Phosphor Deterioration in Fluorescent Lamps

Abstract

The well‐known deterioration of phosphors in fluorescent lamps consists essentially of two parts, a short‐time degradation over roughly one hour possibly due to color center formation, and a long‐time effect extending over thousands of hours explained by a slow build‐up of a disordered and non‐luminescent layer on the phosphor particles. Such layer has been observed on deteriorated zinc silicate, it is very thin. Its optical absorption is the main reason of decreasing lamp brightness. Mercury buried in, but not absorbed on, the dead layer may contribute to the optical absorption. The brightness‐time function of the long‐time degradation is B/B0=expfalse(−√normalt/τfalse) with τ as a time constant. This model agrees well with observations. Conclusions are drawn concerning the stability of phosphors in lamps and its dependence on some parameters.

Cathodoluminescence of yttrium oxide and yttrium and zinc silicate films

“…4 we see that the Y 2 O 3 :Eu films are most stable under electron bombardment. We established that the dependence of the luminescence intensity on exposure time t is approximated well by the expression proposed in [9]: During bombardment of the films by an electron beam, the optical transparency decreases and additional bands appear in the optical absorption spectra. This is probably due to the fact that during electron bombardment, formation of new layers occurs that are responsible for the decrease in the luminescence intensity.…”

On the role of traps in the BaMgAl10O17:Eu2+ fluorescence mechanisms

“…As a result, several hypotheses have been proposed [15][16][17] but the most probable is linked to the vacuum ultra violet excitation of the plasma discharge [18]. In this hypothesis the degradation is related to the influence of traps on the fluorescence mechanism of BAM.…”

Multi-Photon Phosphor Feasibility Research

“…Interaction with the glass envelope with e.g. sodium ion diffusion from glass onto the phosphor particles where they could act as seeds for Hg-absorption [45];…”

“…The structural damage in hypothesis (2) can be caused by the mechanisms indicated in (1), followed by diffusion of defects into lattice. This way useful energy transfer channels from the site where excitation is absorbed to the activator ions can be destroyed [45,47]. Photochemical processes in (3) are caused by absorbing a photon of incident radiation and require significantly less energy than ion displacement in (2).…”