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 Dy 3+ 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: Dy 3+ phosphors showed two peaks at 481 nm and 572 nm corresponding to 4 F9/2→ 6 H15/2 and 4 F9/2→ 6 H13/2 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).

Titania (TiO2)/silica (SiO2) nanospheres or NSs amalgamated on a pencil graphite electrode to sensel-ascorbic acid electrochemically and augmented NSs for antimicrobial behaviour

“…38 For determining the average crystallite size of particles, Scherrer's equation for the line broadening XRD data was applied. 49 The crystallite size for TiO 2 , SiO 2 NPs and TiO 2 @SiO 2 NSs was estimated to be 26.6 nm, 14.48 and 41.0 nm, respectively. Zeta potential of TiO 2 NPs, SiO 2 NPs and TiO 2 @SiO 2 NSs was determined using a Zeta Analyzer Litesizer 500.…”

Chromium activated Ca9Al (PO4)7 nanophosphors: synthesis, morphology and dosimetry characteristics

“…So, enhancement of their TL characteristics can be made either by the defects or impurities that can be added intentionally within the phosphor structures and this might lead to novel functionalities, including optical absorption, as well as luminescence characteristics [24,25]. In literature, Ca 9 Al (PO 4 ) 7 phosphor incorporated with different transitions and/or rare earth ions has been subjected to different studies for different purposes [25][26][27][28][29]. The aforementioned structure belongs to whitlockite phosphors with Ca 9 R (PO 4 ) 7 general chemical formula (R = RE 3+ , Al 3+ , Ga 3+ , Bi 3+ ) are highly luminescent media when doped with active-optical ions and possesses several advantages as lower chemical toxicity, lack of radioactive elements and high stability [30][31][32].…”