Electrical properties of vanadate-glass threshold switches

The electrical properties of thick-film vanadate-glass switches, with both planar and sandwich geometries, have been investigated using a remote double-pulse technique. The effect on delay time of pulse separation, overvoltage and polarity were examined. No forming step was required for any of the devices. Photographic evidence of filament formation confirmed the thermal model of switching suggested by these experiments. Additional evidence, such as the effect of temperature on threshold voltage and electrical conductivity, established the importance of the semiconductor-metal transition in the VO₂ present in the material for the switching action. A computer simulation based on the discontinuous change in electrical conductivity, occurring at 68°C, and due to this transition, was shown to be in broad agreement with the experimental facts.