LFPs were visualized using an optimized powder undoubtedly with high contrast, selectivity and low background interference on various porous and non-porous surfaces.. The photometric stu[r]
Trang 1M Dhanalakshmia,b, H Nagabhushanac,*, G.P Darshand, R.B Basavarajc,
a Department of Physics, Govt Science College, Bengaluru 560 001, India
b Research and Development Center, Bharathiar University, Coimbatore 641046, India
c Prof C.N.R Rao Centre for Advanced Materials, Tumkur University, Tumakuru 572103, India
d Department of Physics, Acharya Institute of Graduate Studies, Bangalore 560 107, India
e Department of Physics, BMS Institute of Technology and Management, VTU, Belagavi-affiliated, Bangalore 560 064, India
a r t i c l e i n f o
Article history:
Received 19 December 2016
Received in revised form
31 January 2017
Accepted 9 February 2017
Available online 16 February 2017
Keywords:
Sonochemical synthesis
Latent fingerprint
Cheiloscopy
JuddeOfelt analysis
a b s t r a c t
Nanostructured materialsfind potential benefits for surface-based science such as latent fingerprints (LFPs) and lip print detection on porous and non-porous surfaces To encounter the drawbacks viz low sensitivity, high background hindrance, complicated procedure and high toxicity associated with traditional fluo-rescent powders were resolved by using hollow/solid BaTiO3:Dy3þ(1e5 mol %) microspheres The visu-alization of LFPs stained by the optimized BaTiO3:Dy3þ(2 mol %) hollow/solid microspheres exhibits
well-defined ridge patterns with high sensitivity, low background hindrance, high efficiency and low toxicity on various surfaces The powder X-ray diffraction results revealed the body centered cubic phase of the pre-pared samples The emission spectra exhibit intensive peaks at ~480, 575, and 637 nm, which were attributed to transitions4F9/2/6HJ(J¼ 15/2, 13/2, 11/2) of Dy3þions, respectively Surface morphologies were extensively studied with different sonication times and concentrations of the used barbituric acid The Commission International De I-Eclairage (CIE) and Correlated Color Temperature (CCT) analyses revealed that the present phosphor is highly useful for the fabrication of white light emitting diodes
© 2017 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
1 Introduction
In a crime spot investigation, LFPs are the most important
physical evidence for identification of criminals [1,2] When a
criminal touches any surface in a spot, skin sweat transferred to the
surface through pores leading to an invisible ridge pattern is well
known as latentfingerprints In a forensic analysis, LFPs are the most
influential method due to its unique and immutable features[3,4]
Because of invisibility of LFPs, enhancement of LFPs was required for
identification and visualization Nowadays, several methods have
been used to make LFPs visible Among them, the powder dusting
method allows for LFPs to be visualized within a short period of time
and without any complicated requirements The conventional
dusting powders were mainly classified into regular, metallic and
luminescent materials Regular and metallic powders constituent of resinous polymers and meshed metals which are hazard to in-vestigators' health[5] These conventional powders are not capable
of enhancing LFPs on some complicated surfaces Luminescent nanopowders are potential solutions to overtake such limitations, making LFPs visible Luminescent nanopowders were explored as labeling agents for visualization of LFPs and exhibit good contrast, sensitivity and adhesion efficiency These factors provide new possible applications of nano powders in surface science
In addition, lip prints are form of wrinkles and grooves including normal lines,fissures and are present in the zone of transition of human lip between the inner labial mucosa and outer skin[6] Lip prints are also a main evidence for identification of an individual in
a forensic dentistry due to its uniqueness, except in monozygotic twins The revelation of lip prints was well known as cheiloscopy
[7] The cheiloscopy plays a major role in forensic science for person identification in crime investigations, ethnic studies, mass di-sasters,fire victims, and vehicle accidents
* Corresponding author.
E-mail address: bhushanvlc@gmail.com (H Nagabhushana).
Peer review under responsibility of Vietnam National University, Hanoi.
http://dx.doi.org/10.1016/j.jsamd.2017.02.004
2468-2179/© 2017 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license
Trang 2The ultrasonic sonochemical method has received a great
attention for the fabrication of phosphors with unusual and
tailored properties Further, an ultrasound assisted synthesis route
has great commercial potential advantages with high production
rates, syntheticflexibility on choosing host materials as high
pu-rity nano powders, rapid reaction rate, narrow size distribution,
stable colloidal dispersion, uniform mixing, less synthesis time,
and less energy usage[8] In this method, the chemical reactions
arise from acoustic cavitations, i.e., formation, growth and
implosive collapse of bubbles in the liquid The growth of the
bubble happens through the diffusion of solute vapor into the
volume of the bubble, while the collapse of the bubble arises when
the bubble size reaches its maximum value When the solution was
exposed to ultrasound irradiation, the bubbles were implosively
collapsed by acousticfields in the solution[9] According to the hot
spot theory, very high temperatures (>5000 K) were achieved
upon the collapse of a bubble Since this collapse occurs in less
than a nanosecond, very high cooling rates (>1010 K/s) was also
obtained These extreme environments can drive several chemical
reactions and physical modifications occur as a result, allowing
shape and size of the phosphors to be effectively tuned[10] There
is a pressing need for synthesis of nano/micro structured materials
at reasonably low temperature for industrial applications
To the best of our knowledge, there have been no reports on an
ultrasound assisted sonochemical method for fabrication of
BaTiO3:Dy3þ (1e5 mol %) powders using Barbituric acid as a
sur-factant The prepared optimized samples were employed to
visu-alize LFTs and lip prints on various porous and non-porous surfaces
In addition, the structural and photoluminescent properties were
analyzed, and photometric properties were systematically studied
2 Experimental
Titanyl nitrate was prepared by taking N-butyl titanate in a petri
dish and a minimum quantity of doubled distilled water was added
to yield titanyl hydroxide Further, nitric acid was added to this
redox mixture which gave titanyl nitrate The corresponding chemical reactions can be given by[11]
TiðOC4H9Þ4þ 3H2O/TiOðOHÞ2þ 4C4H9OH (1)
Stoichiometric amount of barium nitrate and titanyl nitrate were dissolved in 100 ml deionized water and thoroughly mixed
in a magnetic stirrer to get uniform solution The stoichiometric amount of dysprosium nitrate (1e5 mol %) was added to the above resultant solution Further, different concentrations of barbituric acid (0.05e0.25% W/V) were added to the resultant mixture slowly Ultrasound irradiation was accomplished with a high-intensity ultrasonic probe (~2.5 cm diameter; Ti horn,
20 kHz, 150 W/cm2) immersed directly in the reaction solution Then, the solution mixture was stirred with high-intensity ul-trasound irradiation under ambient air (the ultrasonic frequency ~ 20 kHz, the power ~ 150 W) at afixed temperature of
75 C and by varying ultrasonic time (1e6 h) The solution was kept undisturbed until a white precipitate was formed The pre-cipitate wasfiltered and washed several times by using distilled water and ethanol to remove any unreacted material The ob-tained product was dried at 60 C for 3 h in a vacuum oven Finally, the dried precipitate was grinded thoroughly into the powder form and used for further studies
2.1 Characterization The obtained product was well characterized by using Shimadzu
7000 powder X-ray diffractometer using Cuka radiation Morphology of the product was studied by means of TM 3000, Hitachi table top Scanning electron microscopy and Hitachi H-8100 Transmission electron microscope The Perkin Elmer (Lambda-35) spectrometer was used to study the reflectance of the samples For
Fig 1 Fingerprints on the surface of glass stained by (a) TiO 2 powder (b) BaTiO 3 :Dy3þ2 mol % powder, (c) Fe 2 O 3 powder, and (d) BaTiO 3 :Dy3þpowder synthesized by mechanical
Trang 3PL measurements Jobin Yvon Spectroflourimeter Fluorolog-3
operational with 450 W Xenon lamp was used
2.2 Mechanism of visualization of LFPs and lips print using
BaTiO3:Dy3þhollow/solid microspheres
FPs collected from healthy volunteers with the age group of ~21
years were deposited on porous and non-porous surfaces namely
microscopic slides, aluminum foils, scratched CDs, leafs, coins,
magazines, pen, colored plastic bag etc Before deposition,fingers of
volunteers were thoroughly washed with water and dried in air
without touching any surfaces The optimized BaTiO3:Dy3þ(2 mol
%) powder was carefully sprinkled and gentle dusted uniformly on
LFPs using a special“Marabou” feather brush Further, an UV lamp
(4 W, 254 nm) was illuminated on the stained LFPs and then
pho-tographed using 50 mm f/2.8G ED lens Nikon D3100/AF-S digital
camera For visualization of latent lip prints, lips were cleaned
thoroughly using smooth tissue paper and then with sterile cotton The lips were lightly pressed against a glass slab for ~3e5 s The latent lips prints acquired on glass slab were visualized by spraying the optimized powder with a smooth brushing method and pho-tographed using a digital camera
3 Results and discussion
To determine effectiveness and selectivity of the prepared BaTiO3:Dy3þ(2 mol %) powder as afluorescence labeling agent for the visualization of LFPs on glass slide, conventionally used iron oxide (Fe2O3) and titanium dioxide (TiO2) powders were used as a control It was found that, LFPs developed by Fe2O3, TiO2 and BaTiO3:Dy3þpowders fabricated by mechanical stirring could not resolve fullfingerprint patterns (Fig 1(a, c& d)) However, LFP stained by BaTiO3:Dy3þ(2 mol %) hollow/solid microspheres under
254 nm UV light revealed well defined friction ridges (Fig 1b) It is
Fig 2 LFPs on (a) a green leaf, (b) a plastic sheet, (c) a plastic pen edge, (d) a steel pen edge, (e) a TV remote, (f) a mobile screen, (g) a coin, and (h) stainless steel visualized by BaTiO 3 :Dy3þ2 mol % powder under UV 254 nm.
Trang 4evident that the optimized BaTiO3:Dy3þpowder can be used as an
effective labeling agent for visualization of LFPs due to their
supe-rior white light emission Well defined fingerprint images with high
sensitivity were also visualized by BaTiO3:Dy3þ(2 mol %) hollow/
solid microspheres on non-porous materials including green leaf,
plastic sheet, plastic pen edge, steel pen edge, TV remote, mobile
screen, coin, and stainless steel (Fig 2)
In addition, aged (different time periods) LFPs were examined to
exhibit the suitability and robustness of the prepared powder in
advanced forensic detection.Fig 3(aec) shows the aged LFPs with
different time periods (1 day, 2 week, and 1 month) stained by the
optimized BaTiO3:Dy3þ powder Normally, sensitivity of labeling
powder progressively decreases as aging of the LFPs enhances, due
to evaporation of chemical constituents of the LFPs In the present work, even one month aged FP shows defined ridges, indicate the practicability of the prepared powder The LFPs on different textured marbles visualized by optimized BaTiO3:Dy3þ(2 mol %) powder under 254 nm illumination demonstrate the well-defined ridge patterns withfine contrast and without or less background hindrance (Fig 3 (def)) The differently magnified SEM images of LFP enhanced by prepared BaTiO3:Dy3þ(2 mol %) powder were shown inFig 4 The prepared powder particles provide uniform distribution and stronger adhesive ability via each static and sur-face absorption interactions and it increases the chemical stability,
Fig 3 LFPs aged on the non-porous glass surface for various time periods ((a) 1 day, (b) 2 weeks, and (c) 1 month) and (def) on different textured marbles visualized by
3þ
Trang 5permitting the long protection of light and affording affinity with
LFPs
The above obtained results demonstrated that, the optimized
BaTiO3:Dy3þ(2 mol %) powder was explored as an efficient
fluo-rescent labeling agent for visualization of LFPs on various porous
and non-porous surfaces The prepared optimized powder can
visualize LFPs as a whole, with high sensitivity, efficiency and low
background interference
Lip prints similar tofingerprints have many elevations and
de-pressions providing evidence in individual identification and
criminal investigation in a forensic dentistry The study of such lip
prints called as Cheiloscopy Usually, lip prints can be found where
the surface in contact with the lips[12] Most commonly in glasses,
cigarettes, straws, food items etc However, some extra effort has
been required to make lip prints visible Therefore, we explored
BaTiO3:Dy3þ(2 mol %) powder for visualization of lip prints on glass
under UV 254 nm Fig 5 shows the lip print stained by the
optimized BaTiO3:Dy3þ(2 mol %) powder From thefigure, it was clearly evident that the whole lip prints with Tsuchihashi's Type V, Type I, Type I0and Type III grooves (Fig 5(bee)) were visualized with high sensitivity and contrast due uniform smaller size and adhesive nature of the powder
In the ultrasound assisted sonication method, many experi-mental parameters namely sonication time, concentration of sur-factant, pH value and sonication power etc., may affect greatly the size and morphology of the products In the present study, the morphology of the prepared samples was extensively studied with different sonication times and concentrations of the surfactant.Fig 6
(aee) shows SEM images of BaTiO3:Dy3þ(2 mol %) with different sonication times (1e5 h) with a 0.25% W/V concentrated barbituric acid When the sonication time was ~1 h, several splintered parts having small lotusflower e like morphology was observed (Fig 6
(a)) The petals offlowers started blossoming, when the sonication time was increased to 3 h Further, increase of the sonication time
Fig 4 Differently magnified SEM images of fingerprints stained by BaTiO 3 :Dy3þ(2 mol %) powder ((b) is a magnified portion of (a)).
Trang 6(4 and 5 h), large number offlowers closed to form a uniform hallow
spherical shaped morphology was obtained (Fig 6(d& e)) The
obtained spherical morphology preserved even after 5 h sonication
irradiation Series of trials were conducted to ascertain the impact of
surfactant concentration on theflower morphology and are shown
inFig 6(fej) When the concentration of barbituric acid was 0.05%
W/V, a yolk-shell shaped structure consisting of many particles was
observed (Fig 6(f)) A hallow yolk-shell shaped micro structure
appeared, when the concentration of barbituric acid was increased
to 0.10% W/V (Fig 6(g)) However, with increase of concentration to 0.15% W/V, more hallow was observed and retained even further extended concentration (0.20% W/V) When the barbituric acid concentration was increased to 0.25% W/V, significantly condensed hallow space was observed (Fig 6(j))
Fig 7depicts TEM, HRTEM, SAED patterns, and EDAX images of the BaTiO:Dy3þ(2 mol %) powder The TEM image displays layer
Fig 6 SEM images of BaTiO 3 :Dy3þ(2 mol %) powder with (aee) different sonication times (1e5 h), a barbituric acid concentration of 0.25% W/V, and (fej) different concentrations
of the barbituric acid (0.5%e0.25% W/V) for a 5 h sonication.
Trang 7morphology and size ranged from 30 to 50 nm (Fig 7(a)) The lattice
spacing (d) was estimated from an HRTEM image (Fig 7(b)) and
found to be ~0.26 nm and the value was well matched with PXRD
values.Fig 7(c) shows the SAED pattern of the prepared sample and
it confirms the polycrystalline nature of the prepared powder
Further, elemental compositions such as atomic and molecular
weight were obtained from EDAX, which is shown inFig 7(d)
Fig 8(a) shows the PXRD profiles of BaTiO3:Dy3þ(1e5 mol %)
powder fabricated with a 6 h sonication time and barbituric acid
(0.25% W/V) The sharp and intense diffraction peaks were in good
agreement with the cubic phase with JCPDS no 31-0174 [13]
Further, it was observed that small impurity peak of dopant Dy2O3
ions was identified, indicating the successful substitution of Dy3þ
ions in the Ba2þsites The intensity of impurity peak increases with
increasing the concentration of dopant ions
The average crystallite size (D) was estimated using the
Scher-rer's formula[14]and listed inTable 1 It was evident from the table
that, the variation in crystalline size is dependent on dopant Dy3þ
concentration This was due to the increase in strain, leading to the
replacement of Ba2þions by smaller radius Dy3þions Generally,
broadening of the PXRD peaks was associated with crystallite sizes
or the strains present within the sample or both Therefore, the
WilliamsoneHall fitting method (Fig 8 (b)) [15]was utilized to
estimate the strain induced in the prepared samples and the
ob-tained results were given inTable 1
Fig 8(c) displays the diffuse reflectance spectra of the pure and
Dy3þdoped BaTiO3powders The spectra exhibited peaks at ~1071,
887, 796, 381, 364, 348 and 320 nm, which were due to the 4fe4f transition of the Dy3þions[16] The KubelkaeMunk (KeM) theory was utilized to estimate optical energy band gap of BaTiO3:Dy3þ (1e5 mol %) powders from the DRS spectra[17] The optical energy band gaps (Eg) values of the prepared powders were shown in
Fig 10(d) and inTable 1 The changes in Egwere mainly ascribed to degree of order and disorder in the matrix as well as variations in distribution of energy levels within the band gap[18]
The PL excitation spectrum of BaTiO3:Dy3þ (2 mol %) under
480 nm as emission was shown inFig 9(a) The spectrum exhibited peaks at ~350, 365, 387 and 435 nm, which were attributed to6H15/
2 / 6P7/2, 6H15/2 / 6P5/2, 6H15/2 / 4I13/2 and 6H15/2 / 4G11/2 respectively.Fig 9(b) shows the PL emission spectra of BaTiO3:Dy3þ (1e5 mol %) excited at 387 nm at RT The spectra exhibited distinct emission peaks at ~480, 574 and 637 nm, which were attributed to
4F9/2/6H15/2,4F9/2/6H13/2and4F9/2/6H11/2respectively[19] From thefigure, it was clear that peak at ~574 nm was more prom-inent as compared to other two peaks, which was due to a forced electric dipole transition The peak at ~480 nm was due to magnetic dipole transitions and is much less sensitive to the coordination environment The yellow emission peak at 574 nm (4F9/2/6H13/2) was stronger than the blue emission 480 (4F9/2/6H15/2), indicating that Dy3þwas located in a more non centro-symmetric position in
Fig 7 (a) TEM, (b) HRTEM images, (c) SAED pattern, and (d) EDAX spectra of BaTiO 3 :Dy3þ(2 mol %) powders prepared with a 5 h sonication time and 0.25% W/V barbituric acid.
Trang 8the BaTiO3host[20].Fig 9(c) shows the partial energy-level diagram
indicating the different excitation and emission mechanism of
BaTiO3:Dy3þpowder Asymmetry ratio (A21) was used to determine
the degree of distortion from the inversion symmetry of the local
environment of the Dy3þions in a host matrix[21]
A21¼
H
I2
4F9=2/6H13=2
dl H
I1
4F9=2/6H15=2
where I1and I2the intensities of a magnetic dipole transition at
480 nm and the electric dipole transition at 574 nm, respectively
The variation of A21 with varying Dy3þ concentration in
BaTiO3:Dy3þ(1e5 mol %) powder was shown inFig 10(a) and its
estimated values were listed inTable 3
The effect of doping concentration (Dy3þ) on PL emission
in-tensity in the BaTiO3host was shown inFig 10(a) It was clear from
the figure that, the PL intensity increased with an increase of
concentration of Dy3þup to 2 mol % and afterwards it diminished
The decrease in the PL intensity was due to the well-known
phe-nomenon called as a self-concentration quenching, resulting from
the resonance energy transfer between neighboring Dy3þions[22]
From energy match rule, cross-relaxation lines among Dy3þions
are responsible for population decrease of4F level as follows:
4F9=2þ6H15=2/6H9=2
6F11=2þ6F5=2 (4)
4F9=2þ6H15=2/6H7=2
4F9=2þ6H15=2/6F1=2
6H9=2
In the above process, the excitation energy was transferred from
a Dy3þion in a higher excited state to a neighboring Dy3þion and promotes the latter from the ground state to the metastable level The Dy3þions at4F9/2level undergo de-excitation through a cross relaxation process while Dy3þions in the ground state will allow the energies from Dy3þat6H15/2level simultaneously Finally, all the Dy3þ ions will go in their ground states and thus the lumi-nescence related to4F9/2level was quenched[23]
The non radiative energy transfer among Dy3þions leads to a concentration quenching effect By knowing the critical distance (Rc) between the neighboring Dy3þions, the type of the interaction mechanism can be explored[24] The calculated value of Rc was found to be ~4.47 Å and was almost equal to 5 Å, which leads to the multipoleemultipole interaction in the BaTiO3host and is the main cause for concentration quenching of Dy3þin the powder There were several types of electric multi-polar interactions, which may
be possible, namely, dipoleedipole (ded), dipoleequadrupole (deq), quadrupoleequadrupole (qeq), etc[25] Therefore, it was a
Fig 8 (a) PXRD patterns (b) WeH plots, (c) DR spectra and (d) optical band gap plot of pure and BaTiO 3 :Dy3þ(1e5 mol %) powders prepared with a 5 h sonication time and 0.25% W/V barbituric acid.
Trang 9necessity to know which type of interaction responsible in the
energy transfer between Dy3þions According to the Dexter and
Schulman theory[26], the ratio emission intensity (I) to
concen-tration of activator ion follows the equation;
I
where X; the activator concentration, Q; a constant of multi-polar
interaction and equals 6, 8, or 10 and less than 6 for dipoleedipole;
dipoleequadrupole or quadrupoleequadrupole interactions and
charge transfer mechanism respectively, and K andb; constants for
the given host lattice under the same excitation condition
LogI
whereðA ¼ log k logbÞ.Fig 10(b) shows thefitted linear curve of log (I/X) vs log (X) in BaTiO3:Dy3þ(1e11 mol %) powder and the value of the slope to be ~1.205 The calculated value Q was found
to be 6.346 and was almost equal 6 This result indicates that, the charge transfer mechanism was due to the ded interaction for the concentration quenching in the present powder
The Commission International De I-Eclairage (CIE) chromaticity co-ordinates of the BaTiO3:Dy3þ (1e5 mol %) powders were calculated and listed inTable 2 It was noticed that, the CIE co-ordinates for the present powders were located well within the white region (Fig 10(c)) The Correlated Color Temperature (CCT) was estimated by Planckian locus and their values are listed in
Table 2 The quality of the white light in terms of CCT (Fig 10(d)) was also studied using the McCamy empirical theoretical relation
[27] And the color purity of the powder was estimated according
to the work[28]and their values are shown inTable 2 These re-sults clearly show that the present powder may be quite useful for solid state lighting applications
The JuddeOfelt (JeO) theory has been widely utilized to study the radiative transitions of rare-earth ions in several host materials
[29] Various radiative properties such as J-O intensity parameters (U2&U4), emission peak wavelengths (lpin nm), radiative tran-sition probability (AT), calculated radiative (trad) lifetime, branching ratio (bR) and asymmetric ratio (A21) were estimated by using the
PL emission spectra[30] The relation between radiative emission rates and the integrated emission intensities were estimated by using the equation reported elsewhere[31]
A02;4
A01 ¼I02;4
I01 ¼ hy01
Fig 9 (a) PL excitation spectra of BaTiO 3 :Dy3þ(2 mol %) powder atlemi ¼ 480 nm; (b) PL emission spectra of BaTiO 3 :Dy3þ(1e5 mol %) powder atlexc ¼ 387 nm; and (c) Energy levels diagram of Dy3þdoped BaTiO 3 powder.
Table 1
Estimated average crystallite size, strain and energy gap (E g ) values of BaTiO 3 :Dy3þ
(1e5 mol %) powders.
Dy3þconc.
(mol %)
Crystallite size
(nm) [DeS approach]
Crystallite size (nm) [WeH approach]
Strain (10 4 )
E g (eV)
Table 2
Photometric characteristics of doped BaTiO 3 :Dy3þ(1e11 mol %) powders.
BaTiO 3 :Dy3þconc.
(mol %)
1 0.33403 0.34009 0.20834 0.47728 5427 92.52
2 0.33459 0.34072 0.20848 0.47769 5403 90.48
3 0.33464 0.34082 0.20849 0.47773 5401 94.85
4 0.33468 0.34053 0.20863 0.47759 5399 89.78
5 0.3344 0.34016 0.20857 0.47737 5411 90.63
Trang 10where I0 eJand hn0 eJ; integrated emission intensity and energies
corresponding to transition4F9/2/6HJ(J¼ 15/2, 13/2 and 11/2)
respectively
The radiative emission rates A0 eJ(J ¼ 2, 4) related to forced
electric dipole transitions can be obtained and written as a function
of the J-O intensity parameters:
Að0JÞ¼ 64p4w3
J
3hð2J þ 1Þ
n
n2þ 22 9
X
l¼2;4
UlD
7F9=2UðlÞ6HJE2
(10)
where Að0JÞ; the coefficient of spontaneous emission, e; the
elec-tronic charge,wJ; the wave number of the corresponding
transi-tion, h; the Planck's constant, Smd; the strength of the magnetic
dipole and n; the RI of the prepared sample.D
4F9=2UðlÞ6HJE2
; squared reduced matrix element of Dy3þions and were 0.2457 and 0.4139 for J¼ 2 and 4 respectively and these values were inde-pendent of the chemical environment Thus, by using Eqs.(9) and (10), the values of U2 and U4 were calculated and listed in
Table 3 The JeO intensity parameters (U2andU4) for different host matrices have been observed[15]and are listed inTable 4 The total radiative transition probability (ATðjJÞ) can be calcu-lated and expressed as
ATðjJÞ ¼X
J 0
The radiative lifetime (tradðjJÞ) of an excited state in terms of
ATðjJÞ is given by
Fig 10 (a) Effect of concentration of Dy3þon the 574 nm emission and the variation of asymmetric ratio in BaTiO 3 powders, (b) Relation between log(x) and log (I/x), (c) CIE and (d) CCT diagram of BaTiO 3 :Dy3þ(1e5 mol %) powders.
Table 3
JuddeOfelt intensity parameters (U2 ,U4 ), Emission peak wavelengths (lp in nm), radiative transition probability (A T ), calculated radiative (trad ) lifetime, branching ratio (bR ) and asymmetric ratio (A 21 ) of BaTiO 3 :Dy3þ(1e5 mol %) powder (lex ¼ 387 nm).
BaTiO 3 :Dy3þconc.
(mol %)
JuddeOfelt intensity parameters (10 20 cm 2 )
Emission peak wavelengthlp in nm
A T (s1) trad (ms) bR A 21