Synthesis of Pb3O4-SiO2-ZnO-WO3 glasses and their fundamental properties for gamma shielding applications

In this research, we prepared zinc lead silicate glass system with the composition 35Pb3O4-60SiO2- (5-x) ZnO-xWO3 (0 ≤ x ≤ 5 mol %) via the melt-quench method. XRD is explored the nature of the glass system. Ultrasonic velocity, and elastic modulus were experimentally investigated and then the results were confirmed by using the theoretical calculations. It was found that because of molar volume reduction inter-ionic distance\({R}_{i}\), polaron radius \({r}_{p}\), and inter-nuclear distance, \({r}_{i}\)of the investigated glasses are reduced with WO3 content. The basic attenuation factors; mass and linear coefficients denoted by µ/ρ and µ, respectively, were determined employing several simulations for each energy via FLUKA code. As WO3 content increased from 0 to 5 mol %, the µ increased from 0.728 cm− 1 to 0.856 cm− 1 achieving high shielding performance for the sample with x = 5 mol %. At 0.6 MeV with x = 5 mol %, we found that the dose rate of the prepared glass system decreases from 2.35 × 107 R/h at 1 mm to 4.71 × 106 R/h at 4 mm. The values of MFP and HVL are lower than those of the conventional photon shields indicating that our prepared glass samples (especially G5 glass sample) have promising shielding properties to use for x/gamma rays applications.

Racah Parameter and Nephelauxetic Effect on Er3+/Nd3+ Codoped Lithium Niobate Tellurite Glass

The modification of absorption characteristics in rare-earth doped tellurite glasses is important in photonics application. The Er3+/Nd3+ doped glasses of the form (69-x)TeO2-15Li2CO3-15Nb2O5-1Er2O3-(x)Nd2O3 with x= 0.4, 0.8 and 1.0 mol % are successfully made by using conventional melt-quenching technique. Physical properties such as polaron radius, interionic distance, field strength and average distance between acceptors and donors are determined. The absorption spectra reveal eleven prominent peaks centered at 6535.9 cm-1, 10245.9 cm-1, 11415.5 cm-1, 12437.8 cm-1, 13369.0 cm-1, 15267.2 cm-1, 15949.2 cm-1, 17127.1 cm-1, 19084.0 cm-1, 20449.9 cm-1 and 22271.7 cm-1 which corresponding to the transitions from ground state to various states of Nd3+ ions. The crystal field site increases from 8.120 to 8.169 cm-1 due to increase in contraction of Nd3+-ligand. The nephelauxetic function, increase 0.104 to 0.107. The increasing in value describes, the increasing in ionic bond from-0.0004 to-0.0011. The increment in exhibits the increase in the number of effective positive charge connected to neodymium atom and attracts the electrons from ligands as it increases from 1.0004 to 1.0011. These present glass shows the potential candidate of broadband amplifiers and lasers as it is comparable with other Nd3+ doped another host.

Effect of Nd3+ on the Properties of Lithium Niobium Borate Crystal and Glass

1 mol% of neodymium-doped lithium niobium borate (NdLNB) glass and crystal have been produced by using melt-quenching and Czochralski technique, respectively. The synthesis, growth and characterizations of the samples were reported. X-ray diffraction (XRD), Differential thermal analyzer (DTA), Ultraviolet-Visible-Near-Infrared (UV-Vis-NIR) and Photoluminescence (PL) spectroscopic characterizations were made to examine the influence of Nd3+ on the physical, structural and optical properties of the samples. Various physical properties such as density, molar volume, ion concentration, polaron radius, inter-nuclear distance and field strength were calculated. The as-quenched glass was amorphous whereas crystal was crystalline as established via XRD studies. UV-Vis-NIR spectra exhibited eight prominent bands centered at 353, 475, 524, 583, 681, 745, 803, 875 nm corresponding to the transitions from the ground state to 4D3/2, 2G9/2, 4G7/2, 4G5/2, 4F9/2, 4F7/2, 4F5/2, 4F3/2 excited states, respectively. Moreover, the emission spectra at 355 nm excitation displayed several peaks that contributed to the transition of(4F3/2→4I9/2) and (4F3/2→4I11/2), respectively. Fluorescence lifetime was recorded at 53.69 µs for the glass whereas the crystal was recorded at 43.62 µs. It was found that Nd3+ ions affected the physical, structural and optical properties of the glass and crystal samples.

Physical and optical properties of sodium borate glasses doped with Dy3+ ions

The photoluminescence, optical and physical properties of sodium borate (NB) doped with different concentrations of Dy[Formula: see text] were determined and well discussed. The samples were prepared by the melt-quenching technique and characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Photoluminescence and absorption spectra of NB glasses doped with different concentrations of Dy[Formula: see text] are reported. Ten absorption bands with hypersensitive transition at 1272 nm ([Formula: see text] [Formula: see text][Formula: see text]) and two emission bands for the transitions at [Formula: see text] [Formula: see text][Formula: see text] (blue color) and [Formula: see text] [Formula: see text][Formula: see text] (yellow color) with an excitation of 330 nm have been recorded. A series of considerable physical properties (oscillator strengths, refractive index, ions concentration, polaron radius) was calculated for each dopant concentration.

The effect of electric field on the coherence time of a 2D RbCl parabolic quantum dot qubit

The effects of the electric field on the coherence time of a 2D RbCl parabolic quantum dot (PQD) qubit are studied by using the variational method of Pekar type (VMPT) and the Fermi Golden Rule. We calculate the excitation energy of an electron strongly coupled to bulk longitudinal optical (LO) phonons in the 2D RbCl PQD under an applied electric field. The phonon spontaneous emission causes the decoherence of the qubit. The investigated results indicate that the coherence time increases with increasing strength of the electric field and the effective confinement length, whereas it decreases with increasing polaron radius. Our research results would be useful for the design and implementation of the solid-state quantum computation.

The effect of magnetic field on RbCl quantum pseudodot qubit

Under the condition of strong electron–LO–phonon coupling in a RbCl quantum pseudodot (QPD) with an applied magnetic field (MF), the eigenenergies and the eigenfunctions of the ground and the first excited states (GFES) are obtained by using a variational method of the Pekar type (VMPT). A single qubit can be realized in this two-level quantum system. The electron’s probability density oscillates in the RbCl QPD with a certain period of [Formula: see text] fs when the electron is in the superposition state of the GFES. The results indicate that due to the presence of the asymmetrical structure in the z direction of the RbCl QPD, the electron’s probability density shows double-peak configuration, whereas there is only peak if the confinement is a symmetric structure in the x and y directions of the RbCl QPD. The oscillating period is an increasing function of the cyclotron frequency and the polaron radius, whereas it is a decreasing one of the chemical potential of the two-dimensional electron gas and the zero point of the pseudoharmonic potential (PP).

Structural and Physical Properties ofFe2O3-B2O3-V2O5Glasses

The structural and physical properties ofxFe2O3-(40-x)B2O3-60V2O5 (0≤x≤20)glass system have been investigated. The samples were prepared by normal melt-quench technique. The structural changes were inferred by means of FTIR by monitoring the infrared (IR) spectra in the spectral range 600–4000cm-1. The absence of boroxol ring (806 cm-1) in the present glass system suggested that these glasses consist of randomly connectedBO3andBO4units. The conversion ofBO3toBO4andVO5toVO4tetrahedra along with the formation of non-bridging oxygen's (NBOs) attached to boron and vanadium takes place in the glasses under investigation. The density and molar volume of the present glass system were found to depend onFe2O3content. DC conductivity of the glass system has been determined in the temperature range 310–500 K. It was found that the general behavior of electrical conductivity was similar for all glass compositions and found to increase with increasing iron content. The parameters such as activation energy, average separation between transition metal ions (TMIs), polaron radius, and so forth have been calculated in adiabatic region and are found consistent with Mott's model of phonon-assisted polaronic hopping.

Effect of Dimensionality and Anisotropy on the Holstein Polaron

We apply weak-coupling perturbation theory and strong-coupling perturbation theory to the Holstein molecular crystal model in order to elucidate the effects of anisotropy on polaron properties in D dimensions. The ground state energy is considered as a primary criterion through which to study the effects of anisotropy on the self-trapping transition, with particular attention given to shifting of the self-trapping line and the adiabatic critical point. The effects of dimensionality and anisotropy on electron-phonon correlations and polaronic mass enhancement are studied, with particular attention given to the polaron radius and the characteristics of quasi-l-D and quasi-2-D structures. Perturbative results are confirmed by selected comparisons with variational calculations and quantum Monte Carlo data.

Discrete lattice model for the large polaron

The energy states of a polaron in the weak-coupling limit were first obtained by Fröhlich and co-workers, assuming that the polarization of the lattice due to the electron is continuous. If the polaron radius is comparable to the lattice constant then the assumption is inappropriate. A model based on the discrete nature of the lattice is more suitable. Such a model, based on the semiclassical zero-point energy, is proposed. We have calculated the ground-state energy of the polaron and the energy of the polaron near the bottom of the conduction band. The first discussion of the effect of lattice discreteness on the polaron energy was presented by Lepine and Frongillo who used for their calculations, a method based on the "kq" representation. Our method differs from the method of these earlier authors but the results of the two approaches are similar. Some differences exist nevertheless. The main aim of this paper is, therefore, to provide an alternate method for calculating the effect of discreteness on the polaron energy. The differences arising between the results of the two methods are discussed.

Polaronic conduction in lanthanum strontium chromite

In many polycrystalline ceramic materials the transport properties are strongly affected by internal barrier effects or by the presence of contact barriers. The transport properties of La1−xSrxCrO3, 0 ≤ x ≤ 0.2 have been investigated and the degree to which these barriers affect the measured transport properties has been established. Measurements of the dc and ac conductivity in the range 77 K ≤ T ≤ 1300 K are consistent with the hopping of polarons in a defect band of localized states at the Fermi energy with the thermopower essentially independent of temperature. A polaron radius of 3.5 Å has been determined with room temperature mobility of 5 × 10−4 cm2 V−1 s−1.