Influence of PrCl3/PrF3 on the optical and spectroscopic properties of fluorogallate and fluoro-gallo-indate glasses
OPTICAL MATERIALS
Authors: Duverger-Arfuso, C; Boulard, B; Jestin, Y; Ferrari, M; Chiasera, A
Abstract
Thermal, optical and spectroscopic properties of fluorogallate PZG (PbF2-ZnF2-GaF3) and fluoro-gallo-indate PIG (PbF2-InF3-GaF3) glasses doped with PrCl3 and PrF3 have been investigated. Absorption and luminescence properties of these glasses have been studied in the visible and in the second telecom window around 1.3 mu m. Fluorescence lifetimes of the (1)G(4) level have been compared between prascodymium chloride and fluoride doped glasses. Longer decay constants have been obtained for PrCl3 doping at low concentration (0.05 mol%). This effect has been related to a reduction of both the phonon energy in the surrounding of the rare earth ion and the electron-phonon coupling, leading to a decrease of the non-radiative multiphonon relaxation rate. (c) 2005 Elsevier B.V. All rights reserved.
Solar Thermal Electrolytic Process for the Production of Zn From ZnO: The Electrolysis of ZnO From 1275-1500 K
JOURNAL OF SOLAR ENERGY ENGINEERING-TRANSACTIONS OF THE ASME
Authors: Schroeder, R.; Matthews, L.; Leatzow, D.; Kondratko, J.; Will, J.; Duncan, S.; Sheline, W.; Lindeke, N.; Palumbo, R.; Neves, Pedro
Abstract
The solar thermal electrolytic production of Zn from ZnO was studied in the temperature range of 1275-1500 K in a cavity-solar receiver located at the focal point of a concentrating solar furnace. This study establishes how cathode material, solvent, current levels, and operating temperature influence the electrolytic cell's performance. For a nominal current density of 0.1 A cm(-2) at temperatures from 1275 to 1425 K, we found that our performance parameters, the back work ratio and substituted-solar fraction, are within 25% and 20% of the ideal values, respectively. This behavior was true whether the cathode was Mo or W and whether the electrolyte was pure cryolite or a 35 mol. % cryolite-CaF2 mixture. When the electrolytes were cryolite-CaF2 mixtures in the temperature range of 1275-1425 K, there was no measurable difference in the performance, but at 1500 K with a MgF2 electrolyte, the performance dropped significantly. We have some evidence that the performance of the cell is better at current densities above 0.1 A cm(-2) when the cathode is Mo as opposed to W. Furthermore, the difference in the performance values can be attributed to higher kinetic over voltages associated with W versus Mo as a cathode. Our data also suggest that kinetic over voltages increase as the operating temperature increases. The experimental evidence suggests the reaction mechanism at the cathode for ZnO in cryolite involves a reaction between Na+ and ZnF2, and the anode reaction involves a reaction between the anions Al2OF62- and ZnO22-. Both Mo and W worked as cathode materials, but both the Mo and the W became brittle. Pt worked well as an anode without showing any evidence of degradation. Our SiC crucible may have suffered some carbothermic reaction with ZnO at temperatures exceeding 1275 K, with solvent mixtures of cryolite, CaF2, and MgF2. [DOI: 10.1115/1.4004706]