Optical absorption and photoluminescence studies of Dy3+ doped alkaline earth bismuth borate glasses

Optical absorption and photoluminescence studies of Dy3+ doped alkaline earth bismuth borate glasses

Author’s Accepted Manuscript Optical Absorption and Photoluminescence studies of Dy3+ Doped Alkaline earth Bismuth Borate Glasses M. Veeramohan Rao, B...

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Author’s Accepted Manuscript Optical Absorption and Photoluminescence studies of Dy3+ Doped Alkaline earth Bismuth Borate Glasses M. Veeramohan Rao, B. Shanmugavelu, V.V. Ravi Kanth Kumar www.elsevier.com/locate/jlumin

PII: DOI: Reference:

S0022-2313(16)30155-7 http://dx.doi.org/10.1016/j.jlumin.2016.09.012 LUMIN14241

To appear in: Journal of Luminescence Received date: 3 February 2016 Revised date: 2 September 2016 Accepted date: 4 September 2016 Cite this article as: M. Veeramohan Rao, B. Shanmugavelu and V.V. Ravi Kanth Kumar, Optical Absorption and Photoluminescence studies of Dy 3+ Doped Alkaline earth Bismuth Borate Glasses, Journal of Luminescence, http://dx.doi.org/10.1016/j.jlumin.2016.09.012 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.

Optical Absorption and Photoluminescence studies of Dy3+ Doped Alkaline earth Bismuth Borate Glasses M. Veeramohan Rao, B. Shanmugavelu and V.V. Ravi Kanth Kumar* Department of Physics, Pondicherry University, Puducherry-605014, India *Corresponding author email id: [email protected] ABSTRACT Dy3+ doped barium bismuth borate glasses were prepared by the conventional meltquenching method. The prepared glasses were characterized by absorption, excitation, emission and decay curves. Judd-Ofelt parameters were obtained from the absorption spectra recorded at 400 – 2000 nm. All the samples were excited at different wavelengths from UV (350) to blue (450-470) light and respective emission spectra are recorded. The intensity ratio of yellow to blue (Y/B)

indicates that Dy3+ ions are present in low symmetry site. B2O3-

Bi2O3-BaO glasses emit efficient white light under different excitation wavelengths, which match well with the emission of commercial GaN-based blue LEDs and InGaN-based LEDs respectively. CIE coordinates were calculated from the emission spectra and found that they fall in white light region. Decay curves show single exponential nature up to 1 mol% of Dy3+ concentrations and then turn into non-exponential for 2 mol% of Dy3+ ions. Lifetime of these glasses decreases with increase of Dy3+ ion concentration.

1. INTRODUCTION Now-a-days white light emitting diodes (WLEDs) are receiving technologically great attention as they became potential replacement for conventional bulbs and incandescent fluorescent lamps because of their longer lifetime, higher efficiency, better reliability and eco-friendly in nature [1-18].

Although commercially available WLEDs generate white

light by excitation of yellow phosphor (Ce3+: YAG) using a blue emitting GaN semiconductor chip,

the current trend to develop glasses for realization of white light

emission started after the first stimulation of white light in Borate glasses[1]. The main reason is being that glasses with wide variety of composition or dopants can be easily prepared at low cost. At the same time glasses possess a wide transparency, halo effect and the narrow line emission spectra of the lanthanide ions make them a promising alternative to phosphors [2-11]. So in recent days there is a great interest on glasses doped with rare earth ions (RE) and transition metals for producing white light generation [2-26]. Borate based glasses have important properties like lower melting point, high transparency, better chemical durability, thermal stability and good rare earths solubility compared to the other glasses. The main drawback of the borate glass is

high phonon energy due to which the non-radiative

decay process cannot be suppressed. This phonon energy can be reduced by adding heavy metal oxides to the borate glasses [8-11]. Moreover, borate glasses containing heavy metal oxides exhibit the significant properties such as high refractive index, large polarizability, high optical basicity, small metallization criterion and large third order harmonic generation [12]. Especially, alkaline earth oxide containing borate glasses with heavy metal oxides exhibit good solubility of the rare earth ions [13]. Alkaline earth oxides enhance the glass forming capability while the heavy metal oxide gives good optical properties viz., second harmonic generation [14]. Among RE ions, by doping materials with dysprosium Dy3+ alone white light can be achieved [5, 14-18]. The exact white light or any other colour from Dy3+

doped glasses can be obtained by changing the integrated intensity ratio of yellow to blue emission (Y/B) by adjusting the host composition or content of Dy3+ or excitation wavelength [17,18]. The main aim of this paper is to work in this direction to generate white light by studying the photoluminescence properties of Dy3+ doped alkaline earth bismuth borate glasses.

2. EXPERIMENTAL Table 1 gives the composition in mol% and respective labels of the glasses studied in the present paper. The appropriate composition of mixture of the chemicals H3BO3, BaO, SrO, CaO, Bi2O3 and Dy2O3 were taken and glasses were prepared by the melt-quenching method. The respective mixtures were melted at 1050 ΟC for 30 min and the melt were casted between stainless steel plates to obtain glass samples. The prepared glasses were annealed below the glass transition temperature in order to remove the internal stress and were polished with cerium oxide to get glass samples of optical quality. The prepared Dy3+ doped alkaline bismuth borate (RBB, where R= Ba, Sr & Ca) glasses are transparent and colourless. The density of the glasses is measured by Archimedes principle where water is used as immersion liquid. Refractive index of the glasses has been measured by Brewster angle method using a He-Ne laser (=632.8 nm). The absorption spectra were recorded using UV-Vis-NIR spectrophotometer. The excitation and emission spectra were recorded at room temperature with 450-W Xenon CW lamp source and decay measurements were carried out with 75-W Xenon pulsed lamp source at 50 ms time per flash and 5 sample window using Fluor log Spectrofluorometer (HORIBA Jobin Yvon).

3. RESULTS AND DISCUSSION 3.1.Absorption spectra and Judd-Ofelt analysis The absorption spectra of BBB and RBB (R= Ba, Sr & Ca) were recorded in the range 400 – 2000 nm and are presented in Fig. 1a and Fig. 1b respectively. The absorption spectra consists of eight peaks located at 452, 474, 700, 803,1094,1277 and 1685 nm ascribed to 6

H15/2 to

4

I15/2,

4

F9/2,

6

F3/2,

6

F5/2,

6

F7/2,

6

F9/2+6H7/2,

6

F11/2+6H9/2 and

6

H11/2 transitions

respectively. Among the observed transitions in Fig. 1, the strong absorption band 6

H15/2→6F11/2+6H9/2 is located at around 1277nm and the peak at 452 nm which will well

match with the laser output corresponding to the commercially available blue-LED [19]. According to Jorgensen and Judd [20], the position and intensity of certain electric-dipole transitions of RE3+ ions are found to be very sensitive to the host environment. Such transitions are termed as hypersensitive transition and obey the selection rules ‖ ‖ 6

‖ and ‖

‖.



As it is evident from Fig. 1, the strong absorption band

H15/2→6F11/2+6H9/2 is located at around 1277nm for all the studied glasses. Moreover, this

transition is a hypersensitive transition and has large value of squared reduced matrix element ‖

‖ [27].The intensities of observed peaks are expressed in terms of oscillator strengths

and can be calculated by measuring the integrated area under the bands through the following expression [31].

( )

( )

(1)

Where m and e are mass and charge of an electron respectively, c is the velocity of light, N is the Avogadro’s number, ( )is the molar absorptivity of a band at wavenumber

(cm-1).

The calculated oscillator strength of ƒ-ƒ transitions can be obtained by using the Judd-Ofelt

theory [30, 31]. From this theory, the calculated oscillator strength of an induced electricdipole transition from the ground state ( (

)

)



to an excited state 𝝍′ ′ is given by [29] (

where n is refractive index of the medium, Planck’s constant.





)

(2)

is the energy of the transition in cm-1 and h is

is the total angular momentum of the ground state,

intensity parameters and ‖

(𝞴=2,4,6) are J-O

‖ are the double reduced matrix elements of the unit tensor

operator that can be evaluated from the intermediate coupling scheme a for transition 𝝍 to 𝝍′ ′. A least square fitting approach has been used to determine the JO parameters, (𝞴=2,4,6), which gives the best fit between the ƒexp and ƒcal values. The reduced matrix elements ‖

‖ (=2, 4 & 6) were less affected by environment and therefore values are

taken from literature [32]. The quality of fit known as the root mean square deviation (σrms) between the ƒexp and ƒcal is given by

σrms =√

Where

and



(

)

(3)

are the respective experimental (ƒexp) and calculated (ƒcal) oscillator

strengths of ith level and N refer to the total number of levels included in the fit. The experimental and calculated oscillator strength along with Judd-Ofelt parameters for all the samples are given in Table. 2. The obtained root mean square deviation values between the experimental and calculated oscillator strength was deduced to be small, demonstrating that the values obtained from least square fit are reliable. The Judd-Ofelt intensity parameters, obtained from transition intensities, are dependent on the local environment. The significance of the 33]. The

are useful to describe the bonding, symmetry and rigidity of the host matrices [29, parameter is supposed to be allied with asymmetry and bond covalence between

rare earth ion (Re3+) and surrounding ligands, whereas

and

properties like as viscosity and rigidity of the host matrix respectively.

indicates the bulk

Among RBB glasses

and

values decrease in the order BBB1 > SBB1 > CBB1, thus an

environment around Dy3+ ion in BBB glass is more asymmetric and covalent in nature as value increases as Dy3+ content

well as highly rigid. However, within BBB glass system in glass raises up to 1 mol% and then decreases whereas Tanabe et al. [34] showed that the variation of

6

increases till 0.5 mole% of Dy3+.

with composition was related to the change

in asymmetry of the ligand field of Eu3+ ions due to the structural mixing of borate groups in alkali-metal borate glasses. Also according to polarizability classification, the more or less overlap between O2- and metal valence orbital makes oxide glass acidic or basic respectively [35-37]. The present studied glasses are formed using two types of oxides namely acidic semi-covalent oxide (B2O3) and basic ionic oxides (Bi2O3, BaO, SrO and BaO). The addition of ionic oxides to B2O3 glass decreases the average single bond strength of more covalent BO-B or M-BO (bridging oxygen) groups and increases the formation of more ionic groups like Bi-O-B, or M-NBO (non-bridging oxygen) etc. along with B-O-B [35]. A good correlation exists between the optical basicity of glass and average single bond strength where decrease of optical basicity increases average single bond strength.

The optical

basicity of present glasses are evaluated as explained by Dimitriv et al [35-37] and their values vary in the order CBB (0.69) < SBB (0.76) < BBB (0.97). This establishes that the presence of more mixed borate groups or M-NBO in BBB glass led to high

value.

3.2.Luminescence spectra and Radiative properties Excitation spectra of Dy3+ doped BBB glasses recorded by monitoring emission at 575 nm is shown in Fig. 2, look alike as a representative case of RBB glasses, exhibit several characteristic excited peaks at 324 (6H15/2→

4

M17/2), 350 (6H15/2→ 4M15/2, 6P7/2),

364

(6H15/2→ 4I11/2), 387 (6H15/2→4I13/2, 4F7/2), 425 (6H15/2→ 4G11/2), 452 (6H15/2→ 4I15/2) and 473 nm (6H15/2→ 4F9/2). The presence of several excitation peaks in the 350-480 nm range entail

that Dy3+ ions can be competently excited by 440-470 nm (commercial blue) and 350-420 nm (LED chips) which is of importance for generating white light [38, 39]. Emission spectra of Dy3+ doped BBB glasses (look alike, as representative case of RBB glasses) recorded for various excitation wavelengths namely 351, 365, 390, 426 and 452 nm is displayed in Fig. 3. Since emission spectra excited at 452 nm exhibited high intense peaks so this 452 nm has been chosen as excitation wavelength for further emission studies. Emission spectra of Dy3+: BBB for various concentrations of Dy3+ and 0.1 mol% doped RBB obtained while excited at 452nm are presented in Fig. 4a and Fig. 4b respectively. All the glass samples exhibit intense bands centred at 484nm (blue), 575nm (yellow) and 664nm (orange), which can be attributed to the Dy3+ ion transitions originated from energy level 4F9/2 to 6H15/2, 6H13/2 and 6H11/2energy levels respectively. Primarily two features can be seen from Fig. 4. Firstly, the peaks are shifted to shorter wavelengths when alkaline earth ion in bismuth borate glass composition is changed in the order SBB, CBB and BBB. Secondly, in terms of intensity both yellow (4F9/2 →6H13/2, electrical dipole transition) and blue (4F9/2→ 6

H13/2, magnetic dipole transition) emissions show a decrease with the variation of glass

matrix composition in the order of BaO, SrO, and CaO. The change is regular with the reduced radius, or the increased electronegativity of these alkaline earth ions. It is known that a cation with larger electronegativity tends to attract more electronic cloud from O2- ions. Thus, the ionicity of the system increases which weakens emissions of the doped rare-earth ions [38]. Another possible reason might be due to the increased phonon energy (PE) of glasses containing cations with the smaller atomic ordinal number. The higher PE increases the rate of non-radiative relaxation. Among the observed emission bands, 6

4

F9/2 →

H13/2transition is hypersensitive in nature and its intensity is strongly influenced by the

ligand field around the Dy3+ ion site. The emission intensity of the electric dipole transition is found to be higher compared to the magnetic dipole transition for all the prepared glasses.

The intensity variations can be quantified in terms of yellow-to-blue luminescence intensity ratios (Y/B)and values are given in Table 3 which increase in the order of BBB>SBB>CBB. The higher magnitude of Y/B ratios illustrates the fact that the Dy3+ ions are located at higher asymmetrical ligand environment which is also confirmed from the higher

values of the

studied glasses.Fig. 4a shows the luminescence intensity variation of peaks within BBB glass with respective to Dy3+ content. It is clearly evident from Fig. 4a that the luminescence intensity increases with the increase in Dy3+ion content up to 1.0 mol%, beyond which intensity decreases due to the non-radiative energy transfer process which takes place between nearby Dy3+– Dy3+ ions and thus led to concentration quenching.

)

Radiative properties of the Dy3+ doped RBB glasses such as transition probability ( radiative lifetime (

) and branching ratio (

) are calculated from the absorption spectra by ) from the

using the J-O parameters [29-31]. The spontaneous transition probabilities ( initial level 𝝍 to 𝝍′ ′ can be obtained from the following relation ( Where

(

)

and

(

)

)

(

(4)

)

are the electric dipole and magnetic dipole line strengths ∑

(





)

(5)

and ∑ The term (

(

)

(





)

) is the local field correction for electric-dipole transitions and

magnetic dipole transitions. The total radiative transition probability ( level is given by the sum of the (

(6)

)



( (

for

(𝝍 )) for an excited

) terms calculated over all terminal levels. )

(7)

The radiative lifetime ( ) of an excited level 𝝍′ ′ is given by the reciprocal of the

(𝝍 ),

(

(8)

)

The fluorescence branching ratio (

) corresponding to the emission from excited level 𝝍′ ′

to 𝝍 can be calculated from the transition probabilities by using the relation (

)

(

)

(9)

From emission spectra of the Dy3+ doped barium bismuth borate glasses, the stimulated emission cross section between and ′ level are determined using the following relation ( Where

)

)(

(

)

(10)

is the peak wavelength of the fluorescence line and

is the effective band

width of the fluorescence line, which is given as ( )

The obtained values of stimulated emission σ(

(11) ) and other radiative parameters for all the

samples that have been calculated using above equations (from eq.(4) to eq.(11))

are

presented in Table 3. From the tabulated values it is evident that the 4F9/2→6H13/2 transition shows higher stimulated emission compared to the other transitions. Among the alkaline earth metal containing bismuth borate glasses RBB1 (where R=Ca, Sr & Ba) shows the highest stimulated emission for CBB1. It is evident from Table 3 that the stimulated emission increases with decreasing ionic radii BBB (135pm) < SBB (118pm) < CBB (100pm) and within BBB glass the value is higher for 2 mol% doped of glass (6.7x10-21 m2). The reason for getting higher stimulated emission cross-section is due to less distorted environment around the Dy3+ ion where the asymmetry of ligand field around Dy3+ decreases with increasing ionic radii. The glasses having higher stimulated emission cross- section (

) are

suitable for low threshold and high gain laser applications [38]. The branching ratio is another critical parameter that indicates the possibility of attaining stimulated emission from

any specific transition. The experimental branching ratios of β15/2+β13/2 related to 4F9/2 →4H15/2, 4H3/2 transition of the presently studied glasses are found to be unity suggesting that stimulated emission with higher efficiency can be obtained from these transitions.

3.3.Fluorescence Decay The fluorescence decay curves for various concentrations of Dy3+ doped BBB glasses and 0.1 mol% Dy3+: RBB glasses were recorded at room temperature by exciting at 452nm and monitoring the emission at 575nm, Fig. 5 (a & b).

From decay curves the obtained

experimental lifetime values (τexp) of Dy3+ doped RBB glasses are presented in Table 4. All the decay curves are well-fitted with the single exponential up to 1 mol% and for 2 mol% it turn to non-exponential. The non-exponential decay curves for 2 mol% well fitted with Inokuti-Hiryama (IH) model in order to understand the decay process [41]. The IH model expression is given by. ( )

[

( ) ]

(12)

where S can be 6, 8 and 10 for dipole–dipole, dipole–quadruple and quadruple–quadruple interaction, respectively. The energy transfer parameter (Q) is given as. ( Where the

(

)

(13)

) is function is equal to 1.77 in the case of dipole–dipole interaction

(S=6), 1.43 for dipole–quadruple interaction (S=8) and 1.3 for quadruple–quadruple interaction (S=10). Na is the concentration of acceptors, which is equal to the concentration of RE3+ ions and Ro is the critical transfer distance defined as the donor–acceptor separation for which the rate of energy transfer to the acceptors is equal to the rate of intrinsic decay of the donors. The donor–acceptor coupling constant (CDA) is given by CDA=

(14)

the decay curve of the glass doped with 2 mol% of Dy3+ ion has been well fitted to the IH model for S=6 and the values of Q, R0 and CDA are found to be 1.

, .

, 5.84 X 10-40

cm6/s, Lifetime of Dy3+ doped BBB glass decreases with increasing Dy3+ ion concentration due to non-radiative energy transfer process from excited state to neighbouring unexcited state of Dy3+ ions. Once Dy3+ ions are in the excited state, these ions may relax to their ground state by means of radiative transition or non-radiative transitions via the emission of photons and phonons, respectively. Two of the prominent mechanisms which may be employed to explain concentration quenching, as shown in partial energy level diagram of Dy3+RBB glasses (Fig. 6) , are resonance energy transfer (RET) and cross relaxations (among neighbouring Dy3+ ions). 3.4.Chromaticity diagram The white light can be successfully generated from Dy3+ doped systems by tuning Y/B intensity ratio to unity and its value can be optimized in three ways such as by varying the chemical composition, Dy3+ ion concentration and the excitation wavelengths. Therefore, the emission spectra of 0.1 mol% of Dy3+: RBB glasses are studied for various excitation wavelengths of 351, 365, 390, 426 and 452 nm is shown in Fig. 3 and respective Y/B ratios along with chromaticity coordinates are presented in Table 4. To obtain colour coordinates, the emission spectra have been analysed in the framework of CIE 1931 chromaticity diagram [40]. The colour of any light source can be described just by three variable

(λ), y (λ and

(λ (colour matching functions), which are dimensionless quantities [43]. For a given power-spectral density, P(λ), the degree of stimulation required to match the colour ofP(λ is given by. 

̅ ( ) (  ) 



̅ (  ) ( ) 

(16)

̅ ( ) ( ) 

(17)



(15)

Where X, Y and Z are the tristimulus values gave the stimulation (i.e. power) for each of the three primary red, green and blue colours needed to match the colour P(λ . The chromaticity coordinates x and yare calculated from the tristimulus values according to equations (18)

(19)

The calculated colour coordinates of Dy3+ doped glass excited with different excitation wavelengths which fall in white light region are shown in the chromaticity diagram, Fig. 7.All CIE coordinates very closely match with the standard value. Among the Dy3+ doped barium bismuth borate

glass samples BBBDy0.1 material possess CIE coordinates

(0.33,0.32) which are very close to standard equal energy white illuminate (0.33,0.33) value compared with other reported values BBS0.1 (0.29,0.33) [44], D65 illuminate (0.31,0.33) [45], PKAZLFDy0.1 (0.29,0.31) [46], TCZNBDy0.5 (0.28,0.32) [47]. These results show that in general RBB glasses, more specifically the glass BBBDy0.1, are promising materials in solid state lighting for producing the white light emission.

4. Conclusions In summary, the developed Dy3+-doped RBB glass produces white light because it emit simultaneously blue and yellow light as well as a weaker red light under 351, 365, 390, 426 and 452 nm excitation, respectively. Based on excitation and emission spectra as well as luminescence decay analysis, some spectroscopic parameters for Dy3+ ions were determined. Especially, yellow-to-blue luminescence intensity ratios Y/B corresponding to 4F9/2 → 6H15/2 and

4

F9/2 →

6

H13/2 transitions of Dy3+ have been analyzed for glass samples. Our

investigations clearly indicate that the relative intensities of the 4F9/2 → 6H13/2 transition to the

4

F9/2 → 6H15/2 transition of Dy3+ ions can be modulated by varying the glass host

compositions, content of Dy3+ and excited wavelength to get a better white light. The better white light emission can be observed in Barium bismuth borate glass doped with 0.1% Dy3+ glass with chromaticity coordinates (0.33, 0.32). Thus Dy3+ RBB glasses are suitable materials for solid state lighting.

Acknowledgements We acknowledge Department of Physics & Central Instrumentation Facility, Pondicherry University for providing characterization facilities. Also, we acknowledge UGC-SAP-DRSII (F.530/1/DRS-II/2015 (SAP-I) for providing financial support.

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Figure Captions 1a. Absorption spectra of the Dy3+ doped BBB glasses 1b. Absorption spectra of the Dy3+ doped RBB glasses. 2. Excitation spectra of the BBB glasses with different Dy3+ concentration emission with 575nm wavelength 3. Emission spectra of the RBB glasses with different Dy3+ concentration different excited with 351nm, 365nm, 391nm and 426nm wavelength. 4. a. Emission spectra of the BBB glasses with different Dy3+ concentration excited with 452nm wavelength 4 b. Emission spectra of the RBB glasses with different Dy3+ concentration excited with 452nm wavelength. 5 a. Decay curves for 4F9/2 level of BBB glasses with different Dy3+ concentrations. 5 b. Decay curves for 4F9/2 level of RBB glasses with different Dy3+ concentrations. 6. Energy level diagram for the 2.0 mole% of Dy3+ ion in BBB glass. 7. CIE colour coordinate diagram of the BBB glasses with various Dy3+ concentration excitation with 452nm wavelengths

Fig. 1a

Fig. 1b

Fig. 2

Fig. 3

Fig. 4a

Fig. 4b

Fig. 5a

Fig. 5b

Fig. 6

Fig. 7

Table 1 Glass composition and given label Glass Label BBB1 BBB2 BBB3 BBB4 BBB5 SBB1 CBB1

BaO 10 10 10 10 10 0 0

SrO 0 0 0 0 0 10 0

Glass Composition (in mol%) CaO Bi2O3 0 20 0 20 0 20 0 20 0 20 0 20 10 20

B2O3 69.9 69.7 69.5 69.0 68.0 69.9 69.9

Dy2O3 0.1 0.3 0.5 1.0 2.0 0.1 0.1

) and calculated ( ) oscillator strengths, root mean square deviation( ), refractive index ( ), density (d)(g/cm3) and Judd-Ofelt parameters ( x 1020 cm2) for Dy3+ ions in BBB glasses Table 2 Experimental (

Transitio ns 6

H15/2

6

H11/2

6

H9/2+6F1

6

H7/2+6F9

1/2

/2

6

F7/2

6

F5/2

6

F3/2

4

F9/2

4

I15/2

BBB1

2.3 3 17. 6 1.3 3 4.5 6 1.0 3 0.3 5 0.1 2 0.1 0

2.6

19. 3 5.8 9 3.8 9 1.5 9 0.3 0 0.2 9 0.8 4 0.77 5.88 1.81 16.4 5.4 3.2

BBB2

8.4 9 19. 1 9.5 7 6.9 7 2.9

6.25

1.4 5 0.0 5 0.3 6

1.08

19.3 8.65 10.3 9 5.73

0.82 2.28

0.19 5.87 1.81 18.8 1.15 1.13

BBB3

3.9 5 21. 2 7.5 1 3.8 0 0.9 1 1.7 1 0.0 2 0.2 0

3.1 6 21. 3 7.1 8 4.9 9 2.1 2 0.4 0 0.3 7 1.0 5 0.87 5.86 1.81 17.7 6.1 4.2

BBB4

2.2 5 19. 3 5.6 6 4.8 7 1.0 5 2.0 8 0.0 2 0.4 6

2.8 3 17. 5 1.7 1 2.9 2 1.7 6 0.3 3 0.2 3 0.9 7 0.74 5.85 1.81 20.76 1.8 3.5

BBB5

5.5 7 20. 5 8.5 3 5.5 9 1.5 1 0.2 1 0.1 3 0.4 9

4.3 4 20. 7 8.0 7 7.1 6 3.5 1 0.6 6 0.5 5 1.5 1 0.10 5.84 1.81 17.7 3.9 7

SBB1

1.4 4 13. 4 5.9 2 2.6 1 1.1 6 0.4 5 0.1 0 0.9 1

1.5 9 13. 9 5.1 6 2.7 9 0.9 5 0.1 8 0.2 0 0.5 0 0.15 7.8 1.78 11.7 6.7 2.2

CBB1

1.8 9 16

1.8 9 15. 9 5.1 5.9 8 1 3.1 3.2 5 2 1.0 1.1 3 0 2.2 0.2 4 0 0.4 0.2 3 3 0.6 0.5 1 9 0.72 7.0 1.73 9.54 5.9 1.9

Table 3 Peak wavelength of the fluorescence lines (

), effective bandwidths (Δλeff),

radiative transition probabilities (AR , stimulated emission cross sections (σ(λp)) and branching ratios (β for Dy3+ ions in BBB glas Transitions F9/2→6H15/2

4

4

parameters (nm) ( ) (s-1) σ(λp) βR(exp) βR(cal)

BBB1 482 20 475 0.52 0.33 0.13

BBB2 482 21 150 0.15 0.281 0.04

BBB3 481 20 611 0.66 0.284 0.14

BBB4 481 20 446 0.48 0.26 0.11

BBB5 482 23 894 0.85 0.27 0.14

SBB1 CBB1 481 482 10 15 386 334 0.84 0.48 0.30 0.31 0.13 0.14

(nm) ( ) (s-1)

575 18 1388 6.06 0.47 0.68

575 20 2315 5.12 0.41 0.75

575 19 2773 6.46 0.41 0.67

575 19 2861 6.66 0.32 0.71

575 20 3046 6.64 0.44 0.65

575 12 1862 6.87 0.37 0.66

575 10 1544 6.84 0.35 0.64

665 19 273 6.06 0.019 0.076

665 18 285 5.12 0.18 0.93

665 18 299 6.46 0.14 0.14

665 19 325 6.66 0.019 0.065

665 19 307 6.64 0.015 0.073

665 15 208 6.87 0.028 0.073

665 15 174 6.84 0.024 0.073

F9/2→6H13/2

σ(λp)

4

F9/2→6H11/2

βR(exp) βR(cal) (nm) ( ) (s-1)

σ(λp)

βR(exp) βR(cal)

Table 4 Color coordinates (x, y) and Y/B intensity ratios ( Life time (τ ms) values of 4F9/2→6H13/2 ( of Dy3+ doped RBB glasses Glass

Y/B Ratio

Colour Coordinates (x,y)

BBB1 BBB2 BBB3 BBB4 BBB5 SBB1 CBB2

1.290 1.358 1.297 1.477 1.373 1.288 1.200

(0.34, 0.33) (0.37, 0.40) (0.34, 0.32) (0.28, 0.32) (0.30, 0.34) (0.33, 0.37) (0.33, 0.39)

) and experimental ) transition Life time (τ 660.55 402.17 345.01 322.51 199.13 390.02 384.32

ms

Table 5 Excitation wavelength (nm), color coordinates (x, y) and Y/B intensity ratio for the Dy3+ ion doped RBB glass Glass BBB1

BBB2

BBB3

BBB4

BBB5

SBB1

CBB1

Excitation wavelength (nm) 351 365 390 426 452 351 365 390 426 452 351 365 390 426 452 351 365 390 426 452 351 365 390 426 452 351 365 390 426 452 351 365 390 426 452

Color coordinates(x, y) (0.33,0.32) (0.27,0.25) (0.25,0.22) (0.32,0.32) (0.34,0.33) (0.26,0.31) (0.30,0.43) (0.35,0.27) (0.28,0.35) (0.37,0.40) (0.27,0.25) (0.26,0.26) (0.25,0.23) (0.27,0.31) (0.34,0.32) (0.25,0.24) (0.25,0.25) (0.29,0.27) (0.27,0.29) (0.28,0.32) (0.30,0.27) (0.25,0.23) (0.25,0.24) (0.27,0.31) (0.30,0.34) (0.33,0.31) (0.31,0.33) (0.32,0.37) (0.26,0.35) (0.33,0.37) (0.28,0.27) (0.27,0.27) (0.26,0.25) (0.24,0.30) (0.33, 0.39)

Y/B intensity ratios 0.807 0.868 1.019 1.177 1.290 0.796 0.887 0.835 0.695 1.358 0.864 1.042 1.061 0.913 1.297 0.993 1.282 1.498 1.077 1.477 0.741 0.982 1.192 0.905 1.373 1.073 1.440 1.355 1.244 1.288 0.869 0.833 0.983 0.792 1.200

Research Highlights 

Among alkaline earth bismuth borate glasses, the Dy3+ ion possess higher asymmetry and covalent environment in Barium Bismuth Borate glasses.



White light generation is successfully demonstrated in Dy3+: alkaline earth bismuth borate glasses. Especially, glasses excited at 452 nm exhibit better white light characteristics.