Electrical properties of oxide glasses containing bismuth and selenium granules

DC and AC resistivities of some oxide glasses containing either Bi₂O₃ or selenium have been measured over a temperature range of -160 degrees C to 500 degrees C. The microstructure of bismuth-containing glasses consists of spherical metallic bismuth particles having diameters in the range 50 to 500 AA dispersed in a glass matrix. In the selenium containing glasses selenium crystals of dimensions varying between 50 and 2000 AA are present. The DC resistivity data at temperatures below 120 degrees C indicate that a tunnelling mechanism of charge carriers between the conducting granules is operative. The dielectric relaxation spectra of bismuth-containing glasses confirm this model of electron transport. The surface layers of the ion-exchanged and reduced samples of the selenium-containing glasses show a threshold switching from a low-resistance to a high-resistance state.