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.

This work deals with the identification of In+ ions in octahedral symmetry and the study of their optical properties in crystalline Rb2KInF6:Ce3+ and Rb2KInF6:Tb3+. The presence of In+ ions in the sites of In3+ has been confirmed exciting the Ce3+-doped sample at 41 600 and 32 360 cm−1 and exciting the Tb3+-doped sample at 41 600 cm−1. An hypothesis based on the In3+–Ce3+ and In3+–Tb3+ redox couples for the Ce3+- and Tb3+-doped elpasolite-type fluoroindates has been proposed in order to explain the presence of In+ at the mentioned excitation energies. This redox process is more efficient for the In3+–Ce3+ couple than for the In3+–Tb3+ one. Emission spectra and luminescence decays of In+ have been investigated at 5–300 K in both samples under the above mentioned excitations. Our experimental results have been compared to those obtained for In+-type ions as In+, Ga+, and Tl+ in alkali halides in literature. The transitions between the 5s5p excited configuration and the 5s2 configuration of In+ ions modified by the elpasolite matrix in Oh symmetry explain the optical data, if we take into account the spin-orbit coupling and Jahn–Teller effect (JTE). Finally, an additional fluorescence has been found in the Tb3+-doped sample; it has been assigned to In+ ions in potassium sites.

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