Crystal structure and pale-yellow emitting properties of K3Gd1–x Dy x B6O12 solid solutions

A new potassium dysprosium polyborate, K3DyB6O12, has been prepared via the high-temperature molten salt method and structurally characterized by single-crystal X-ray diffraction analysis. The structure can be described as a three-dimensional framework composed of isolated bicyclic [B5O10]5− groups and Dy3+ and K+ ions. The Fourier transform IR (FT–IR) and ultraviolet–visible (UV–Vis) spectra were investigated. A series of K3Gd1–x Dy x B6O12 phosphors was prepared and their photoluminescence properties were studied. The K3Gd1–x Dy x B6O12 phosphors exhibit a strong yellow emission band at 577 nm (the 4F9/2→6H13/2 transition of Dy3+) under UV excitation of 275 nm (the 8S7/2→6I J transition of Gd3+), suggesting the occurrence of the energy transfer Gd3+→Dy3+. The optimized doping concentration of the Dy3+ ion was 8 mol%. We may expect that K3Gd1–x Dy x B6O12 is a promising pale-yellow emission phosphor for visual displays or solid-state lighting.

The Fabrication of Ag Islands on AlN/GaN/AlN/Si(111) by Using Thermal Evaporator and Thermal Annealing Methods

In this paper, we studied growth of AlN/GaN/AlN on Si (111) by using plasma assisted molecular beam epitaxy (PA-MBE) system. The structural and optical characteristics of the sample have been investigated by using high resolution X-ray diffraction (HR-XRD), Raman spectroscopy and photoluminescence (PL). PL spectrum of the sample has shown sharp and intense band edge emission of GaN with the absence of yellow emission band, indicating good crystal quality of the sample. The silver (Ag) metal contact was then deposited on the sample followed by thermal treatment at 500°C and 700°C, respectively. Treated sample at 700°C showed good spherical Ag islands on sample compared to the treated sample at 500°C. The effect of Ag islands on the electrical characteristics of sample was also examined by usingI-Vmeasurement. The results showed that the treated sample at 700°C has decreased the photo-current of Schottky diode.

Preparation and Properties of Ti, Eu Co-Doped Y2O2S:0.06Ti,0.08Eu Phosphor with Red Long Afterglow

Ti,Eu co-doped Y2O2S:0.06Ti,0.08Eu phosphor with red long afterglow emission from Eu ions was synthesized via traditional sintering method. Results showed that sintering temperature has great influence on the crystal structure, luminescence and afterglow property of the phosphors. The best luminescence and afterglow properties were obtained for the phosphors sintered at 1200°C for 2.5h. Furthermore, only emissions originated from charge transition of Eu3+ was found in the luminescence spectra whereas the afterglow spectra were composed of two sets of emissions: a broad yellow emission band around 565nm and a group of narrow peaks in the wavelength range above 530 nm. The origin of afterglow spectra was discussed: the former is likely related to emission from Ti related traps and the latter is supposed to come from the Eu3+ through an energy transfer process from Ti emission to Eu3+.