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The most recent research and developments are driven by colossal permittivity (CP) materials due to their potential use in modern microelectronics and high-energy density storage applications. Even though, to date, many CP materials have been discovered, the task of developing them with the required high performance remains highly challenging. We present a tangible example, polycrystalline ZnO ceramic, that presents a highly frequency-stable CP (> 104) as well as a low dielectric loss (~ 0.3) over a broad temperature range from 278 to 433 K. Multifunctional polycrystalline ZnO nanoceramics are prepared through one-pot hydrothermal route and sintered at 300 °C and 600 °C. The highly magnified scanning electron microscopic images reveal excellent grain growth at high temperature. Temperature-dependent impedance spectroscopy is employed for pellet sintered at (600 °C) to explore different conduction mechanisms at various temperature ranges. The distribution of relaxation times (DRT) method is used to design the best equivalent circuit model for fitting impedance data. The non-Debye behavior of real permittivity (ɛ′) is well explained by fitting with Cole–Cole formalism. The change in the conduction mechanism is estimated around 343 K, and an adiabatic polaronic model is used to estimate activation energies of cations through different electroactive regions. The correlate barrier hopping (CBH) model is applied to measure electrical trapping parameters (like binding energy, hopping distance, barrier height, etc.) at various temperatures. Our finding presents a systematic approach toward frequency-independent ZnO ceramics with a stable colossal permittivity which can potentially be applied to develop energy storage devices. [ABSTRACT FROM AUTHOR]