Detailed study of structural and luminescent properties of Y2-xEuxZr2O7 (0 LT = x LT = 1) nanophosphors
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Ahrenkiel, Scott Phillip
Jovanović, Dragana J.
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Nanocrystalline Y2-xEuxZr2O7 (0 LT = x LT = 1) phosphor particles were prepared by polymer facilitated combustion and subsequent calcination at 800 degrees C. The thorough study of Eu-concentration influence on particles structure, morphology and luminescence is presented. This type of synthesis provides particles of similar to 5 nm in diameter, which crystallize in a defect fluorite structure (space group Fm-3m), and where each particle consists of a single crystallite, as revealed by X-ray diffraction and high-resolution transmission electron microscopy. With the increase of Eu concentration, the unit-cell parameter slightly increases to accommodate larger Eu3+ ions at sites of smaller Y3+, while the shape and size of particles remain the same. Analysis of emission intensity and decay dependence on Eu concentration showed that this host material could be heavily doped with Eu since concentration quenching of emission occurs at high Eu content of 25-30 at.% (with respect to Y ions). T...he critical distance for energy transfer between Eu ions is estimated to 10.28 A and dipole-quadrupole interaction is found as the dominant mechanism responsible for the concentration quenching of emission. Radiative and non-radiative transition rates, the quantum efficiency of emission, Omega-intensity parameters, and branching ratios of Eu3+ emission are calculated for nanocrystals of all doping concentrations. It is found that more to-the-point expression 86% of emission comes from D-5(0) - GT F-7(2) and D-5(0) - GT F-7(1) transitions. Therefore, this phosphor emits pure red light with (0.661, 0.338) CIE color coordinates. (C) 2017 Elsevier B.V. All rights reserved.