Spectroscopic study of Cr3+ ions in fluorochloro- and fluorobromozirconate glasses

Abstract

Chromium doped fluorochloro- and fluorobromozirconate glasses have been prepared following and modifying standard methods. Electron probe microanalysis has been carried out to obtain the actual chlorine and bromine content of the samples. Optical absorption, steady-state excitation and emission, luminescence decay, and time-resolved spectroscopy measurements have been performed in order to study the Cr3+ neighborhood and its optical properties. The results have been interpreted in terms of the progressive substitution of the fluorine ions in the first coordination shell of Cr3+ by chlorine or bromine ions when their concentration increases in the glasses. From the analysis of the Fano antiresonances of the A2g4(F)→Eg2(G), T1g2(G) intraconfigurational transitions, up to five Cr3+ environments have been identified and assigned to: 6 F−, 5 F− and 1 Cl− or 1 Br−, 3 F− and 3 Cl− or 3 Br−, 1 F− and 5 Cl− or 5 Br− and 6 Cl− or 6 Br−. It is deduced that less than 10% of fluorine ions substitution is enough to have all the Cr3+ ions hexacoordinated to chlorine or bromine ions. Values for the crystal field and Racah parameters, the Stokes shift, and the Huang–Rhys factor have been estimated from the absorption and luminescence data. The luminescence decay and time-resolved measurements of the T2g4(F) level of Cr3+ have been explained by the presence of two opposite mechanisms: nonradiative transitions and energy transfer processes which predominate, respectively, in fluorozirconate and in the most substituted glasses.

Eu oxidation state in fluorozirconate-based glass ceramics

“…Both glasses containing InF 3 have the same Eu 2+ -to-Eu 3+ ratio within experimental error ͑see Table II͒. The interactions within the material between the multiple cations and the halides are very complex. It is known that fluorine and chlorine 19 evaporate during the melting process; exact measurements are ongoing but preliminary ion chromatography results show that this could be up to 25% by weight. In the remelting process, it is likely that further halide is lost and so the redox conditions could change as there is less fluorine and chlorine to bond to the cations.…”

New developments in X-ray storage phosphors

“…For the uorochlorozirconate glasses, the nominal content of the substituted Cl − ions was close to 14% of the total number of anions, i.e. 52 ZrF4, 10 BaF2, 10 BaCl2, 20 NaCl, 3.5 LaF3, 3 AlF3, 0.5 InF3, and 1 EuF2 (values are in mol%); the actual Cl − content could be lower due to chlorine evaporation during the heating cycle, which has been reported in similar glasses containing Cl (Almeida and Mackenzie, 1982;Bunuel et al, 1998).…”

Energy transfer between Cr3+ and Ni2+ in transparent glass ceramics containing β-Ga2O3 nanocrystals

“…15 The photographs of Cr 3+ and Ni 2+ single-doped and codoped glasses and GCs are shown in Fig. 1͑B͒ [17][18][19][20][21] The two broad bands in the absorption spectra for Cr 3+ -doped GC have the same transition as those of the glasses. There is also a shift to higher energy side for absorption peak due to octahedral Cr 3+ after the heat treatment.…”