Untitled

Effects of Cr3+ concentration on the optical properties of Cs2NaAlF6 single crystals

“…When doped with 0.5% of Cr 3 þ interesting optical properties have been reported [14,23]. Considering the ionic radii and valence of Cr 3 þ (0.64Å), Na þ (0.98Å) and Al 3 þ (0.57Å) ions, it can be inferred that the replacement of Al 3 þ by Cr 3 þ ions is more likely [13]. Indeed, based on X-ray and neutron diffraction [27] and photoluminescence measurements for this system [14], such assumption was confirmed.…”

“…In general, these systems are attractive because the transitions occur in the visible and infrared regions, if the ions are in octahedral sites [1], or only in the infrared region, if ions are in tetrahedral sites [11]. As fluoride systems doped with transition metals have these properties, they are promising materials for use in the applications mentioned above [12][13][14][15][16].…”

Cs2NaAl1−xCrxF6: A family of compounds presenting magnetocaloric effect

“…Other successful examples consist of perovskite-type oxides [11], metal-organic frameworks containing gadolinium [12], and molecular nanomagnets, such as Mn 32 [13] and Fe 14 [14]. However, very few studies have so far reported on caloric effects in fluoride systems [15][16][17], which is the aim of this paper.From the point of view of optical and structural properties, Cs 2 NaAl 1−x Cr x F 6 elpasolite single crystals, which crystallize in the R3m space group, have been thoroughly investigated [18][19][20][21][22][23][24][25][26][27]. The choice of the Cr 3+ ion as a doping impurity is justified by the fact that its 3d unfilled shell produces electronic transitions that increase the luminescent properties and the quantum yield of the material [20,[27][28][29].…”

“…From the point of view of optical and structural properties, Cs 2 NaAl 1−x Cr x F 6 elpasolite single crystals, which crystallize in the R3m space group, have been thoroughly investigated [18][19][20][21][22][23][24][25][26][27]. The choice of the Cr 3+ ion as a doping impurity is justified by the fact that its 3d unfilled shell produces electronic transitions that increase the luminescent properties and the quantum yield of the material [20,[27][28][29].…”

“…For the structure refinement, it was assumed that the Cr 3+ ions are statistically distributed in the Al sites [21]. Following this procedure, the goodness of fit values were 1.166 and 1.151 for x = 0.01 and 0.62 samples, respectively.…”