Dy Impurities Research Articles

Role of dysprosium substitution on microscopy architecture, structural stability, and crack propagation mechanism in Bi-2212 engineering ceramics

Abstract This study achieves a strong link between microscopy architecture and fundamental characteristics including electrical conductivity, superconducting, and key mechanical design properties of Bi2.1-xDyxSr2.0Ca1.1Cu2.0Oy (Bi-2212) ceramic structures with different dysprosium molar ratio ranges of 0.00 ≤ x ≤ 0.10. The Dy/Bi substituted Bi-2212 ceramics are characterized by scanning electron microscopy (SEM), electrical resistivity (ρ-T), Electron Dispersive x-ray (EDX) investigations, and microindentation Vickers hardness (Hv) tests. Powder x-ray diffraction (XRD) experimental inspection is also studied to support SEM and Hv results. All experimental findings show significant improvement with an increase in the Dy impurity molar ratio to x = 0.01. On this basis, the Bi2.09Dy0.01Sr2.0Ca1.1Cu2.0Oy ceramic structure exhibits the lowest resistivity of 8.95 mΩ.cm at 300 K and transition width of 4.75 K, and the highest T c o n s e t of 85.00 K and T c o f f s e t of 80.25 K. Additionally, XRD examinations show that optimum Dy ion substitution in the Bi-2212 system stabilizes the high superconducting phase by improving crystallinity, crystallite size, grain orientation distributions, texturing, and interlayer interactions. In contrast, excessive substitution severely deteriorates crystallographic properties. Further, SEM images reveal that the presence of optimum Dy impurity enhances the crystallinity, couplings between the adjacent layers, homogeneous surface appearance, and microstructure. Moreover, the key mechanical design features and stability of the durable tetragonal phase improve significantly for x = 0.01. As a result, the material exhibits superior mechanical properties, including a microhardness of 0.5556 GPa, fracture toughness of 0.5390 MPa.m1/2, elastic modulus of 45.5389 GPa, shear modulus of 18.2156 GPa, yield strength of 0.1852 GPa, and resilience of 0.3766 MPa under a 0.295 N load.

Magnetic behavior and Curie temperature of Dy doped MgSe: Ab-initio calculations

In this paper, we have studied the structural, electronic and magnetic properties of Magnesium selenide (MgSe) doped with a rare earth magnetic impurity “Dy” in the zinc blende structure (Mg1−xDyxSe). The ab-initio calculations are performed using the Akai-KKR code, based on the density functional theory. The host compound is a nonmagnetic semiconductor with a gap energy of 1.45 eV. Doping with only 6% of Dy gives MgSe a metallic behavior with a spin polarization of 83% at the Fermi level. In addition, the ferromagnetism is the most stable magnetic phase in the doped system. The Dy impurity contributes with various magnetic moments ranging from 0.23 muB to 0.31 muB for concentrations of 6% and 20% respectively. Besides, Vegard's law is used in order to evaluate the variation of the lattice parameter as a function of Dy concentration. Lastly, the Curie temperature is also calculated, it turns out to be equal to 260 K, which is lower than the room temperature. Doped MgSe is an excellent choice for electronic devices owing to its metallic characteristic below the Tc temperature.

Dosimetric features and kinetic parameters of a glass system dosimeter.

Lithium borate (LB) glasses doped with dysprosium oxide (Dy2 O3 ) have been prepared by utilizing the conventional melt-quench technique. The prepared glass samples were exposed to 60 Co to check their dosimetric features and kinetic parameters. These features involve glow curves, annealing, fading, reproducibility, minimum detectable dose (MDD), and effective atomic number (Zeff ). Kinetic parameters including the frequency factors and activation energy were also determined using three methods (glow curve analysis, initial rise, and peak shape method) and were thoroughly interpreted. In addition, the incorporation of Dy impurities into LB enhanced the thermoluminescence sensitivity ~170 times. The glow from LB:Dy appeared as a single prominent peak at 190°C. The best annealing proceeding was obtained at 300°C for 30 min. Signal stability was reported for a period of 1 and 3 months with a reduction of 26% and 31%, respectively. The proposed glass samples showed promising dosimeter properties that can be recommended for personal radiation monitoring.

Temperature dependent magnetic properties of Dy-doped Fe16N2: Potential rare-earth-lean permanent magnet

Using the full potential linearized augmented plane wave method, we explored the magnetocrystalline anisotropy of Dy impurity doped α″-Fe16N2. Here, we considered two different Dy concentrations (1.56 and 3.125%). We also investigated the temperature dependence of the magnetic properties. The Dy site occupancy was found to be concentration dependent. The magnetic moments of Fe atoms near the Dy impurity was suppressed. However, we found a large magnetic moment in Dy atom (4.85–4.87 μB). Compared with the magnetic anisotropy constant in the pristine α″-Fe16N2 (0.57 MJ/m3), we obtained an enhanced perpendicular magnetic anisotropy. The calculated anisotropy constants in 1.56% Dy doping was 0.97 MJ/m3 while it became 1.27 MJ/m3 in 3.125% Dy doping. The Curie temperature in the pristine structure was about 820 K and it was suppressed to 765 K and 605 K in 1.56% and 3.125% Dy doping. At room temperature (300 K), the coercive field of 3.125% Dy doped system was enhanced almost 50% compared with that of the pure Fe16N2. We also found a maximum energy product of 50.9 MGOe for 3.125% Dy doping at 300 K. Our finding may suggest that the α″-Fe16N2 can be a potential permanent magnet with a lean Dy doping.

Synthesis and dosimetry features of novel sensitive thermoluminescent phosphor of LiF doped with Mg and Dy impurities

Lithium fluoride doped with Mg and Dy was fabricated for the first time using melting method. The optimum concentrations of impurities and thermal treatment were studied to achieve high thermoluminescence (TL) sensitivity. TL sensitivity of the fabricated phosphor is close to that of TLD-100 powder. Tm-Tstop technique was used to identify the number of overlapped TL glow peaks. Initial rise, isothermal decay and computerized glow curve deconvolution (CGCD) methods were applied to obtain kinetic parameters of the prepared TL material. Three component glow peaks were distinguished at temperatures 395, 448 and 510 K. Other TL properties such as fading, linearity of dose response and reusability are also presented and discussed.

Paramagnetic dysprosium-doped zinc oxide thin films grown by pulsed-laser deposition

Dysprosium(Dy)-doped zinc oxide (Dy:ZnO) thin films were fabricated on c-oriented sapphire substrate by pulsed-laser deposition with doping concentration ranging from 1 to 10 at. %. X-ray diffraction (XRD), Raman-scattering, optical transmission spectroscopy, and spectroscopic ellipsometry revealed incorporation of Dy into ZnO host matrix without secondary phase. Solubility limit of Dy in ZnO under our deposition condition was between 5 and 10 at. % according to XRD and Raman-scattering characteristics. Optical transmission spectroscopy and spectroscopic ellipsometry also showed increase in both transmittance in ultraviolet regime and band gap of Dy:ZnO with increasing Dy density. Zinc vacancies and zinc interstitials were identified by photoluminescence spectroscopy as the defects accompanied with Dy incorporation. Magnetic investigations with a superconducting quantum interference device showed paramagnetism without long-range order for all Dy:ZnO thin films, and a hint of antiferromagnetic alignment of Dy impurities was observed at highest doping concentration—indicating the overall contribution of zinc vacancies and zinc interstitials to magnetic interaction was either neutral or toward antiferromagnetic. From our investigations, Dy:ZnO thin films could be useful for spin alignment and magneto-optical applications.

Spectroscopy of the CaB4O7 and LiCaBO3 glasses, doped with terbium and dysprosium

A series of borate glasses of high optical quality with CaB4O7:Tb, LiCaBO3:Tb, CaB4O7:Dy, and LiCaBO3:Dy compositions containing 0.5 and 1.0mol% Tb2O3 and Dy2O3 impurity compounds were obtained from corresponding polycrystalline compounds using standard glass technology. By electron paramagnetic resonance (EPR) and optical spectroscopy it was shown that the Tb and Dy impurities are incorporated as Tb3+ (4f8, 7F6) and Dy3+ (4f9, 6H15/2) ions in the Ca and Li(Ca) sites of CaB4O7 and LiCaBO3 glasses network, respectively. The luminescence excitation and emission spectra as well as luminescence kinetics of the Tb3+ and Dy3+ centres in the CaB4O7 and LiCaBO3 glasses have been investigated and analysed in comparison with obtained earlier results for Tb3+ and Dy3+ centres in the Li2B4O7 glasses. All observed f–f transitions of the Tb3+ and Dy3+ centres in the luminescence excitation and emission spectra have been identified. Luminescence kinetics show single exponential decay for Tb3+ and Dy3+ centres in the CaB4O7 and LiCaBO3 glass network. The lifetime values for the main emitting levels of the Tb3+ and Dy3+ centres in all investigated glasses were determined at room temperature and their dependencies on the basic glass compositions and impurity concentrations are discussed. The obtained results show that the CaB4O7 and LiCaBO3 glasses are promising luminescent materials, operating in green and yellow–blue spectral regions, when activated with Tb3+ and Dy3+ ions, respectively.

KCl:Dy phosphor for thermoluminescence dosimetry of ionizing radiation

The thermoluminescence (TL) characterizations of γ-irradiated KCl:Dy phosphor for radiation dosimetry are reported. All phosphors were synthesized via a wet chemical route. Minimum fading of TL intensity is recorded in the prepared material. TL in samples containing different concentrations of Dy impurity was studied at different γ-irradiation doses. Peak TL intensities varied sublinearly with γ-ray dose in all samples, but were linear between 0.08 to 0.75 kGy for the KCl:Dy (0.1 mol%) sample. This material may be useful for dosimetry within this range of γ-ray dose. TL peak height was found to be dependant on the concentration (0.05-0.5 mol%) of added Dy in the host.

Thermoluminescence characteristics of the novel CaF2:Dy nanoparticles prepared by using the hydrothermal method

Dysprosium doped calcium fluoride (CaF2:Dy) nanoparticles were produced for the first time by using the hydrothermal method. X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) patterns were utilized to characterize the synthesized material. The particle size of about 43nm was evaluated from XRD data and supported by the SEM images. The Tm−Tstop and the computerized glow curve de-convolution (CGCD) methods were employed to determine the number of component glow peaks and kinetic parameters of the synthesized nanoparticles. Thermoluminescence glow curve of this phosphor exhibits six overlapping glow peaks. The optimized concentration of Dy impurity was found at 3mol%. The prepared nanoparticles exhibit a roughly linear dose response to absorbed dose of 1000Gy received from 60Co gamma source. This finding recommends this nanomaterial as a good candidate for high dose dosimetry. Other dosimetric features of this novel phosphor are also presented and discussed.

Composition Profiles of Silicon–Silicon Oxide and Silicon–Rare Earth Oxide Structures

Elemental composition profiles of the structures comprising the layers of dysprosium oxide (Dy2O3), lutetium oxide (Lu2O3), or silicon oxide (SiO2 with Dy and Lu impurities) on silicon substrates have been studied by means of Rutherford backscattering spectrometry and nuclear reaction analysis. The structures were prepared by high-temperature diffusion in oxygen or air. The results of depth profiling are compared to the concentrations of electrically active impurities in the diffusion layers on silicon, which were determined from measurements of the capacitance-voltage characteristics and the surface resistance and from the data of transmission electron microscopy and X-ray diffraction.

Calculated crystal-field parameters for rare-earth impurities in noble metals

From first-principles density-functional calculations of the charge distribution the crystal-field (CF) parameters for 4f states of Er and Dy impurities in Ag and Au have been evaluated. The calculations are based on an optimized linear combination of atomic orbitals scheme, where the local-density approximation (LDA) is used for the conduction-electron states, while the localized rare-earth 4f states are treated as ``open core shell.'' As the 4f localization cannot be properly described within LDA, a self-interaction correction for the 4f states is included. In this way, any artificial constraints on the 4f charge density employed in earlier first-principles CF calculations are avoided. The calculated CF parameters agree well with recent neutron scattering data.

Electron-electron interactions in the presence of magnetic impurities: Effect on the temperature dependence of resistivity

We investigate the effect of the addition of magnetic impurities on the temperature dependence of the electrical resistivity ϱ(T) of 3-dimensional amorphous alloys at low temperatures (T<20K). The non-magnetic sample YNi presents the √T dependence characteristic of electron-electron interactions effects. With the introduction of Dy impurities, the samples (Dy xY 1−x) Ni with x<0.12 present an additional contribution varying as 1/√T and proportional to the inelastic spin dephasing rate τ s -1 (and x), determined independently through weak localization magnetoresistance. These results are analyzed in terms of the theories developed for the electron-electron interaction effects and localization corrections in the presence of magnetic impurities.

Role of Dy in the Thermoluminescence of CaSO4:Dy

Abstract Building on recent models of the thermoluminescence (TL) process in CaSO4:Dy, work is undertaken to delineate more specifically the role of the Dy impurity in the TL process. Thermally stimulated currents observations show that the recombination mechanism for peak 3 is bimolecular while that for peak 1 is monomolecular. TL results clearly show that the absence of Dy removes the dosimetric peak 3 near 220 oC in this material. Apparently, only Dy impurity develops the appropriate SO4 --VCa centres needed for observation of these peaks. The peak-3-related centres are shown to be quite different in behaviour from that of the structurally similar peak-1 - related SO4 --VCa centres. These results emphasise the importance of Dy impurities in stabilising the TL process needed to observe the dosimetric peak in this system.

Role of Dy in the Thermoluminescence of CaSO4:Dy

Building on recent models of the thermoluminescence (TL) process in CaSO4:Dy, work is undertaken to delineate more specifically the role of the Dy impurity in the TL process. Thermally stimulated currents observations show that the recombination mechanism for peak 3 is bimolecular while that for peak 1 is monomolecular. TL results clearly show that the absence of Dy removes the dosimetric peak 3 near 220 oC in this material. Apparently, only Dy impurity develops the appropriate SO4--VCa centres needed for observation of these peaks. The peak-3-related centres are shown to be quite different in behaviour from that of the structurally similar peak-1 - related SO4--VCa centres. These results emphasise the importance of Dy impurities in stabilising the TL process needed to observe the dosimetric peak in this system.

An electron spin resonance study of thermoluminescence mechanisms in CaSO4:Dy

Mechanisms of thermoluminescence (TL) in CaSO4:Dy are studied using electron spin resonance (ESR) in single-crystal samples. The ESR analysis indicates the presence of several variations of a distorted SO4- centre locally stabilised by a nearest neighbour Ca vacancy. This centre's structure, which has not been reported previously, relates to several centres observed in this system and could also explain results in related compounds. The presence of the Dy impurity, which increases the concentration of Ca vacancies due to charge neutrality requirements, enhances both the concentration of these centres and the intensity of the major TL peaks near 220 and 350 degrees C. The specific role of these and other previously reported centres in the TL of this material is followed using heat treatments. This enables one to identify centres that change in the range of the observed TL peaks as well as centres that seem to be related to one another by charge transfer or rearrangement. The behaviour of the observed centres and their relationship to the TL behaviour of the system reemphasises the complexity of this system.

Optical absorption and luminescent processes in thermoluminescent CaSO4:Dy

Optical absorption in irradiated and non-irradiated single crystals of CaSO4 and CaSO4:Dy is studied. The intrinsic defect centres SO4-, SO3-, SO2-, O3-, and O- are identified in irradiated samples. However, these centres are generally observed only if stabilised by Dy impurity ions within the structure. Dy2+ absorption is also observed in irradiated doped samples. Luminescence via energy transfer to Dy ions is corroborated by this study. Areas where these results may be used to develop further understanding of the thermoluminescence process in CaSO4:Dy are discussed.

Thermoluminescent spectra and optical absorption in CaSO4:Dy

The CaSO4:Dy TL emission spectrum between 400 nm and 800 nm is studied using real-time spectroscopy. The emission spectrum is found to be independent of exposure between 460 R and 104 R, and in the temperature range between room temperature and 400 degrees C the TL emission spectrum is solely the result of characteristic trivalent Dy transitions. Optical absorption bands observed in CaSO4:Dy are correlated with optical transition of the Dy2+ and Dy3+ ions to determine that Dy3+ is photo-reduced during irradiation and oxidised during subsequent heating. The effect of thermal treatments on the behaviour of the SO3- and SO4- radicals produced by ionising radiation, as determined in independent ESR results, is discussed in terms of the concurrent changes in the Dy impurity that results in the thermally stimulated release of luminescence. It is concluded that the model of the TL process most consistent with the various experimental results is one in which the Dy impurity acts as an electron trap, with charge recombination at the radical sites resulting in energy transfer to Dy3+ ions which de-excite by luminescent emission.

E.P.R. and susceptibility measurements in XAl2 (X = Sc, Y, La, Yb, Lu) compounds containing Gd, Er, Dy and Nd impurities

and W [I]. E.P.R. and magnetization measurements of the rare earth in metals give information about the C.E.F. and about the exchange interaction between the impurities and the conduction electrons (C.E.). In this paper we report E.P.R. of Er, Dy and Nd ions in cubic Laves phase compounds XAl, (X

Magnetoresistance of silver single crystals containing rare-earth impurities

We present magnetoresistance measurements on single crystals of silver containing Tb or Dy impurities together with the analysis of the contributions from quadrupole and exchange scattering.

Measurements of orbit-lattice coupling of Er and Dy impurities in Ag and Al hosts

Measurements of orbit-lattice coupling of Er and Dy impurities in Ag and Al hosts