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SPECTROSCOPIC CHARACTERISATION OF CRYSTALLINE PHASES DEVELOPMENT FROM AMORPHOUS PRECURSORS

S. Simon1,*

Affiliation

  1. Babes-Bolyai University, Faculty of Physics, 3400 Cluj-Napoca, Romania

Abstract

The development of LaAl2.03B4O10.5 (124) lanthanum aluminoborate crystalline phase from amorphous xerogels is characterised by Magic Angle Spinning Nuclear Magnetic Resonance (MASNMR), Electron Paramagnetic Resonance (EPR) and Fourier Transform Infrared (FTIR) spectroscopies. The crystallisation of amorphous xerogels takes place between 760 and 860 oC. The major changes are evidenced both in the boron and aluminium surrounding. These structural results are correlated with those obtained from 27Al and 11B MAS NMR spectra. The boron environment is changed from three-coordinated in amorphous samples to tetra-coodinated in the crystalline samples. Aluminium occurs in amorphous samples as hexa-, penta- and tetra-coordinated by oxygens while in the crystalline ones it appears preponderantly penta-coordinated. From FTIR measurements it results, also, that the local structure dramatically changes when in amorphous matrices are developed crystalline phases. Three different sites for Fe3+ ions in crystalline samples were identified by EPR measurements..

Keywords

Porous aluminates, Oxide glasses, Magnetic resonances, Infrared spectroscopy.

Submitted at: July 22, 2002
Accepted at: March 12, 2003

Citation

S. Simon, SPECTROSCOPIC CHARACTERISATION OF CRYSTALLINE PHASES DEVELOPMENT FROM AMORPHOUS PRECURSORS, Journal of Optoelectronics and Advanced Materials Vol. 5, Iss. 1, pp. 147-152 (2003)