ISSN:
1573-4846
Keywords:
thorium
;
tin
;
phosphate xerogels
;
EPR
;
DSC
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Different transparent phosphate xerogels were synthesized using concentrated solutions of metal chlorides and phosphoric acid with a proper mole ratio of both components. By this method we prepared bulk samples of thorium and tin(IV) phosphate xerogels by drying at room temperature or at 350 K. Some properties of these amorphous materials were studied by means of differential scanning calorimetry (DSC) and electron paramagnetic resonance (EPR) techniques. Depending on mole ratio metal/phosphate, these xerogels show, near 180 K, inflection points which we interpret asT g . Samples dried at 425 K lose their transparency and have noT g . Thus, it seems that the “glassy” state is due to water molecules remaining in the material. The same properties were confirmed by EPR studies of the xerogels doped with Cr3+ and Fe3+ ions as probes. These results show the existence of two different phases in the xerogels: a liquid-like one, in the range from 190 K to 350 K and a solid-like one, in the range from 4 K to 190 K.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02436858
Permalink
