Electrical properties of Cr2O3–Fe2O3–P2O5 glasses. Part II

The electrical properties of xCr2O3–(40−x)Fe2O3–60P2O5, 0 ≤ x ≤ 10, (mol%) glasses have been investigated by impedance spectroscopy. In the glasses containing up to ~ 5 mol% Cr2O3, electrical conductivity increases due to the increase in the Fe2+/Fetot ratio. The conduction in these glasses is independent on Cr2O3 and it is controlled by the polaron hopping between iron ions.The electrical conductivity of the partially crystallized sample with 10 mol% Cr2O3 slightly increases although the Fe2O3 content and the fraction of Fe2+ ions are smaller. This effect is related to the formation of highly disruptive regions around the β-CrPO4 and Fe3(P2O7)2 crystallites in the glass matrix of this sample. These interconnected disruptive regions form the easy conductive pathways leading to a higher conductivity.Changes in the dielectric permittivity in chromium iron phosphate glasses are dependent on the Fe2+/Fetot ratio and, therefore, associated with the concentration of polarons related to Fe2+ and Fe3+ sites.