Dielectric property, AC conductivity, and electric modulus studies of pristine and green-synthesized ZnO nanoparticles

Frequency-dependent dielectric constant and dielectric loss of pristine and green-synthesized (using Tabernaemontana divaricata flower extract) ZnO nanoparticles (NPs) are studied at different temperatures. Below 1 kHz frequency and at temperatures above 100 °C, ZnO NPs have giant dielectric constant values (≈3 × 10${}^4$). At lower frequencies and at/below 100 °C, the nature of temperature dependence of dielectric constant for pristine and green-synthesized ZnO NPs are reversed, and this anomalous temperature dependence is correlated with the in-plane and out-of-plane thermal expansions of ZnO. A temperature-dependent poly-dispersive relaxation mechanism in ZnO has been observed. The electrical conduction mechanism is found to be significantly modulated by the use of flower extract. The electric modulus study suggests similar mechanism of electrical conduction and dielectric polarization followed in these materials. A plausible growth mechanism of the ZnO NPs in presence of the flower extract is explored. Variations in the dielectric constant, dielectric loss, conductivity, and polarization mechanisms of the ZnO NPs are understood as signatures of the capping effect of the phytochemicals present in the flower extract on the crystal growth and formation of grain boundaries. (© 2023 Wiley‐VCH GmbH)