Bluish-green color emitting Ba2Si3O8:Eu2+ ceramic phosphors for white light-emitting diodes

Luminescence and mechanoluminescence of Ba4Si6O16:Eu2+, RE phosphors

The luminescence properties of green Ba4Si6O16:Eu2+, rare-earths (RE) (RE = Sc, Y, La and Lu except Pm) phosphors are reported. Their long-lasting phosphorescence is discussed in view of trap depths and concentrations determined from thermally stimulated luminescence experiments. A second emission band centered at 439 nm was evidenced at low temperatures, which stems from the substitution of Eu2+ in the two non-equivalent Ba2+ sites of Ba4Si6O16. The mechanoluminescence properties of Ba4Si6O16:Eu2+, RE phosphors are described, and a new mechanoluminescence mechanism is proposed, in the case where RE = Ho3+, involving a trap distribution from 0.694 to 0.924 eV. Mechanical loading (post UV irradiation) induces a decrease in depth of the trap distribution, leading to an increase of the luminescence intensity, whereas a drop of the luminescence intensity is observed upon unloading, following the faster release of the charge carriers.

Identifying and explaining vibrational modes of sanbornite (low-BaSi2O5) and Ba5Si8O21: A joint experimental and theoretical study

We report here the analysis of vibrational properties of the sanbornite (low-BaSi₂O₅) and Ba₅Si₈O₂₁ using theoretical and experimental approaches, as well as results of high temperature experiments up to 1100-1150 °C. The crystal parameters derived from Rietveld refinement and calculations show excellent agreement, within 4%, while the absolute mean difference between the theoretical and experimental results for the IR and Raman vibrational frequencies was <6 cm^-1. The temperature-dependent Raman study renders that both sanbornite and Ba₅Si₈O₂₁ display specific Ba and Si sites and their BaO and SiO bonds. In the case of the stretching modes assigned to specific Si sites, the frequency dependence on the SiO bond length exhibited very strong correlations. Both phases showed that for a change of 0.01 Å, the vibrational mode shifted 10 ± 2 cm^-1. These results are promising for using Raman spectroscopy to track in situ reactions under a wide variety of conditions, especially during crystallization.

Combining experiment and computation to elucidate the optical properties of Ce3+ in Ba5Si8O21

A comprehensive study of a new and complex inorganic silicon-based luminescent material through computational and experimental methods.

Intrinsic optical bistability and frequency upconversion in Tm3+–Yb3+-codoped Y2WO6 phosphor

Intrinsic optical bistability (IOB) behaviour in the Tm³⁺–Yb³⁺ codoped Y₂WO₆ phosphor.

Effect of surface modification on photoluminescence properties of Y3Al5O12:Ce3+, Gd3+ nano-phosphors

In this study, a series of Y(3)Al(5)O(12):Ce(3+), Gd(3+) nano-phosphors were prepared using a simply wet chemical process with polyvinyl pyrrolidone as a modifier. The crystal and bonding structures of Y(3)Al(5)O(12):Ce(3+), Gd(3+) nano-phosphors prepared with different weight percentages of polyvinyl pyrrolidone were characterized by X-ray diffractometry and infrared spectrometry. The decomposition process of dried precursor gel with adding 1.37 wt% polyvinyl pyrrolidone was investigated by differential thermal and thermogravimetric analysis. The effect of surface modification on photoluminescence properties for the samples was studied. The results show that the steric hindrance effect of polyvinyl pyrrolidone leads to high dispersion and good crystallinity of Y(3)Al(5)O(12):Ce(3+), Gd(3+) nano-phosphors prepared with adding a proper weight percentages of polyvinyl pyrrolidone. Adding polyvinyl pyrrolidone is beneficial for the photoluminescence enhancement of the samples, which is attributed to the promotion of the incorporation of Ce(3+) and Gd(3+) into the Y(3)Al(5)O(12) nanocrystal and the surface passivation of the nano-particles by the polyvinyl pyrrolidone molecules.