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The present study examines the structural, morphological, and photoluminescence properties of yttrium niobium titanate (YNbTiO6) induced with trivalent samarium (Sm3+) ion (YNT:Sm3+) phosphors synthesized with the help of a high-temperature solid-state reaction (SSR) route. X-ray diffraction (XRD) confirmed the single-phase structure of the YNbTiO6 (YNT) and Sm3+induced YNT lattices with an orthorhombic system (Pbcn (60) space group). Scanning electron microscopy (SEM) revealed an irregular and agglomerated morphology, with nonuniform microscale particle formation in the synthesized YNT host lattice. Various vibrational linkages of the synthesized YNT host lattice were identified with the help of Fourier transform infrared (FT-IR) spectroscopy. Under ultraviolet (UV) and near-UV (n-UV) excitation, the synthesized YNT:Sm3+ phosphors emit various characteristic peaks of Sm3+ ions, and prominent emission peaks were observed in the orange-red region (610 nm). The colorimetric properties of the synthesized phosphors were determined under UV and n-UV excitations. The decay profile for the optimized YNT:xSm3+ (x = 5.0 mol.%) phosphor exhibited bi-exponential behavior under n-UV excitation. These results indicate that the synthesized YNT:Sm3+ phosphor is an excellent candidate for optoelectronic device applications. [ABSTRACT FROM AUTHOR]

Li2-3xLnxGeTeO6 phosphors with doping of Ln3+ (Ln = Eu3+,Tb3+:0.0 < x < 0.1) were successfully prepared. Parent Li2GeTeO6 was obtained by the solid-state method, while Ln-doped compositions were synthesized by the facile ion-exchange method. The prepared phosphors were characterized by powder x-ray diffraction (P-XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy techniques. All of the samples were crystallized in rhombohedral structure with space group R3/(146). The photoluminescence (PL) and thermoluminescence (TL) characteristics of Li2-3xLnx3+GeTeO6 were studied. The excitation spectra of Eu3+/Tb3+-doped samples were obtained by monitoring the 611/544 nm emission line. The emission spectra of Eu3+/Tb3+-doped samples were recorded by excitation at 394/372 nm. The Li2-3xEuxGeTeO6 phosphor exhibited red emission with a maximum intense band at 611 nm. The Li2-3xTbxGeTeO6 phosphor gave a strong emission band at 544 nm in the green range. The variation in emission with dopant concentration was studied. It was found that the concentration quenching was predominant above 0.05 mol.% in both Eu3+- and Tb3+-doped phosphors, which was demonstrated based on Blasse's equation and Dexter's theory. The chromaticity coordinates of Eu3+- and Tb3+-incorporated phosphors were located at red and green regions, respectively, as per NTSC standards. The colour purity values for 0.05 mol.% of Eu3+ (Tb3+)-doped Li2GeTeO6were 54% and 43%, respectively. The correlated colour temperature (CCT) values of Li2-3xEuxGeTeO6and Li2-3xTbxGeTeO6 were 2763 K and 4562 K, respectively, indicating their suitability for use in warm and cool white-light devices. The parameters of trap-depth/activation-energy, order of kinematics and frequency-factor of the synthesized samples were calculated using the Chen glow curve peak-shape method. The investigation shows Eu3+- and Tb3+-doped Li2GeTeO6 compositions can be utilized as white-LEDs. [ABSTRACT FROM AUTHOR]

In this study, undoped and (Ni/Co, Fe/Co, Fe/Ni) co-doped ZnO thin films were deposited on glass substrates by a low-cost sol-gel spin coating technique. The effect of Ni/Co, Fe/Co, Fe/Ni co-doping on the structural, morphological, and optical properties of ZnO thin films was investigated. All films exhibited hexagonal wurtzite nanocrystalline structures with a preferred orientation in the (0 0 2) plane. The crystallite size was found to decrease upon co-doping ranging from 34.4 to 30.2 nm. Raman spectra confirmed the incorporation of all doped ions into ZnO lattice. The morphological analysis of all samples revealed a smooth and crack-free surface, with an average particle size distribution ranging from 50 to 70 nm. All prepared samples showed high transparency in the visible region (~90%) and optical band gap values ranging from 3.263 eV to 3.275 eV, with a high band gap energy of 3.275 eV for the Fe/Co co-doped ZnO thin films. The PL spectra of co-doped samples exhibited a relatively similar features of emission spectra, in both ultraviolet (UV) and visible regions except for Fe/Co-ZnO presented a quenching of visible emission. The systematic investigation into the possible mechanisms underlying defect luminescence in each sample revealed that co-doping with Fe/Ni and Ni/Co lead to a slight increase in the abundance of Oi in the ZnO film. The examination of the chromaticity color coordinates showed that only co-doping with Fe/Co induces a shift to a different color region on the CIE chromaticity diagram. The properties of prepared ZnO thin films demonstrated their suitability for light-emitting and optoelectronic applications. Highlights: Undoped and (Ni/Co, Fe/Co, Fe/Ni) co-doped ZnO thin films were deposited on glass substrates by a low-cost sol-gel spin coating technique. The structure, surface morphology, transmittance, and photoluminescence were studied in detail. X-ray diffraction study revealed the formation of nanocrystalline thin films highly oriented along the c-axis in the (002) plane with a pure hexagonal wurtzite structure. SEM micrographs revealed a granular surface that was free of cracks and had a homogeneous distribution of particles with an average particle size between 50 and 70 nm. All prepared samples showed high transparency in the visible region (~90%) and optical band gap values ranging from 3.263 eV to 3.275 eV. [ABSTRACT FROM AUTHOR]

We have studied the optical and luminescence properties at room temperature of ultrathin colloidal semiconductor cadmium selenide nanoscrolls with a thickness of 2.5 monolayers. For colloidal synthesis of the objects under study, cadmium acetate dihydrate Cd(CH3COO)2·2H2O and trioctylphosphine selenide were used as precursors of cadmium and selenium, respectively, and solutions of oleic acid and octadecene were also used. Luminescence spectrum of cadmium selenide nanoscrolls was recorded using a fiber charge coupled device spectrometer. Spectrally resolved photoluminescence decays for nanoparticles were measured with the use of time-correlated single photon counting technique. The emission of the cadmium selenide nanoscrolls consists of interband and recombination luminescence bands. We found that the normalized photon numbers of recombination luminescence are larger than the normalized photon numbers of interband luminescence. We determined dominant wavelengths, chromaticity coordinates, and correlated color temperatures of ultrathin colloidal semiconductor cadmium selenide nanoscrolls. These ultrathin cadmium selenide nanoscrolls are promising for application in light-emitting diodes.

The article elucidates the possibility of using the yellow dye, obtained from saffron petals (Carthamus Tinctorius L.) in the food industry. This powdered dye, added to yoghurt in concentrations of 0.3 - 0.4%, in addition to its yellow color, gives the yoghurt samples a light aroma of saffron flowers and demonstrates high stability during storage at 4° C. for 28 days. The values of the chromatic coordinates, L *, a *, b *, of the yogurt samples did not undergo considerable changes during the storage stage, the color difference ∆E being ≤ 0.79, which indicates a high stability of the dye in yogurt. samples. The chromatic analysis data correlate with the results obtained by the reverse phase HPLC method, which identified the presence of four intact yellow chalcones in the yoghurt. The results of this study will encourage the cultivation of saffron, the extraction of natural dyes and their use in the food industry.

The application of phosphorescence for the modification of face mask materials is motivated by the need to appreciably increase their visibility while using graphical elements with a relatively small area. Phosphorescent dyes absorb part of the visible spectrum while emitting radiation at wavelengths that are longer than the absorbed ones. Thus, a phosphorescent substance can emit light even if it is not being illuminated at a given time (but was before). This paper describes studies of the optical properties based on parameters such as the reflectance coefficient, chromaticity coordinates, as well as luminance measured from digital images for two models of smog-protective face half-masks differing in terms of their inner layer with filtration properties and outer printed layer. The external surface of one mask type is printed with a phosphorescent solid star pattern, while the other with a phosphorescent open star pattern. The influence of the inner filter layer was assessed in correlation with the colour of the outer layer and the type of printing. Moreover, the phenomenon of phosphorescence was identified. The study resulted in developing a material with properties providing better visibility under defined use conditions. [ABSTRACT FROM AUTHOR]

Determining the authenticity of documents is an important task when conducting investigative measures. In practice, for the examination of documents to determine the prescription of their creation, a spectral method is used, in which it is necessary to make clippings from the document under study, which leads to damage to the document under study, and also requires the use of expensive equipment, which affects the price of the examination of the document. The article describes a method for determining the authenticity of a document based on computer colorimetry, which does not require expensive equipment for conducting an examination. This method for determining the authenticity of a document uses a change in the color of the strokes of a ballpoint pen over time, which is caused by the drying of the solvent in the ink of the pen, and also lacks the disadvantage of the need to damage the document under study.

The use of standard instruments (colorimeters) when measuring the color coordinates and chromaticity of multicolored objects and having relatively large dimensions is practically impossible. This is due to the fact that ordinary colorimeters, no matter what method is implemented in them, are designed to determine the color of a specific point of the measured object. This article discusses a method for determining the color of a multicolored and relatively large object, for example, a car, color photography, art painting, etc. Let us call this method computer colorimetry. A practical solution to this method can be used in such areas of the national economy, as, for example, repainting a car after damage to certain parts of the body with damage to the paintwork, automatic control and video surveillance of forest and peatland areas to detect fires, in the examination of the authenticity of documents and works of art, and other areas of the national economy.

• Li 2 ZnTi 3 O 8 :Eu3+ phosphors were synthesized by solid state reaction method. • Intense red emission at 612 nm under 309 and 393 nm excitations. • The internal quantum efficiency was 48.91 %. • Possess excellent thermal stability, high color purity and warm CCT values. • Potential candidate to be used in pc-WLEDs under UV excitation. Embracing phosphor converted white light-emitting diodes (pc-WLEDs) represent a significant step towards efficient and sustainable energy sources, herein we report the synthesis, structural and optical properties of Eu3+ doped Li 2 ZnTi 3 O 8 phosphor for the first time. A series of Li 2(1- x) ZnTi 3 O 8 : x Eu3+ phosphors (x = 0, 0.02, 0.05, 0.08, 0.1 and 0.3 mol) were prepared by the high temperature solid state reaction method. The structural and morphological characterisation of prepared samples were done using X -ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM), Energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared (FTIR) spectroscopy. The XRD analysis confirmed the cubic structure and purity of the samples with the incorporation of Eu3+ ions. The presence of functional groups was detected from FTIR and compositional elements from EDX. FESEM and TEM images revealed similar agglomerated block like structures. The optical properties were analysed using diffuse reflectance spectrum (DRS) and photoluminescence (PL) spectra. Under 309 and 393 nm excitation, characteristic emission peaks of Eu3+ ions corresponding to 5D 0 → 7F J (J = 0,1,2,3 and 4) transitions were observed in which the intense emission was recorded at 612 nm. Under both the excitations, the optimum concentration of prepared phosphor was 8 mol% (x = 0.08 mol) and the mechanism for concentration quenching was found to be dipole - dipole interaction. The decay lifetime of prepared phosphors was in the milliseconds range and the internal quantum efficiency was measured to be 48.91 %. Li 2(1- x) ZnTi 3 O 8 : 0.08Eu3+ phosphor has an activation energy of 0.163 eV and holds good thermal stability. Also, for the optimum sample, the Commission International de I'Eclairage (CIE) coordinates were detected at (0.6333, 0.3663) and (0.6344, 0.3651) for 309 and 393 nm excitation respectively, which lies in the orange - red region with super color purity and warm correlated color temperature (CCT) values. Therefore, obtained results suggest that the prepared Li 2(1- x) ZnTi 3 O 8 : x Eu3+ phosphors are suitable candidates for its use in pc-WLEDs. [ABSTRACT FROM AUTHOR]

A new method to predict the junction temperature of white light-emitting diode (LED) using dual parameters is designed. The spectral distributions of white LEDs are measured with a spectrometer at different ambient temperatures and currents, which include single yellow phosphor and mixture of yellow and red phosphors. Firstly, the changes in spectral parameters of two types of LEDs are analyzed with changes in junction temperature and current, a parameter model of LED with a single phosphor is constructed between the drive current, the center wavelength, the relative parameter of chromaticity coordinates, and the junction temperature. Then, according to the spectral distributions of the LEDs under the actual lighting conditions, the corresponding junction temperature of the LEDs is calculated by combining them with the dual parameter model. The junction temperatures detected by the new method are compared with those measured by T3ster and a single parameter. The results show that the new method can accurately measure the junction temperature of white LED, and the average error of the junction temperature obtained by this method is about 1.25 °C compared with the T3ster, and the error is reduced compared to predicting junction temperature with a single parameter. • Using a combination of central wavelength and relative parameters of chromaticity coordinates to characterize the junction temperature of white LED. • The experimental results show that the average measurement error of this method is 1.25 °C, and compared with single parameter prediction of junction temperature, the error is reduced. • This method can accurately measure the junction temperature of white LED. [ABSTRACT FROM AUTHOR]

In this paper, a description is given of the method of colorimetry of an image of an object under investigation according to its photograph or scanned copy. Further, in the text of the article, more briefly, this method will be called photo colorimetry. In general, in the science of color measurement, there are two directions: it is just colorimetry, where color is measured using a colorimeter, and the second is indirect colorimetry, in which color coordinates are calculated using known formulas from the measured optical spectrum or reflected from the object of light or the emission spectrum (for self-luminous objects). Photo colorimetry is based on specially developed software and includes having a computer with a monitor screen running this program. A photo of the object under study is displayed on the computer monitor, which can be a part of the human body (skin), on which some injuries or unwanted objects are visible. The process of measuring the coordinates of color and chromaticity itself is carried out by the method of pixel scanning of the image and the program determines the quantitative values of the primary colors of the monitor screen. Knowing the chromaticity coordinates of the primary colors of the screen (the triangle of color gamut), you can accurately calculate the chromaticity coordinates of the object under study. This is the principle of photo colorimetry.

The physical and chemical processes of surface discharge are more complicated than other discharge forms due to the influence of gas composition and dielectric properties. Spectral diagnosis can be used to analyze the main species in the discharge process. However, the chromaticity characteristics are the comprehensive representation of all emission spectra. This article presents a new method to diagnose the state of surface discharge using chromaticity coordinates in color space. It is observed that the chromaticity coordinates slide along a straight line between the equal energy white point and a specific spectral color with the development of surface discharge. The relative position of the chromaticity coordinates on the line indicates the different states of the surface discharge. The slope of the line is affected by the material characteristics while external factors such as the camera’s exposure time and the color of materials have no effect on it. It is found that the slope of the chromaticity coordinate curve has a fixed range, which means that there exists a specific color space of surface discharge. Finally, the effects of the ambient noise are corrected. This method uses the chromaticity coordinates in a long time scale to diagnose the microscopic process of surface discharge and it can be extended to other state diagnoses of partial discharge phenomena. From the point of view of potential application, this method also provides a new simple method to meet the requirement of long time scale state monitoring in industrial application. [ABSTRACT FROM AUTHOR]

The influence of five nitrogen (N) application rates (60, 90, 120, 150 and 180 kg N/ha) were evaluated using limestone ammonium nitrate on the curd fresh and dry mass, size, chromaticity coordinates, L*, a*, b* and ascorbic acid content in cauliflower varieties (Largardo, Eskimo and CF-744) during the 2015 and 2016 seasons. Commercial standard 120 kg N/ha was included as a control. Variety ‘Largardo’ showed weak response to N application rates and can be regarded as the least sensitive variety for lower N use. Curd fresh and dry mass and size were not affected at lower N application rates of 60 and 90 kg/ha in ‘Largardo’ compared to the other two varieties. However, L*, b* colour value and ascorbic acid content was higher at lower N application rates

The series of rare-earth (RE) ions-activated Sr 2 YF 7 nanoparticles were successfully synthesized at room temperature. The phase structure, elemental composition, morphology, and photoluminescence performances were investigated in detail. The optimal Sr 2 YF 7 : x Eu3+ was found to be x = 0.3 mol. Additionally, the Eu3+-activated Sr 2 YF 7 :Dy3+ nanoparticles emitted warm white light and the valid energy transfer (ET) efficiency in Sr 2 YF 7 :Dy3+/Eu3+ nanoparticles was approximately 79.77%. Meanwhile, the Eu3+-activated Sr 2 YF 7 :Tb3+ nanoparticles could emit near-warm white light with excellent ET efficiency (97.78%). Besides, the concentration quenching mechanism and thermal stability of the resultant samples were analyzed. Eventually, the white lighting-emitting diodes based on the resultant samples were fabricated, exhibiting good color rendering index and correlated color temperature values. [ABSTRACT FROM AUTHOR]

A multicolour LED is a miniaturized, long-lasting, and easy-to-achieve colour adjustable emission light source. It is widely used in outdoor displays and room lighting fields. However, the increase in the cost and the decrease in luminous efficiency when adjusting lighting colours have constrained the development of multicolour LEDs. In this study, we initially designed a phosphor conversion pixel array through optical simulation and then prepared the phosphor conversion pixel arrays with different layouts using a semi-cured template method. Finally, we packaged the phosphor conversion pixel array with the blue LED array as a remote phosphor LED. The measurement of the luminous performance indicated that the colour gamut of multicolour LEDs was included in the simulated colour gamut, and the colour of the light was consistent with the design guidelines. Notably, the multicolour LED emission efficiency packaged with a phosphor conversion pixel array could reach 125 lm/W, and the hexagonal phosphor conversion pixel array had better emission performance than the square phosphor conversion pixel array. • Based on the Monte Carlo principle, multicolour LEDs composed of array phosphor-converted film and blue-LED chip are designed. • Phosphor-converted pixel arrays are prepared by semi-cured template method with high moulding quality. • By comparing the experimental and simulation results, colour-tuneable characteristics of the multicolour LEDs is verified. • The luminous efficiency of multicolour LEDs reach up to 125.0 lm/W and changing pixel can reduce the secondary reabsorption of fluorescence. [ABSTRACT FROM AUTHOR]

The researcher working in the field of illumination can use a number of measurement methods, depending on the requirement. Many practical evaluation methods employ varieties of a configuration where test stations are positioned next to or opposite each other for comparison purposes. Test stations can consist of test booths or even full-sized test rooms when using indoor evaluations. The number of test booths for indoor application may differ from one to three. Most colour and light perception studies thus depend on human observers to provide some feedback or input. It is the human observer who uses illumination devices and it is important that human response to these products be measured. Results achieved from these measurements can, in turn, be used by the lighting designer to optimize the design of illumination products. Many studies in the field of colour perception and/or matching rely on the method of “psychophysics” where humans are used. Reliability of results achieved when using human observers can be questioned. Results achieved with psychometric testing cannot be compared with an established benchmark and/or standard as such a benchmark was itself generated using human observers, endangering the researchers to become entangled in a closed circle of cause and effect where one depends on the other. This study investigated the reliability of human observers when studying colour perception. Repeatability of results achieved when using human observers was measured. A test was repeated using the same set of observers. Even this approach is not safe as human memory may serve the observer so well, that results can be selected, or at least influenced, on the basis of memory and not perception. The solution was to implement extended time between measurements, thereby hoping that sufficient time will lapse to erase details from the observer’s memory. A colour matching task had to be completed to test observers of two distinct age groups. One group was older than 50 years of age and the second group was younger than 40 years of age. The two groups were tasked to complete the same colour matching test at the beginning of a year and after one year. Test procedures and test equipment were identical before and after the year.

Highlights • Sensor response of single porous Si to the liquid analytes was analyzed using CIE1931 chromaticity parameters. • CIE1931 chromaticity parameters characterize spectrum as whole contrary to the conventional analysis of interference peaks. • Adsorption/desorption of ethanol, water, ethanol-water solutions was studied with colorimetric parameters. • The measured spectral dependences were compared with simulated. Abstract A single porous silicon (PS) layer sensor structure was applied to analyze the kinetics of adsorption/desorption processes of water, ethanol and ethanol-water solution using CIE1931 chromaticity coordinates based parameters such as dominant wavelength λ dom , complementary wavelength λ com and excitation purity (EP). Matrix method was used to obtain reflectance spectra dependences on porosity (P), PS layer thickness (L PS), refractive index of analyte (n analyte). Dependences of λ dom , λ com , EP on P, L PS , n analyte were computed on the base of computed reflectance spectra, and optimal parameters were determined for distinction of model analytes such as water and ethanol. Time dependences of λ dom , λ com were experimentally obtained using CCD-based spectrometer for water, ethanol and ethanol-water solution. Advantage of characterisation of whole complex multiple peaks spectra using chromaticity parameters as opposed to sensor characterization with parameters of individual interference peaks as peak position was demonstrated. [ABSTRACT FROM AUTHOR]

The researcher working in the field of illumination can use a number of measurement methods, depending on the requirement. Many practical evaluation methods employ varieties of a configuration where test stations are positioned next to or opposite each other for comparison purposes. Test stations can consist of test booths or even full-sized test rooms when using indoor evaluations. The number of test booths for indoor application may differ from one to three. Most colour and light perception studies thus depend on human observers to provide some feedback or input. It is the human observer who uses illumination devices and it is important that human response to these products be measured. Results achieved from these measurements can, in turn, be used by the lighting designer to optimize the design of illumination products. Many studies in the field of colour perception and/or matching rely on the method of "psychophysics" where humans are used. Reliability of results achieved when using human observers can be questioned. Results achieved with psychometric testing cannot be compared with an established benchmark and/or standard as such a benchmark was itself generated using human observers, endangering the researchers to become entangled in a closed circle of cause and effect where one depends on the other. This study investigated the reliability of human observers when studying colour perception. Repeatability of results achieved when using human observers was measured. A test was repeated using the same set of observers. Even this approach is not safe as human memory may serve the observer so well, that results can be selected, or at least influenced, on the basis of memory and not perception. The solution was to implement extended time between measurements, thereby hoping that sufficient time will lapse to erase details from the observer's memory. A colour matching task had to be completed to test observers of two distinct age groups. One group was older than 50 years of age and the second group was younger than 40 years of age. The two groups were tasked to complete the same colour matching test at the beginning of a year and after one year. Test procedures and test equipment were identical before and after the year. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Analyzed TM-doped ZnO via XPS, AFM, and PL. • Identified various valence states for Mn, Ni, Cu, and Co. • Revealed how coexisting valence states affect ZnO's luminescence and morphology. [ABSTRACT FROM AUTHOR]

We consider the problem of calculating chromaticity coordinates estimates of triangle vertices gamut for displays with maximum area of color reproduction. Initial data for the evaluation are tabulated data on the shape of the spectral locus interpolated by Bezier splines. Research results are chromaticity coordinates of the triangle vertices gamut maximum area specified on the color chart according to the standards of the International Commission on Illumination.

We consider evaluation problem of chromaticity coordinates increment for an image displayed by indicating means (liquid crystal panels and etc.). Display device profile set by the weight matrix for components of primary colors serves as basic data for quantitative calculation. Research results have the form of mathematical expressions allowing calculation of increment values of chromaticity coordinates of the image displayed on indicating means and histograms of increment distribution.

Subject of Research.We consider the problem of evaluation of chromaticity coordinates shift for image displayed on liquid crystal panels with various properties on color reproduction. A mathematical model represents the color reproduction characteristics. The spread of the color characteristics of the screens has a statistical nature. Differences of color reproduction for screens are perceived by the observer in the form of different colors and shades that are displayed on the same type of commercially available screens. Color differences are characterized by numerical measure of the difference of colors and can be mathematically compensated. The solution of accounting problem of the statistical nature of the color characteristics spread for the screens has a particular relevance to aviation instrumentation. Method. Evaluation of chromaticity coordinates shift of the image is based on the application of the Grassmann laws of color mixing.Basic data for quantitative calculation of shift are the profiles of two different liquid crystal panels defined by matrixes of scales for components of primary colors (red, green, blue). The calculation is based on solving the system of equations and calculating the color difference in the XY-plane. In general, the calculation can be performed in other color spaces: UV, Lab. The statistical nature of the spread of the color characteristics for the screens is accounted for in the proposed mathematical model based on the interval setting of coordinate values of the color gamut triangle vertices on the set of commercially available samples. Main Results. Carried outresearches result in the mathematical expressions allowing to recalculate values of chromaticity coordinates of the image displayed on various samples of liquid crystal screens. It is shown that the spread of the color characteristics of the screens follows bivariate normal distribution law with the accuracy sufficient for practice. The results of simulation are given. We present the ellipses of section for histograms of distribution of chromaticity coordinates for five randomly defined colors that are consistent with the theoretical expressions. Practical Relevance. Research results are usable for engineers designing modern indication equipment based on LCD-panels and for manufacturers while colorimetric calculations and estimation of technological tolerance of chromaticity coordinates among display units in mass production as well.

Subject of Research. The influence of radiation spectra from the source of artificial night light on colorimetric characteristics of image perceived by the pilot in the aircraft cockpit has been studied. The image is displayed on the LCD screen of multifunctional color indication equipment unit. Night illumination of the cockpit is performed with the use of artificial lamps of red, green, blue and, rarely, white light. Method. Any given color to be displayed on the screen is perceived by an observer differently with presence and absence of external illumination. When external light of white color is used, perceived color depends upon color temperature of the light source; if illumination source has any arbitrary spectral characteristics, then perceivable color depends upon whole spectral content of the used source. The color, perceived by an observer, is formed as the mixture of the color displayed on the screen (image element color) with the color presented by diffuse reflection of external illumination source from the surface of the screen. The brightness of both colors is added. Mathematical expressions, that define calculation rule for chromaticity coordinates of color perceived by an observer, are based on the Grassmann’s law of additive color mixing. Quantitative analysis of the effect, caused by radiation spectra from an external source of artificial light on color gamut area, corresponding to image, perceived by an observer, has been performed through simulation in MathCad 15.0. Main Results. It was shown, that the color palette of on-board indication equipment, obtained on automated working place for any preset source of external illumination of fluorescent spectrum, corresponding to white light, is not usable correctly in the aircraft night flight mode. An observer loses ability to perceive properly saturated primary colors of red and blue in the case of green-blue light source of external illumination; and the same issue occurs with green and blue for red light source. Using of sources with high illumination level of “warm” white color causes significant shift of the colors perceived by an observer, from the area of saturated blue and green colors in the direction towards the white point defined by illumination source. Using the sources with high illumination level of smooth white color and also with the white color, which white point coordinates coincide with the white point coordinates the color gamut triangle of the tested screen, lead to offset of colors, perceived by an observer, equally for each primary color (red, green, blue) and yellow, cyan and magenta as well. And finally, dealing with sources with high illumination level of “cold” white color, significant offset of colors, perceived by an observer, occurs; those seeming colors are drifting from the area of saturated red and green colors in the direction towards the white point defined by illumination source. Practical Relevance. The results are usable by developers of indication equipment and the manufacturers of LCD panels for colorimetric calculations with account of an influence of external illumination with various spectral content on the screen.

Subject of research. The problem of software-based compensation of technological variation in chromaticity coordinates of liquid crystal panels is considered. A method of software-based compensation of technological variation in chromaticity coordinates is proposed. The method provides the color reproduction characteristics of the series-produced samples on-board indication equipment corresponding to the sample equipment, which is taken as the standard. Method. Mathematical calculation of the profile is performed for the given model of the liquid crystal panel. The coefficients that correspond to the typical values of the chromaticity coordinates for the vertices of the triangle color coverage constitute a reference mathematical model of the plate LCD panel from a specific manufacturer. At the stage of incoming inspection the sample of the liquid crystal panel, that is to be implemented within indication equipment, is mounted on the lighting test unit, where Nokia-Test control is provided by the formation of the RGB codes for display the image of a homogeneous field in the red, green, blue and white. The measurement of the (x,y)-chromaticity coordinates in red, green, blue and white colors is performed using a colorimeter with the known value of absolute error. Instead of using lighting equipment, such measurements may be carried out immediately on the sample indication equipment during customizing procedure. The measured values are used to calculate individual LCD-panel profile coefficients through the use of Grassman's transformation, establishing mutual relations between the XYZ-color coordinates and RGB codes to be used for displaying the image on the liquid crystal panel. The obtained coefficients are to be set into the memory of the graphics controller together with the functional software and then used for image displaying. Main results. The efficiency of the proposed method of software-based compensation for technological variation of chromaticity coordinates of liquid crystal panel was estimated by the ratio criterion of the areas of cross sections of the histograms p(x,y) at a given probability confidence level, calculated before and after compensation procedure. The sections of histograms, representing distributions of chromaticity coordinates were obtained by mathematical simulation in MathCad 15.0. The simulation software of the method of software-based compensation gives the possibility to obtain the mutual arrangement between the figures formed by sections of the histograms of (x,y)-chromaticity coordinates, and it may be observed as significant reduction of the area after compensation procedure is performed, and changes in the geometry of the cross section shape as well. Sets of dependency curves were obtained, depicting the efficiency criterion value versus resolution of the colorimeter that is used for measuring the chromaticity coordinates. Practical relevance. Research results are usable for engineers who are designing modern indication equipment based on LCD-panels and by manufacturers for colorimetric calculations and for estimation of technological tolerance of chromaticity coordinates among display units in mass production as well.

The influence of five nitrogen (N) application rates (60, 90, 120, 150 and 180 kg N/ha) were evaluated using limestone ammonium nitrate on the curd fresh and dry mass, size, chromaticity coordinates, L*, a*, b* and ascorbic acid content in cauliflower varieties (Largardo, Eskimo and CF-744) during the 2015 and 2016 seasons. Commercial standard 120 kg N/ha was included as a control. Variety ‘Largardo’ showed weak response to N application rates and can be regarded as the least sensitive variety for lower N use. Curd fresh and dry mass and size were not affected at lower N application rates of 60 and 90 kg/ha in ‘Largardo’ compared to the other two varieties. However, L*, b* colour value and ascorbic acid content was higher at lower N application rates <90 kg N/ha in all three varieties. With increasing N application rates, curd became darker and less intense in yellow colour. Increasing rates of N application clearly posed a negative effect on ascorbic acid content. Therefore, ‘Largardo’ can be recommended as a suitable variety that produces higher yield and ascorbic acid content at 60 or 90 kg N/ha, with the application rates lower than the commercially recommended rate (120 kg N/ha). [ABSTRACT FROM AUTHOR]

This work evaluates the chemical stability of the composition YIn 0.95 Mn 0.05 O 3 , through exposure of the material to different acidic, basic and neutral media and the incorporation into an aqueous base of white paint. A high structural stability is evidenced for the different used media except for the acidic solvents, which causes a strong degradation of the optical properties of the material. The latter is due to the presence of a MnO 2 -type phase, possibly amorphous and/or in a low concentration, evidenced at the microscopic level and associated with an oxidation of Mn 3+ cation at the surface of the material. Nevertheless, the integration of the pigment into a water-based paint presents suitable properties to the chemical attack of alkali and acid solvents, favouring the future application of the material in the industrial sector of paints and coatings. [ABSTRACT FROM AUTHOR]

Vacuum ultraviolet (VUV) phosphors are indispensable material to the development of a new generation white-LED, visual display and etc. Searching an ideal host of phosphors from NLO materials is one of effective approaches. Employing excellent NLO crystal β-BaB 2 O 4 (β-BBO) as matrix material, we have synthesized lanthanide ions (Eu 3+ or Tb 3+ )-doped β-BBO phosphors by solid-state reaction, and have investigated their luminescent properties, the optimal doping amount of RE 3+ (Eu 3+ and Tb 3+ ) by ultraviolet wave excitation, decay curves and lifetimes, respectively. For red phosphor, the measured dominating emission peak (610 nm) was attributed to 5 D 0 → 7 F 2 transition of Eu 3+ . For green phosphor, β-BBO:Tb 3+ emits bright green at 542 nm with 278 nm excited light. The concentration quenching curve showed that the optimal concentration of Eu 3+ and Tb 3+ in β-BBO were about 22.00 mol% and 10.00 mol% (theoretical value), corresponding to the effective value of 20.60 mol% and 9.20 mol% measured by ICP, respectively. The variety of lattice parameters of β-BBO:RE 3+ (RE 3+  = Eu 3+ , Tb 3+ ), by contrast to β-BBO, has been calculated according to the XRD data. The luminescence mechanism of RE 3+ -doped β-BBO (Eu 3+ and Tb 3+ ) were analyzed. Chromaticity coordinates, color temperature of β-BBO:RE 3+ (Eu 3+ and Tb 3+ ) were also calculated separately according to the emission spectra, the value of CIE coordinates indicated that the synthesized phosphors have good color purity. The impact of flux-grown synthetic method on the luminescence intensity of as-prepared β-BBO:RE 3+ (RE 3+  = Eu 3+ , Tb 3+ ) was also investigated. [ABSTRACT FROM AUTHOR]

Transparent conducting Stannous Oxide (SnO) thin films were obtained by chemical spray pyrolysis method on glass substrates for 0.1 M and 0.25 M concentration of precursor solutions. Their structural, morphological, optical and electrical properties were investigated. X-ray diffraction (XRD) study shows polycrystalline nature of the films with orthorhombic crystal structure. The morphological analysis was carried out by Scanning electron microscopy (SEM) and elemental analysis was done by Energy dispersive X-ray spectroscopy (EDX). The band gap of 0.1 M and 0.25 M thin film samples were found to be 3.58eV with 82% transmission and 3 eV with 30% transmission respectively. The film thickness, refractive index (n) and extinction coefficient (k) of the films were obtained by ellipsometric technique. Hall effect measurements reveal p-type conduction with mobility 7.8 cm 2 V −1 s −1 and 15 cm 2 V −1 s −1 and conductivity of 8.5 S/cm and 17.1 S/cm respectively for the 0.1 M and 0.25 M samples. Photoluminescence (PL) spectrum of the samples show a broad emission which covers near band edge (NBE) as well as deep level emission (DLE) in the region 380 nm-620 nm. [ABSTRACT FROM AUTHOR]

[Display omitted] • The red light emitting Gd 2-x Si 2 O 7 :xEu3+ (x = 1–8 mol%) phosphors were fabricated through urea assisted solution combustion (SC) synthetic route. • Nanosamples were crystallized into the stable triclinic structure. • The electrically dipole (ED) transition at ∼612 nm corresponding to 5D 0 → 7F 2 transition was accountable for relevant red-light emission. • Dipole-dipole interactions were responsible for the non-radiative energy transfer among dopant ions. • Radiative decay times were estimated by exploiting PL spectra using Auzel's model. A series of Eu3+-doped silicate-based red light-emitting nanocrystalline materials is fabricated via the solution combustion technique. Triclinic crystalline powders with a P-1 space group are formed containing irregularly sized grains. Three-lifetime values indicates the presence of three different local environments surrounding the Eu3+ ion. Upon near-UV excitation, the photoluminescence (PL) spectrum shows a red emission owing to the electronic band at ∼612 nm, consistent with the electronic transition 5D 0 → 7F 2. The energy bandgap is probed using diffuse reflectance spectroscopy. The critical distance between adjacent Eu3+ ions was evaluated to be ∼18.70 Å and multipolar exchanges were found accountable for the concentration quenching. The obtained chromaticity coordinates fall in the red regime of the CIE (1931) triangle, which replicates the potency of designated nanomaterials in the design and architecture of R-G-B (red–green–blue) phosphor-based LEDs. [ABSTRACT FROM AUTHOR]

• Ca 9 Al(PO 4) 7 :Sm3+ nanophosphors have been synthesized via urea-assisted solution-combustion method. • Crystal structure analysis of Ca 9 Al 0.90 (PO 4) 7 :0.10Sm3+ nanophosphor has been reported on Rietveld treatment. • Optical properties for Ca 9 Al(PO 4) 7 host lattice are calculated from DFT. • Energy band gap for Ca 9 Al(PO 4) 7 host is obtained experimentally and theoretically. • These nanophosphors have potential applications in solid state lighting devices. Nanocrystalline phosphors of composition Ca 9 Al(PO 4) 7 : x Sm3+ (x = 0.01–0.16) were successfully synthesized using a urea-assisted highly efficient solution combustion technique. The structural, morphological, and photoluminescence features of the series of white powdered samples were studied using powder X-ray diffraction, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and photoluminescence characterization techniques. The structural framework and crystal phase purity of Ca 9 Al 0.90 Sm 0.10 (PO 4) 7 phosphor were investigated by Rietveld refinement analysis. The results showed that the replacement of Al3+ ions with Sm3+ ions in Ca 9 Al 0.90 Sm 0.10 (PO 4) 7 nanophosphor didn't alter the host lattice crystal structure and a trigonal lattice having R3c (161) space group was established. Meanwhile, the average particle size evaluated from the Scherrer equation was further confirmed by transmission electron microscopic studies revealing a size domain ranging from 35-60 nm. Structural optimization of the pure host via first-principle routing disclosed the density of states and electronic band structure having a band gap of 4.738 eV, which was found to be quite comparable to the experimentally observed value (4.37 eV) from the diffuse reflectance spectra. Many key optical properties, such as optical conductivity, extinction coefficient, loss function, and refractive index were determined by using a calculated dielectric function. Furthermore, photoluminescence studies inferred that 10 mol% of Sm3+ ion in Ca 9 Al(PO 4) 7 host matrix gave the best luminescence emission intensity. Detailed photoluminescent analysis of Ca 9 Al(PO 4) 7 : x Sm3+ phosphors demonstrated that on excitation at 401 nm, an intense reddish-orange emission was received at 600 nm (4G 5/2 → 6H 7/2 transition). The critical distance for energy migration came out to be 22 Å which strongly favors the mechanism behind luminescence quenching as dipole-quadrupole interactions resulting from the over-doping of activator ions. The chromaticity coordinates (0.5216, 0.3630) were obtained using MATLAB computations. These results favor the applicability of Sm3+ doped Ca 9 Al(PO 4) 7 phosphors as the reddish-orange emitter in near-ultraviolet excited white light-emitting diodes. [Display omitted] [ABSTRACT FROM AUTHOR]

Obtener estándares del color del fruto de café durante su desarrollo y maduración es necesario para diferentes procesos relacionados con la cosecha y poscosecha de este producto. Las coordenadas L*, a*, b*, C* y h* en la representación de color CIELab y la reflectancia en el espectro visible (400-700 nm) fueron medidas sobre tres diferentes puntos de la epidermis del fruto de Coffea arabica, var. Colombia. La medición se realizó cada siete días, desde 182 hasta 238 días después de la antesis (DDA), utilizando un espectrofotómetro de esfera, con el objetivo de determinar cuantitativamente el color del fruto en diferentes estados de desarrollo. Los resultados obtenidos indican que los frutos de diferentes días de maduración presentan diferencias de color definidas por la luminosidad, las coordenadas cromáticas y la cantidad de luz reflejada por la superficie del epicarpio, dependiendo de la región del espectro visible analizada. A través de las coordenadas cromáticas a* y h* y de varias longitudes de onda luminosa reflejadas se pueden diferenciar frutos de café de 31, 32, 33 y 34 semanas de desarrollo. El croma b* no permite diferenciar los frutos pintones de los maduros. La saturación C* puede discriminar algunos estados de desarrollo pero no permite establecer diferencias entre los estados inmaduros. Las longitudes de onda 520, 570 y 580 nm permiten discriminar significativamente nueve estados diferentes de desarrollo del fruto. El conocimiento de la colorimetría de los frutos de café puede ser usado para el diseño de sistemas de recolección y clasificación poscosecha, y para la adecuada discriminación entre diferentes estados de desarrollo del fruto, los cuales están relacionados con la calidad de la bebida y con la productividad.Obtain coffee fruit color standards during its development and maturation for different processes related to the harvest and postharvest from this product is necessary. The Coordinates L*, a*, b*, C* and h* in the CIELab color representation and visible spectrum reflectance (400-700 nm) were measured on three different points of the epicarp of coffee fruits (Coffea arabica var. Colombia). The readings were taken every seven days since 182 to 238 days after anthesis (DAA), using a sphere spectrophotometer, with the objective of determining the fruit color for different development stages. The results indicate that fruits of different days of growth display color differences defined by luminosity, chromatic coordinates and the amount of light reflected by the epicarp according to the analyzed region of the visible spectrum . Through the chromatic coordinates a* and h* and from several reflected luminous wavelengths can be differentiated fruits of 31, 32, 33 and 34 weeks of development. The chroma b* doesn't allow to differentiate undermature and mature fruits. The saturation C* can discriminate some stages of development but it doesn't allow to establish differences among immature stages. The wavelengths of 520, 570 and 580 nm allow significantly discriminations of nine different stages of the fruit development. The coffee colorimetry knowledge may be used for design of harvesting and post-harvesting sorting systems, and for discrimination among different stages of the fruit development, which are related to the quality of coffee beverage and with productivity.

[Display omitted] • Urea assisted solution combustion (SC) method has been used for the first time to prepare Gd 4 Al 2 O 9 :xEr3+ (x = 1–6 mol%) nanophosphors. • Crystallographic and refinement parameters were procured by XRD and Rietveld refinement measurements. • The crystallite size and lattice microstrain were calculated by Debye-Scherrer's and Williamson-Hall method. • Dipole-quadrupole interactions are accountable for the concentration quenching effect. • Radiative decay lifetime was computed from emission spectra using Auzel's model. Green emitting Gd 4-x Al 2 O 9 :xEr3+ [x = 1 to 6 mol%] nanophosphors were synthesized via urea assisted solution combustion (SC) synthetic pathway and characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) observations and spectrofluorophotometric measurements. The structural results obtained by XRD measurements and Rietveld refinement confirm that all prepared nanomaterials are crystallized in monoclinic structure, space group P2 1 /c. The strongest excitation located at ∼382 nm is strongly matched to the distinct wavelength of commercially accessible NUV excitable LEDs. Under the excitation at 382 nm, all prepared samples exhibit a series of sharp emission bands centred at 411 nm (2H 9/2 → 4I 15/2), 528 nm (2H 11/2 → 4I 15/2), 558 nm (4S 3/2 → 4I 15/2) and 665 nm (4F 9/2 → 4I 15/2), corresponding to transitions of Er3+ ions. The optimum doping concentration of Er3+ ions in the host is determined to be 3 mol%. The photoluminescence lifetime (τ avg)determined in Gd 3.97 Al 2 O 9 :0.03Er3+ phosphor is observed to be around 2.0191 ± 0.0371 ms. The calculated Commission Internationale de L'Eclairage (CIE) chromaticity coordinates for the optimized phosphor is (x = 0.305, y = 0.592), which is close to the Society of Motion Picture and Television Engineers (SMPTE) (x = 0.310, y = 0.595) coordinates. The study reveals that optimized phosphor could be a potential candidate for near ultra-violet (NUV) excited photonic appliances. [ABSTRACT FROM AUTHOR]

A new series of Zinc telluro-fluoroborate glasses (ZTFB) doped with Dy 3+ ions with the chemical composition (30−x) B 2 O 3 + 30TeO 2 + 16ZnO + 10ZnF 2 + 7CaF 2 + 7BaF 2 + xDy 2 O 3 (where x = 0.05, 0.1, 0.25, 0.5, 1 and 2 in wt%) have been synthesized by the conventional melt quenching technique and the prepared glass samples were characterized through XRD, FTIR, UV-Vis-NIR optical absorption, photoluminescence and decay spectral measurements. The XRD patterns have been recorded to confirm the amorphous nature. The FTIR spectral measurements were carried out to identify the functional groups present in the title glasses. From the energy band positions of the absorption spectra, bonding parameters ( β ¯ and δ) have been calculated to identify the covalent/ionic nature of the metal-ligand bond present in the prepared glasses. The Judd-Ofelt (JO) intensity parameters Ω λ (λ = 2, 4 and 6) have been calculated from the oscillator strengths of the different absorption bands to understand the nature of the ligand environment around the Dy 3+ ions. The radiative parameters such as transition probability (A), stimulated emission cross-section ( σ P E ), radiative lifetime (τ R ) and branching ratios (β R ) corresponding to the 4 F 9/2 → 6 H 15/2 , 4 F 9/2 → 6 H 13/2 , and 4 F 9/2 → 6 H 11/2 emission transitions have been determined using JO parameters and the refractive index values. The CIE chromaticity coordinates were calculated from the luminescence spectra to explore the dominant emission colour of the title glasses and the obtained results were discussed in detail and reported. [ABSTRACT FROM AUTHOR]

Eu 3+ doped fluorozirconate glass ceramics containing BaCl 2 nanocrystals were successfully fabricated by melt quenching method, and their structural and luminous properties were investigated. The existence of BaCl 2 nanocrystals in the glass ceramics plays an important role on the improvement of luminescent properties. The emission intensity in glass ceramics was remarkably enhanced, which attributes to the phonon energy decrease by Eu 3+ ions into BaCl 2 nanocrystals. Meanwhile, the extended average fluorescence decay lifetime from 4.60 ms to 5.42 ms and the decreased Red/Orange ratio and spark splitting of 7 F 1 energy level also confirmed this view. Additionally, the excitation spectra showed that glass ceramics could be effectively excited by NUV light. The CIE chromaticity coordinates of glass ceramics (GC320) were calculated as (0.611, 0.371), which was close to the NTSC standard values for red (0.67, 0.33). The results suggested that the glass ceramics may be used as potential red phosphors under UV light excitation for white light-emitting diodes. [ABSTRACT FROM AUTHOR]

The results of the comparative study of light and color characteristics of compact fluorescent (CFL) and LED lamps in the process of service life are shown. It is shown that commercial samples of LED lamps, which come to the Ukrainian market, have an advantage over CFLs on service life, luminous efficiency, stability of light and color parameters in the process of service life. Lumen maintenance factor of the investigated CFL parties after 6000 hours is 77-62 %. CFLs color temperature in the process of service life is reduced for 6000 hours approximately 100-300 K for lamps with a color temperature of 2700-4000 K for the lamps of 13-32 Watt and 600-900 K color temperature of 6500 K for the lamp of 55-85 Watt. Lumen maintenance factor of the investigated parties of LED lamps after 6000 hours is 99-93 %. Deviation of the chromaticity coordinates of the initial value of 6000 hours no more than one degree of MacAdam ellipses. The color temperature is changed at the same time not more than 100 K. The cost of the light energy generated by modern light sources is calculated. Cost of light energy unit using LED lamps below, compared with CFL, about 1,3 times for electricity tariffs and prices for the lamps in Ukraine in May 2016. [ABSTRACT FROM AUTHOR]

The objective of this study is to develop a measurement system for blue light blocking lens. The main features of the system are using a light pulse modulator and filtering circuit technology to prevent ambient light interference, no any expensive optical filters are needed. Our system is composed of a transmitter circuit, a receiver circuit and a signal processing circuit. The transceiver driving circuit including the modulated LED of 10 kHz and measured the light signals from unwanted noise and unmodulated all light by a photodiode, and then converted by the transimpedance amplifer. The transmitter circuit uses Darlington drive circuit to optimize the LED operating current. The percentage error of the transmittance data is nearly 6%, compared with that of the OCEAN USB 2000 spectrometer's, so proved that this device is feasibility. This experiment has also shown that the chromaticity coordinates will be changed when using blue light lens. Based on the experiment, the brightness of the blue light blocking lenses cannot be too low which will cause color deviation problems. From the analysis result in table 4, the color deviation is nearly 17% at green blocking blue light lenses and 21% at yellow blocking blue light lenses on y coordinates. Therefore, these two blocking blue light lenses are not suitable for use as blue light blocking lenses. The color deviation of coated blue film and brown 20% blocking blue light lens have nearly 3% on x-y coordinates. But, those of 8% in 30% brown and 17% in green lenses are also not suitable for blue light blocking lens using. Thus the most suitable for blue light blocking lenses using is 20% brown blocking lens. In the future, this proposed device may be used as a powerful measurement tool on the eyeglasses test line. [ABSTRACT FROM AUTHOR]

Self-propagating solution combustion (SC) synthetic method has been used to prepare single-phase Gd 4-x Al 2 O 9 :xTb3+ (x = 1–6 mol%) powdered samples. Various structural, morphological and optical studies are performed in order to characterize the designated nanocrystalline materials. Phase recognition and refinement parameters of doped phosphors are explored via X-ray diffraction (XRD) assisted Rietveld refinement technique which authenticates that powdered samples are crystallized into monoclinic crystal system having P2 1 c space group. Williamson-Hall (W–H) linearly fitted method along with Scherrer's formula is employed to calculate the average crystallite size of doped materials which are found to be in the domain of nano-range. Transmission electron microscopy (TEM) reveals the presence of non-uniform agglomerated particles with characteristics porosity. The emission profile of all doped samples possesses sharp emission lines centred at 416, 438, 460, 486, 543, 591 and 621 nm due to 5D 3 → 7F 5 , 5D 3 → 7F 4 , 5D 3 → 7F 3 , 5D 4 → 7F 6 , 5D 4 → 7F 5 , 5D 4 → 7F 4 , and 5D 4 →7F 3 intra-configurational transitions of Tb3+ ion, respectively. The optimized doping concentration of Tb3+ ion for Gd 4 Al 2 O 9 host is found to be 4 mol%. The resulting chromaticity coordinates (x, y) and high correlated color temperature (CCT) values of doped phosphors endorsed their usage in near ultra-violet NUV energized solid-state display appliances. [Display omitted] • Solution combustion method was employed to prepare novel green light emitting Gd 4 Al 2 O 9 :Tb3+ nanophosphors. • Powdered samples have been crystallized into pure monoclinic crystal system. • Critical distance (R c) among dopant ions has been measured for the energy transfer. • Radiative lifetime, quantum efficiencies and non-radiative rates were estimated. [ABSTRACT FROM AUTHOR]