The Effects of Thermal History and Irradiation on the DC Conductivity of High Purity Germanium Dioxide Glasses.

The dc electrical properties of a series of high purity GeO(,2) glasses fused and equilibrated at various temperatures (T(phi)) in air were measured. T(phi) ranged from 1350(DEGREES)C to 1690(DEGREES)C. The charge carriers are shown to be the Na ions. The mobility is found to obey an Arrhenius function with enthalpy of activation of approximately 1.01 ev in the as-quenched state for all T(phi)'s. The changes observed in the mobilities of the Na ions for the various T(phi)'s are suggested to be caused by changes in the configurational coordinates of the average interstitial sites through which the Na ion moves with changes in T(phi). These changes are manifested in the entropy of activation. Subsequent annealing treatments at 420(DEGREES)C (15(DEGREES) below the Littleton softening point) for the times observed in these experiments do not change the general behavior of the mobility with T(phi) even though they do change the observed values of mobilities. These changes are suggested to result from thermal compaction changing the average well structure through which the Na ion moves. The (gamma) irradiation of these glasses causes a decrease in the mobility of the Na ion for all T(phi) samples. The mobilities decreases with increasing dose. These decreases in mobilities are suggested to be caused by radiation induced compaction and by change of defect concentrations. These two processes result through relaxation processes and coulombic forces in changes in the average well structure. The implication of these T(phi) dependencies is that point defects through coulombic interactions and relaxation have an effect on the overall structure frozen into the glass upon cooling.