Efficient luminescent emission of trivalent rare earths-doped cesium based complex fluoride hosts

With an insight into the efficacy of various impurity-doping upon the luminescence properties, experiments were initiated to manipulate the structural amenities of pyrochlore-derived cesium based complex (Cs2K/NaAl3F12) fluorides. Difficulty in producing expected results in lab-synthesized fluorides is not new to the researchers. Though fluorides with more than one cation appears complicated, triumph in synthesis of Cs2KAl3F12 and Cs2NaAl3F12 complexes have been achieved via simple precipitation method. Photo-luminescence (PL) results showed that all attempted rare-earth ions got successfully incorporated into the crystal lattices during synthesis process itself. Consequences of dopant concentration on PL intensity for all impurity-ions have been summarized along with their calculated CIE parameters such as Correlated Color Temperature (CCT) and Color purity, particularly for the activators exhibiting emissions in the visible range. However, Ce, Tb and Dy showed as usual characteristic emissions, two phosphors Cs2KAl3F12:Eu3+ (1%) and Cs2NaAl3F12:Eu3+ (1%) acquire exceptional color purity. CCT for most of the phosphors proposed in the present study reflects promising applications in the household LED lighting. Radius percentage discrepancy (Dr) values were found helpful in understanding the underlying prospects of ionic replacement of cationic sites within the lattice structures by the various substituting impurity-ions. Additional studies related to phase purity, morphology and elemental analysis of the compounds were also included, by means of different x-ray diffraction (XRD), Scanning Electron Microscopic (SEM) and Energy-dispersive X-ray spectroscopy (EDAX) techniques.