Hopping mechanism and impedance spectroscopy study in tellurite-modified lithium borate glasses: electric modulus formalism

The conductivity and electric modulus formalism in tellurite-modified lithium borate glasses with composition (100– x ) − (33.35Li 2 O–66.65B 2 O 3 ) − ( x )TeO 2 , ( x = 0, 5, 10, 15, 20 and 25 mol%) have been prepared. Electric modulus, relaxation mechanism and conductivity parameters were investigated to understand the dielectric properties of the glass matrix in the temperature range between 403 and 583 K, and the frequency range between 100 Hz and 5 MHz. The experimental data of ac conductivity was fitted to Jonscher’s power law. The parameters like dc conductivity ( σ dc ), frequency exponent ( S ) and crossover frequency ( W H ) were extracted. The conductivity of the glass matrix was found to exhibit anomalous increasing behaviour with TeO 2 content. The decreasing trend in the values of the frequency exponent with the temperature rise demonstrates the correlated barrier hopping mechanism in the conduction process. The electric modulus data fitted to Davidson–Cole model and Kohlrausch–Williams–Watts model have revealed nearly the same values of β (Kohlrausch exponent), which depict the conductivity relaxation process. Other electrical parameters such as bulk resistance ( R b ), capacitance ( A o ) and stretching exponent ( n ) were also extracted by fitting the impedance data to the R-CPE model using Zview software. The dc conductivity of lithium boro tellurite glasses was found to follow Arrhenius behaviour and the corresponding activation energy was determined (0.5847–1.0004 eV).