A carnegieite type red emitting NaAlSiO4:Eu3+ phosphor: Concentration dependent time resolved photoluminescence and Judd-Ofelt analysis

This work discusses about synthesis of relatively unexplored carnegieite type NaAlSiO4 and designing it as efficient europium ion doped red phosphor. The synthesized powder has been systematically characterized using powder X-ray diffraction (XRD), Raman spectroscopy, Thermogravimetry - Differential Thermal Analysis (TGDTA) and photoluminescence (PL) techniques. The effects of Eu(3+)concentration on the photoluminescence properties were investigated. Concentration dependent emission spectroscopic studies suggested quenching at 0.5% doping level due to multipolar interaction. Stark splitting analyses revealed that the point group around Na+ ions decreases with Eu3+ doping and it is found to be C4v in Eu3+ doped NaAlSiO4. The asymmetry ratio was found to increase monotonically with europium concentration due to increasing density of sodium ion vacancies (V-Na) which further distort the structure of NaAlSiO4. Lifetime spectroscopic studies suggested stabilization of europium ion at sodium site in two different environment; one nearer to charge compensating defect and one at far off distance. Judd-Ofelt analysis suggested asymmetric and highly polarizable environment around europium ion lead to enhanced red emission. The structure-property correlations indicate the potential of such structures for enhanced luminescence, scintillation and other optoelectronic properties.