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

doi:10.21203/rs.3.rs-224262/v1

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

https://doi.org/10.21203/rs.3.rs-224262/v1

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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_xAl_(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 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 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 11332 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).

Biological Chemistry

Rietveld Refinement

Solution-combustion

Scherrer Equation

Concentration Quenching

Chromaticity

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Ethic statement

The content of our research paper “Single Phase Cool White Light Emitting Novel Ca₉Al(PO₄)₇:Dy³⁺ Nanophosphor under NUV excitation” has been synthesized successfully via urea assisted solution combustion route. The nanoparticles have been characterized using different techniques and were found to have good luminescent properties which can be utilized for the fabrication of display devices. The paper has not been published in any other journals. The authors declare that there are no conflicts of interest. We will follow all norms of the publication like copyright etc.

Acknowledgment

One of the authors, Manju Dahiya is thankful for financial help in the form of a senior research fellowship from the Council of Scientific and Industrial Research, India (CSIR), New Delhi, India (Award No. 09/1063/0014/2017-EMR-I).

Table 1. The comparison of crystal structure parameters of Ca₉Dy_0.03Al_0.97(PO₄)₇ nanophosphor system with Ca₉Al(PO₄)₇ host lattice.

Formula	Ca₉Al(PO₄)₇ (Published)	Ca₉Dy_0.03Al_0.97(PO₄)₇
Formula weight (g/mol)	1052.47	1056.56
Crystal shape	Trigonal	Trigonal
Space group	R3c	R3c
a (Å)	10.3191(0)	10.3169
b (Å)	10.3191(0)	10.3169
c (Å)	37.2(0)	37.2389(16)
α (degree)	90	90
β (degree)	90	90
γ (degree)	120	120
Volume (Å³)	3430.5(0)	3432.65(16)
Z	6	6

Table 2. The crystal size, dislocation density, and strain parameters of Ca₉Dy_xAl_(1-x)(PO4)₇ (where x = 0.01 – 0.15 mol) nanophosphors.

Sr.No.	Dy³⁺ Concentration (mol)	FWHM (β) (degree)	D (nm)	δ (10 ^-4nm^-2)	ε (strain)
1.	0.01	0.240	35.96	7.73	0.0037
2.	0.02	0.237	36.37	7.55	0.0037
3.	0.03	0.225	38.33	6.80	0.0035
4.	0.05	0.243	35.39	7.98	0.0037
5.	0.10	0.250	34.48	8.41	0.0039
6.	0.15	0.201	42.89	5.43	0.0031

Table 3. Photoluminescence life time and Y/B ratio of Ca₉Dy_xAl_(1-x)(PO₄)₇ (x = 0.01 – 0.15 mol) nanophosphors.

Sr. No.	Dy³⁺ Concentration (mol)	Average Life time (ms)	Y/B ratio
1.	0.01	0.69	0.55
2.	0.02	0.68	0.57
3.	0.03	0.64	0.58
4.	0.05	0.61	0.60
5.	0.10	0.59	0.56
6.	0.15	0.52	0.54

Table 4. CIE 1931 Color Coordinates, color purity, (u’, v’), and CCT values for Ca₉Dy_xAl_(1-x)(PO4)₇ (x = 0.01 – 0.15 mol) nanophosphors.

Sr. No.	Dy³⁺ Concentration (mol)	Color Coordinates (x, y)	(u’, v’)	CCT(K)
1.	0.01	(0.247, 0.268)	(0.172, 0.421)	16774
2.	0.02	(0.254, 0.280)	(0.172, 0.433)	13867
3.	0.03	(0.260, 0.30)	(0.173, 0.443)	11332
4.	0.05	(0.257, 0.290)	(0.172, 0.438)	12052
5.	0.10	(0.248, 0.287)	(0.173, 0.421)	13464
6.	0.15	(0.240, 0.250)	(0.172, 0.435)	23796

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

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