials  due  to  their unique  combination  of  low  thermal  expansion  and  low  Young?s  modulus.  These  are  adequate  for insulating  and  severe  thermomechanical  applications  [1].  Based  in  X-Ray  and  neutron  diffraction studies, Al2TiO5 was found to be one of several materials, which are isomorphous with the mineral pseudobrookite (Fe2TiO5) [2]. In this structure, each Al3+ or Ti4+ cations are surrounded by six oxygen ions  forming distorted  oxygen  octahedral.  Apparently,  these  AlO6  or  TiO6  octahedra  form  (0  0  1) oriented double chains weakly bonded by shared edges. This structural feature might be responsible for  the  strong  thermal  expansion  anisotropy,  which  generates  localized  internal  stresses  to  cause severe micro-cracking.  In  this  study  we  present  an  Al-K  XANES  and  a  Ti-K  XANES/EXAFS  study  of  two  different aluminum titanates: one obtained from the calcination (1500 °C) of Alumina and Anatase [1], and another from commercial powder (industrial grade). Complementary XRD - Rietveld analysis was also performed for long-range order studies. Spectra features obtained for the two different samples were described and compared. No important differences  were  observed  between  both  studied  powders.  In  agreement with  the  mentioned experimental evidence, the detected local structure consists in distorted octahedral sites in both cases.  [1] N.M. Rendtorff, G. Suárez, and E.F. Aglietti, Cerâmica, 60 (355), 411-416 (2014).[2] R.D. Skala, D. Li, and I.M. Low, J. of the Eur. Ceram. Soc. 29(1), 67-75 (2009).