On the physical properties of 20Fe2C380 [3B2O3 (1−x)PbO x GeO2] glasses
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The results of X-ray, electron microscopy, magnetic measurements, Mössbauer effect, electron paramagnetic resonance and electrical resistivity studies on 20Fe2O380 [3B2O3 (1−x)PbOxGeO2] glasses are reported. Two sets of samples with 0⩽x⩽25 mol % GeO2 equilibrated at 1250° C and 1150° C, respectively, were investigated. All the samples were in the amorphous state. The number of ferrous ions in glasses equilibrated at 1250° C decreased by increasing the GeO2 content. In the case of the samples melted at 1150° C no evidence of Fe2+ ions was shown by magnetic and Mössbauer effect measurements. The magnetic susceptibility for T>80 K obeys a Curie-Weiss law and the effective moments of iron cations may be described by the free-ion values. The influence of the glass matrix composition and the equilibration temperatures on the intensities of g=2.00 and g=4.20 resonance lines is analysed. The EPR data suggest a clustering tendency of the iron ions in samples equilibrated at 1150° C. The resistivity measurements may be described by a mechanism involving electron hopping. The presence of two activation energies is shown. Finally, the experimental data are correlated in order to give a unitary description of the physical behaviour of the analysed glass system.
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