Abstract:
Zn sub((1-x)) Co sub(x) O nanoparticles with (x = 0.05, 0.10, 0.15 and 0.20) were prepared by combustion method. Here we report our findings on electrical properties carried out on these materials from room temperature to 500 degrees C. Thermopower investigations carried out on the materials resulted in Seebeck coefficient showing a transition from positive to negative values with 'x' dependent enhancements. The material that exhibits a p-type semiconductor character at room temperature translates into an n-type of semiconductor at higher temperatures beyond 90 degrees C marked by a first order transition. Electrical resistivity and the activation energy being interrelated are seen to decrease with rising temperature due to increase in charge carrier concentration. Dielectric constant (epsilon) and dielectric loss (tan delta) investigated as a function of frequency showed nearly exponential decline in their values with increasing frequency for all the samples. However temperature dependent 'epsilon' and 'tan delta' show a peaking behaviour at lower temperatures with increasing trend at higher temperature as a result of increase in dielectric polarization. The DMS materials being ferromagnetic at room temperature are good temperature dependent semiconductors with high dielectric constant.
