Colossal dielectric response of HfxZr1-xO2 nanoparticles

TL;DR

This study demonstrates a colossal dielectric response in small oxygen-deficient HfxZr1-xO2 nanoparticles, revealing potential for silicon-compatible nanomaterials with high dielectric permittivity and ferroelectric-like behavior.

Contribution

It reports the first observation of colossal dielectric permittivity in HfxZr1-xO2 nanoparticles and models their behavior using the Heywang barrier and variable range hopping conduction models.

Findings

Dielectric permittivity reaches up to 1.5×10^5 at low frequencies.

Dielectric response shows a diffuse ferroelectric-paraelectric transition.

Resistivity and dielectric permittivity features are correlated and well-described by combined models.

Abstract

We reveal a colossal dielectric response of small (5 - 10 nm) oxygen-deficient HfxZr1-xO2 nanoparticles (x = 1 - 0.4), prepared by the solid-state organonitrate synthesis. The effective dielectric permittivity of the pressed HfxZr1-xO2 nanopowders has a pronounced maximum at 38 - 88 C, which shape can be fitted by the Curie-Weiss type dependence modified for the diffuse ferroelectric-paraelectric phase transition. The maximal value of the dielectric permittivity increases from 1.5*10^3 (for x = 1) to 1.5*10^5 (for x= 0.4) at low frequencies (~4 Hz); being much smaller, namely changing from 7 (for x = 1) to 20 (for x = 0.4) at high frequencies (~500 kHz). The frequency dispersion of the dielectric permittivity maximum position is almost absent, meanwhile the shape and width of the maximum changes in a complex way with increase in frequency. The temperature dependencies of the dielectric permittivity and resistivity are almost mirror-like turned over in respect to each other, which means that all their features, such as position and shape of maxima, plateau, minima and inflexions, almost coincide after the mirror reflection in respect to the temperature axis. These correlations of resistivity and dielectric permittivity are well-described in the Heywang barrier model applied together with the variable range hopping conduction model in semiconducting ferroelectrics. The ferroelectric-like behavior of the small oxygen-deficient HfxZr1-xO2 nanoparticles is expected from the Landau-Ginzburg-Devonshire approach and density functional theory calculations. Obtained results may be useful for developing silicon-compatible functional nanomaterials based on HfxZr1-xO2 nanoparticles.