Nano phosphors for light emitting diodes (LEDs) Syntheses and Characterization

Syntheses of phosphors for Light Emitting Diodes (LEDs) of various host matrices by different preparative methods are very import and need of the day for the phosphor industry.  Role of preparative variables in synthesis of nano phosphors and display phosphors along with basic requirements are discussed in the present paper.  Nano phosphors are preferred over micron size phosphors in a number of applications not only due to their particle size but also better optical properties.  Some of the techniques such as solid state diffusion, flame and laser pyrolysis and sol-gel process are being employed to manufacture. The main advantages nanophosphors in potential applications such as solid state lighting, medical, security, displays, remote thermometry and thermoluminescence radiation dosimetry. The present paper discusses the synthesis of display phosphors applicable in Color Picture Tube (CPT) and Plasma Display Panels (PDP) and Phosphor coated LEDs (PLED) for lighting applications

Synthesis and Optical Properties of Ce3+ Doped Gadolinium Silicate Phosphors

The present paper reports the optical properties of rare-earth-doped Gadolinium Silicate Phosphors. The Cerium Oxide (Ce3+) was used as rare-earth-doped. The phosphor is prepared by using the Solid-state reaction method (conventional method) heated at 1200oC for 2 hrs. The received cakes are grounded for 30 minutes each. The phosphors are prepared and the received powder is subjected to PL, XRD, SEM, and EDAX analysis. The following section discusses and the experimental results are mentioned in these phosphors. The present Phosphor can act as a host for blue light emission in many display devices and technological applications

Design and Optimization of Leaf Spring Using Composites

Leaf spring are designed for  the suspension in wheeled vehicles.  Now a days all The automobile industries increased interest in the replacement of steel spring with fiberglass composite leaf spring for high strength to weight ratio. In this work a leaf spring  are designed for heavy vehicle.  In this designing leaf spring following four cases are considered: by modifying the thickness, and no. of leaves, changing camber and changing span. These cases are also considered: Modeling of Road Irregularity, Variation of moving frequency with vehicle speed. Present used material is Steel for leaf spring. In this work, the material is replaced with composites since they are less dense than steel and have good strength The composites used are S2 – Glass Fiber and Epoxy Matrix Composite reinforced by 50% Kevlar fibers. The design is made for leaf spring using Mild Steel, S2 – Glass Fiber and Epoxy Matrix Composite reinforced by 50% Kevlar fibers and all the models are designed in CATIA. . The strength validation is done using FEA software ANSYS. Analysis is done by layer stacking method for composites by changing reinforcement angles for 3 layers, 5 layers and 11 layers. Frequency analysis is also determine the frequencies. CATIA software is used for modeling and ANSYS is used for analysis

TL glow curve and kinetic of gamma irradiated quartz collected from Rasmada mines of C.G. basin

Present paper reports the TL glow curve and kinetic parameter of Quartz. The sample of natural quartz collected from Rasmada mines of C.G. basin is irradiated with gamma source. For gamma exposure Co60 gamma source was used and the exposure of 1 hour to 4 hour was given to the sample with dose 0.5kGy to 2 kGy. TL glow for quartz crystal shows the peaks at temperature 242, 256, 250 and 2520C for doses 2kGy to 0.5 kGy respectively. The powder sample shows TL glow peak at 236, 251, 254 and 2530C respectively. The corresponding activation energy and frequency factor is calculated by peak shape method. The activation energy found to be 0.79 eV for powder and 1.26 eV for quartz crystal, frequency factor is found to be 4X108 to 3X1013sec-1. The maximum activation energy is found for quartz crystal with gamma exposure of 2kGy. The sample shows first and second order kinetics. The sample was characterized by XRD. The Induction coupled plasma activated emission spectra (ICP - AES) analysis was done to find out the percentage of elements in the quartz mineral

Investigation of UV emission and energy transfer process in Ce3+, Gd3+, Pr3+ and their combination doped nano crystallite La2O3 phosphors

Despite being a harmful radiation, there are many useful applications of UV radiation. This includes its use in the biomedical field. Hence, it is required to generate the UV radiation with desired characteristics. In this work, seven rare earth based compounds i. e. 1 % Ce3+: La2O3, 1 % Gd3+: La2O3, 1 % Ce3+ – 1 % Gd3+: La2O3, 2 % Ce3+ – 1 % Gd3+: La2O3, 1 % Pr3+: La2O3, 1 % Pr3+ – 1 % Gd3+: La2O3, and 2 % Pr3+ – 1 % Gd3+: La2O3 have been synthesized to study their UV emission properties and related energy transfer process. The synthesis process is also relatively simple and eco-friendly, with fewer elements used and giving a higher yield of products. The XRD & EDAX analysis reveals that the obtained compounds possess high purity and are in hexagonal phase state with crystallite size in the nanometer range. The bandgap and refractive index were calculated from absorption spectra obtained by UV – Visible spectrometry. From the PL Spectroscopy, the emission of 1 % Gd3+: La2O3 falls in UVB region, while that of 1 % Ce3+: La2O3 & 1 % Pr3+: La2O3 – in UVA region. Both, UVA and UVB emission were recorded in 1 % Ce3+ – 1 % Gd3+: La2O3, 2 % Ce3+ – 1 % Gd3+: La2O3 due to the resonance transfer and radiative transfer of energy from Ce3+ ion to Gd3+ ion. In 1 % Pr3+ – 1 % Gd3+: La2O3 and 2 % Pr3+ – 1 % Gd3+: La2O3, the emission was obtained in UVA with very low intensity and another intense peak was observed in the visible region due to the energy transfer from Gd3+ ion to Pr3+ ion. The parameters like redshift D, centroid shift Ɛc and crystal field splitting Ɛcfs were calculated for Ce & Ce – Gd based La2O3 compounds. Based on these calculations, the model for energy levels of Ce3+ in La2O3 is proposed

Investigation of a new way of synthesis for Nano crystallites of La2O2S & 1%Ln3+ (Ln = Pr, Eu, Tb, Dy, Er) doped La2O2S and study their structural and optical properties

Nano-crystallite Lanthanum oxysulfide (La2O2S), a versatile compound with a wide range of applications, has been synthesized by the Solid State, Hydrothermal, and a novel Furnace Combustion technique. The last one limits the precursors, thus minimizing the resource usage, does not require passing of the H2S, CS2, or any of the hazardous gasses during the reaction and is less time-consuming while providing the maximum yield output. Thus, the novel Furnace Combustion method is marked for potential industrial use. The comparative XRD analysis showed the highest phase purity of the samples created by the Furnace Combustion technique, which was then employed for the synthesis of 1% Ln3+:La2O2S (Ln = Pr, Eu, Tb, Dy, Er) samples. The crystallite size was estimated by the Scherrer equation. The EDAX spectra proved the successful incorporation of doped elements. The samples showed absorption peaks in the UV region attributed to the excitation into 4f5d for Pr3+ and Tb3+, charge-transfer state for Eu3+, host absorption for Dy3+ and 4f levels for Er3+ doped samples. The emission spectra showed 4f - 4f transitions typical for the doped rare-earth ions. The bandgap energies are estimated by the Tauc plot. The 4.95 eV band-gap of pristine La2O2S is significantly dropped by doping. The refractive index values slightly increased by doping with rare-earth ions from 2.00 for the pure sample to ca. 2.20 for the doped samples. © 2020 Elsevier B.V

Studies on the luminescence properties of CaZrO3:Eu3+ phosphors prepared by the solid state reaction method

CaZrO3:xEu3+ (x = 1.0, 2.0, 3.0, 4.0, and 5.0 mol%) phosphors were successfully prepared by a solid state reaction method. The crystal structure of sintered phosphors was hexagonal phase with space group of Pm-3m. The near ultra-violet (NUV) excitation, emission spectra of the CaZrO3:xEu3+ phosphors were composed of sharp line emission associated with the transitions from the excited states 5D0 to the ground state 7Fj (j = 0, 1, 2, 3, 4) of Eu3+. The results indicated that CaZrO3:xEu3+ might become an important orange-red phosphor candidate for use in white light emitting diodes (WLEDs) with near-UV LED chips. The mechanoluminescence (ML) intensity increases linearly with increasing impact velocity of the moving piston, suggesting that the sintered phosphors can also be useful as a stress sensor

Synthesis, structural characterization and thermoluminescence properties of ?-Irradiated wollastonite nanophosphor

Nanocrystalline wollastonite (?-CaSiO3) phosphor powder has been synthesized by low temperature combustion method and characterized by powder XRD (X-ray diffraction). The structural morphology and the particle size have been analyzed by SEM (scanning electron microscopy) and TEM (transmission electron microscopy) respectively. The powder has been subjected to ?-irradiation and the resulted thermoluminescence (TL) behaviour has been investigated. The TL glow curves reveal that the TL intensity increases with the radiation dose, a property desired by a TL dosimeter. The trapping parameters like activation energy (E) and order of kinetics (b) were estimated by deconvolution method using peak shape of 60 Gy glow curve and the results are discussed. © 2011 The Indian Ceramic Society