Electrical conductivity and dielectric relaxation of bulk Se70Bi(30 − x)Tex, x = (0, 15) chalcogenide glasses

• The frequency and temperature dependences of ε1 and ε2 are studied for Se70Bi30 and Se70Bi15Te15 glassy alloys.
• Study of Cole–Cole diagrams reveals some dielectric relaxation parameters.
• σac(ω) obeyed the Aωs law; the temperature dependence of s and σac(ω) suggests the applicability of CBH model.
• The presence of the Meyer–Neldel's rule MNR is validated for both studied alloys.
• The effect of Te addition on the studied parameters has been reported and discussed.

Frequency and temperature dependences of dielectric constant, dielectric loss and ac electrical conductivity were studied for bulk Se70Bi30 and Se70Bi15Te15 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 Se70Bi30 and Se70Bi15Te15 samples. The addition of Te atoms leads to an increase in the density of localized states in the tails and consequently increases ac conductivity.