Single Phase Cool White Light Emitting Novel Ca9Al(PO4)7: Dy3+ Nanophosphor under NUV excitation

Abstract

A series of novel single-phase white light-emitting Dy3+ doped Ca9Al(PO4)7 nanophosphors was successfully synthesized at 1100 ˚C via solution combustion route. X-ray diffraction (XRD) and Rietveld refinement analysis of Ca9Dy0.03Al0.97(PO4)7 sample confirmed that this phosphor had a trigonal crystal structure with space group R3c(161). Meanwhile, as-observed from the transmission electron microscopy (TEM) study; particles of Ca9DyxAl(1−x)(PO4)7 samples were found to have a quadrilateral shape with crystallite sizes around 40–60 nm which were also confirmed by the Debye Scherrer equation. Under near-ultraviolet (NUV) excitation at 350 nm, photoluminescence (PL) emission spectra of nanocrystalline Ca9Al(PO4)7: Dy3+ phosphors showed two peaks at 481 nm and 572 nm corresponding to 4F9/2→6H15/2 and 4F9/2→6H13/2 transitions, respectively. The optimum concentration was found to be x = 0.03 mol. The critical energy transfer distance was calculated to be 20 and further Huang analysis concluded the exact mechanism i.e. dipole-dipole interactions responsible for concentration quenching in Ca9DyxAl(1−x)(PO4)7 samples. Furthermore, the Commission Internationale de I’Eclairage (CIE) chromaticity coordinates of Ca9Dy0.03Al0.97(PO4)7 nanophosphor was calculated to be (0.260, 0.297) and this nanophosphor had correlated color temperature (CCT) of 11332 K which is located in a cool white area. Existing results indicate that Ca9Dy0.03Al0.97(PO4)7 nanophosphor may be considered as a favorable candidate in NUV based single-phase cool White light-emitting diodes (WLEDs).