RE Dopants Research Articles

First-principles study on defect chemistry and migration of oxide ions in ceria doped with rare-earth cations

Oxygen transport in rare-earth oxide (RE(2)O(3)) doped CeO(2) with fluorite structure has attracted considerable attention owing to both the range of practical usage (e.g., fuel cells, sensors, etc.) and the fundamental fascination of fast oxide ion transport in crystalline solids. Using density-functional theory, we have calculated the formation energies of point defects and their migration properties in RE(2)O(3) doped CeO(2)(RE = Sc, Y, La, Nd, Sm, Gd, Dy, and Lu). The calculated results show that oxygen vacancies are the dominant defect species obtained by RE(3+) doping. They form associates with the RE(3+) ions, and the corresponding defect association energy is a strong function of the ionic radii of the RE(3+) dopants. The migration of an oxygen vacancy was investigated using the nudged elastic band method. The lowest activation energy for oxygen vacancy hopping is obtained for a straightforward migration path between two adjacent oxygen sites. The migration energy of an oxygen vacancy also strongly depends on the ionic radii of the neighbouring dopant cations. Accordingly, we have identified two factors that affect the oxygen vacancy migration; (1) trapping (or repelling) of an oxygen vacancy at the NN site of the RE(3+) dopant, and (2) reduction (or enlargement) of the migration barrier by RE(3+) doping. These findings provide insight for atomistic level understanding of ionic conductivity in doped ceria and would be beneficial for optimizing ionic conductivity.

Optical Property of Hybrid Material Including Crystalline in Amorphous Matrix

This paper presents results and observations obtained from a study of crystallization effect on optical property by doping Sm2O3 in amorphous material. The heat treatments, according to Differential Thermal Analyzer (DTA) results, have been performed in order to generate crystallization of amorphous material. The crystalline phase has been analyzed by X-Ray Diffractor (XRD). In this work, we have observed the emission intensity changes by increasing the concentration of Sm3+ ions up to 1.0mol%. As a result, we have confirmed the solubility of RE dopant in this composition glass by comparing the emission intensity at three strong emission bands [4G5/2-6H5/2 (564 nm), 4G5/2-6H7/2 (602 nm) and 4G5/2-6H9/2 (647 nm)]. Beside, the up-conversion of photoluminescence by the optimum crystalline size of host matrix has been shown by Fluorimeter data. In conclusion, we have estimated the effect of crystalline on optical property in amorphous matrix from this research.

Dependence of thermo-mechanical and mechanical properties of novel fluorophosphate glass on various rare earth dopants

The dependence of thermo-mechanical, and mechanical properties on various rare earth dopants (RE) including Nd2O3, Er2O3, and Yb2O3 in 0.4MgF2-0.4BaF2-0.1Ba(PO3)2-0.1Al(PO3)3 glasses (MBBA system) is systematically investigated. MBBA system doped with RE dopants presented the potential application in the field of communication and high power layer system in the previous reports. In this work, it is found that the density of the doped glass increases with an increasing of RE concentration, which could be understood in terms of cationic field strength (CFS) effect. The Knoop hardness is found to decrease with the loading time and dopant concentration due to the indentation size effect (ISE) effect. The observed decrease of thermal expansion coefficient and the increase of glass transition temperature Tg with increasing dopant concentration are elucidated in terms of the increasing number of strong covalent bonds with increasing RE dopant concentration. Those results will be of paramount importance before designing optical devices.

The effect of rare earth doping on the glow peak positions of [formula omitted

Thermoluminescence of the rare earths (Ho, Tb, Gd, Sm, Ce or La) doped LiNaSO 4 and irradiated at room temperature was studied in the temperature range 300–673 K. The glow curves of this material consistently illustrate the presence of two groups of glow peaks that behave differently. The first group occurs in the temperature range 350–450 K, and the individual peaks occur at the same temperature for all dopants. The second group (500–650 K), which contains the dosimetric peak, is noted to move in temperature with the size of the RE dopants. The switch in behavior of the glow peaks is attributed to a possible phase transition of the host material near 500 K. Additionally, the relatively simple glow curve, low fading and the presence of the dosimetric peak at high temperatures with 80–100% of the total glow-curve area contained within the complex above 500 K make the material suitable for radiation dosimetry at high temperature.

Refractive Index and Low Dispersion Properties of New Fluorophosphate Glasses Highly Doped with Rare-Earth Ions

A new series of 0.4MgF2–0.4BaF2–0.1Ba(PO3)2–0.1Al(PO3)3 glasses highly doped with rare-earth dopants (RE; Nd2O3, Er2O3, and Yb2O3) have been successfully developed for laser applications. Linear refractive index, dispersion properties including Abbe number (ν), dispersion parameter (A′, B′), electronic osciallator energy (Eo), and electronic osciallator strength (Ed) were determined as a function of RE dopants. The refractive index (nD=1.5872 to 1.6047) was found to linearly increase with dopant concentrations irrespective of types of rare earth dopants, while the Abbe number (ν = 65.7 to 68.8) and dispersion parameters including A′ (∼62), B′, Eo (13 ± 0.5 eV), and Ed (19 ± 1 eV) exhibit a concentration independence. It is remarkable that the refractive index of those new glasses increased with increasing RE dopant concentration, while the relatively large Abbe number of those glasses was independent of dopant concentration. The dependence of refractive index (n) on RE cations with high polarizabilities are discussed in terms of molar volume (Vm) and molar refractivity (Rm). Electronic oscillator strengths (Ed), the average electronic energy gap (Eo), and their respective dependence on RE dopant concentration were also investigated using linear refractive index (n) and Abbe number (ν). Those results suggest the present new series of glasses are strong candidates for stable laser hosts with extremely low dispersion.

New thermostimulated luminescence phosphors based on CaSO 4 : Ag, RE

Ag co-dopant in CaSO 4 : RE phosphors shifts its major TSL peak from 200°C to ∼375–400°C. Similar to the case of CaSO 4 : RE phosphors, the emission spectra of CaSO 4 : Ag, RE is, however, characteristic of the RE 3+ ion. Tm and Dy are the two RE dopants in CaSO 4 : Ag, RE which give the highest TSL sensitivity to gamma radiation. Their sensitivities are comparable to those of CaSO 4 : Tm/Dy. The TSL response of CaSO 4 : Ag, Tm/Dy was found to be linear with γ-dose and irradiation temperature independent up to 280°C.