Hamburg 2001 – wissenschaftliches Programm
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M: Metallphysik
M 10: Diffusion und Punktdefekte II
M 10.5: Fachvortrag
Montag, 26. März 2001, 12:45–13:00, S12
Coincident Doppler broadening and positron lifetime spectroscopy of TiOy with structural vacancies on both the titanium and oxygen sublattice — •A.A. Valeeva1, M.A. Müller2, A.A. Rempel1,2, W. Sprengel2, and H.-E. Schaefer2 — 1Institute of Solid State Chemistry, Russian Academy of Sciences, 620219 Ekaterinburg, Russia — 2Institut für Theoretische und Angewandte Physik, Universität Stuttgart, 70550 Stuttgart, Germany
Titanium monoxide TiOy with a B1 lattice structure and structural vacancies on both the titanium and oxygen sublattice was synthesized in vacuum at 1770 K from mixtures of TiO2 and Ti powders. This method allows the tailoring of the ratio of the vacancy contents on the two sublattices by adjusting the chemical composition of the compound. The titanium and oxygen vacancy contents determined by the simultaneous use of a chemical analysis, the x-ray lattice constant and pycnometric density measurements was varied from a few percent to 23 at.%.
The titanium vacancy with an oxygen environment was identified as positron trap by coincident Doppler broadening spectroscopy which is due to the negative electric charge of this vacancy. The oxygen vacancy in this compound has a positive charge and does not trap the positron. The atomic and vacancy ordering confirmed in
TiOy by X-ray superstructural reflection analysis and heat capacity measurements affects the positron lifetime and coincident Doppler broadening spectra very little because the redistribution of atoms at the phase transformation leads only to a minor change of the titanium vacancy volume of about 0.7 %.