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 Ca9Dy0.03Al0.97(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 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 Å 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 11,332 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).
Highlights
Nowadays, nano-scaled crystalline materials like rare-earth-doped luminescent nanophosphors are considered as the future generation lighting sources and components of future technology due to their unique features such as low power consumption, high energy efficiency, and long service life over the bulk materials [1,2,3,4,5,6,7]
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 confirmed by the Debye Scherrer equation
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
Summary
Nano-scaled crystalline materials like rare-earth-doped luminescent nanophosphors are considered as the future generation lighting sources and components of future technology due to their unique features such as low power consumption, high energy efficiency, and long service life over the bulk materials [1,2,3,4,5,6,7]. There are two methods to fabricate WLEDs i.e. the first method is by combining blue LED chip with yellow phosphors (YAG: Ce3+) but this method has several drawbacks such as low color rendering index (CRI) and high color temperature [13,14]. The direct illumination of white light by a single component excited by a blue LED chip is the best alternation process to fabricate WLEDs as compared to the multi-components emitter. It is a simple and better reproducible fabrication approach [19,20,21]. Commission international de I’Eclairage (CIE) color and Correlated color temperature (CCT) coordinates were calculated which showed that as-obtained nanophosphors might have practical applicability in single-phase WLEDs
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