X-ray Induced Luminescence Properties Research Articles

X-ray induced luminescence properties of Ce-doped BaF2-Al2O3-B2O3 glasses

In this study, we have synthesized xCeF3-(30-x)BaF2-20Al2O3-50B2O3 (x = 0, 0.3, 1.0, 3.0, 5.0 and 10.0 mol%) glasses by the conventional melt-quenching method and then investigated the optical properties (transmittance spectra, photoluminescence (PL) spectra and PL decay times), scintillation properties under X-rays irradiation (scintillation spectra and scintillation decay times) and thermally-stimulated luminescence (TSL) properties (glow curves and dose response functions). The PL spectra of the Ce-doped samples consist of an intense emission band due to the 5d-4f transitions of Ce3+ ion peaking at 350–400 nm, and PL quantum yield value was 70.1%. The decay time of the latter emission slightly varied in a range of 32–36 ns depending on the Ce concentration. The Ce-doped samples have also shown strong scintillation under X-ray irradiation having a spectrum of an intense emission band. The peak position around 300–400 nm with the Ce3+ concentration, and the decay time ranged 19–44 ns. The scintillation light yield of 5.0% Ce-doped sample was the highest among the present samples, and the measured value was 1,800 ph/MeV under 137Cs γ-ray exposure.

Identification and structures of the X-ray induced luminescence centers in the zeolites Zr,X,Cs,Na-LTA, X = Cl, Br, and I

Abstract Zr4+ and halide anions were introduced into zeolite A (LTA) by treating Cs,Na-A with ZrX4(g), X = Br and I, under anhydrous conditions. The crystal structures of Zr,Br,Cs,Na-A and Zr,I,Cs,Na-A were determined by single-crystal crystallography with compositional confirmation by scanning electron microscopy energy-dispersive X-ray (SEM-EDX) analysis. Their X-ray induced luminescence (XIL) properties were throughly studied. These structures and XIL properties were compared with those of previously reported Zr,Cl,Cs,Na-A. In both structures, most Na+ and Cs+ ions occupy positions similar to those found in Cs,Na-A and Zr,Cl,Cs,Na-A. About 9% of the large cavities of Zr,Br,Cs,Na-A are centered by ZrBr62− ions. In Zr,I,Cs,Na-A, about 6% are centered by ZrI62−. These octahedral ZrX62− ions are each held in place and stabilized in their large cavities by 24 bonds between all six of its halide ions and eight surrounding Cs+ ions. They are further bridged by 8-ring Cs+ ions to form a cubic 3-dimensional Cs11ZrX69+ continuum in the surface volume of the crystal. Their XIL domain peaks have red-shifted from 495 nm for Zr,Cl,Cs,Na-A, to 520 nm for Zr,Br,Cs,Na-A, and to 640 nm for Zr,I,Cs,Na-A. This may be because the self-trapped excitons (STE) of ZrBr62− and ZrI62− have smaller band gaps than that of ZrCl62−, a result of the valence band maximum 4p energy level in Br− being higher (5p in I− even higher) than the 3p energy level in Cl−.

Photoluminescence, γ-irradiation and X-ray induced luminescence studies of Sm3+-doped oxyfluorosilicate glasses and glass-ceramics

Sm3+-doped oxyfluorosilicate glasses were fabricated through traditional melt quenching technique. After the heat treatment of the prepared glass, transparent SrF2 nanocrystalline glass-ceramics (GC) were obtained. The amorphous nature of the prepared glasses and crystalline phase (SrF2) of the GC were confirmed by XRD analysis. Abbe number was calculated for all the prepared glasses by measuring refractive index at different wavelengths. In the framework of Judd-Ofelt (JO) theory, the JO intensity parameters were obtained from the absorption spectra of 1.0mol% Sm2O3-doped glass. The photoluminescence spectrum was recorded with 401nm excitation. From the analysis of optical spectra and JO parameters, the radiative properties like radiative transition probabilities, branching ratios and radiative lifetimes for the fluorescent levels of Sm3+ ions were determined. The effect of γ-irradiation on luminescence properties and X-ray induced luminescence properties were also studied. The emission intensity was increased for GC where as it decreases with increase of γ-irradiation dosages. There are no noticeable changes in the position as well as intensity in photoluminescence and X-ray induced luminescence spectra for GC sample but after the γ-irradiation, the emission intensity was decreased moderately. The luminescence decay profiles for 4G5/2 level were recorded and it is changed from exponential to non-exponential nature for higher Sm3+ ion concentrations. The decay profiles which exhibit non-exponential nature are well fitted to the Inokuti-Hirayama model and determined the energy transfer parameters. By using the integrating sphere, the quantum yield values were obtained for all the prepared glasses. The detailed study of the present glasses reveals that these glasses could be useful for radiation shielding and scintillation applications.

Physical, vibrational, optical and luminescence investigations of Dy3+-doped yttrium calcium silicoborate glasses for cool white LED applications

The Dy3+-doped yttrium calcium silicoborate glasses of composition of 25Y2O3 + 10CaO + 10SiO2 + (55-x)B2O3 + x Dy2O3, where x = 0.05, 0.1, 0.5, 1.0, 1.5, 2.0 and 2.5 mol%, have been synthesized and are characterized through optical, photoluminescence and X-ray induced luminescence properties. The Judd-Ofelt model has been adopted to evaluate the radiative properties of the 4F9/2 → 6HJ (J = 15/2, 13/2 and 11/2) emission transitions. The concentration quenching effect of Dy3+ ion concentration on the emissions from the 4F9/2 excited level is discussed in details. The luminescence decay curves of the 4F9/2 level transform from exponential to non-exponential nature for higher Dy3+ ion concentration. The yellow to blue (Y/B) intensity ratio, CIE Chromaticity coordinates and correlated color temperatures (CCT) were calculated from the emission spectra and were found that they fall in yellowish white light region. Thus, these results showed that the present YCaSBDy glasses could be aptly suitable for cool white light emitting diodes as well as glass scintillation applications.

Emission properties of Ce3+ centers in barium borate glasses prepared from different precursor materials

The photoluminescence (PL) and X-ray induced luminescence properties of Ce-doped barium borate glasses prepared from different precursor materials have been investigated. Oxidation of Ce3+ takes place during the melting process performed using a pre-vitrified non-doped glass. Residual groups originated from the precursor materials, such as fluorine atoms and OH groups, are found to affect the optical and emission properties of the glasses. Moreover, both the PL and the X-ray induced luminescence properties of the glasses depend on the precursor materials used for their synthesis. Based on a thorough analysis of the emission properties, we conclude that the best synthesis conditions involve melting a batch containing Ce(CH3COO)3·H2O, BaCO3, and B2O3 in Ar atmosphere.

X-ray induced luminescence of Sn2+-centers in zinc phosphate glasses

Photo- and X-ray induced luminescence properties of Sn2+-doped zinc phosphate glasses with different chemical compositions were investigated. Decay constants of the glasses decrease with increasing the ZnO amount, which are independent of excitation light sources. By comparison of emission properties, we have found that the glass structure affects both luminescence properties. The broader emission band in the P2O5-rich glasses suggests that the site variation of Sn2+ centers is mainly due to the P2O5 sub-networks. It is expected that the P2O5 sub-networks are effective for not only photoluminescence but also the X-ray induced radio-luminescence and storage luminescence.

X-ray induced luminescence properties of (Y,Eu)AlO3 single crystals

We investigated photoluminescence, scintillation and dosimeter properties of (Y1-x Eux)AlO3 (x = 0.001, 0.5 and 1) single crystals (hereafter denoted as Eu:YAP for x = 0.001, EYAP for x = 0.5 and EAP for x = 1). The samples were prepared by the Floating Zone method. In photoluminescence (PL), we observed a broad emission around 300–400 nm due to host under excitation of 280 nm, and emissions due to the 4f state transitions of Eu3+ appeared around 590 nm and 615 nm. Scintillation spectra also show emission peaks around 590 and 615 nm due to the 4f state transitions of Eu3+ in all the samples. In addition, emissions around 300–400 nm due to YAP host and around 550–700 nm due to 5d-4f transitions of Eu2+ appeared in Eu:YAP. The PL and scintillation decay time profiles consisted of several exponential decay components. The fast (ns) component group was possibly due to host emission, and especially Eu:YAP demonstrated a very fast PL decay time of 16 ns. The intermediate (μs) component group was due to the 5d-4f transitions of Eu2+. The slow (ms) component group was ascribed to the 4f state transitions of Eu3+ ion. The Eu:YAP sample showed intense thermally-stimulated luminescence (TSL) with peaks at 46, 155, 255 and 443 °C. The intensity was much higher than those of EAP and EYAP. In particular, the peak at 254 °C, which showed the highest intensity, was due to doping with Eu. The TSL dose response function showed a good linearity (R2 > 0.99) over a wide dose range from 0.1 mGy to 100 mGy for Eu:YAP, which showed the highest sensitivity among the present samples.