Temperature-dependent dielectric properties of carboxymethyl cellulose-polyethylene oxide films doped with zinc oxide and copper oxide for energy storage

Abstract

Metal oxide nanoparticle-polymer hybrids are appealing solid materials that combine enhanced chemical and physical characteristics with elasticity, making them highly suitable for electrical device applications. This study focuses on the preparation and characterization of hybrid films composed of carboxymethyl cellulose (CMC) and polyethylene oxide (PEO) in a 70:30 weight ratio, incorporated with zinc oxide and copper oxide nanoparticles (ZCNP). The films were fabricated using a solution casting method, with the nanoparticles synthesized via the sol-gel technique. The temperature dependence of key electrical properties, including dielectric constant (ε'), dielectric modulus, relaxation behavior, AC conductivity, and activation energy, was systematically analyzed. At frequency (f) = 10 Hz, ε' of the CMC/PEO and CMC/PEO-ZCNP (2 wt%) samples was 56.34 and 7916.36 at 308 K respectively, while it reached 6222.65 and 152364 when the temperature changes to 333 K. Their relaxation time (τ) dropped from 59.5 and 0.40 µs to 1 and 0.18 µs in the same temperature range. At f = 10 Hz and T=308 K, electrical conductivity (σ') improved, with CMC/PEO showing log(σ') = -9.3605 (σ' = 4.36E-10 Ω·m⁻¹) and 2% ZCNP achieving log(σ') = -7.3142 (σ' = 4.85E-8 Ω·m⁻¹). The results demonstrated a significant enhancement in the dielectric constant of the hybrid films compared to the unmodified polymer blend, while maintaining a low dielectric loss. These enhancements are attributed to the incorporation of zinc oxide and copper oxide nanoparticles, which promote multiple polarization mechanisms and enhance charge carrier dynamics. The findings suggest that these hybrid films hold great potential for use in high-density energy storage devices and integrated thin-film capacitors, offering a scalable and efficient solution for next-generation electronic applications.