The dielectric and electric modulus properties of BaZr0.85Ho0.10Y0.025Nd0.025O3-δ ceramic were studied in the broad range of frequency and temperature to understand the relaxation mechanism in the material. The two relaxation peaks were observed in the frequency-dependent imaginary part of electric modulus, which could be associated with the contribution of grain and grain boundary (GB). The frequency-dependent \({M}^{{\prime}{\prime}}\) was studied using the Kolrausch-Williams-Watts (KWW) parameter ( \(\beta\) ). The Kolrausch-Williams-Watts (KWW) parameter ( \(\beta\) ) associated with the grain and grain boundary were found to be less than one and are temperature-dependent within the measurement range. The colossal dielectric constant was observed in the dielectric spectra of BaZr0.85Ho0.10Y0.025Nd0.025O3-δ ceramic. Maxwell–Wagner phenomena is responsible for this colossal dielectric constant in the material. Two broad relaxation peaks with activation energy 0.23 eV and 0.42 eV were identified in the temperature-dependent dielectric loss revealing the thermally activated relaxation due to the hopping of oxygen vacancies. A modified empirical Cole–Cole model was introduced for understanding the frequency-dependent permittivity and dielectric loss spectra.
