Eu+2 Activation in Some Alkaline Earth Strontium Phosphate Compounds

Abstract

type alloy. However, slow growth rates resulted in an increase in its electrical resistivity. The resistivity increase in the p-type alloy was interpreted on the basis of Te re-solution from the Te-rich second phase present in the alloy. Consistent with this interpretation are the results of an annealing study of these alloys. The annealing effects, while less pronounced, were essentially similar to those brought about by variations in the growth rate. AcknowledgmentsThe authors are grateful to E. J. Stofko and T. V. Pruss for their valuable contributions in materials preparation and thermoelectric measurements. Constructive comments by F. D. Rosi during the course of this work are gratefully acknowledged.

Strontium magnesium phosphate, Sr2+xMg3−xP4O15(x∼ 0.36), from laboratory X-ray powder data

“…Sr 2 Mg 3 P 4 O 15 :Eu 2+ was recently reported to show potential for application as a blue phosphor for a white LED under excitation of near-UV light (Ngee et al, 2009;Guo et al, 2010). The existence of a single phase in the system SrO-MgO-P 2 O 5 was first confirmed over 40 years ago (Hoffman, 1968), but only un-indexed X-ray diffraction data were reported and its crystal structure has remained unknown. In the present study, during the course of crystal structure determination, we have discovered that the compound previously known as Sr 2 Mg 3 -P 4 O 15 is in fact nonstoichiometric Sr 2+x Mg 3Àx P 4 O 15 (x $ 0.36).…”

Discovery of novel phosphors for use in light emitting diodes using heuristics optimization-assisted combinatorial chemistry

“…Eu 2+ -doped alkali-alkali earth-phosphate phosphors have been investigated by many research groups in an attempt to use them in LED applications. [17][18][19][20][21][22][23][24][25] In fact, a large number of different structures have been revealed in this composition space but only a few have been reported as acceptable phosphor hosts for the Eu 2+ activator, e.g., Ae(PO 3 ) [17][18][19][20][21][22][23][24][25] The aim of the present investigation was to discover a new alkali-alkali earth-phosphate phosphor, which can be used for LED applications. In addition, we aimed to achieve a red-shift of the 4f-5d transition of Eu 2+ and thereby to discover novel green-light-emitting phosphors.…”

Eu2+ and Ce3+ emission in sulphate based phosphors

“…Two-photon excitation reveals the excited states of Eu 2+ , f-f configuration, lying higher than the 4f 6 5d band, as was found in the first two-photon spectroscopic study of rare earth ion [2]. Efficient Eu 2+ emission has been obtained in many compounds [3,[4][5][6][7][8][9][10][11][12][13] and also in sulphate-based compounds [14,15] The Ce 3+ ion has the [Xe] 4f 1 configuration, which results in only two 4f 1 energy levels: the 2f 5/2 ground state and 2f 7/2 excited state. These energy levels are approximately 2000 cm À1 apart.…”