INFLUENCE OF HALOGEN IONS ON PHYSICAL PROPERTIES OF SOME BORO-VANADATE GLASSES

Some sodium boro-vanadate glasses containing various halogen ions (chlorine, bromine or iodine) were prepared by melting at 1000oC for 2hrs and annealed at 300oC for 3hrs. These glasses were characterized by measuring the experimental densities, dc conductivities and volume-magnetic susceptibilities. Then the empirical densities, experimental and empirical molar volume values, electrical activation energies, mass- and molar-magnetic susceptibilities as well as the total mass attenuation coefficients of all glasses were calculated.
It was found that, the activation energy decreased as the halogen content was increased which may be due to the increase in the mobility of sodium ions and the gradual formation of some terminal non-bridging halogens, in addition to the electron hopping process between different oxidation states of vanadium. It decreased also ongoing from chlorine to iodine that can be ascribed to the differences in ionic radii of halogen ions. Also, the decrease in activation energy may be due to the increase in the interstitial vacancies. This was confirmed by the density and the molar volume results.
It was supposed that the increase in the paramagnetic character of the studied glasses with the increase of halogen content may be due to the formation of VXO3 groups. Also, the magnetic properties were found to decrease as the ionic radius of the introduced halogen ions increased. This can be attributed to the increase in the internal vacancies through the network.
Correlations were established between the experimental values of both the activation energy and molar susceptibility with the calculated molar volume values of the studied glasses.
According to the results of the mass attenuation coefficients, it was found that, the sample contains 25 mol% NaI is the best one that can be used as -ray attenuator, but only at gamma-ray energies up to 356 keV.