arXiv subjects

O. Bezkrovnyi

Publications and source records attributed to O. Bezkrovnyi.

3 recordsLinked to original sources

arXiv2026

The influence of nonradiative relaxation on laser induced white emission properties in Cr:YAG nanopowders

Laser Induced White Emission (LIWE) is the subject of research worldwide. Since its discovery, the understanding of this phenomenon has progressed successfully enough to reach industrial applications. However, a lack of understanding of the nature of this phenomenon limits its potential. This article is devoted to the study of the influence of nonradiative relaxation processes on the properties of laser induced white emission in Cr:YAG nanopowders. The concentration series of Cr:YAG nanopowders was synthetized by Pechini method. The microstructure, optical and LIWE properties were studied. The influence of chromium concentration on the number of photons involved in LIWE process (N parameter) is shown. The increase of N parameter is associated with an increase in the probability of non-radiative recombination processes with an increase of chromium concentration. A multiphoton ionization model is proposed to describe LIWE phenomenon.

cond-mat.mtrl-sci↗

arXiv2026

Spectroscopic properties of Cr,Yb:YAG nanocrystals under intense NIR radiation

Laser induced white emission (LIWE) was thoroughly studied in recent decades. However, despite the progress in understanding of this phenomenon, the mechanism behind LIWE remains unclear. The present paper focuses on the influence of Yb content on the LIWE properties of Cr,Yb:YAG nanocrystals. Microstructure and optical properties of the samples were characterized and the influence of the concentration of Yb3+ ions on the spectroscopic properties of Cr,Yb:YAG and energy transfer processes between Cr3+ and Yb3+ ions was revealed. Multiphoton ionization theory was used to explain the findings of the paper.

cond-mat.mtrl-sci↗

arXiv2025

Heat Capacity of Thermally Reduced Graphene Oxide: Compaction and Thermal Annealing Effects

We present a comprehensive investigation of the low-temperature heat capacity of thermally reduced graphene oxide (trGO) as a function of compaction pressure and annealing temperature. Graphene oxide was synthesized using a modified Hummers method and subsequently thermally reduced at 300\,°C, 500\,°C, and 700\,°C under vacuum to systematically vary the oxygen content and structural ordering. The specific heat data in the 2--300\,K range reveal that the thermal response is governed by phonons, including contributions from a Schottky-type anomaly, a defect-related linear term, a Debye term, and a dispersive term with a negative coefficient associated with out-of-plane flexural (ZA) phonons. Increasing compaction pressure alters interlayer coupling and leads to non-monotonic changes in heat capacity, while higher annealing temperatures enhance graphitization, reduce disorder, and modify phonon dispersion. The absence of a boson peak -- similar to that observed in carbon nanotubes -- supports the dominance of two-dimensional vibrational modes. These findings elucidate the relationship between dimensionality, structural disorder, and processing parameters in shaping the phonon dynamics of trGO, providing guidance for tailoring its thermal behavior in advanced carbon-based functional materials.

cond-mat.mtrl-sci↗