Author’s Accepted Manuscript Structural, thermal and optical investigations of Dy3+-doped B2O3‒WO3‒ZnO‒Li2O‒Na2O glasses for warm white light emitting applications G. Lakshminarayana, S.O. Baki, A. Lira, I.V. Kityk, U. Caldiño, Kawa M. Kaky, M.A. Mahdi www.elsevier.com/locate/jlumin
PII: DOI: Reference:
S0022-2313(16)31816-6 http://dx.doi.org/10.1016/j.jlumin.2017.02.049 LUMIN14562
To appear in: Journal of Luminescence Received date: 8 December 2016 Revised date: 23 January 2017 Accepted date: 22 February 2017 Cite this article as: G. Lakshminarayana, S.O. Baki, A. Lira, I.V. Kityk, U. Caldiño, Kawa M. Kaky and M.A. Mahdi, Structural, thermal and optical investigations of Dy3+-doped B2O3‒WO3‒ZnO‒Li2O‒Na2O glasses for warm white light emitting applications, Journal of Luminescence, http://dx.doi.org/10.1016/j.jlumin.2017.02.049 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Structural, thermal and optical investigations of Dy3+-doped B2O3‒ WO3‒ZnO‒Li2O‒Na2O glasses for warm white light emitting applications G. Lakshminarayanaa,*, S.O. Bakib, A. Lirac, I.V. Kitykd, U. Caldiñoe, Kawa M. Kakya, M.A. Mahdia a
Wireless and Photonic Networks Research Centre, Faculty of Engineering, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia b Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia c Department of Physics, Faculty of Science, Autonomous University of Mexico State, C.P. 50000 Toluca, Mexico d Faculty of Electrical Engineering, Czestochowa University of Technology, Armii Krajowej 17, PL-42-217 Czestochowa, Poland e Departamento de Física, Universidad Autónoma Metropolitana-Iztapalapa, P.O. Box 55-534, México, D.F. 09340, Mexico *
Corresponding author‒ E-mail:
[email protected]
Abstract Optically transparent Dy3+-doped borate glasses with the chemical composition (60-x) B2O3-10 WO3-10 ZnO-10 Li2O-10 Na2O-x Dy2O3 (x=0.1, 0.25, 0.5, 0.75, 1.0, and 1.5 mol %) have been synthesized by melt quenching technique and were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy and Energy Dispersive X-ray Analysis (SEM-EDX), Attenuated Total reflectance-Fourier transform Infrared (ATR-FTIR) spectroscopy, Raman spectroscopy, Thermo-gravimetric analysis (TGA), Differential scanning calorimetry (DSC), optical absorption and luminescence techniques. The amorphous nature of the prepared glasses has been confirmed through XRD and SEM measurements, and the EDX spectra show all the elements present in the respective glasses. The vibrational features of various functional groups like stretching vibrations of B‒O linkages in BO4 tetrahedra, asymmetric stretching vibrations of B‒O bond in trigonal BO3 units, stretching vibrations of W–O–W in WO4 or WO6 units, vibrations of Zn–O bonds from ZnO4 groups, bending modes of ZnO4 units, and vibrational modes of BO3 and BO4 due to 1
alkali borates were identified by ATR-FTIR and Raman spectroscopy. For the prepared glasses; weight loss, and the glass transition (Tg), onset crystallization (Tx), crystallization (Tc) and melting (Tm) temperatures were determined from TGA and DSC measurements, respectively. Following the obtained Tg, Tx, Tc, and Tm values, the thermal stability (∆T) and Hruby’s values (HR) were determined, the calculated ∆T values increased in the temperature range 131–143 °C and HR values varied in the range 0.766‒1.014 with Dy3+ concentration increment from 0.1 to 1.5 mol %, and the increasing stability of the glasses shows that they are thermally resistant. The optical properties of the titled glasses have been explored from the absorption, photoluminescence excitation (PLE) and photoluminescence (PL) spectra. For the 0.5 mol % Dy3+-doped glass, to obtain the information concerning the nature of the ligand field environment around the Dy3+ ions, the Judd-Ofelt (JO) intensity parameters Ωλ (λ=2, 4 and 6) were evaluated from the measured oscillator strengths (f) of various absorption bands. Further, the radiative parameters such as radiative transition probabilities (AR), branching ratios (βR), and the radiative lifetimes (τR) of 4F9/2→6H15/2, 4F9/2→6H13/2, 4F9/2→6H11/2 and 4F9/2→6H9/2 main emission transitions were calculated by using JO parameters. The photoluminescence properties were examined under ultraviolet (UV)/near UV (NUV) and blue excitations. Luminescence spectra measured for different concentrations of Dy3+-doped glasses by exciting the glasses at 350, 364, 386, 400, 425 and 452 nm wavelengths show concentration quenching beyond 0.5 mol % and the luminescence quenching has been explained by using cross-relaxation (CR) channels and resonant energy transfer (RET). For the 0.5 mol % Dy3+-doped glass, the measured decay lifetime and the evaluated quantum efficiency values are ~211.8 μs and 68.1 %, respectively. Following the luminescence spectra, the yellow-to-blue (Y/B) luminescence intensity ratios, color chromaticity coordinates (x, y) and correlated color temperatures (CCT) of the glasses have
2
also been estimated to evaluate the white light generation with respect to Dy3+ ion concentration. The color coordinates and CCT values for 0.5 mol % Dy3+-doped glass (optimum concentration) represent the warm white light region for all the selected UV and blue excitation wavelengths. The obtained results indicate that the optimized 0.5 mol % Dy3+-doped glass may be useful for the warm white light emitting applications as well as for solid state yellow laser emission and luminescent display devices. Graphical abstract
(a)
3
(b) Keywords: Borate glasses; Fourier transform infrared spectroscopy; Raman spectroscopy; Simultaneous thermal analysis; Luminescence properties; White light emission
1. Introduction Recently, Solid-state lighting (SSL) technology is emerging as the main alternative to the existing technology in lighting industry due to increasing importance of energy saving and environmental friendliness globally, and it has become an interesting field for researchers, especially with respect to white light sources. Particularly, white light-emitting diodes (W-LEDs) make remarkable breakthrough in SSL technology and show high potential for the replacement of conventional incandescent light bulbs and fluorescent lamps due to the advantages of low power consumption, high energy efficiency, compactness, longer lifetime (>100,000 h), good reliability, high brightness, safety and excellent low-temperature performance [1‒5]. It is well4
known that the combination of three primary colors (i.e., red, green and blue (RGB)) or two complementary colors, primary – secondary mixtures: red – cyan, blue – yellow, or green – magenta, generate white light emission [6, 7]. Conventionally, there are two principal methods available to produce warm W-LEDs for general illumination purpose, and one of them is phosphor-converted W-LEDs (pcW-LEDs), which are commercially available WLED's that are made up of InGaN blue LED chip coated with crystalline YAG: Ce yellow phosphors. However, they show drawbacks of inhomogeneous white light emission, poor luminescence intensity, halo effect, poor color-rendering index (CRI, Ra~70–80), high Correlated Color Temperature (CCT, ~7750 K) and lower lifetime due to lack of red color emitting element [8‒10]. Further, another method of designing W-LEDs makes use of RGB phosphors excited by an ultraviolet (UV) chip or violet LED, and this method has the advantages like higher CRI values (Ra>90), but it suffers from low luminescent efficiency due to re-absorption of blue light by green and red components [8, 9]. Also, in both above W-LEDs manufacturing methods, an epoxy resin will be used to fasten the powder phosphors securely onto the LED chip and the difference in refractive index between phosphors and organic resins used increases the amount of scattered light, and degrades luminous intensity including the color output of the W-LEDs apart from having a thermal stability issue [9, 11‒14]. Considering these problems, there is an urgent need to explore more promising materials for developing cheap, pollution-free and highly efficient W-LEDs. Rare-earth (RE) doped various glass systems could be used as favorable candidates substituting for phosphors to develop W-LEDs due to their advantages such as lower fabrication cost, simpler manufacture procedure, easy to shape, homogeneous light-emitting, free of halo effect, epoxy resin-free in assembly process including good thermal and mechanical stabilities [15–19]. Among the several glasses forming oxides (e.g., SiO2, P2O5, GeO2 etc.) boric acid (B2O3) is one
5
of the important glass formers because of its high strength of the covalent B‒O bonds, smaller cation size, smaller fusion heat and +3 valence of boron, and comparing with various glass hosts (e.g., silicate, phosphate etc.) borate based glasses are identified to be suitable candidates for RE ions doping due to their large glass forming ability, high optical transparency, higher thermal stability, low melting point and good RE ion solubility etc., [20‒22]. However, borate glasses possess drawbacks like low refractive index and relatively higher phonon energy (~1300‒1500 cm‒1), which leads to non-radiative transitions and causes the quantum efficiency of the doped RE ions emissions to reduce [22, 23]. With the addition of network modifier oxides like alkali (e.g. Li2O, Na2O) or heavy metal/transition metal (e.g. WO3) oxides, mechanical stability can be improved and phonon energy of the borate glasses can be reduced to enhance the quantum efficiency [24, 25]. Further, modifier oxides changes some BO3 triangles to BO4 tetrahedra (boron has the ability to exists in both three- and four-coordinated environments with randomly distributed BO3 triangles connected by B‒O‒B linkages and BO4 tetrahedra) and results in the formation of various well-defined and stable structural units such as di-, tri-, tetra- or pentaborate groups including non-bridging oxygens (NBOs) [20, 26]. In borate glasses, the addition of WO3 increases the chemical stability and devitrification resistance to make them suitable for optoelectronic devices [25, 27]. It is well known that ZnO could enter the glass network structure as a modifier or network former depending on the ZnO molar concentration, and it increases the glass forming ability (GFA) as well as produces low rates of crystallization [28, 29]. In borate glasses, as a network modifier (usually at lower concentrations), ZnO breaks B–O–B bonds and leads to the formation of NBOs. When ZnO played a network former role (at higher concentrations), it enters the glass network as ZnO4 structural units, where Zn is linked to four
6
oxygen ions in a covalent bond configuration [30]. Thus, for a particularly required application, the selection of suitable glass host matrix and RE3+ ion plays an important role. Among the trivalent lanthanide (Ln3+) ions, Dy3+ (4f9) is selected in the present work as a dopant ion as the Dy3+ ion doped glasses are the materials of much attention and best suited for generation of white light emission because they exhibit two characteristic intense emission bands due to the 4F9/2 → 6H15/2 (blue, 470–500 nm) and 4F9/2 → 6H13/2 (yellow, 570–600 nm) transitions, along with a weak red (645–665 nm) luminescence band, which corresponds to 4
F9/2→6H11/2 transition in the visible region [15‒20, 22, 23]. An appropriate coexistence of these
visible luminescence bands leads to the generation of white light emission in the glass under the ultraviolet or blue excitation wavelengths. Usually, a relative luminescence intensity ratio of the 4
F9/2→6H13/2 to 4F9/2→6H15/2 transitions, also known as (Y/B) intensity ratio indicates the local
symmetry around the environment of Dy3+ ions as well as shows the degree of covalency between Dy3+ and O2– ions [31]. In a glassy material, the variation in Y/B intensity ratio of Dy3+ ions to emit white light can be achieved by changing the Dy3+ ion concentration, glass chemical composition, excitation wavelengths and heat treatment [18, 23, 31]. Here the 4F9/2→6H13/2 forced electric-dipole (ED) transition is hypersensitive in nature with |∆J| = 2 and its intensity exhibits considerable dependency on the nature of the ligand field environment around the Dy3+ ions, whereas the intensity of the 4F9/2 →6H15/2 magnetic-dipole (MD) transition exhibits less dependency on the glass host matrix [18]. Further, Dy3+-doped glasses are also used as promising materials for one of the telecommunication window applications due to their near-infrared (NIR) emission at 1.32 μm (6H9/2→6H15/2) apart from the display device applications [32]. In the present study, B2O3-WO3-ZnO-Li2O-Na2O glasses with different Dy3+ ion concentrations were prepared. All the synthesized glasses structural and thermal properties were examined by
7
using different characterization techniques like XRD, SEM-EDAX, FTIR, Raman spectroscopy, and TGA/DSC. The optical absorption and photoluminescence properties of the prepared glasses were studied with an aim to develop these glasses for W-LED applications by exciting with the UV light. The Judd–Ofelt (J–O) theory has been applied for 0.5 mol % Dy3+-doped glass to evaluate various spectroscopic properties such as spectral intensities (f), intensity parameters Ωλ (λ = 2, 4 and 6), predicted radiative transition probabilities (AR), radiative lifetimes (τR) and branching ratios (β). The Dy3+ ion concentration dependent luminescence properties of the synthesized borate glasses have been systematically analyzed and the quenching of luminescence has been explained in detail by using cross-relaxation (CR) channels and resonant energy transfer (RET). From the emission spectra in the visible range, the Commission Internationale de I’Eclairage (CIE) chromaticity coordinates (x, y) and CCT values are calculated and the application of the prepared glasses for warm white light emission is discussed.
2. Experimental 2.1. Synthesis The conventional melt quenching technique was used to synthesize six borate glasses doped with different Dy2O3 concentrations. The starting materials used in the present work were high purity B2O3 (99.98%), WO3 (99.995%), ZnO (99.99%), Li2CO3 (99.99%), Na2CO3 (99.5%), and Dy2O3 (99.99%). All the chemicals were purchased from Sigma‒Aldrich. During the glasses preparation, due to instability of Li2O, and Na2O in air, lithium carbonate (Li2CO3), and sodium carbonate (Na2CO3) respectively, were taken in appropriate amounts using gravimetric factors of 2.473, and 1.71 and these compounds are known to give glasses which exhibit properties identical to those obtained from respective Li2O, and Na2O oxides. The nominal compositions of the six glasses prepared in this work are summarized in Table 1 and labelled as “a”, “b”, “c”, “d”, “e”, and “f”, respectively. All the appropriate chemicals were weighed in stoichiometric 8
ratio in 20 g batch each separately, thoroughly mixed using an agate mortar and a pestle for 1 h, and then each of those powders are collected into high purity alumina crucible and heated in an electric furnace for melting at 950 °C for 40 min.. The obtained homogeneous melts were subsequently poured onto a stainless steel plate and then quickly pressed with another steel plate. The obtained glass disks were clear, optically transparent, having a diameter of 3–4 cm and a thickness of ∼0.3 cm. The internal stress induced in the glasses during the melt-quenching was released by annealing the samples below glass transition temperature at 300 °C for 5 h in air, and then allowed to cool slowly to ambient temperature. Further, to get smoothness on both sides of all the glasses, they were cut to 20 mm × 20 mm × 2.0 mm size by using low speed saw machine and mechanically polished to a mirror-like surface using SiC/water. Finally, these glass samples were prepared in two forms: powders were characterized by employing different structural and thermal techniques; solid form for optical analysis to understand their potential optical applications. 2.2. Characterization Thickness of the glass samples was measured using a sliding caliper gauge. The density of the glasses was measured using the buoyancy method based on the Archimedes principle with toluene as an immersion liquid to a precision of 0.001 g. An Abbe refractometer was used to measure the refractive indices of the glasses at nd (589.3 nm) wavelength using sodium lamp with an error ±0.0001. Structural investigations of the prepared glasses were performed using several techniques. To determine glass quality i.e., lack of crystalline phase, the conventional X-ray Diffraction (XRD) technique was used. Measurements were performed on glass powder samples using Ital Structure APD 2000 diffractometer with CuKα (λ=1.542 Å) radiation with an applied voltage of 40 kV and 20 mA anode current. The scan rate was 2°/min., and the scan range was varied 9
between 10° and 80°. The surface morphology was monitored using FE-SEM equipment FEINOVA NanoSEM 230 with an acceleration voltage 5 kV, equipped with an EDX detector from EDAX-Ametek that allowed semi-quantitative analysis of elements. Sample preparation was performed by adhering glass powder samples on a carbon tape for direct observation without the requirement of any conductive coating on the surface for EDAX analysis. The attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra of the glass powders were measured over the 400–4000 cm−1 range by a Perkin Elmer Spectrum 100 FTIR spectrometer with a spectral resolution of ∼4 cm−1. The finely ground glass powder was pressed directly onto the ATR diamond crystal for the FTIR measurement. The Raman spectra of the glasses were obtained with a WITec alpha 300R Confocal Raman system equipped with an Nd: YAG laser (532 nm) as the excitation source. An incident power of 10 mW was typically used. The Raman spectra were recorded within the spectral range of 0–3800 cm-1 for the Raman shift, with an integration time of 5 s for each single Raman spectrum. The basic thermal properties of glasses were determined by TGA and DSC measurements, simultaneously. Thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC) measurements were performed with a Mettler Toledo TGA/DSC 1 HT Integrated Thermal Gravimetric Analyzer with high purity nitrogen as a carrier gas and a flow rate of 50 mL/min. About 20‒30 mg glass powders were used in an alumina pan for the measurement. The samples were heated from room temperature to 1000 ºC at a heating rate of 10 K/min., using Al2O3 as a reference sample. The average size of all the powders was below 0.5 mm, so that the weight loss of the samples was controlled by reaction kinetics. We performed the TGA/DSC test three times for each glass powder sample, and then we conclude that there is an error bar of ± 0.5 °C.
10
For all the synthesized Dy3+-doped glasses room temperature optical absorption spectra in the wavelength range 300–2000 nm were recorded using a Perkin-Elmer Lambda-950 UV–Vis–NIR spectrophotometer with a spectral resolution of 1.0 nm, to obtain the absorption data from which the oscillator strength of the absorption bands could be measured experimentally. For the Dy3+doped
glasses,
the
room
temperature
photoluminescence
excitation
(PLE)
and
photoluminescence (PL) spectra in the wavelength range 300–800 nm were recorded with a spectral resolution of 1 nm on an Edinburgh Instruments FLS920 steady-state and time-resolved fluorescence spectrometer by using a continuous wave 450 W Xe lamp as the excitation source. Decay lifetime for the 4F9/2 state (yellow emission) of 0.5 mol % Dy3+-doped glass was measured with a Horiba Jobin-Yvon Fluorolog FL3C-21 Spectrofluorimeter at room temperature in the phosphorescence mode by a pulsed Xe lamp with a delay time of 0.001 ms after the excitation pulse (Slit: 2 nm Bandpass). Here, the decay lifetime profile was recorded in the time-correlated single photon counting (TCSPC) technique.
3. Results and discussion 3.1. Physical properties From the measured values of both density (ρ) and refractive index (nd), various other related physical parameters of the Dy3+-doped glasses have been computed by using the relevant expressions available in the literature [13, 33] and are presented in Table 2. For the synthesized glasses, the incorporation of Dy2O3 in place of B2O3 changes the boron (B) to oxygen (O) ratio creating more BO4 units, as a result it causes compactness of glass network structure and hence density of glasses increases. Here the increment in the refractive index is due to increase in the density and dielectric constant. Further, the increase in the values of molar refractivity (Rm) and molar polarizability (αm) with the addition of Dy2O3 in the studied glasses network confirms an
11
increase in the number of BO4 units which in turn increases the refractive index of the glasses. Also, the optical basicity and electronic polarizability of the oxide species (αoxide-(II)) of the Dy3+doped glasses are calculated and given in Table 2. For all the cations present in the glass matrices; Pauling electronegativity (Xi), optical basicity moderating parameter [γi] and optical basicity (˄) are given in Table 3. Here the [γi] is evaluated using the formula given in [34]. For the 0.1 to 1.5 mol % Dy3+-doped glasses, the increase in (˄) and (αoxide(-ІІ)) values indicate that the ability of oxide ions to donate electrons to surrounding cations is increased with Dy3+ ion addition. 3.2. Structural analysis Fig. 1 (a) shows the XRD profiles for all the Dy3+-doped glasses. These XRD patterns exhibit only a broad hump and didn’t show any crystalline features like sharp peaks, clearly revealing the amorphous nature of all the synthesized glasses. Further, SEM micrograph of 0.5 mol % Dy3+-doped glass also reveals the formation of glass/amorphous structure with high homogeneity and smooth surface without any grain boundaries, clusters or crystals (Fig. 1 (b)) and similar SEM images are obtained for other glasses also. Fig. 1 (c) presents the EDAX spectrum for 0. 5 mol % Dy3+-doped glass and from this spectrum, main elements O, Na, Zn, W, and Dy in the glass were confirmed. Similar EDAX profiles are obtained for other Dy3+-doped glasses also and were not shown here due to their repetitive nature with same elements. However, by the EDX measurement, in the studied glasses it is difficult to detect and quantify precisely the light elements like Li, and B (though the peak of ‘B’ is assigned by the built-in software available with the EDX equipment) due to their too low energy (K α Ω6>Ω4
0.361
Present work
NbFSDy10
10.05
1.37
2.16
Ω2>Ω6>Ω4
0.634
[16]
TZPPN
5.66
0.84
2.17
Ω2>Ω6>Ω4
0.387
[17]
LSBP0.5Dy
5.73
2.19
1.92
Ω2>Ω4>Ω6
1.140
[18]
BTLN0.5D
6.329
1.715
1.141
Ω2>Ω4>Ω6
1.503
[19]
1.0Dy:ZnAlBiB
4.659
1.614
2.710
Ω2>Ω6>Ω4
0.595
[22]
48
Trends of Ωλ χ (Ω4∕ Ω6)
Reference
0.5DZTFB
8.281
2.794
1.898
Ω2>Ω4>Ω6
1.472
[23]
Dy: LiLTB
8.75
2.62
2.07
Ω2>Ω4>Ω6
1.266
[57]
D10:PbO-Sb2O3-B2O3
5.81
1.13
2.68
Ω2>Ω6>Ω4
0.422
[58]
PbPKANDy10
11.74
2.64
2.86
Ω2>Ω6>Ω4
0.923
[59]
BZBDy1
4.03
1.14
1.65
Ω2>Ω6>Ω4
0.691
[60]
Dy: LiFP
6.83
3.14
1.60
Ω2>Ω4>Ω6
1.962
[61]
Ω2>Ω4>Ω6
1.142
[62]
LGSiBDy10
5.0627 3.5101 3.0723
Table 10. Emission transitions (SLJ SLJ), wavelength (nm), predicted radiative transition probabilities (AR, s-1), branching ratios (βR) and radiative decay times (R, s) of luminescent levels of 0.5 mol % Dy3+ -doped glass Transition
6 6
H13/2 H15/2
Wavelength (nm)
AR
H11/2 H15/2 6 H13/2 6 6
F11/2+6H9/2 H15/2
βR
(s-1) 8049
2980
124
6 6
(μs)
1.00 2046
1680 4375
461 27
1272
2841
0.94 0.06 311
49
0.88
6 6
H13/2 H11/2
F9/2+6H7/2 H15/2 6 H13/2 6 H11/2 6 F11/2+6H9/2
2443 5531
341 32
1092 1724 3120 7717
2017 557 90 8
902 1294 1948 3101 5184
2834 265 463 111 45
801 1095 1531 2136 3006 7154
1825 745 169 190 107 6
751 1004 1358 1834 2405 4486 12031
392 1058 118 197 86 9 0
482* 575* 662* 752* 834 995 1155 1278
778 2039 180 110 72 21 19 0
6 6
F7/2+6H5/2 6 H15/2 6 H13/2 6 H11/2 6 F11/2+6H9/2 6 F9/2+6H7/2
374
6
F5/2 H15/2 6 H13/2 6 H11/2 6 F11/2+6H9/2 6 F9/2+6H7/2 6 F7/2+6H5/2 F3/2 H15/2 6 H13/2 6 H11/2 6 F11/2+6H9/2 6 F9/2+6H7/2 6 F7/2+6H5/2 6 F5/2 F9/2 H15/2 6 H13/2 6 H11/2 6 F11/2+6H9/2 6 F9/2+6H7/2 6 F7/2+6H5/2 6 F5/2 6 F3/2 I15/2 H15/2 6 H13/2 6 H11/2 6 F11/2+6H9/2 6 F9/2+6H7/2 6 F7/2+6H5/2 6 F5/2
0.21 0.57 0.06 0.11 0.05 0.00 0.00 311
4 6
0.60 0.24 0.06 0.06 0.04 0.00 538
4 6
0.76 0.07 0.13 0.03 0.01 329
6 6
0.75 0.21 0.03 0.01 269
6 6
0.11 0.01
0.24 0.63 0.06 0.03 0.02 0.01 0.01 0.00 328
452 533 618 701 771 906 1037
2342 364 115 146 74 3 1 50
0.77 0.12 0.04 0.05 0.02 0.00 0.00
6 4
F3/2 F9/2
1135 10181
3 1
425 496 569 638 696 804 905 979 4188 7115
219 444 33 390 177 98 2 0 35 9
387 445 503 556 599 678 749 799 2129 2691 4328
4085 1320 2628 3584 1980 463 129 91 242 47 35
365 416 466 512 548 613 671 710 1599 1896 2585 6421
4477 5571 5123 3601 15545 9544 4355 1227 247 27 35 8
348 394 439 479 511 567 615 649
13028 7756 5839 9591 16298 5640 1672 866
4
G11/2 H15/2 6 H13/2 6 H11/2 6 F11/2+6H9/2 6 F9/2+6H7/2 6 F7/2+6H5/2 6 F5/2 6 F3/2 4 F9/2 4 I15/2 6
I13/2+4F7/2 6 H15/2 6 H13/2 6 H11/2 6 F11/2+6H9/2 6 F9/2+6H7/2 6 F7/2+6H5/2 6 F5/2 6 F3/2 4 F9/2 4 I15/2 4 G11/2
711
4
I11/2+6P5/2 H15/2 6 H13/2 6 H11/2 6 F11/2+6H9/2 6 F9/2+6H7/2 6 F7/2+6H5/2 6 F5/2 6 F3/2 4 F9/2 4 I15/2 4 G11/2 4 I13/2+4F7/2 P7/2 H15/2 6 H13/2 6 H11/2 6 F11/2+6H9/2 6 F9/2+6H7/2 6 F7/2+6H5/2 6 F5/2 6 F3/2
0.28 0.09 0.18 0.24 0.14 0.03 0.01 0.01 0.02 0.00 0.00 20
6 6
0.15 0.32 0.02 0.28 0.13 0.07 0.00 0.00 0.02 0.01 69
4 6
0.00 0.00
0.09 0.11 0.10 0.07 0.31 0.19 0.09 0.02 0.00 0.00 0.00 0.00 16
51
0.21 0.13 0.10 0.16 0.27 0.09 0.03 0.01
4
F9/2 I15/2 4 G11/2 4 I13/2+4F7/2 4 I11/2+6P5/2
1317 1513 1921 3453 7472
4
144 80 10 6 5
0.00 0.00 0.00 0.00 0.00
*Experimental data
Table 11. Yellow to blue (Y/B) ratio, chromaticity color coordinates (X, Y) and color correlated temperature (CCT, K) for (І) all the synthesized Dy3+-doped glasses under 350 nm excitation including some other glass systems and standards (ІІ) 0.5 mol % Dy3+-doped glass under different excitation wavelengths (І)
Sample code
Y/B ratio Chromaticity coordinates CCT (K) x
y
Reference
a
3.14
0.422
0.448
3574
Present work
b
3.30
0.424
0.449
3546
Present work
52
c
3.16
0.422
0.448
3574
Present work
d
3.10
0.421
0.447
3586
Present work
e
3.29
0.425
0.450
3535
Present work
f
2.98
0.420
0.446
3597
Present work
BBS05
1.12
0.31
0.34
6602
[9]
NbFSDy01
0.82
0.33
0.37
5593
[16]
LSBP0.5Dy
1.809
0.394
0.418
3943
[18]
BTLN0.5D
2.321
0.37
0.43
4465
[19]
0.5DZTFB
1.116
0.358
0.409
4769
[23]
Standard White
-
0.33
0.33
5455
[9]
Fluorescent tube
-
-
-
3937
[69]
Tungsten lamp
-
-
-
2836
[69]
YAG + Blue chips
-
0.29
0.30
5610
[70]
(ІІ) Excitation wavelength (nm)
Y/B ratio
364
Chromaticity coordinates
CCT (K)
x
y
3.08
0.421
0.447
3586
386
3.14
0.426
0.450
3518
400
3.09
0.424
0.448
3540
425
3.15
0.426
0.449
3511
53
452
3.29
0.428*
0.453*
*The emission spectrum with 452 nm excitation was recorded from 460 nm
(a)
54
3502*
(b)
55
0.5 mol % Dy3+-doped glass
(c) Fig. 1
56
(a)
(b) Fig. 2
57
(a)
(b)
(c)
(d)
(e)
(f) 58
(g)
(h)
(j) (i)
59
(k)
(l) Fig. 3
(a) 60
(b) Fig. 4
61
Fig. 5
62
(a)
(b) 63
(c)
(d)
64
(e) Fig. 6
65
Fig. 7
66
(a)
(b) Fig. 8 67
