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Luminescent Germanate Garnets with Terbium on Dodecahedral and Octahedral Lattice Sites

IP.com Disclosure Number: IPCOM000050397D
Original Publication Date: 1982-Oct-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Avouris, P: AUTHOR [+5]

Abstract

High efficiency, persistent, non-saturating rare-earth phosphors are described. The improved persistence reduces the flicker observed in some display applications.

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Luminescent Germanate Garnets with Terbium on Dodecahedral and Octahedral Lattice Sites

High efficiency, persistent, non-saturating rare-earth phosphors are described. The improved persistence reduces the flicker observed in some display applications.

(Ca(Tb))(3) Ga(2)Ge(3)O(12) and Sr(3)(Y(Tb))(2) Ge(3)O(12) garnets provide a cubic structure with trivalent terbium, a luminescent rare earth, in dodecahedral 8 oxygen neighbors) and in octahedral (6 oxgyen neighbors) sites, respectively. In the materials examined, Tb+++ in octahedral sites has a narrower fluorescence emission spectrum, higher luminescence efficiency and a longer lifetime than in dodecahedral sites. The luminescence properties and the unit cell size of the Ca(3)Y(2)Ge(3)O(12) garnet, where Tb+++ is expected to be located on octahedral sites, are between those of the CaGa and SrY garnets. All these garnets are phosphorescent. On the basis of the variation with temperature of the phosphorescence decay law, it is proposed that the radiative electron-hole recombination process proceed via a tunneling mechanism at temperatures below the thermal glow peaks, and via a free carrier diffusion mechanism at temperatures above the thermal glow peaks.

All three Tb+++ -doped germanate garnets have sufficiently high efficiency and persistence under electron-beam excitation to be suitable for practical phosphor applications. The strontium yttrium germanate Tb material has a cathodoluminescence decay time nearly thr...