THERMALLY STIMULATED POLARIZATION AND DC CONDUCTION IN IRON PHOSPHATE-GLASSES

Thermally stimulated polarization (TSPC) and depolarization current (TSDC) techniques were used to study electrical polarization and conduction mechanisms in iron phosphate and sodium iron phosphate glasses. TSDC measurements from 120 to 350 K show two current peaks, P1, attributed to the polarization caused by intrinsic dipolar defects, and P2, due to space-charge relaxation. The electrical conductivity was examined on the basis that the activation energy for electronic conduction is lower than that for ionic conduction. The dc conductivity depends upon iron oxide content and distance between iron ions, which suggests electronic conduction. The difference in activation energy between TSDC peaks and dc conductivity is discussed. Infrared absorption spectra indicate that iron ions can act as a network former and/or modifier depending upon the Fe(II)/Fe(III) ratio in the glass.