I am having trouble to understand the Eu spectra doped in A2B2O7, I have obtained two sets of spectra for Eu, S5- as in the spectrum, the spectra for pyrochlore structure and S1- for regular fluorite like cubic structure. Especially, I can see the difference in spectra for both transitions 5D0-7F1, 5D0-7F2, there is variation in intensity too.Can anybody help me explaining this spectral difference between the two structures?
It has been reported a gradual increase of the total intensity of the luminescence spectrum and a relative increase in the intensity of the hypersensitive transition 5D0–7F2 as a function of time and as a function of increase in temperature of dehydration of gels. You can surely find some more relevant information and references here: K. Binnemans, Chem. Rev., 2009, 109, 4283–4374.
Thanks Vazquez, I will go through the reference and let you know whether I can find the correlation between spectra and the crystal phase
You're welcome. I have only experience with solution spectra, and the relative intensity of the band gives indeed information about the coordination environment. I imagine that would still hold true in the solid phase. Good luck
Mr. Pokhrel,
definitively you have pertirbation of the f-transitions in Eu3+, meaning that it has change of the geometry of the metal-cromophore, but the problems with the pyrochlore stuctures consisted on the possibility for nonstoichometric compositions, solid-solutions, and ordered-disordered systems. So that Fs spectroscopy cannot provided significantly meaningful structural information.
It should be better to perform single crystal X-ray diffraction, than you would correlate exactly structure-to-ptical phenomena. If your substances are, however solid-solutions or glasses, that the IR-spectroscopy would be very informative for the coordination environment arround Eu3+. Please find a paper on actinides, where we have done correlation structure/properties of nonstoichometric compositions of uranium substances:
1. Environmental Science and Pollution Research 2014, 21, 1548-1563
Uranyl–water-containing complexes: solid-state UV-MALDI mass spectrometric and IR spectroscopic approach for selective quantitation, Bojidarka Ivanova, Michael Spiteller
Please find as well recent papers exactly on your question topic by other authors. They most probably would be useful for the structural assignment because of contain data on structures, IR, Raman, Fs and more on pzrochlores of the same type:
2. Nonstoichiometry in A2B2O7 Pyrochlores, Christopher R. Stanek, Licia Minervini, and Robin W. Grimes, J. Am. Ceram. Soc., 85, 2792–98 (2002)
3. Journal of Solid State Chemistry 160, 21, 32 (2001)
doi:10.1006/jssc.2000.9142, The Structural Transformation from the Pyrochlore Structure,A2B2O7 to the Fluorite Structure,AO2,Studied by Raman Spectroscopy and Defect Chemistry Modeling, Marianne Glerup, Ole Faurskov Nielsen, and Finn Willy Poulsen
4.JOM, 52, 2000, 19-21, Order-disorder phenomena in A2B2O7 pyrochlore oxides, Wuensch, B.J. , Eberman, K.W.
5. Structural, FT-IR, XRD and Raman scattering of new rare-earth-titanate pyrochlore-type oxides LnEuTi2O7 (Ln = Gd, Dy), I. Ben Taazayet-Belgacem, M. Férid, Journal of Alloys and Compounds, 573, 2013, 43–52
6. Relaxor dielectric properties of a (Ca1.5Ti0.5)(NbTi)O7 ‘misplaced-displacive’ cubic pyrochlore synthesised via metallorganic decomposition, Binh Nguyen,Y un Liu, Ray L. Withers, Solid State Communications, 145, January 2008, 72–76
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