Influence of the Doping Ion Nature and Content on Defect Creation Processes under the Effect of Ionizing Radiation in Aluminoborosilicate Glasses

Effects of ionizing irradiation on defect creation processes have been studied in rare earth (RE)-doped (RE = Sm, Gd, Eu, Ce, Nd) aluminoborosilicate glass with use of the electron paramagnetic resonance (EPR) and optical spectroscopy. As a function of RE ion nature, we observe that doping significantly influences the nature of the defects produced during irradiation and more specifically the relative proportions between hole and electron defect centers. Strong decrease of defect production efficiency under ionizing radiation independence on both the RE doping content and on the relative stability of the RE different oxidation states is also clearly revealed. The results could be explained by dynamical reversible trapping of the electron-hole pairs produced during irradiation on the different RE charge states as well as by RE segregation and pre-existing defects speciation in ABS glass structure

b-Irradiation Effect in Aluminoborosilicate Glasses: The Role of RE Codoping (RE= Sm, Gd)

International audienceThe effect of Sm and Gd codoping on the structural modifications of β-irradiated aluminoborosilicate glasses has been studied by electron paramagnetic resonance (EPR) and Raman spectroscopy. The EPR spectra showed that the relative amount of Gd3+ ions occupying network former positions ( ) follows a nonlinear behavior as a function of the Sm/Gd ratio. This suggests that codoping favors the occupation by Gd3+ ions of the network former positions rather than the modifier positions in aluminoborosilicate glasses. The appearance of a superhyperfine structure of EPR lines attributed to boron–oxygen hole centers (BOHC) with increasing Sm/Gd ratio was observed. This suggests that Gd3+ ions are diluted in the vicinity of the BOHC defects. The concentration of defects created by irradiation reveals a nonlinear dependence on Sm and Gd codoping for the lowest irradiation dose (105 Gy). Therefore, codoping also affects the defect creation processes at least at the lowest irradiation dose. Raman spectroscopy measurements suggest that the irradiation-induced structural changes vary nonlinearly with the Sm/Gd ratio. In fact, the shift of the Si–O–Si bending vibration modes reveals a clear minimum for samples containing equal amounts of Sm and Gd (1 : 1) in the investigated glasses

Effect of Sm-, Gd- codoping on structural modifications in aluminoborosilicate glasses under beta-irradiation

Two series of Sm-, Gd-codoped aluminoborosilicate glasses with different total rare earth content have been studied in order to examine the codoping effect on the structural modifications of beta-irradiated glasses. The data obtained by Electron Paramagnetic Resonance spectroscopy indicated that relative amount of Gd3+ ions located in network former position reveals non-linear dependence on Sm/Gd ratio. Besides, codoping leads to the evolution of the EPR signal attributed to defects created by irradiation: superhyperfine structure of boron oxygen hole centres EPR line becomes less noticeable and resolved with increase of Gd amount. This fact manifests that Gd3+ ions are mainly diluted in vicinity of the boron network. By Raman spectroscopy, we showed that the structural changes induced by the irradiation also reveal non-linear behaviour with Sm/Gd ratio. In fact, the shift of the Si-O-Si bending vibration modes has a clear minimum for the samples containing equal amount of Sm and Gd (50:50) in both series of the investigated glasses. In contrast, for single doped glass there is no influence of dopant's content on Si-O-Si shift (in case of Gd) or its diminution (in case of Sm) occurs which is explained by the reduction process influence. At the same time, no noticeable effect of codoping on Sm3+ intensity as well as on Sm2+ emission or on Sm reduction process was observed

Tunable luminescence from Ce-doped aluminoborosilicate glasses

International audienceA series of aluminoborosilicate glasses were prepared using the melt-quenching technique for mixture of stoichiometric amounts of SiO 2 , Al 2 O 3 , H 3 BO 3 , Na 2 CO 3 , and ZrO 2 with adding of different amounts of CeO 2. The samples were investigated by means of luminescence spectroscopy. Tunable luminescence from violet to blue/green was observed from these glasses with different Xe-lamp excitation wavelengths ranging from 370 to 480 nm as well as with laser excitation of 266 and 355 nm. Moreover it was found that the possibility of tuning the light by changing of excitation wavelength was not unique. The same effect was observed by adjusting conditions for luminescence measurements as well as under exposure to β-irradiation. The obtained phenomena could be explained taking into account structural characteristics of this glass and it could be concluded that tunable luminescence results from the presence of different Ce-sites the glass matrix. Thus the results suggest that Ce-doped glasses could be considered as conversion materials for blue light-emitting diode chips to generate white light-emitting diodes. Ce 3+ ions were widely used as activators in various fluoride and oxide materials. The preparation of RE-doped phosphor materials for application in advanced illumination technologies has been the subject of intense research during recent decades. These researches are stimulated by the necessity of increasing the efficiency in white light emitting solid state devices which represent an alternate lightning source [1

Divalent Europium in beta irradiated aluminoborosilicate glass

International audienceThe reduction processes of Eu3+ ions in aluminoborosilicate glasses were studied using both high-temperature melting in air and b-irradiation by time-resolved luminescence and electron paramagnetic resonance spectroscopies. The Eu2+ ions produced during the synthesis are characterized by the UV excited broadband luminescence in the blue region due to the 4f 65d1–4f7 transition. This band revealed the presence more than one Eu2+ site participating in the emission with different crystalline fields and with different covalency of surrounding ligands. In irradiated glasses, the observed redshift of the Eu2+ emission band is related to the different relative proportion between Eu2+ sites

Luminescence of Aluminoborosilicate Glasses Doped with Gd3+ Ions

International audienceThe twophoton absorption that leads to the ultraviolet upconversion luminescence in the SiO2–Al2O3–B2O3–Na2O3–Zr2O : Gd3+ glass has been investigated. The inference has been made that no photon cascade emission takes place under excitation by monochromatic light corresponding to the maximum of the absorption band of the Cd3+ ion (204 nm). The mechanisms of concentration quenching and energy transfer between Cd3+ ions and optically active defects of the aluminoborosilicate glass have been discussed

Irradiation effects in oxide glasses doped with transition and rare-earth elements

International audienceThe effect of -irradiation on silicate and aluminoborosilicate glasses doped with transition metals (TM) and rare earth (RE) elements has been studied using Electron Paramagnetic Resonance (EPR), Raman and luminescence spectroscopy. Irradiation leads to the reduction of both Cr and Mn ions in both types of glass matrix. It is shown that even small amounts of TM dopants completely block defect production, as occurs under irradiation in non-doped glasses. As well, TM doping results in the disappearance of structural changes in the glass (densification, polymerization increase and Na migration) for doses of ~ 10 Gy. Unlike TM-doped matrices, incorporation of RE ions into aluminoborosilicate glass blocks neither defect production nor structural changes in glass matrices during irradiation. Simultaneously, we observe a reduction of RE ions, most clearly demonstrated for Ce ions in aluminoborosilicate glasses. We propose that the relative stability of the different charge states of the RE ions is linked to the efficiency of the reduction process, and therefore to the evolution of the glass structure during irradiation

From 11% Thin Film to 23% Heterojunction Technology (HJT) PV Cell: Research, Development and Implementation Related 1600 × 1000 mm2 PV Modules in Industrial Production

Plasma-enhanced chemical vapor deposition (PECVD) developed for thin film (TF) Si:H-based materials resulted in large area thin film PV cells on glass and flexible substrates. However, these TF cells demonstrate low power conversion efficiency PCE = 11% for double and PCE = 13% for triple junction cells below predicted PCE ≈ 24%. PV cells on crystalline silicon (c-Si) provide PCE ≈ 17–19%. Cost of c-Si PV cells lowered continuously due to reducing price of silicon wafers and enlarging their size. Two factors stimulated a combination of PECVD films and c-Si devices: (a) compatibility of the technologies and (b) possibility for variation of electronic properties in PECVD materials. The latter results in additional build-in electric fields improving charge collection and harvesting solar spectrum. We describe a transformation of PECVD TF solar cell technology for 11% efficiency modules to heterojunction technology (HJT) c-Si modules with 23% efficiency. HJT PV structure comprises c-Si wafer with additional junctions created by PECVD deposited layers allowing development of single wafer PV cells with PCE ≈ 24% and the size limited by wafer (15.6 x 15.6 cm2). The chapter starts with background in PECVD and c-Si PV cells. Then, in Section 2, we describe electronic properties of PECVD materials in HJT PV structures. Section 3 deals with structure and fabrication process for HJT devices. In Section 4, we present and discuss performance characteristics of the devices. Section 5 describes implementation of the developed HJT module (1600 x 1000 mm2) based on HJT single wafer cells in industry with presentation and discussion of characteristics related to industrial production. Finally, Section 6 presents the outlook and summary of the chapter

Reduction of Eu3+ to Eu2+ in aluminoborosilicate glasses under ionizing radiation

International audienceEu2O3-doped aluminoborosilicate glasses were prepared by melting in air at high temperature (1500 8C). It was shown by luminescence and Electron Paramagnetic Resonance (EPR) measurements that both Eu3+ and Eu2+ ions can exist simultaneously in the glass matrix studied after glass synthesis as well as after exposure to ionizing radiation. Increase of total Eu2O3 concentration leads to the increase of Eu3+ luminescence intensity while the luminescence intensity of Eu2+ ions tends to decrease. In contrast the EPR indicates that the amount of Eu2+ ions in the glass increases with total Eu2O3 concentration. The difference in the results of the two spectroscopies is explained in terms of energy transfer from Eu2+ to Eu3+ leading to an Eu2+ luminescence quenching. Irradiation results in the increase of reduced Eu2+ quantity detected by EPR measurements. It was shown that Eu2+ ions are located in both high (g 4.6) and low symmetry (‘‘U' spectrum) sites in the structure of aluminoborosilicate glasses. The increase of Eu2+ content by the increase of the irradiation dose manifests the strong reduction process Eu3+!Eu2+

Природа веры и ее роль в процессе производства высказываний

Belief is considered as a complex phenomenon of super subject-realization nature. This consideration is based on the combination of philosophical-anthropological approach and semiotic approach. Differences between personal belief and religious, confessional belief are revealed. Functions of belief in statements producing process are determined.Вера рассмотрена как комплексный феномен суперсубъектной природы. Данный аспект основан на соединении философско-антропологического подхода с семиотическим. Выявлены различия между личностной верой и религиозной, конфессиональной верой. Определены функции веры в процессе производства высказываний