Abstract
Heterogeneous Ni
0.5
Cu
0.5−
x
Zn
x
Fe
2
O
4
(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 Ni
0.5
Cu
0.5−
x
Zn
x
Fe
2
O
4
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 (
L
A
) and octahedral (
L
B
) lattice sites are found to increase with the increase in Zn
2+
content, while X-ray (
ρ
xrd
) and bulk (
ρ
bulk
) densities decrease slightly due to increasing lattice volume. Ni
0.5
Cu
0.5−
x
Zn
x
Fe
2
O
4
nanoparticles with (
x
= 0.2, 0.3, 0.4) exhibit excellent dielectric performance with high permittivity (ε̍ = 92–111) and suppressed dielectric loss (ε̎ = 1.8–2.8) at high frequency (~ 10
6
Hz). The polarization mechanism is discussed, involving major contributions from the electron hopping (Fe
2+
↔ Fe
3+
) at the octahedral sites. The influence of Cu
2+
and Zn
2+
concentration on the cationic distribution and dielectric performance is analyzed. The electrical conductivity is found to follow the power law (
σ
ac
=
Aω
n
) with
n
= 0.7, which confirms the ac conduction phenomenon driven by the electron hopping mechanism. The dielectric behavior of Ni
0.5
Cu
0.5−
x
Zn
x
Fe
2
O
4
nanoparticles reveals their potential for applications in high-frequency microwave devices.