Solid-state synthesis of heterogeneous Ni0.5Cu0.5-xZnxFe2O4 spinel oxides with controlled morphology and tunable dielectric properties

Abstract

Heterogeneous Ni0.5Cu0.5−xZnxFe2O4 (0.0 ≤ x ≤ 0.5) nanoparticles are prepared via a green, solventless and additive-free, soft mechanochemical process at room temperature. This solid-state synthetic procedure yields ternary and quaternary oxide nanoparticles with uniform morphology (average particle size: 104–136 nm). X-ray diffraction analyses of Ni0.5Cu0.5−xZnxFe2O4 nanoparticles reveal a cubic spinel structure with crystallite size in the range of 24–31 nm. The lattice parameter (a) and hopping length for tetrahedral (LA) and octahedral (LB) lattice sites are found to increase with the increase in Zn2+ content, while X-ray (ρxrd) and bulk (ρbulk) densities decrease slightly due to increasing lattice volume. Ni0.5Cu0.5−xZnxFe2O4 nanoparticles with (x = 0.2, 0.3, 0.4) exhibit excellent dielectric performance with high permittivity (e = 92–111) and suppressed dielectric loss (e = 1.8–2.8) at high frequency (~ 106 Hz). The polarization mechanism is discussed, involving major contributions from the electron hopping (Fe2+ ↔ Fe3+) at the octahedral sites. The influence of Cu2+ and Zn2+ concentration on the cationic distribution and dielectric performance is analyzed. The electrical conductivity is found to follow the power law (σac = Aωn) with n = 0.7, which confirms the ac conduction phenomenon driven by the electron hopping mechanism. The dielectric behavior of Ni0.5Cu0.5−xZnxFe2O4 nanoparticles reveals their potential for applications in high-frequency microwave devices.