Electrical conductivity and breakdown properties of some erbium oxide doped phosphovanadate glasses

Electrical conductivity and breakdown properties have been investigated for 70%V₂O₅.(30-x)%P₂O₅.x%Er₂O₃ glasses with (0 ≤ x ≤ 0.9). The conductivity measurements are carried out at frequency range from 80 to 3 x 10⁶ Hz, and at temperature range from 303 to 463 K. The dc electrical conductivity (s_dc) and dc activation energy (E_dc) are shown to be relatively sensitive to the composition. s_dc is found to vary between 3 × 10⁻⁴ and 0.024 Ω⁻¹ m⁻¹, and E_dc is estimated to be in the range 0.36–0.44 eV. On the other hand, s_ac is found to vary between   7 × 10⁻⁴ and 0.15 Ω⁻¹ m⁻¹. Both s_dc and s_ac are discussed according to the multi phonon hopping process of weak electron-lattice coupling, they are found to be proportional to T^p   with the exponent p between 11.5 and 13.15. All the samples exhibit a threshold type switching with a maximum current of about 3 mA. All the samples are found to present breakdown properties at different critical voltages. The threshold voltage (V_th)values are affected by ambient temperature, sample thickness and composition ratio. Measured surface temperature during the switching cycles and the calculated core temperature confirms the repeatedly switching of the samples without any internal thermal destruction occur.