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Ba3Ca2(PO4)3F, having been proven beneficial for ancient geological surveys, was also found to be an efficient fluorescence emitter when doped with various rare-earth and transition ions. Advancing the respective properties further, dysprosium (Dy3+) was added as an activator into the Ba3Ca2(PO4)3F host lattice. The Dy ion in its trivalent form possesses emission in two regions, blue at 481 nm and green at 575 nm, opening a new window towards its plausible use in white-light-emitting diode (LED) lighting appliances. Subsequent analyses including x-ray diffraction, Rietveld refinement, photoluminescence, and lifetime observed in milliseconds (ms) revealed a similar nature of the decay curves as given in the literature. Further, a CIE coordinate calculation predicted near-ideal white light emission. [ABSTRACT FROM AUTHOR]

Calcium molybdate (CaMoO 4) and Dy3+ doped CaMoO 4 (Dy3+ = 0.5, 1, 1.5, 2 and 2.5 at.%) nanoparticles were successfully obtained by mechanochemical approach. The influence of Dy3+ ion concentration on the structure, morphology, and photoluminescent properties were investigated. The CaMoO 4 and Dy3+ doped CaMoO 4 phases with tetragonal structure were completely prepared after 30 min milling time with applied milling speed of 850 rpm. TEM analysis shows that the synthesized samples consist of mainly spherical particles with narrow particle size distribution. According to both XRD and TEM analysis, the average particles size is below 40 nm. The UV–vis absorption spectra show one peak at 240–245 nm. The calculated optical band gap of pure CaMoO 4 is 3.96 eV and it decreases to 3.65 eV with increasing the concentration of Dy3+ ion up to 2.5 at %. The excitation spectra of the Dy3+-doped CaMoO 4 samples contain absorption peaks corresponding to the MoO 4 group and to the Dy3+ ion. The green and blue light emissions were observed for pure CaMoO 4 and Dy3+ doped CaMoO 4 samples under different wavelengths excitation (250 and 350 nm) typical for absorption of the host matrix. Emission spectra of all doped powders consist of the characteristic peaks of Dy3+ in the blue (∼480 nm) and yellow (∼575 nm) regions which are assigned to the 4F 9/2 → 6H 15/2 and 4F 9/2 → 6H 13/2 transitions, respectively. The weak peak at 660 nm also is observed due to 4F 9/2 → 6H 11/2 transition of Dy3+ ion. The highest photoluminescence emission intensity was detected when the sample is doped with 1.5 at.% Dy3+ concentration. It was found that the color coordinates (x and y) of 1.5 at.% and 2 at.% Dy3+-doped CaMoO 4 fall close to the white light region in the CIE diagram. The results indicate that the mechanochemically obtained Dy3+ doped CaMoO 4 nanoparticles can find application in different optical instruments. [ABSTRACT FROM AUTHOR]

CaWO4 nanoparticles were obtained by facile mechanochemical synthesis at room temperature, applying two different milling speeds. Additionally, a solid-state reaction was employed to assess the phase composition, structural, and optical characteristics of CaWO4. The samples were analyzed by X-ray diffraction (XRD), transition electron microscopy (TEM), and Raman, infrared (IR), ultraviolet–visible (UV–Vis) reflectance, and photoluminescence (PL) spectroscopies. The phase formation of CaWO4 was achieved after 1 and 5 h of applied milling speeds of 850 and 500 rpm, respectively. CaWO4 was also obtained after heat treatment at 900 °C for 12 h. TEM and X-ray analyses were used to calculate the average crystallite and grain size. The Raman and infrared spectroscopies revealed the main vibrations of the WO4 groups and indicated that more distorted structural units were formed when the compound was synthesized by the solid-state method. The calculated value of the optical band gap of CaWO4 significantly increased from 2.67 eV to 4.53 eV at lower and higher milling speeds, respectively. The determined optical band gap of CaWO4, prepared by a solid-state reaction, was 5.36 eV. Blue emission at 425 (422) nm was observed for all samples under an excitation wavelength of 230 nm. CaWO4 synthesized by the solid-state method had the highest emission intensity. It was established that the intensity of the PL peak depended on two factors: the morphology of the particles and the crystallite sizes. The calculated color coordinates of the CaWO4 samples were located in the blue region of the CIE diagram. This work demonstrates that materials with optical properties can be obtained simply and affordably using the mechanochemical method. [ABSTRACT FROM AUTHOR]

Y2Sr3B4O12 phosphors doped with europium ions were synthesized by a modified conventional solid-state reaction method. Characterizations of the prepared samples, viz., X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL), and Commission Internationale de I'Eclairage were studied. The XRD analysis confirmed the formation of mixed phase due to polyborate and has a hexagonal crystalline yttrium orthoborate phosphor. SEM images showed the irregular morphology of the sample. The grain size distribution was broad and the average size was found to range from 2 μm to 100 nm. PL measurements showed excitation and emission characteristics of the prepared phosphor with different concentrations of the doping ion. From the emission spectra, it was clearly observed that the emission intensity of the magnetic dipole was higher than that of electric dipole transition owing to the Eu3+ ions occupying a higher symmetry site in the Y2Sr3B4O12 host. The intensity of PL increased with increasing concentration of the doping ion up to 2.0 mol.%; after that, the PL intensity decreased owing to the concentration-quenching phenomenon. The results indicated that Y2Sr3B4O12:Eu3+ phosphors can be selected as a potential candidate for solar cell/photovoltaic application. [ABSTRACT FROM AUTHOR]

Current study is aimed at evaluating Eu-doped barium-bismuth phosphate glasses as potential visible laser medium operating in red spectral region. Samples with composition x Eu 2 O 3 –20BaO–20Bi 2 O 3 -1.5Al 2 O 3 -(58.5- x)P 2 O 5 (x = 0, 0.5, 1.0, 1.5) were prepared using melt-quenching technique. Physical parameters, such as, density, molar volume, oxygen packing density, rare-earth ion concentration, inter-nuclear distance and field strength were evaluated. Thermal stability of prepared glass samples was observed using Thermogravimetric Analysis (TG). The influence of rare-earth oxide content on glass transition temperature T g , crystallization temperature T c and onset of crystallization temperature T x was studied through Differential Thermal Analysis (DTA). Optical band gap and related optical properties were evaluated from absorption spectrum recorded in the range 225–1000 nm. Judd-Ofelt parameters, branching ratio, radiative lifetime, emission cross-section and other radiative properties were evaluated from photoluminescence emission spectrum in the range 500–750 nm. High value of emission cross-section observed for transition 5D 0 →7F 4 in 0.5-EuBiPBa sample signifies its potential use in the development of visible lasers. [ABSTRACT FROM AUTHOR]

We discuss new features of Sm3+-doped LaCePO4 phosphor as a potential candidate for display applications. Mainly, the traditional modified solid-state synthesis technique was used to prepare the samples. The X-ray diffraction technique was used for the structural studies. LaCePO4:Sm3+ phosphor production was verified by Fourier transform infrared studies. It was customary to use scanning electron microscopy to learn more about the morphology of the prepared samples. Additionally, photoluminescence (PL) analysis of the phosphor samples was presented for different doping ion concentrations with various excitations. In the presence of Sm3+, LaCePO4 emits powerful blue and orange emissions. In-depth research was carried out on the transitions between the concentration quenching effect and the doping ion. The distribution of the spectral region estimated from PL emission spectra was shown in the 1931 Commission International de l'Éclairage (x, y) chromaticity coordinates and was located (0.20, 0.22) in the blue region. According to our research, as-prepared phosphor may find useful application in display devices, especially because of its blue and orange content. [ABSTRACT FROM AUTHOR]

The study examines the optical and electrical characteristics of n-ZnO:Al (AZO) thin films that were deposited on p-Si using the sol-gel dip-coating process, with thicknesses ranging from three to six cycles. The I-V characteristics of the diode device exhibited a high and low current under forward and reverse bias, respectively. The ideality factors were found to decrease from 2.78 to 2.13 with an increase in the number of layers from 3C to 6C. However, it was revealed that the barrier height increased from 0.72 to 0.79 eV. Similarly, the rectification ratio increased from 3196 at ±4 V to 5253 at ±4 V with an increase in the thickness of the emitter layer. Some diode parameters were calculated according to the thermionic and Chueng models and found to be in a range comparable to the literature. The optical study based on photoluminescence under UV excitation showed typical emission spectra of n-AZO/-Si heterostructure characterized by a high emission band around 389 nm, which is due to the recombination of excitons (e-=h+). The various intrinsic defects present in ZnO-doped Al thin films are attributed to the broad emission band in the visible range. The chromaticity study with color properties indicated that the correlated color temperature value of the sample 3C (1380 K) falls in the warm white light region. However, the correlated color temperature value of sample 6C (4454 K) is located in the cool white light source region, which is more suitable as an LED lighting source. It was found that by increasing the emitter layer thickness, the correlated color temperature value of the 6C sample is getting closer to 6504 K - the Commission Internationale de l'Eclairage (CIE) standard for daylight (D65). However, unlike the Duv value of the 6C sample (0.011), the one of the 3C sample (0.0032) is located within the acceptable shift range (±0:006). Based on this study, these heterostructures might be an appealing option for manufacturing W-LEDs with n-UV/blue LED chips as the excitation source for use in displays and lighting. [ABSTRACT FROM AUTHOR]

Antimony-lead-oxyfluoroborate (SbPbOFB) glasses doped with various concentrations of Eu3+ ions were prepared by employing melt quenching and their luminescence activity was characterized using different spectroscopic methods such as optical absorption, photoluminescence (PL) excitation, PL emission, and PL decay. The Raman spectrum was recorded for an un-doped SbPbOFB glass to identify various functional groups present. The optical absorption spectra recorded for Eu3+ ion-doped SbPbOFB glasses showed five bands corresponding to 7F0→5L6, 7F0→5D2, 7F1→5D1, 7F0→7F6 and 7F1→7F6 transitions. The PL spectra measured under 394-nm excitation wavelength show five peaks corresponding to 5D0→7F0, 5D0→7F1, 5D0→7F2, 5D0→7F3 and 5D0→7F4 transitions at 578, 592, 613, 652 and 701 nm, respectively. Among them, that pertaining to the 5D0→7F2 transition appeared at 613 nm in the visible red region showing relatively high intensity. The Judd-Ofelt (J-O) parameters evaluated from the absorption spectral data are correlated with the prominent emission spectral features such as 5D0→7F1 (592 nm), 5D0→7F2 (613 nm) and 5D0→7F4 (701 nm) to estimate radiative properties such as transition probabilities (AR), branching ratios (βR) and emission cross sections (σ se). Quantum efficiency (η%) of the prepared glasses was estimated by correlating the radiative lifetimes with the experimental lifetimes measured from the PL decay spectral features. The PL emission spectral features are used to estimate the CIE color coordinates (x, y) of the studied glasses. The measured βR, σ se, η%, and the CIE coordinates estimated for the studied glasses revealed their suitability for visible red light-emitting device applications. [ABSTRACT FROM AUTHOR]

A novel tetradentate Schiff base ligand, 3-((2-(-(1-(2-hydroxyphenyl)ethylidene)amino)ethyl)imino)-2-pentone and its Ni(II) complex have been synthesized by green chemical, ultrasonication method. The ligand and metal complex were characterized analytically and spectroscopically by elemental analysis, HRMS, IR, 1H NMR, 13C NMR, UV–vis absorption spectroscopy, molar conductance, and magnetic susceptibility measurements. Powder XRD analysis was done to show the crystalline nature of the samples. The surface morphology and size of both ligand and complex were monitored by SEM and TEM microscopic techniques. Based on the various physicochemical measurements and spectral analysis, Ni(II) complex is assigned to an octahedral geometry. The optical bandgap energy, fluorescence spectrum lifetime analyses and chromaticity studies were accomplished to encounter the possibilities of optical applications. The fluorescence nature of both ligand and complex was found to be in the visible range. Optical bandgap energy values fall in the range of semiconductor materials. The chromaticity studies give the CIE 1931 coordinates and colour correlation temperature values of the samples. The ligand and the Ni(II) complex were screened for biological activities such as antimicrobial, antioxidant, and larvicidal activities. The results implied that the Ni(II) complex shows better antimicrobial, antioxidant and larvicidal activities than the free ligand.

Ce3+/Dy3+ (CDBB) and Ce3+/Sm3+ (CSBB) co-doped barium borate glasses were prepared by melt quenching technique. These glasses are made of B2O3 as a glass former and contain the luminescence activators of Ce3+, Dy3+ and Sm3+ rare earth ions. FT–IR spectra figured out the presence of various stretching and bending vibrations of borate groups in the prepared glasses energy dispersive X-ray spectroscopy (EDX) combined with SEM, enabled the study of near-surface elements and their quantities at various locations, resulting in a sample map. Optical absorption, optical band gap energy (Eg), Urbach energy (ΔE) and the linear refractive index (n) were calculated from the wavelength range observed from 1200 to 200 nm using UV-Vis spectrometer. The emitting wavelengths including 435 (blue), 560 (green), 600 (reddish orange) and 645 nm (red) were observed simultaneously in the luminescent spectra of CSBB at the prominent excitation wavelength of 400 nm, and the mixture of these four emissions yields the white light emission. Further, the energy transfer process occured due to sensitizer-activator ion pairs via a non-radiative mechanism. Notably, co-doping Ce3+and Sm3+ ions increased red emission by efficiently transferring energy from Ce3+ to Sm3+ in the CSBB glass. The CIE chromatograph coordinate (x = 0.339, y = 0.331) of the emission from the CSBB glass is close to the standard white-light illumination (0.320, 0.348). The measured excitation purity (Pe) and colour purity (Pc) of these glasses revealed the quality of their light emission. Furthermore, the synthesized CDBB glasses have reasonable non-linear optical (NLO) properties with stronger SHG intensity of 11.0 mV. [ABSTRACT FROM AUTHOR]

Eu3+/Nd3+ co-doped multicomponent borosilicate glasses (ND1E: 10BaO +10ZnF 2 +10K 2 O +20SiO 2 +(49-x) B 2 O 3 +1Nd 2 O 3 +xEu 2 O 3) were prepared by conventional melting and rapid quench technique to evaluate the effect of Eu3+ ions in the Nd3+ doped glasses. Thermal stability, structural and spectroscopic characteristics of the ND1E glasses were investigated by using DSC, XRD, FTIR, Optical absorption, excitation and emission measurements. The Judd – Ofelt (JO) analysis is implemented to the absorption spectrum of the prepared glassy matrix in order to identify their potential applicability in lasing devices. Enhancement of 7F 0 → 5L 6 band (394 nm) with the increasing concentration of Eu3+ ion in the Nd3+ excitation spectra (λ emi = 1060 nm) reveals the possibility of obtaining the characteristic fluorescence spectra of Nd3+ ion with the typical excitation wavelengths (Nd3+ = 584 nm and Eu3+ = 394 nm) of both rare earth ions and it is further verified from the emission spectrum. This interesting luminescence effect of showing excellent visible and NIR emission under 394 nm excitation mainly attributes the energy transfer mechanism between the RE3+ ions and the reason underlying this effect is discussed in detail with the help of partial energy level diagram. Energy transfer efficiency between the Eu3+ and Nd3+ ions were evaluated by using the radiative lifetimes of the prepared glasses. Also, a comparison of radiative properties and lasing characteristics of Eu3+/Nd3+ co-doped glasses with other Nd3+ glasses are reported. The emission intensities were characterized using CIE chromaticity diagram and the observed CIE coordinates shows a shift towards reddish – orange region with the increase in Eu3+ concentration. The quantum efficiency of the prepared glasses was determined experimentally. The obtained results suggest that the ND1E glassy system can be considered as a potential candidate for visible and NIR luminescence applications. Image 1 [ABSTRACT FROM AUTHOR]

Visible Light Communication (VLC) technology uses white Light Emitting Diodes (LED) for providing illumination and communication at the same time. White LEDs have excellent illumination properties but their communication properties need improvement. This article proposes a way how to evade the communication limitations of white LEDs. A part of original white LED spectrum is suppressed by an optical filter. Then the suppressed part is replaced by another LED. The correct choice of suitable LED enables to reconstruct the original spectrum. This solution removes the limitations because the white LED emits continuously. Data are carried by the communication LED only. The evaluation of reconstruction of original white light is measurement of the colour coordinates x and y. Furthermore, the communication properties of this transmitter were tested and obtained results are shown in this paper. EVM parameter was measured.

A series of Dy3+ doped aluminoborosilicate glasses with general formula 20SiO 2 -(40-x) B 2 O 3 –10Al 2 O 3 –20NaF 2 –10ZnO-xDy 2 O 3 (x = 0, 0.1, 0.5, 1.0. 1.5, 2.0 and 2.5 mol %) were prepared by melt-quenching method. The FTIR analysis confirms the presence of stretching and bending vibrations of BO 4 , BO 3 and SiO 4 units in the prepared glasses. DTA results show that Tg is decreasing with addition of Dy3+ ions in the glass system. Theoretically calculated mechanical properties such as elastic modulus, bulk modulus, shear modulus and Poisson's ratio suggest the increase in mechanical stability of glasses with dysprosium addition. Also experimental analysis carried out using Vicker's microhardness suggests glass stability with applied loads. Absorption spectrum shows twelve bands that exist due to transition from 6H 15/2 level to different excited levels. Nephelauxetic ratio and bonding parameter calculated shows decreasing ionicity of glasses with increase in Dy3+ ions. Judd-Oflet parameter calculated for all the glasses follow the trend Ω 6 > Ω 4 > Ω 4. Luminescence study shows three emission peaks having transitions from 4F 9/2 → 6H 15/2 (blue), 4F 9/2 → 6H 13/2 (yellow) and 4F 9/2 → 6H 11/2 (red). Radiative parameters calculated suggest higher stimulated emission cross-section for present glasses having 4F 9/2 → 6H 13/2 transition. The decay measurement for all the glass samples were recorded with an excitation at 350 nm and monitoring emission at 575 nm corresponding to the 4F 9/2 → 6H 13/2 transition and decay curves were fitted to bi-exponential fit. The CIE colour chromaticity coordinates were determined using CIE chromaticity diagram and the values were found to be in close proximity with the standard white light (0.33. 0.33) for all the glasses. Further colour correlated temperature values were found to lie in the near bright white region with CCT around ~4000 K. • Various concentrations of Dy3+-doped SiO 2 –B 2 O 3 –Al 2 O 3 –NaF–ZnO glasses were synthesized. • Mechanical properties of these glasses were studied along with experimental analysis. • Optical bandgap and Urbach energy of these glasses were calculated. • Energy transfer mechanism and radiative parameters were studied. • All Dy3+- doped glasses CIE (x, y), and CCT values represent the bright white light region. [ABSTRACT FROM AUTHOR]

Abstract Individually and doubly doped Ce3+/Eu3+:CaLa 2 ZnO 5 (CLZO) phosphors were synthesized by a conventional sol-gel method as highly efficient luminescence-based phosphor materials. X-ray diffraction and field-emission scanning electron microscope were used to analyze the structural and morphological properties. The elements and their ionic states were determined by energy-dispersive spectroscopy and X-ray photoelectron spectroscopy studies, respectively. The assignment of the functional groups was analyzed using Fourier-transform infrared spectral studies. Bright red emission was obtained from Eu3+-doped CLZO phosphors due to its hypersensitive transition of 5D 0 →7F 2 at 626 nm with a royal blue excitation source. By increasing the Eu3+ content, the emission features were rapidly enhanced. Moreover, the red emission related to Eu3+ was further increased by the addition Ce3+ ions as a co-dopant along with Eu3+ in the CLZO matrix due to energy transfer. The energy migration from Ce3+ to Eu3+ is systematically illustrated by several fluorescent approaches, such as photoluminescence analysis, spectral overlap, CIE coordinates, lifetime dynamics, luminescence quantum yields, and color purity. Surprisingly, the CIE coordinates were very close to the NTSC coordinate values. Based on the results, these phosphors could be suitable materials for luminescence-based optoelectronic devices. Highlights • Dazzling red emission is obtained from Ce3+/Eu3+: CaLa 2 ZnO 5 phosphors. • Red emission of Eu3+ was remarkably enhanced by co-doping with Ce3+. • Effective sensitization of Ce3+ ions and enhanced quantum yield have been elucidated. • Energy transfer from Ce3+ to Eu3+ ions by several fluorescence dynamics. • Meritorious CCT, CIE coordinates and high red color purity have obtained. [ABSTRACT FROM AUTHOR]

Visible Light Communication (VLC) technology uses white Light Emitting Diodes (LED) for providing illumination and communication at the same time. White LEDs have excellent illumination properties but their communication properties need improvement. This article proposes a way how to evade the communication limitations of white LEDs. A part of original white LED spectrum is suppressed by an optical filter. Then the suppressed part is replaced by another LED. The correct choice of suitable LED enables to reconstruct the original spectrum. This solution removes the limitations because the white LED emits continuously. Data are carried by the communication LED only. The evaluation of reconstruction of original white light is measurement of the colour coordinates x and y. Furthermore, the communication properties of this transmitter were tested and obtained results are shown in this paper. EVM parameter was measured. [ABSTRACT FROM AUTHOR]

The Sr 0.95 Ba 0.05 La 2-x O 4 :xRE 3+ (RE = Eu,Er,Ce and Ho) phosphors are synthesized through high temperature solid-state reaction method at steps of 1000, 1100, 1200 °C. The impact of temperature on phase structures, functional group, luminescence properties and decay lifetime are investigated. The prepared Sr 0.95 Ba 0.05 La 2-x O 4 phosphors exhibit abundant luminescent properties with doping of different RE 3+ ions under ultraviolet–visible and infrared excitation (980 nm) excitation. The Sr 0.95 Ba 0.05 La 2-x O 4 :xEr 3+ particles characterize red emission ( 4 F 9/2 → 4 I 15/2 ) through up-conversion emissions at 980 nm NIR irradiation. The chromaticity (CIE 1931) colour coordinates of the titled phosphors have also been evaluated. The merits of multicolor emissions in the visible region endow the synthesized material by UV irradiation reveals potential candidate in the field of light display systems, lasers and optoelectronic devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • New red emitters based on ring-opened rhodamine derivatives (CR1 and CR2) were synthesized and characterized. • Single novel mixture CR2:CG:CB produced pure white light emission with CIE coordinates of (0.32, 0.33). • White light mechanism proposed a highly efficient FRET system from spectral overlap integral and Förster distance. • RGB emitters exhibit good thermal stability and efficient charge transfer from electrochemical and DFT studies. The mixture of red, green, and blue (RGB) organic fluorophores in a single blend is becoming more relevant to produce metal-free, low cost and color tunable white light emission. Herein we describe the combination of pure organic molecules based on the coumarin and rhodamine frameworks that generated broad or multi-band emission in both solution and solid forms. The derivatives of coumarin (CB), furocoumarin (CG) and rhodamine (CR1 and CR2) were synthesized and characterized using 1H NMR, 13C NMR, FTIR and ESI-MS spectroscopic techniques. The "closed-form" of the synthesized rhodamines have been further elucidated with the single crystal X-ray analysis. Their photophysical, thermal stability and electrochemical properties have been investigated, accompanied by DFT calculations to assess the plausible mechanism responsible for white light along with their eminent characteristics. Single mixture of ethanol-solubilized CR2 : CG : CB in the ratio of 3:10:3 showed extremely pure white light fluorescence with CIE coordinates of (0.32, 0.33) when excited at 360 nm while CR1 : CG : CB revealed almost pure white light (0.27, 0.32) in the ratio of 1:2:1 when excited at a much longer wavelength (λ ex = 395 nm). The results obtained are very encouraging in such a way that only minimal proportions of the blue and green fluorophores are required in the single mixture for a highly efficient FRET system when combined with the newly synthesized rhodamine derivatives. The ratio differences can be down to 30–42 % as compared to white light mixture with the commercial red R640. Furthermore, all of the synthesized RGB components exhibit reasonably good thermal stability with onset of decomposition above 210 °C, endowing their suitability for general applications of optoelectronic devices. The HOMO-LUMO energy band gaps from the cyclic voltammetry and geometrical optimized structures of the ground state are generally in nice agreement. White light emission was also generated when the polymer mixtures containing each RGB emitters was coated on a commercial UV-LED, demonstrating potential low cost and purely organic device set-up. [ABSTRACT FROM AUTHOR]

• P 2 O 5 -Gd 2 O 3 /GdF 3 -BaO-ZnO were synthesized by traditional melt quenching method. • The JO-parameter trend for both the glasses is Ω 2 > Ω 4 > Ω 6. • The FWHM (full-width-half maximum) of ZBaOEr and ZBaFEr is 51 nm and 45 nm • Bandwidth-quality where evaluated that are 249 and 274 for ZBaOEr and ZBaFEr. • The CIE color coordinates for various concentrations fall emit yellowish-green light. We develop two Er3+-ions-doped Phosphate glass systems, 69 P 2 O 5 -10Gd 2 O 3 -10BaO-10ZnO-1Er 2 O 3 and 69 P 2 O 5 -10GdF 3 -10BaO-10ZnO-1Er 2 O 3 , labeled as ZBaFEr and ZBaOEr, respectively, by the melt-quenching technique and study systematically their physical, optical, and luminescence properties such as densities, refractive indexes, ultraviolet-visible near-infrared (UV-Vis-NIR) absorption, photoluminescence spectra in Vis-NIR region, CIE coordinates and lifetime. The absorption spectra revealed the Er3+ peaks at 378, 405, 451, 489, 522, 652, 803, 978, and 1537 nm, attributed to the transition from 4I 15/2 level to 4G 11/2 , 2G 9/2 , 4F 5/2 , 4F 7/2 , 2H 11/2 , 4F 9/2 , 4I 9/2 , 4I 11/2 and 4I 13/2 levels, respectively. We find that at 380-nm excitation, the emission peak at 1543 nm in the near-infra-red (NIR) region has a higher intensity for ZBaFEr than for the ZBaOEr. Furthermore, we employ the Judd-Ofelt (JO) and McCumber theory to study the stimulated emission cross-section for 4I 13/2 →4 I 15/2 transitions of Er3+ ion. We find the bandwidth-quality [FWHM x σ emi (λ)] to be 249 and 274 for ZBaOEr and ZBaFEr, respectively. The NIR-emission for both glasses covers the S-, C- and L -band of low-less-communication-window. The present results suggest that these glasses can be potentially used in optical amplifiers and tunable lasers. [ABSTRACT FROM AUTHOR]

• Dysprosium doped alkali lead bismuth borate glasses were prepared. • Under 387 nm, the glasses exhibit intense yellow and blue emission. • Calculated CIE coordinates fall in yellowish white region of visible spectrum. • Lifetime decay from 4F 9/2 excited state found to display non-exponential behavior. A series of different modifiers infused Dy3+ ions doped Alkali lead bismuth borate glasses were synthesized and their potential for photonic applications were analyzed through some mandatory characterizations like XRD, FTIR, Raman, optical absorption, photoluminescence and decay measurements. In this work, effort was taken to show the structural differences that occur in the host network when different modifiers were introduced into it. Amorphous nature of all the glasses was proven with XRD profile and the absorption of Dy3+ ions to different excited states was observed. The Judd-Ofelt (JO) parameters for the glasses follows the trend as Ω 2 > Ω 4 > Ω 6 and from the luminescence spectra, emissions corresponding to blue (4F 9/2 → 6H 15/2), yellow (4F 9/2 →6H 13/2) and red (4F 9/2 →6H 11/2) color were observed while exciting the prepared glasses at 387 nm. Radiative parameters like transition probability, stimulated emission cross-section, branching ratios and radiative lifetime were calculated using JO parameters and refractive index values. Yellow to blue intensity ratio (Y/B), CIE chromaticity coordinates and correlated color temperature (CCT) values are calculated using the emission spectra to evaluate the emitted light. The obtained CIE values were found to be in excellent proximity with the standard white light (0.33, 0.33). The lifetime of the 4F 9/2 excited state was measured and found to exhibit non-exponential behavior. The obtained results suggest the utility of the glasses for potential w-LED applications. [ABSTRACT FROM AUTHOR]

Terbium (Tb3+) ions doped calcium aluminozincate (CAZ) phosphors with different concentration of Tb3+ ions (0.0–5.0 mol%) have been successfully prepared by sol-gel method. The crystal phase analysis and morphology of the as prepared phosphors have been studied from X-ray diffraction (XRD) patterns and field emission scanning electron microscope (FE-SEM) image. The luminescence behaviour of Tb3+ doped CAZ phosphors have been studied relative to variable dopant ion concentration. The intense emission has been observed at 543 nm under 238 nm excitation for all the phosphors. The decay curve analysis manifests the energy transfer as a consequence of dipole-dipole interaction between Tb3+ ions in the host. The colorimetric property has been understood on the basis of evaluated CIE color coordinates. The systematic study of Tb3+ doped CAZ phosphors determine the potential utility of these phosphors in lighting and display applications. Partial energy level diagram of Tb3+ ion in CAZ phosphor. Image 1 • Tb3+ ions doped calcium aluminozincate phosphors synthesized by sol-gel method. • Transition from 5D 3 and 5D 4 levels exhibit emission in blue and green regions. • Energy transfer from 5D 3 to 5D 4 energy level at 4.0 mol%. enhance green emission. • Color tunability is achieved in Tb3+ doped as synthesized phosphors. • These studies suggest the utility of above mentioned phosphors in lighting and display devices. [ABSTRACT FROM AUTHOR]

Neste trabalho, são apresentados os conceitos básicos de calibração radiométrica, fotométrica e colorimétrica de fontes de luz, os quais foram aplicados na prática a três diodos emissores de luz (LEDs) comerciais, utilizados para compor as diferentes sensações de cor que o olho humano percebe na região visível do espectro eletromagnético. Para tanto, um sistema experimental composto por um circuito de controle de corrente para os LEDs e uma esfera integradora artesanal foi montado tanto para a calibração radiométrica e fotométrica inicial quanto para a obtenção de um conjunto de combinações de intensidade e de espectros associadas a diferentes coordenadas colorimétricas CIE (Commission internationale de l'Eclairage). Dessa forma, é possível que o leitor compreenda, de uma forma bastante simples, o processo de composição de cores de um elemento de imagem (pixel) de um monitor ou tela colorida.