Synthesis and characterization of nanocrystalline thoria obtained from thermally decomposed thorium carbonate

Nanocrystalline thoria was synthesized by temperature programmed decomposition of Th(CO3)(2) in an evolved gas analysis mass spectrometer set-up. The structural and stoichiometric changes encountered in the decomposition pathway were studied by off-line thermogravimetry (TGA), X-ray diffraction and X-ray photoelectron spectroscopy (XPS). Accurate conversion temperature for transformation of Th(CO3)(2) --> ThO2 was arrived from the XPS measurements. Fourier transform infrared (FT-IR) measurements were used to compare vibrational activities of nano and bulk polycrystalline thoria. Raman spectroscopic studies indicated optical phonon confinement effects in nanocrystalline thoria. High resolution transmission electron microscopic examination on starting material, intermediates and nanocrystalline final product were carried out for studying the microstructure in the nanometer scale. (C) 2002 Elsevier Science B.V. All rights reserved.