Electrical conductivity and dielectric relaxation of bulk Se_(70)Bi_((30 ? x))Tex, x = (0, 15) chalcogenide glasses

摘要

Frequency and temperature dependences of dielectric constant, dielectric loss and ac electrical conductivitywere studied for bulk Se_(70)Bi_(30) and Se_(70)Bi-(15)Te-(15) chalcogenide glasses, in the frequency range (1-100 kHz) and temperature range below glass transition temperatures. Both dielectric constant and dielectric loss are found to decrease with increasing frequency and decreasing temperature. An analysis of dielectric loss data obeyed the Guintini's theory of dielectric dispersion based on hopping model. The Cole-Cole diagram has been used to determine some parameters such as the distribution parameter, molecular relaxation time and activation energy for relaxation. The ac conductivity was found proportional to ωs. The variation of both the frequency exponent and ac conductivity with temperature suggested that, the ac conductivity is explained according to correlated barrier hopping (CBH) model, with activation energy decreasing with increasing frequency for Se_(70)Bi_(30) and Se_(70)Bi-(15)Te_(15) samples. The addition of Te atoms leads to an increase in the density of localized states in the tails and consequently increases ac conductivity.