Chromaticity Color Coordinates Research Articles

Structural, optical, and thermal traits of Sm³⁺-doped SrB₂O₄ phosphors for solid-state lighting applications

We synthesized Sm³⁺-doped SrB₂O₄ phosphors through a solid-state reaction method, varying the Sm³⁺ doping concentrations. Structural and morphological characteristics of material were investigated using Fourier-transform infrared spectroscopy (FTIR), X-Ray Diffraction (XRD) and scanning electron microscopy (SEM). Optical transitions were analyzed by recording the diffuse reflectance spectroscopy, while photoluminescent (PL) spectra were used to evaluate luminescence properties. The PL spectra revealed a strong orange emission at 598 nm under 402 nm excitation. The optimal Sm³⁺ doping concentration was determined to be 0.02 mol, beyond which concentration quenching occurred. This quenching is attributed to exchange-type interactions, which facilitate non-radiative energy relaxation. The CIE color chromaticity coordinates of all the synthesized phosphors fell within the orange region of the chromaticity diagram. Temperature dependent photoluminescence revealed lower activation energy and phonon energy. Thermal quenching temperature was calculated which is inline with commercially available LEDs. All of these results indicate the candidature of SrB2O4 phosphor doped with Sm3+ ions for solid state lighting and optical thermal sensing applications.

Spectroscopic investigation of co-formers on Dy3+ ions activated Barium comprised zinc borate glasses for enhancing the solid-state laser applications

The purpose of the existing research is to analyze the luminescence behavior on a set of different co-formers involved Dy3+ ions activated Barium comprised zinc borate glasses fabricated through the utilization of usual melt quenching technique with a glass composition of 64B2O3+20ZnF2+15BaO+1Dy2O3 & 44B2O3+20A+20ZnF2+15BaO+1Dy2O3 (where A = 0, P2O5, TeO2, Bi2O3). Their structural, optical, luminescence and decay behavior were scrutinized by several respective characterization techniques. Some of the physical properties were calculated by utilizing the corresponding formulae. Besides, the bonding parameter and oscillator strength estimation alongside Judd-Ofelt parameter are also computed to find out the radiative properties from luminescence spectra. From these analyses, ionic nature of the glass network was confirmed. The spectroscopic intensity parameter follows the tendency Ω2>Ω6>Ω4. This higher value of Ω2 is owing to the larger oscillator strength value and signalizing that Dy3+ ions are completely doped into the glass network. Among all the as- quenched samples, BZfBaT:Dy glass possesses high stimulated emission cross-section and holds high optical gain width value which implies that the glass is a perfect candidate intended for laser utilization. By utilizing its emission spectra, the colour chromaticity coordinates (x, y), colour purity, colour correlated temperature (CCT), and Y/B intensity ratio were investigated by means of CIE 1931 diagram and confirmed the light emitting capability. Decay curve displays well-fitting with the exponential fit and the efficiency (ɳ) for the BZfBaP:Dy glass is found to be 61 % and possesses high optical gain signalizing that the material is a perfect choice for optoelectronic applications.

Surfactant-Assisted Förster Resonance Energy Transfer from a Quantum Dot Complex for Highly Stable White Light Emission.

Herein we report the fabrication of a surfactant modified quantum dot complex (S-QDC, having λem = 485 nm) nanocomposite (composed of cetyltrimethylammonium bromide surfactants and a zinc-quinolate complex attached ZnS quantum dot), the donor capability of S-QDC in Förster resonance energy transfer (FRET) with an acceptor organic molecule (λem = 573 nm), and finally their utilization in the FRET-based white light emission having features near to mid-day sunlight. The Förster distance, energy transfer efficiency, donor-acceptor distance, number of binding sites, and binding constant are evaluated to be 3.48 nm, 85.74%, 2.58 nm, 0.94, and 1.87 × 104 M-1, respectively, for the current electrostatically driven FRET pair. The solid polymer coated FRET pair composite emits white light having chromaticity color coordinates of (0.33, 0.33) and correlated color temperature of 5350 K and also shows long-term atmospheric white luminescence stability up to 30 days, photostability, and thermal stability with preservation of their pristine morphology.

A novel photocatalytic activity of Bi2S3 nanoparticles for pharmaceutical and organic pollution removal in water remediation

In recent times, there has been a surge of interest in the unique characteristics and possible applications of nanoparticles in various fields, including environmental clean-up. The contamination of water sources with pharmaceutical and organic substances has emerged as a significant environmental concern. Semiconductor nanoparticles, particularly Bi2S3 nanoparticles, have garnered considerable attention due to their efficacy and environmentally friendly nature in advanced oxidation processes (AOPs). These nanoparticles have shown remarkable photocatalytic abilities in the destruction of pollutants when exposed to UV–visible light. This study covers the production, characterization, and degradation of Bi2S3 nanoparticles in relation to organic and pharmaceutical contaminants. By utilizing co-precipitate methods, it becomes possible to precisely manipulate the size, shape, and composition of the nanoparticles, which are crucial factors in determining their catalytic effectiveness. The created nanoparticles are then examined using various analytical techniques, such as Powder X-ray Diffraction (P-XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), UV-visible spectroscopy, Photoluminescence study (PL), colour chromaticity coordinates (CIE), and Dynamic light scattering study (DLS). The catalytic capability of the synthesised compounds was compared to the degradation of Picric acid and paracetamol as model pollutants. The observed photocatalytic activity of these nanoparticles indicates their potential in water purification and environmental clean-up. The findings suggest that incorporating these nanoparticles into practical systems for pollutant degradation is feasible and can be applied in diverse scenarios. The results shed light on the efficient utilization of Bi2S3 nanoparticles as photocatalysts for the oxidation of drugs and organic contaminants. By utilizing Bi2S3 nanoparticles, the elimination of pharmaceutical and organic pollutants from water sources becomes achievable, thereby contributing to the preservation and safeguarding of the environment and public health.

Mixed colors by combustion of mixed homogeneous pyrotechnics and heterogeneous charges

AbstractThe combustion of mixed homogeneous pyrotechnic compositions and heterogeneous charges is studied experimentally with the aim of producing a selectable wavelength signal flare. The heterogeneous charge was perceived as a mixed color by a distant observer. A model for color chromaticity coordinates of homogeneous mixtures was derived that includes the mass, mass‐based burn rate and luminous intensity ratios of the constituting color compositions. This model can predict the expected dominant wavelength of a mixed composition. It can also handle the spacing of chromaticity coordinates of mixed compositions on a straight line in the CIE diagram between chromaticity coordinates of constituting colors. With two series of color composition mixtures, it was demonstrated that the chromaticity coordinates of the mixtures could be at, or slightly deviate, from the straight line connecting the chromaticity coordinates of the constituting compositions. It indicates there is little to no influence of flame temperature and mutual pyrotechnic reactions.

Luminescence and optical thermometry strategy based on emission spectra of Li2Ba5W3O15:Pr3+ phosphors

In this study, a series of Pr3+ ions doped Lithium Barium Tungstate (Li2Ba5W3O15) was synthesized using the conventional high-temperature solid state method. The structure and phase of the phosphors were analysed using X-ray diffraction (XRD) patterns. Fourier Transform Infrared (FT-IR) spectroscopy was used to examine the different vibrational bands present. The optical band gap values of the optimized LBW phosphor and the undoped LBW sample were measured using diffuse reflectance spectra (DRS). Under 319 nm excitation, the photoluminescence (PL) spectra of the Pr3+-activated LBW phosphor exhibited strong visible blue and reddish emissions at 488 nm and 647 nm respectively corresponding to the 3P0 → 3H4 and 3F2 transitions of the Pr3+ ions. The evaluated CIE color chromaticity coordinates of the as-prepared LBW:Pr3+ phosphors lie within the white region. The temperature-dependent PL (TDPL) measurement demonstrated relatively good thermal stability for the synthesized phosphor. Moreover, the fluorescence intensity ratio (FIR) was used to analyze the optical sensing properties of the LBW:Pr1.0 phosphor. A maximum relative sensitivity (Sr) of 1.03 % K−1indicated the potential of these phosphors for optical thermometry applications. A double exponential trend with decreasing lifetime was observed in the PL decay data at 647 nm emission (λem) under 319 nm excitation (λex), with an increase in the Pr3+ ions concentration in the host matrix. In conclusion, the investigations conducted demonstrate that the Pr3+ ions doped LBW phosphors show great potential for applications in solid-state lighting and optical thermometry. Its emission characteristics, thermal stability, and optical sensing capabilities establish it as a suitable candidate for these applications.

Insight into the photoluminescence and morphological characteristics of transition metals (TM = Mn, Ni, Co, Cu)-doped ZnO semiconductor: a comparative study

In this work, undoped and transition metal (TM = Mn, Ni, Co, Cu)-doped ZnO thin films were grown on Si substrate using the ultrasonic spray pyrolysis technique, adhering to the same deposition conditions to compare their morphological and photoluminescent characteristics. X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM), and Photoluminescence (PL) spectroscopy were used to investigate the chemical composition, morphology, and luminescence properties, respectively. XPS results indicate that Mn and Ni ions have bivalent and trivalent electronic states coexisting in the ZnO lattice, Cu ions have both monovalent and bivalent states, and Co ions have only bivalent states. Besides, there is a considerable increase in the level of oxygen vacancies observed upon TM doping. The topographic and phase-contrast AFM images, supported by their associated statistical parameters and mean height distribution histograms, reveal that TM doping increases the tendency for crystalline grains to coalesce in 3D, resulting in a more roughened surface, larger grains with prominent boundaries, increased porosity, and an inhomogeneous height distribution. PL spectra of TM-ZnO show a broadening of the ZnO band gap accompanied by different luminescence behavior compared to pure ZnO regarding both UV and visible emissions. CuZnO is characterized by a green luminescence, CoZnO and MnZnO by a red luminescence, and ZnO and NiZnO by a broad visible luminescence. The possible mechanism for defect luminescence in each TM-ZnO sample was systematically investigated. The chromaticity color coordinates of the PL emissions show that the films provide different color regions well distributed on the CIE chromaticity diagram. The findings regarding the coexistence of two valence states of TM doping, the level of oxygen vacancies, the grain coalescence process, and the luminescence characteristics are carefully correlated and discussed herein.

Structural, optical, and luminescence properties of Dy3+ -activated potassium calcium silicate phosphor for white light-emitting diodes.

A dysprosium (Dy3+ )-activated potassium calcium silicate (K4 CaSi3 O9 ) phosphor was prepared using a solid-state synthesis route. The phosphor had a cubic structure with the space group Pa as confirmed using X-ray diffraction (XRD) measurements. Details of surface morphology and elemental composition of the as-synthesized undoped KCS phosphor was obtained using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) spectroscopy. The chemical structure as well as the vibrational modes present in the as-prepared KCS phosphor was analyzed using Fourier transform infrared (FT-IR)spectroscopy. Diffuse reflectance spectra (DRS) were used to determine the optical bandgap of the phosphors and were found to be in the optical range 3.52-3.71 eV. Photoluminescence (PL) spectra showed intense yellow emission corresponding to the 4 F9/2 →6 H13/2 transition under 350 nm excitation. Commission International de l'Eclairage colour chromaticity coordinates were evaluated using the PL spectral data lie within the white region. Dexter theory and the Inokuti-Hirayama (I-H) model were applied to study the nature of the energy transfer mechanism in the as-prepared phosphors. The relatively high activation energy of the phosphors was evaluated using temperature-dependent PL (TDPL) data and confirmed the high thermal stability of the titled phosphor. The abovementioned results indicated that the as-prepared KCS:Dy3+ phosphor was a promising candidate for n-UV-based white light-emitting diodes.

Photoluminescence & structural studies of Ag: Alkali Bismuth Silicate glasses

In this paper, we demonstrate the luminescence enhancement of Alkali Bismuth Silicate glasses through Silver incorporation. Silver has been incorporated into the glass matrix through three methods, namely by melt quench, ion implantation, and in-situ sputtering. Absorption spectra of the glasses show an inhomogeneously broadened surface plasmon resonance (SPR) peak along with the Bi2+ peak of Bismuth. The inclusion of Silver into the glass, by all three methods, enhances the photoluminescence and among them, in-situ sputtering gives better enhancement. Photoluminescence of the glasses is increasing with an increase in Ag-O intensity. Raman spectra is recorded to explore the role of glass structure in enhancement of luminescence viz., Silver oxide formation, Oxygen defect centers, etc,. The ion-implanted samples show Oxygen defect centers which deteriorate the luminescence intensity. CIE 1931 chromaticity colour coordinates (x,y) correlated colour temperature (CCT) and colour purity (CP) values were also determined from the photoluminescence data.

Influence of Ambient Temperature on Optical Characteristics and Power Consumption of LED Lamp for Automotive Headlamp

In this study, the authors propose a method for evaluating the influence of ambient temperature (Ta) on the optical characteristics and power consumption of a LED lamp used for the automotive headlamp, which helps the designer to figure out the acceptable range of the ambient temperature for the LED lamps to work well in the practical case. The LED lamp was fixed on the test holder and placed in a fixed position in the air circulation temperature control oven to measure the illuminance, spectrum in three different directions, and power consumption under various Ta. The experimental results indicate that Ta has little effect on the correlated color temperature (CCT), chromaticity coordinates, and angular distribution of the emitting light. In contrast, Ta has a significant effect on the lamp’s resistance, thus affecting illuminance and power consumption. When the Ta increased from 30 °C to 60 °C, the illuminance of the low beam and high beam decreased on average by 16.6% and 21.7%, respectively, while the power consumption of the low beam and high beam decreased on average by 21.4% and 22.2%, respectively. The drop in the luminous flux output indicates the probability of originally qualified automotive LED headlamps becoming unqualified in high Ta.

Exploration of modifier based structural and spectroscopic traits of Eu3+ doped boro-tellurite glasses for solar UV photons converting applications

A new series of stable host glass with different modifier cations have been formed with the molar composition15XO + 39B2O3 + 25TeO2 + 10Na2O + 10K2O + 1Eu2O3 (X = Li2, Ca, Sr, Ba, Zn) through traditional glass preparation technique of melt quenching. The effect caused by the incorporation of modifier cations on the radiative assets of Eu3+ ions in the present host glass were inspected through X-ray Diffraction (XRD), Fourier Transformed Infra-Red (FTIR), UV–vis-NIR, photoluminescence and luminescence decay spectral studies at room temperature. The broad diffraction band in the XRD pattern confirms glassy or amorphous nature of the synthesized samples. The functional modes of vibration and structural modules in the prepared glass samples were inspected through FTIR spectra. The 4f − 4f electronic transitions pertaining to the trivalent europium (Eu3+) ions in the new host glasses were scrutinized by UV–vis-NIR absorption studies where in the dominant covalent bonding nature of the Eu3+ ions with its nearby ligands have been confirmed via average nephelauxetic ratio (β) and bonding parameter(δ) values. Optical bandgap (indirect and direct) values were testified to identify the photon energy transparent window and to explore the tendency of the formation of non-bridging oxygens. Luminescence ability of the prepared samples was inspected by exciting at a wavelength of 465 nm. Among the prepared samples, Eu3+ ions emissions were observed and the highest intensity of emission occurred at 612 nm (5D0→7F2) for BTLi:Eu glass. The Judd-Ofelt parameters were estimated and used to evaluate the radiative parameters such as radiative lifetime (τrad), transition probability (A), branching ratio (βR), stimulated emission cross-section (σPE) of all the emissions observed in the produced glasses and the outcomes were equated with the related literature. The colour chromaticity coordinates and colour correlated temperature (CCT) were explored from the emission spectra using CIE 1931 diagram and the CCT values found to lie in the range of 2000–4000 K. The luminescence decay comfortably fitted to the single exponential decay profile which further confirms the non-appearance of energy transfer via mutual interaction amongst Eu3+ ions in all the present glasses. All the observed results indicate the fact that the incorporation of Li+ cations induces more attractive radiative features with 77 % of UV to visible quantum converting efficiency than all other cations used in this contemporary study and among the prepared glasses, BTLi:Eu glass exhibits a better capability in red light emitting electro-optical applications.

Structural, morphological and optoelectronic aspects of YAlO3:Dy3+ doped nanocrystalline materials for NUV energized WLEDs

Cost-effective urea assisted solution combustion (SC) synthetic method was employed to prepare a series of doped YAlO3:xDy3+ (0.01–0.08 mol) phosphors. The resulting powdered samples were comprehensively examined through various structural as well as optical measurements. Rietveld refinement studies concluded that prepared nanomaterials structured into the orthorhombic system having Pbnm (62) space group. Energy dispersive spectral (EDS) analysis was executed to observe the relative proportions of constituent elements in all doped nanophosphors. Transmission electron microscopy (TEM) micrograph indicated the presence of agglomerated particles with the average size in the nano range. Photoluminescence excitation (PLE) spectra showed that the designated phosphors could be excited by near ultraviolet (NUV) energized lighting sources. The strongest emission centred at 576 nm, corresponding to electric dipole (4F9/2 → 6H13/2) transition of Dy(III) ion. Furthermore, characteristics photometric parameters viz. correlated color temperature (CCT), chromaticity coordinates (x and y), and color purity (%) were figure out with the aid of PL data, which strongly endorsed their usage in NUV energized WLEDs applications.

Spectroscopic characterizations of Dy3+ ions doped phosphate glasses for epoxy-free white LED applications

The present work illustrates a detailed spectroscopic analysis carried out on dysprosium ions doped Zinc Alumino Sodium Phosphate (ZnAlNaP) glasses with chemical composition of (10-x)ZnO–20Al2O3–10Na2O–60P2O5-xDy2O3 (x = 0.1–2.0 mol%). The XRD spectra verified for an un-doped and Dy3+ ions doped ZnAlNaP glasses demonstrate an enormous hump confirming its amorphous behavior. The FT-IR and Raman spectrum recorded for an un-doped ZnAlNaP and ZnAlNaPDy1.0 glass elucidates various functional groups and vibrational modes involved, respectively. The DSC & TGA studies conducted on an un-doped ZnAlNaP glass revealed its thermal stability and overall weight loss. The absorption spectra were used to calculate the optical bandgap for the as-synthesized glasses and were found to be in the range of 2.9 eV–4.7 eV. Photoluminescence (PL) excitation, emission and decay spectral analysis were done to investigate the suitability of the as-synthesized glasses for epoxy-free solid-state lighting (SSL) devices. The PL emission recorded under 350 nm excitation show two significant bands in blue and yellow regions. Temperature-dependent PL studies conducted on ZnAlNaPDy1.0 glass revealed activation energy of 0.212 eV with a 25.6% loss in PL intensity. The CIE color chromaticity coordinates and correlated color temperature (CCT) were calculated from the PL spectral characteristics. All the spectroscopic investigations conducted on the as-synthesized ZnAlNaPDy glasses finally reveal their superior nature for fabricating epoxy-free white-light emitting diodes (w-LEDs).

IMPORTANCE OF THE COLOR TEMPERATURE IN COLD WHITE LIGHT EMISSION OF Ca2MgSi2O7: Dy3+ PHOSPHOR

A promising candidate of white light-emitting (Ca2MgSi2O7: Dy3+) phosphor was successfully synthesized via traditional high-temperature solid-state synthesis technique using boric acid (H3BO3) as a fuel. The synthesized material sample was characterized with the help of powder X-ray diffraction (PXRD), FT-IR (Fourier Transform Infra-red) Spectroscopy, FESEM (Field Emission Scanning Electron Microscopy) and PL (Photoluminescence) spectra. Using the Debye-Scherer formula and UDM method, the crystallite size and crystal lattice strain were evaluated, respectively. Photoluminescence (PL) properties (both excitation & emission spectra) for the prepared phosphor were systematically investigated in detail. Photoluminescence spectra were revealed that the strong transition of spectral emission lines centered at 484nm (blue), 578nm (yellow) and weak transition of spectral emission lines centered at 615nm (red) wavelength. These peaks were assigned to following transitions (4F9/2 → 6H15/2,13/2,11/2), which are responsible for the (f→f) transitions from the ground level (lower energy state) to excited level (higher energy state) in the 4f9electronic configuration of dopant [Dy3+] ions. CIE color chromaticity coordinates and Color Correlated Temperature (CCT) of synthesized Ca2MgSi2O7: Dy3+ phosphor sample is well suited for the generation of cold white light emission with a CIE coordinate value of (X = 0.31, Y = 0.32) and CCT value also calculated as 5167K. Here upon, it is highly applicable to be a novel hopeful phosphor for cold WLEDs.

All-Solution Processed Single-Layer WOLEDs Using [Pt(salicylidenes)] as Guests in a PFO Matrix.

Herein, we report the synthesis and characterization of two Pt(II) coordination compounds, the new platinum(II)[N,N′-bis(salicylidene)-3,4-diaminobenzophenone)] ([Pt(sal-3,4-ben)]) and the already well-known platinum(II)[N,N′-bis(salicylidene)-o-phenylenediamine] ([Pt(salophen)]), along with their application as guests in a poly [9,9-dioctylfluorenyl-2,7-diyl] (PFO) conjugated polymer in all-solution processed single-layer white organic light-emitting diodes. Completely different performances were achieved: 2.2% and 15.3% of external quantum efficiencies; 2.8 cd A−1 and 12.1 cd A−1 of current efficiencies; and 3103 cd m−2 and 6224 cd m−2 of luminance for the [Pt(salophen)] and [Pt(sal-3,4-ben)] complexes, respectively. The Commission Internationale de l’Eclairage (CIE 1931) chromaticity color coordinates are (0.33, 0.33) for both 0.1% mol/mol Pt(II):PFO composites at between approximately 3.2 and 8 V. The optoelectronic properties of doped and neat PFO films have been investigated, using steady-state and time-resolved photoluminescence. Theoretical calculations at the level of relativistic density functional theory explained these results, based on the presence of the Pt(II) central ion’s phosphorescence emission, considering spin-orbit coupling relationships. The overall results are explained, taking into account the active layer morphological properties, along with the device’s electric balance and the emitter’s efficiencies, according to deep-trap space-charge models. Considering the very simple structure of the device and the ease of synthesis of such compounds, the developed framework can offer a good trade-off for solution-deposited white organic light-emitting diodes (WOLEDs), with further applications in the field of lighting and signage.

Development of single phase pink light-emitting Bi3+/ Eu3+ co-doped LaAlO3 phosphors for LED applications

ABSTRACT Pink light emissions are obtained from a sequence of Bi3+/Eu3+: LaAlO3 phosphors. The XRD patterns revealed the rhombohedral phase of LaAlO3 annealed at 700°C. The surface morphology of the prepared samples revealed the spherical morphology of synthesized particles. Photoluminescence (PL) spectroscopy showed pink-red luminescence due to electric dipole mechanism of Eu3+ corresponding to 5D0-7F2 transition at 618 nm. The increased PL intensity in Eu3+ ion’s emission was observed in LaAlO3:Bi3+, Eu3+ phosphors because of effective energy transfer (ET) from Bi3+ to Eu3+ ions in the host lattice. From, decay measurements, the life time and energy transfer efficiency are calculated as 1.96 ms and 76% respectively. . The (CIE) chromaticity colour coordinates have moved from bright blue to pink region as the amount of Eu3+ varies witnessing high-intensity pink light emissions from the Bi3+/Eu3+:LaAlO3 phosphors. The results declare that the developed phosphors are promising materials to develop light-emitting diodes (LEDs).

Synthesis and Photoluminescence characterization of ZnAl12O19 : Sm3+ Phosphor for W-LED

The combustion process was used to create an effective ZnAl12O19:Sm3+ phosphor with reddish emission. Using scanning electron microscopy, the structural and morphological characteristics of the phosphor have been studied. Samarium ions are found in trivalent oxidation states, as demonstrated by the photoluminescence spectrum. The as-prepared phosphor exhibits strong visible red emission at 615 nm under 405 nm excitation. It has been discovered that a concentration of 1.5 mol% Sm3+ ions produce the strongest visible red emission. The synthesized phosphors 615 nm (x = 0.680, y = 0.319) and 661 nm (x = 0.730, y = 0.269) CIE colour chromaticity coordinates are located in the red area of the chromaticity diagram. All of these findings support the suitability of Sm3+-doped ZnAl12O19 phosphor for lighting and display applications.

The Radioluminescence Investigation of Lead Sodium Borate Glass Doped with Eu3+

The effect of Eu3+-doped lead sodium borate glasses in composition of (79-x)B2O3: 20Na2O: xPbO: 1Eu2O3 and x are 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50 and 55 mol%) were studied by using the melt-quenching technique. The absorption spectra show a maximum of 5 transition, where the strongest absorption bands were shown at 394 and 2101 nm in visible light and near-infrared region, respectively. The emission spectra of glasses were measured at 394 nm excitation wavelength. The highest peak of emission spectra corresponding due to 5D0 to 7F2 transition centered at 613 nm. The intensity of emission spectra increased with the increasing of PbO concentration upto 5 mol%. The radioluminescence spectrum (RL) has four peaks similar to photoluminescence, While, the transition at 612 nm strong strongest, identified at 0 mol% of PbO. In addition, the calculated integral scintillation efficiency of 5 mol% is 5.37% as compared with BGO crystal. The values of the color chromaticity coordinates were (0.65, 0.35) locating on the orange region of CIE diagram.

Quantitative relationship between microstructure and optical properties of Er3+-Yb3+ co-doped glass-ceramics containing pyrochlore-type crystalline phases

Er3+-Yb3+ co-doped transparent glass-ceramics (GCs) containing Y2Ti2O7 crystalline phase were prepared by the melting crystallization method. The qualitative relationship between light transmittance and three-dimensional structure parameters of glass-ceramic was studied according to the principle of stereology under different heat treatment conditions. As indicated by the research results, the light transmittance decreased with the increase in the equivalent spherical diameter (D3S) and specific surface area per unit volume of the grains (SV). However, the light transmittance increased linearly with the increase in the discrete grains (SVP) and the mean free distance (λ). The up-conversion luminescence intensity was found to be most vigorous under Er3+ and Yb3+ doping concentrations of 0.5% and 0.9%, respectively, at 980 nm excitation. Considering the correlation between pump power and up-conversion emission intensity, the up-conversion luminescence mechanism was explored. As revealed by the results of color purity and chromaticity coordinates, Er3+-Yb3+ co-doped GCs containing Y2Ti2O7 have promising applications in green up-conversion luminescence.

The effects of precursor concentration and morphology on photoluminescence behavior of Tb2O3 phosphors

AbstractTerbium oxide (Tb2O3) phosphors were prepared the using sol‐precipitation method with the use of different precursor concentrations. The X‐ray diffraction (XRD) patterns showed C‐type body‐centered cubic phase, space group Ia‐3, and the crystallite size values were found in the range of 19.45–32.34 nm depending on the solution composition and calcination temperature. As the crystallinity increased, the defects in the structure decreased, that is, the dislocation density decreased. Under the excitation at 325 nm, although all the Tb2O3 phosphors emitted a single peak around 544 nm (5D4‐7F5 transition) in PL spectra, when the peak was enlarged, the presence of additional peaks shifted to the red/blue region was also observed. The color chromaticity coordinates showed that it exhibited different tones of emission from light yellow to green depending on the precursor concentration and calcination temperature. With increasing the precursor concentration, nucleation rate increased and the particle shape changed from nearly spherical to rod‐like. They may be promising for laser devices and display applications due to their strong green emission.