Synthesis and photoluminescence characteristics of the near white emitting Dy3+ ions activated NaMBi2_x(PO4)3 [M: Ba/Ca/Ca0.5+Sr0.5/Sr/Sr0.5+Ba0.5] phosphors

The present work deals with the preparation and characterization of the NaBaBi2_x(PO4)3:xDy3+ phosphors and the impact of the host cation (M) replacement in the NaMBi1.91(PO4)3:9%Dy3+ (M: Ca/Ca0.5+Sr0.5/Sr/Sr0.5+Ba0.5/Ba) phosphors on the PXRD profile and the PL emission data. All the phosphors are prepared by simple solid state reaction method and their PXRD data confirms the single phase formation. For the NaBaBi2_x(PO4)3:9%Dy3+ phosphor, the morphology, elemental composition and the band gap estimation were carried out by FESEM-EDAX analysis and DRS studies respectively. The PL emission properties revealed that the Dy3+ occupied the low symmetry sites in the NaBaBi2(PO4)3 host lattice and the optimum emission observed for the concentration, xC = 9 mol%. The PL-lifetime of Dy3+ ions in the NaBaBi2(PO4)3 phosphors are in the range of millisecond. The temperature dependent PL studies showed that at 150 degrees C, the phosphor was able to retain 74.7% of its initial PL intensity value (at 27 degrees C) and the activation energy for thermal quenching was determined to be 0.192 eV. For lambda ex = 349 nm, the calculated CIE color coordinates (0.339, 0.359), and the CCT value (5250 K) of the NaBaBi1.91(PO4)3:9% Dy3+ phosphor are found closer to the ideal white light. The Na(Sr0.5,Ba0.5)Bi1.91(PO4)3:9%Dy3+ phosphor has yielded the highest PL intensity, which is twice that of the NaCaBi1.91(PO4)3:9% Dy3+ phosphor. The estimated CIE color coordinates of this phosphor revealed its near white light emission property.