engleski

Electrical Conductivity of Fe2O3-P2O5 Glasses Doped with Cr2O3

Binary iron phosphate glasses behave as typical semiconductors, exhibiting electronic conduction by electron hopping from Fe(II) to Fe(III) ions. Addition of another transition metal oxide results in non-linear variation of electrical properties with composition known as mixed transition ion effect (MTE). The aim of the study was to investigate electrical properties of glasses of ternary glass system xCr2O3-(40-x)Fe2O3-60P2O5, (0&#8804; x&#8804; 10 mol%), containing dissimilar donor ions (Fe and Cr) which can contribute to electronic conductivity. The structural changes in glasses were investigated by Raman spectroscopy, while, Fe(II)/Fetot ratio was calculated by Mössbauer spectroscopy. Electrical conductivity was obtained by measuring complex impedance in the wide frequency and temperature range (0.01 Hz - 2 MHz ; 303 - 473 K). The Raman spectra of glasses containing <10 mol% Cr2O3 show almost identical structure that consists of predominantly pyrophosphate units. The electrical conductivity shows strong dependence on Fe(II)/Fetot ratio, indicating that conduction mechanism is controlled by electron hopping between Fe ions. With increasing Cr2O3 content up to 10 mol% the high tendency for crystallization was observed and confirmed by XRD and SEM. As a result of partial crystallization, the electrical conductivity increases due to the formation of well-conducting regions along the glass-crystallites interfaces.

iron phosphate glasses; electronic conductivity

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