AC conductivity, dielectric and impedance studies of Cd0.8-xPbxZn0.2S mixed semiconductor compounds

The samples of Cd0.8xPbxZn0.2S (x = 0, 0.1-0.8) are prepared by Controlled Co-Precipitation Method. X-ray diffraction studies have confirmed the polycrystalline nature of the samples with Hexagonal and Cubic phases of Wurtzite structure. AC conductivity (sigma(ac)) measurements of Cd0.8xPbxZn0.2S samples at different temperatures (between 40 and 300 degrees C), in the frequency range 5 kHz-20 MHz were made. The results showed that sigma(ac) obeys the relation sigma(ac)(omega) = A omega(s). The exponent s was found to decrease with increase in temperature. Further analysis revealed that, the AC conductivity of the samples follow correlated barrier hopping (CBH) model. The dielectric constant (is an element of') and dielectric loss (Tan delta) were observed to (i) increase with the increase in temperature and the increase is higher at lower frequencies and (ii) decrease rapidly at low frequencies and remains almost constant at higher frequencies. The cole-cole plot showed a single semicircle, indicating an equivalent circuit with a single parallel resistor R-g and capacitance C-g network with a series resistance R-s. The plots also show the grain contribution toward AC conductivity. The relaxation frequencies, determined from these plots are used to calculate the activation energies E-a of relaxation process using Log tau versus 10(3)/T plots. The values of E-a for all the studied compounds range from 0.05 to 0.28 eV and the results are explained based on the defects formed due to the addition of Pb into the Cd0.8Zn0.2S compound. (C) 2014 Elsevier B.V. All rights reserved.