Valence State Control Of Rare-earth Ions And Spectral Properties In B-p And Si-al System Luminescence Glass And Glass Ceramic

Rare earth doped glasses are considered to be one of the promising materials for fiber laser,fluoreseent devices and white light emitting diode(LED). For the past decades,a large amount of luminescene reseach has mainly been focused on two aspects. One is on crystal matrix and another is on the non- crystalline matrix. Glasse ceramic, a composite with glass and crystals,has attracted intense interests for the excellent luminesence properties, machinability, high uniformity and stability. The luminescence glass doped rare earth for white LED package, which can overcome the shortcomings of the tranditional mode of package, is expect to increase thermal stability, enhance the efficiency and simplify the package procedure. In this M. S thesis, we explored the routes to adjust the valence state control and spectral properties of B-P and Si-Al system glass and glass ceramics. The mian achievements obtained are summarized as follows.A. Borophosphate fluorescent glass co-doped with europium and terbium has been prepared by melt quenching method in air condition. The glass shows a combination of blue (430 nm), green (545 nm) and red band (611 nm) and white light was observed when the glass was excited by UV light. The CIE color coordinates of the glass were traced when the composition of the glass as well as the concentration of activator were varied.B. A simultaneous blue- and red-light emitting glass of SrO-B2O3-P2O5 doped with Eu2O3 was obtained in air then heat-treated without any reductive reagents. A combination was found to consist of a band emission peaked at around 430 nm and a series of line emission from 593 nm to 611 nm, corresponding to the typical 4f65d→4f7 transition of Eu²⁺ and 5D0→7FJ (J=0, 1, 2, 3, 4) transitions of Eu³⁺. Some unidentified crystals such as Sr (PO3)2 and SrB2O4 as hosts for Eu²⁺ with stronger crystal field lead to this enhancement of PL intensity and loss of transparency compared to the as-prepared parent glass.C. Rare earth doped Si-Al system luminescence glasses have been synthesized by melt quenching method. The optical properties of different rare earth (Eu, Tb, Sm and Ce) in the Si-Al glass have been studied. The high valence of the rare earth ions can be reduced to low valence, such as Eu²⁺, Ce³⁺, Sm²⁺, in some specific compositions. The band emissions peaked at 438 nm, 437 nm and 430 nm were assigned to electronic transition of Eu²⁺, Ce³⁺ and Sm²⁺, respectively.D. The concept of optical basicity of glass together with micro structure was employed to interpret the underlying mechanisms relevant to the phennmenon of valence change and stability of rare earth ions in glass host. The evolutions in the microstructure of the glass play an important role in the reduction of rare earth ions.