Single phase cool white light emitting novel Ca9Al(PO4)7:Dy3+ nanophosphor under NUV excitation

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 Ca₉Dy_0.03Al_0.97(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 Ca₉Dy_0.03Al_0.97(PO₄)₇ sample 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 ⁴F_9/2?→?⁶H_15/2 and ⁴F_9/2?→?⁶H_13/2 transitions, respectively. The optimum concentration was found to be x?=?0.03 mol. The critical energy transfer distance was calculated to be 20 Å and further Huang analysis concluded the exact mechanism, i.e. dipole–dipole interactions responsible for concentration quenching in Ca₉Dy_xAl_(1?x)(PO₄)₇ samples. Furthermore, the Commission Internationale de I’Eclairage (CIE) chromaticity coordinates of Ca₉Dy_0.03Al_0.97(PO₄)₇ nanophosphor was calculated to be (0.260, 0.297) and this nanophosphor had correlated color temperature (CCT) of 11,332 K which is located in a cool white area. Existing results indicate that Ca₉Dy_0.03Al_0.97(PO₄)₇ nanophosphor may be considered as a favorable candidate in NUV-based single-phase cool white light-emitting diodes (WLEDs).