MAGNETIC RESONANCE STUDIES ON YTTIUM-ALUMINOSILICATE  GLASSES AND VITROCERAMICS

S. Simon1, D. Eniu2, R.V.F.  Turcu1, V. Simon1
viosimon@phys.ubbcluj.ro            
     
1Babes - Bolyai University, Faculty of Physics, 3400 Cluj-Napoca, Romania
2University of Medicine and Pharmacy, Faculty of Pharmacy, 3400 Cluj-Napoca,
Romania

Yttrium-aluminum-silicate glasses are important for internal radiotherapy of malign tissues. In order to take advantage of using these materials simultaneously as radiation carriers and for hypertermia the iron oxide is added to the Y2O3-Al2O3-SiO2 host glass and the magnetic crystalline phases are developed by heat treatment.
27Al MAS-NMR (Magic Angle Spinning Nuclear Magnetic Resonance) and EPR (Electron Paramagnetic Resonance) investigations on iron doped yttrium-aluminosilicate system evidence the changes produced by iron doping in samples structure with respect to the coordination of aluminum atoms and to the vicinity of the iron ions.  Mainly tetra- and six-fold coordinated aluminum atoms and two types of iron environments were identified in the investigated samples. The change in the relative intensity and position of the peaks corresponding to different aluminum species can be assigned to the influence of the iron ions on the samples structure. 
In samples with low Fe2O3 content the iron ions are mainly disposed in isolated sites of low symmetry and strong crystalline fields, but as Fe2O3 content increases to 3 mol % the surrounding of iron ions becomes more symmetric and Fe3+ ions experience dipolar and exchange interactions.