Study on the dielectric property, ac conductivity and electric modulus of pristine and green synthesized ZnO nanoparticles

Abstract

We report the results obtained on the studies made for temperature and frequency dependence of the dielectric constant, loss and ac conductivity for pristine and green-synthesized ZnO nanoparticles as well as investigations of their electric modulus. Frequency-dependent dielectric studies are carried out with the pelletized samples of ZnO at different temperatures. At lower frequencies (< 1 kHz) and at higher temperatures the ZnO nanoparticles have giant dielectric constant values (~ 4x104), and such a temperature-dependent giant dielectric constant has not been seen earlier, to our knowledge, in any pristine ZnO nanoparticle. In the lower frequency region and below 100○C the nature of temperature dependence of the dielectric constant for pristine ZnO is in contrast with that observed for the green-synthesized ZnO nanoparticles. This anomalous temperature dependence of dielectric constant may be correlated with combined effect of the in-plane and out of plane thermal-expansion coefficients of ZnO. A temperature-dependent poly-dispersive relaxation mechanism in these materials have been observed. The electrical conduction mechanism is found to be significantly modulated by the use of the extract. Electric modulus study reveals that the electrical conduction and dielectric polarization follow the same mechanism in these ZnO nanoparticles. The dependences of the dielectric constant, dielectric loss, conductivity and polarization mechanisms observed in the synthesized ZnO nanoparticles are envisaged as the signatures of the effective control of the flour extract on the crystal growth and formation of grain boundaries. A plausible growth mechanism of the ZnO nanoparticles in presence of the flower extract containing phytochemicals is also provided.