arXiv subjects

Anna O. Diachenko

Publications and source records attributed to Anna O. Diachenko.

3 recordsLinked to original sources

arXiv2026

Role of Oxygen Vacancies in Stabilizing the Orthorhombic Phases of Hf0.5Zr0.5O2 Nanoparticles

In this work we study the stabilization of the orthorhombic phases in small Hf0.5Zr0.5O2 nanoparticles (average size ~ 7 nm) annealed under different oxygen partial pressures. Concentration of the oxygen vacancies, which is determined by annealing conditions, was estimated from the electron paramagnetic resonance spectra and X-ray photoelectron spectroscopy. The fraction of the orthorhombic phases, that is determined by the X-ray diffraction and nuclear magnetic resonance, depends on the concentration of oxygen vacancies. Phenomenological calculations based on Landau-Ginzburg-Devonshire theory considering trilinear coupling between nonpolar, antipolar and polar phonon modes, indicate that chemical strain induced by oxygen vacancies can stabilize the orthorhombic phase o-III with the ferroelectric long-range ordering in small Hf0.5Zr0.5O2 nanoparticles. The theory confirms the stability of ferroelectric polarization in the vacancy-enriched Hf0.5Zr0.5O2 nanoparticles. The increase in the intensity of the dielectric permittivity maximum, observed near 350 - 380 K in the PVDF matrix with the Hf0.5Zr0.5O2 nanoparticles annealed in the CO+CO2 atmosphere, is clearly associated with the increase in oxygen vacancies concentration. The vacancies lead to the defect-induced elastic dipole formation and to the increase in ionic conductivity, which decreases the depolarization field and may induce the ferroelectric-like phase transition in the vacancy-enriched Hf0.5Zr0.5O2 nanoparticles. Due to the interfacial effects the negative capacitance states may be realized in weakly screened and spatially isolated Hf0.5Zr0.5O2 nanoparticles embedded in the PVDF matrix.The present approach based on oxygen-vacancy-induced elastic and screening effects may provide a route for engineering ferroelectric-like states in other nanoscale ferroic oxides.

cond-mat.mtrl-sci↗

arXiv2025

Colossal dielectric response of HfxZr1-xO2 nanoparticles

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.

cond-mat.mtrl-sci↗

arXiv2025

Resistive switching and charge accumulation in Hf0.5Zr0.5O2 nanoparticles

We revealed the resistive switching, negative differential resistance and charge accumulation effects in Hf0.5Zr0.5O2 nanopowders sintered by the auto-combustion sol-gel method and annealed at temperatures from 500°C to 800°C. The fraction of the orthorhombic phase, determined by the X-ray diffraction (XRD), decreases from 91 vol.% to 7 vol.% with an increase in the annealing temperature from 600°C to 800°C. The electron paramagnetic resonance (EPR) spectra reveal the great amount of oxygen vacancies in the annealed samples, at that the decrease of the orthorhombic phase fraction (observed with an increase in the annealing temperature) correlates with a decrease in the intensity of EPR spectral lines associated with the oxygen vacancies and impurities. This indicates the participation of oxygen vacancies and other defects in the formation of the orthorhombic phase in the Hf0.5Zr0.5O2 powders. To explain the results of electrophysical measurements, we compare the features of the current-voltage characteristics with the phase composition of the Hf0.5Zr0.5O2 powders and with the peculiarities of their EPR spectra. The analysis allows us to relate the resistive switching and charge accumulation observed in Hf0.5Zr0.5O2 nanopowders with the appearance of the ferroelectric-like polar regions in the orthorhombic phase of the nanoparticles, which agrees with the calculations performed in the framework of Landau-Ginzburg-Devonshire approach and density functional theory.

cond-mat.mtrl-sci↗