Spectrally resolved thermoluminescence in UV excited hexagonal boron nitride nanopowder

Thermally stimulated luminescence (TSL) excitation and emission processes in h-BN nanopowders after UV irradiation were studied. TSL showed the highest response within the 5.4 eV band. 3.0 and 3.9 eV bands, resulting from the radiative donor-acceptor recombination between the electron (1B-H O N -centers) and the hole traps (CN-center), were found. TSL curves quantitative analysis in the context of general order kinetics was made. It was shown that 1B-centers had 0.850.05 eV activation energy and were responsible for the TSL peak at 35010 K. Band structure for TSL excitation and emission mechanisms in h-BN nanopowder was suggested. © Published under licence by IOP Publishing Ltd

Specific features of photoluminescence thermal quenching in hexagonal boron nitride micropowder

Analysis o f the experimental data o f PL thermal quenching in frame of the Mott-Seitz formalism was carried out. It was shown that intensity decrease in temperature range RT - 800 К was characterized by two non-radiative relaxation channels. Values of corresponding activation energies were estimated

Study of Spectrally Resolved Thermoluminescence in Tsarev and Chelyabinsk Chondrites with a Versatile High-sensitive Setup

Thermoluminescence (TL) research provides a powerful tool for characterizing radiationinduced processes in extraterrestrial matter. One of the challenges in studying the spectral features of the natural TL of stony meteorites is its weak intensity. The present work showcases the capabilities of a high-sensitive original module for measuring the spectrally resolved TL characteristics of the Chelyabinsk and Tsarev chondrites. We have analyzed the emission spectra and glow curves of natural and induced TL over the 300–650 nm and RT–873 K ranges. A quasi-continuous distribution of traps active within the 350–650 K range was found in the silicate substructure of both meteorites under study. Based on the general order kinetic formalism and using the natural TL data, we also estimated the activation energies of EA = 0.86 and 1.08 eV for the Chelyabinsk and Tsarev chondrites, respectively. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.This work was supported by the Minobrnauki research project, number FEUZ-2020-0059

Luminescence in anion-deficient hafnia nanotubes

Hafnia-based nanostructures and other high-k dielectrics are promising wide-gap materials for developing new opto- and nanoelectronics devices. They possess a unique combination of physical and chemical properties such as insensitivity to electrical and optical degradation, radiation damage stability, a high specific surface area, and an increased concentration of the appropriate active electron-hole centers. The present paper aims to investigate the structural, optical, and luminescent properties of anodized non-stoichiometric $HfO_2$ nanotubes. As-grown amorphous hafnia nanotubes and nanotubes annealed at 700{\deg}C with a monoclinic crystal lattice served as samples. It has been shown that the bandgap $E_g$ for direct allowed transitions amounts to $5.65\pm0.05$ eV for amorphous and $5.51\pm0.05$ eV for monoclinic nanotubes. For the first time, we have studied the features of the intrinsic cathodoluminescence and photoluminescence of the obtained nanotubular $HfO_2$ structures with an atomic deficiency in the anion sublattice at temperatures of 10 and 300 K. A broad emission band with a maximum of 2.3-2.4 eV has been revealed. We have also conducted an analysis of the kinetic dependencies of the observed photoluminescence for synthesized $HfO_2$ samples in the millisecond range at room temperature. It showed that there are several types of optically active capture and emission centers based on vacancy states in the $O_{3f}$ and $O_{4f}$ positions with different coordination numbers and a varied number of localized charge carriers ($V^0$, $V^-$, and $V^{2-}$). The uncovered regularities can be used to optimize the functional characteristics of developed-surface luminescent media based on nanotubular and nanoporous modifications of hafnia.Comment: 15 pages, 6 figures, 3 tables, 50 reference

Characterization of Excessive Sm3+containing Barium Titanate Prepared by Tartrate Precursor Method

The [Formula presented](BST) samples, where (x = zero, 0.05, 0.1, 0.15, 0.2 and 0.3), have been successfully synthesized by tartrate precursor method at annealing temperature of 600°C under atmospheric pressure. The results revealed that the Sm content causes a decrease in both tetragonality and average grain size of BST samples. The electrical resistivity of BST samples is improved by low Sm content, reaching maximum value at x = 0.15 and then decreases with higher Sm content, suggesting that the conduction has two types of polaron hoping and semiconductor band conduction mechanisms at low and at high temperature ranges, respectively. It is demonstrated that the majority of charge carriers are p-type. The dielectric properties varies nonmonotonically with samarium content, showing strongly enhancement in dielectric constant for high Sm doping samples. It is recommended that BST samples are attractive for capacitor and energy storage applications. © 2020 The Author(s).This project was supported financially by the Academy of Scientific Research and Technology (ASRT) Egypt, Grant No. 6550 . ASRT is the 2nd affiliation of this research

SIGNIFICAN ENHANCEMENT OF OPTICAL PROPERTIES THROUGH METHYLCELLULOSE (MC) / GADOLINIUM OXIDE COMPOSITES

In the present work, Methylcellulose (MC) with Gd2O3 composite films were prepared to study the optical properties. and investigate the effect of adding Gd2O3 nanoparticles with MC in linear optical investigation.W.I.A. and I.I.N. thank Department, Faculty of Science, Tanta University, for financial support

Modified Copper Zinc Ferrite Nanoparticles Doped with Zr Ions for Hyperthermia Applications

The problem of the present work is to synthesize a nanomagnetic material with low TC below 45 °C and its particle size below 30 nm to be appropriate material for convert magnetic loss into heat energy. A series of Cu0.4Zn0.6+yZryFe2–2yO4 nanoparticles compositions where y = (0.05, 0.1) were synthesized via citrate sol–gel method. The prepared samples were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The grains were observed from SEM confirming the crystalline structure of the ferrite which was detected by X-ray diffraction. Magnetic hysteresis loop measurements illustrate that materials exhibit soft magnetic properties at low Zr content, while at higher Zr content all materials behave as superparamagnetically without any saturation magnetization Ms. The initial magnetic permeability (μi) at frequency 10 kHz as a function of temperature was measured. A sudden change in μi appears around Curie temperature, making our samples good candidates for magnetic temperature transducer (MTT) devices. The DC resistivity for sample at y = 0.05, 0.1 was studied. The resistivity decreases linearly with increasing temperature within the given range of temperature up to 666 K for all samples. The dielectric constant of all samples is nearly independent on temperature through the range of 450 to 600 K which is a common character of ferrites. The dielectric loss was found to increase by increasing temperature, which may be related to the increase in AC conductivity. Hyperthermia measurements show the maximum specific power loss and temperature increase were 26 w/gr and 43 °C, respectively, for sample containing Zr = 0.05, after 2 min of measurements. One of the real applications of the material is that it is used as an effective method in tumor treatment by exposing the patient to external magnetic field. © 2022, The Author(s).This project was supported finically by the Academy of Scientific Research and Technology (ASRT), Egypt, Grant No. (6550), which is the 2nd affiliation of this research. Funding. Open access funding provided by The Science, Technology & Innovation Funding Authority (STDF) in cooperation with The Egyptian Knowledge Bank (EKB)

RADIATION SHIELDING PROPERTIES OF METHYLCELLULOSE (MC)/GADOLINIUM OXIDE COMPOSITES

In the present work, the influence of weight percentages of Gd2O3 content (10%-30%) of reinforced MC composites in their photon absorption capabilities for photon energies, ranging from 0.01 to 3 MeV, were investigated. MC with Gd2O3 composite films was prepared via a solution casting method

FERROELECTRIC AND DIELECTRIC PROPERTIES OF STRONTIUM TITANATE DOPED WITH BARIUM

The present work aimed to synthesized ferroelectric (perovskite) material. Structural, morphological, electrical and Polarization-Electric field hysteresis loops were investigated.W.I.A. and I.I.N. thank Minobrnauki research project FEUZ-2020-0059 for financial support