Strong Quenching of Tb3+ Emission by Tb–V Interaction in YPO4–YVO4

Abstract

Solid solutions in the system YPO4–YVO4, with and without 2 mol% of Tb3, were studied to determine the reason for the total inactivity of Tb in YVO4. The comparison of the diffuse reflectivity of Tb-containing solutions with that of Tb-free ones shows a uv absorption at energies below the absorption edge of YVO4 in materials containing both terbium and vanadium. Selective excitation directly into Tb3+ in these wavelength regions produced reduced Tb3+ emission when there was vanadium present. The band emission of the VO43+ groups, and the Tb3+ emission under electron beam excitation, were strongly quenched whenever terbium and vanadium were both present. Emission of Dy3+, present as a 10-ppm impurity in all samples, was also quenched by the presence of both terbium and vanadium, but not by either alone. All these observations imply energy loss by Tb–V interaction. A particular loss mechanism—the well-known intervalence transfer of charge from Tb to V resulting in an abrupt change of bond strength leading to a transfer of electronic excitation into lattice vibrations—is supported by measurements of Tb activity as a function of V concentration. The intensity of Tb emission is proportionate to the probability that none of four metal ion sites about a Tb is occupied by a V. This suggests the intervalence transfer absorption mechanism because only four of the nearest six metal ion sites have Tb–O–M bond angles (about 150°) consistent with good charge transfer from Tb to V; the remaining two sites have a Tb–O–M near 90° and should be relatively inactive in charge transfer.

Luminescence of rare earth vanadate associates in sulfates

“…This has been ascribed to radiationless decay via a charge-transfer state (iee also ref. [8]). In CaSO 4 the rate for energy transfer in the associate from V04 to RE 3+ is estimated to be about 108 s_i.…”

UV-to-red relaxation pathways in CaTiO3:Pr3+

“…This process can therefore induce partial or total quenching of 3 P 0 emission, even at low temperatures, depending on the relative position of the CTS with respect to 3 P 0 and 1 D 2 levels. Such a model was used to explain 3 P 0 $ 1 D 2 non-radiative relaxation in Pr 3+ -doped molybdate and tungstate scheelite crystals [9] and to explain the quenching of the Tb 3+ emission by vanadium in Y(P, V)O 4 [10]. The aim of this paper is to determine the UV-tored relaxation pathways leading to the quenching of 3 P 0 luminescence in CaTiO 3 :Pr 3+ .…”

What makes the luminescence of Pr3+different in CaTiO3 and CaZrO3 ?

“…This process can therefore induce partial or total quenching of 3 P 0 emission, even at low temperature, depending on the position of the charge transfer state relatively to 3 P 0 and 1 D 2 levels. Such a model has been used to explain 3 P 0 -1 D 2 non radiative relaxation in Pr 3+ -doped molybdate and tungstate scheelite crystals [5] and also to explain the quenching of Tb emission by vanadium in Y(P,V)O 4 [6].…”