White light emitting phosphor based on Gd dioxycarbonate

The research on illumination systems with “white” emission is a very relevant and important topic that has attracted reasonable attention with respect to the development of new generation lighting systems. Currently, one way to obtain white light-emitting diodes (WLEDs) is to couple a single LED which emits in the UV or blue region (typically λ < 450 nm) with a luminescent coating able to convert the radiation in a visible emission. The rare-earth dioxycarbonates, RE2O2CO3, are promising compounds that present interesting chemical, physical and luminescent properties [1,2]. They exist in three different crystal structures: tetragonal (type I), monoclinic (type Ia) and hexagonal (type II). The latter phase is the most stable and suitable to host other rare-earths, in fact the partial substitution between different lanthanides is possible in a wide concentration range. Despite these interesting results, no studies on the possibility of co-doping have been reported. Consequently, we have decided to investigate the luminescence properties of several Gd dioxycarbonates, in the hexagonal structure, activated respectively with Sm3+, Eu3+, Tb3+, Dy3+ and Tm3+. The synthesis consisted in a thermal treatment in the presence of molten salts, which allowed to reach the desired phase in a reasonable reaction time. The synthesized samples show interesting emission which can be tuned by varying the excitation wavelengths, obtaining in some cases a “white” emission (Figure 1). Hence, these compounds are potential coatings to produce WLEDs. References [1] V. Caratto et al., NIR Persistent Luminescence of Lanthanide Ion-Doped Rare-Earth Oxycarbonates: The Effect of Dopants, ACS Appl. Mater. Interfaces 6 (2014) 17346. [2] A.M. Kaczmarek et al., Nano- and micro-sized rare-earth carbonates and their use as precursors and sacrificial templates for the synthesis of new innovative materials. K. Van Hecke and R. Van Deun, Chem. Soc. Rev. 44 (2015) 2032