Defect clustering in double doped fluorite crystals with Lu and Gd |
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Authors: | N. Suarez E. Laredo M. Diaz A. Bello M. Puma |
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Affiliation: | Physics Dept. , Universidad Simón Bolívar , Apartado, 89000, Caracas, Venezuela |
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Abstract: | Abstract Solid solutions Ca1 x-yLuxGdy F2+x+y for 10?4 ≤ x ≤ 2 × 10?2 and y=0.0001 have been studied by electron paramagnetic resonance (EPR) and ionic thermal currents (ITC). It has been found that the ITC spectrum from 77 to 420 K is very weak and the main peak is attributed to the relaxation of both Lu3+-F? x and Gd3+F? i nn dipoles. No polarizable clusters are present in the temperature range explored here. The EPR spectra show the presence of Gd3+ tetragonal and cubic centers due to the local and non local compensation, respectively. The continuous decrease in the molar fraction of Gd3+ tetragonal centers together with the low concentration of Lu nn dipoles is an evidence of the existence at these low and intermediate concentrations of large clusters such as the cubo-octahedral hexamer which has been proposed for CaF2 crystals very highly doped with small trivalent cations. |
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Keywords: | the time-evolution Monte Carlo simulation cluster ion the projected range the clearing-the-way effect the acceleration effect |
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