Optical contrast and cycling of bistable luminescence properties in Rb₂KIn_(1−x)Ce_xF₆ compounds

Abstract

Irradiation cycling was performed to evaluate the ageing of the redox process observed on cerium-doped Rb2KInF6 compounds. An on-off switch of monovalent indium luminescence is observed for the lowest cerium doped material, whereas a nice colourimetric contrast between a bluish-green and orange emission is generated for the material with the highest cerium content. Photoluminescent properties combined with X-ray diffraction, chemical analysis and magnetism measurements allowed an accurate characterization of the system. A complete explanation of the optical behaviour is therefore proposed. Finally, printing tests were performed to illustrate the good functionality of the prepared materials for UV sensitivity.

Emission colours of bistable photochromic compounds: Ce-doped alkaline (Rb, K, Na)–indium fluorides

“…After 10 minutes of irradiation at room temperature, 50% of the Rb 2 K signal (Ax component peaking at 650 nm) is lost, whereas this value is equal to approximately 30% for the K 3 compound (Ax component peaking at 610 nm). The decrease in In + is associated with a recovery of Ce 3+ ions, as mentioned previously 8,9.…”

“…Both the compound frameworks are subjected to internal stresses associated with a Goldschmidt tolerance factor, less than 1, causing the tilting of the octahedra chains to satisfy the valence of the whole cation set. 13 As previously shown in our former study devoted to Rb 2 K compound, 8,9 considering a Fm 3̄ m cubic system for the first two compounds (K 2 Na, Rb 2 K), the octahedra rotation results in a positioning of the fluorine ions in the 96j Wyckoff position, with an equiprobable random occupancy of a quarter compared to the 24e position located on the In–B–In axes. The 96j fluorine position is distinguished from the 24e position by off-centering the In–B–In axes by a distance that is characterized by the fluorine z coordinate.…”

“…Low-temperature measurements were performed on the K 3 compound (an equivalent study has been reported for the Rb 2 K elpasolite. 8 A weak thermal quenching of 12% (integrated area), a decrease in the full width at half maximum, and a UV shift are observed from a drop in the temperature down to 8 K. The results are illustrated in Figure SI1.…”

“…Both cerium and indium ions are present at the source of the potential modulation in the emission of the Ce-doped fluorides. Indeed, in such inorganic fluorides: RE-doped A 2 BKInF 6 series (RE: rare earth element), a redox process can be produced between cerium and indium cations, as demonstrated by Chaminade et al, 7 or more recently developed by Cornu et al 8,9 It was shown in the last former article that the UV irradiation of Ce 3+ -doped Rb 2 KInF 6 elpasolite-type compounds induces a reversible redox process.…”

“…The decrease in In + is associated with a recovery of Ce 3+ ions, as mentioned previously. 8,9 The three previously described kinetic models have been applied similarly to the In + ion decreasing curves. The different fitted parameters are listed in Table S3 (ESI †); the residual signals are reported in the inset of Fig.…”