Investigation of Switching and dc Conductivity on Some Vanadium Phosphate Tellurite Oxide Glasses

Abstract

The dc conductivity and switching properties of glassy samples of the system (76V 2 O 5 -24P 2 O 5 ) 1-x (TeO 2 ) x (where x = 0.0, 0.02 and 0.1 mol%) are investigated in the temperature range 303-625 K. The activation energy of conduction ΔE σ , the predominant phonon frequency ν ph and the Debye temperature θ D were deduced. A composition dependence of the samples has been found. Thickness and temperature dependence of the 1-V characteristics of the samples have been studied showing switching at the turnover point (TOP) from high resistance state (off state) to the negative differential resistance state (NDRS). Measurements of the dissipated power P th , the threshold voltage V th and the threshold resistance R th were carried out at TOP for different thicknesses and temperatures of the samples. The activation energies ΔE v , ΔE r and ΔE p (caused by threshold voltage, current and power, respectively) at the turnover point are deduced for different thicknesses of the samples. Temperature and composition dependence of the conduction path temperature (T'), rise in temperature of conduction path ΔT J , specific heat S, density of localized states N(E F ) and the hopping distance have been obtained. The results are interpreted in terms of both electrothermal and the small polaron model.