In this work, a novel high-entropy zirconate, (Ce0.2Nd0.2Sm0.2Ho0.2Yb0.2)2Zr2O7 (RE-HESZ), was successfully synthesized via a conventional solid-state reaction route and comprehensively characterized. X-ray diffraction coupled with Rietveld refinement revealed a temperature-driven structural evolution, where a disordered defect-fluorite phase (Fm \(\:\stackrel{-}{3}\) m) formed at 1673 K transforms into a well-ordered single-phase pyrochlore structure (Fd \(\:\stackrel{-}{3}\) m) upon sintering at 1773–1873 K. Thermal expansion measurements demonstrated excellent thermal stability, with a low average coefficient of thermal expansion of 9.6 × 10⁻6 K⁻1 over the 373–1473 K range, attributed to the rigid [ZrO6] octahedral framework. Optical investigations using UV–Vis diffuse reflectance spectroscopy indicated an indirect optical bandgap of 2.35 eV, confirming the semiconducting nature of the material. Impedance spectroscopy performed between 473 and 673 K revealed non-Debye relaxation behavior and a negative temperature coefficient of resistance, with grain boundaries dominating the dielectric response and accurately described by an equivalent R–C–CPE circuit model. AC conductivity obeys Jonscher’s universal power law, yielding a high-temperature activation energy of approximately 1.09 eV. The frequency exponent analysis indicates that charge transport is mainly governed by the correlated barrier hopping mechanism, with a maximum barrier height of 0.29 eV. Dielectric measurements further revealed a high dielectric permittivity (~ 104) accompanied by strong interfacial polarization effects. These combined structural, thermal, optical, and electrical characteristics demonstrate that RE-HESZ is a robust multifunctional material with strong potential for high-temperature capacitors, thermistors, and optoelectronic applications.
