Table of contentsIntroductionExperimentalResults and discussionConclusionIntroductionRare earth (RE) doped nanophosphors are widely used in light emitting diodes (LEDs), field emission displays (FEDs), scintillators, imaging medical and drug administration. Exceptional electronic and optical properties are derived from the ff and fd transitions. However, many synthesized nanophosphors degrade rapidly when exposed to critical conditions. It is therefore necessary to synthesize a nanophosphorus, stable under high vacuum, with high luminosity, thermal and chemical stability and having adequate mechanical strength. Say no to plagiarism. Get a tailor-made essay on “Why violent video games should not be banned”?Get the original essayInorganic oxide nanophosphors have received considerable attention for the generation of color-tunable materials due to their high brightness characteristic, their long life, low power consumption and low power consumption. ecological nature. Earl Danielson in 1998 reported a new inorganic oxide compound (strontium-cerium oxide), synthesized by a combinatorial chemical procedure, which crystallizes in an orthorhombic crystal system with space group Pbam (no. 55) and parameters of cell: a = 6.11897 (9) Å, b=10.3495(2) Å and c=3.5970(1). This strontium-cerium oxide (Sr2CeO4) is a blue-white emitting oxide and an excellent phosphor with high thermal and chemical stability, making it a promising matrix for various activators. The photoluminescene of Sr2CeO4 is due to the energy transfer between O2- and Ce(IV) localized in one-dimensional chains of the edge-sharing CeO6 octahedron. Regularly located luminescent elements govern the luminescent properties of the oxide, and the interaction of these regular optical centers that promotes spatial delocalization of the excitation energy is an important feature. Sr2CeO4 doped with rare earth (RE) ions gives rise to the emergence of amazing materials with a wide range of elements. excitation band in the UV range and tunable emission. This is due to the efficient transfer of excitation energy from the host to doped centers emitting colors in another spectral range. Additionally, luminescence properties depend on the RE dopant used and the dopant concentration. Several methods have been developed for the synthesis of efficient single-phase RE-doped luminescent Sr2CeO4 nanophosphor. These procedures are still evolving due to various disadvantages of stability, size control and morphology. To help overcome these limitations, we reported here for the first time the synthesis of a rod like luminescent Sr2CeO4: Eu3+ (mol % of Eu = 0, 0.1, 0.5, 1, 1.5, 2 ) by combustion method. A systematic methodology was followed for the synthesis of this highly stable nanophosphorus. Eu3+ was chosen because it acts as a good activator ion with red or orange-red emission in various hosts. The results show white light generation at lower concentration, while red luminescence at higher concentrations of the dopant. The report also covers the synthesis and characterization aspects of the RE doped complex as well as their potential use in lighting and optoelectronic devices. Experimental synthesis of nanophosphorus Sr2CeO4:Eu3+ (0.1–2 mol%) Eu3+-doped nanophosphorus were prepared by a modified solution combustion method. The source of Sr, Ce, Eu was strontium nitrate (Sr(NO3)2).9H2O; 99.99%, Merk Ltd), cerium nitrate (Ce(NO3) 3.6H2O; 99.99%Sigma Aldrich Ltd) and europium nitrate (Eu(NO3) 3.xH2O; 99.99% Sigma Aldrich Ltd) respectively. Many fuels like citric acid, glycine, oxalic acid, oxalyl dihydrazide (ODH), urea, etc. have been used for the synthesis of nanophosphorus materials. Citric acid produces a bulky fluffy product, while urea is environmentally friendly, inexpensive, and readily available have been used compared to hydrazine-derived fuels. The stoichiometric quantities of strontium, cerium, europium nitrate were taken in a beaker with a capacity of 200 ml in order to synthesize Sr2-xCeO4:Eux3+ (x=0.1-2mol %)nanophosphores, taking into account the Eu3+ ions replacing the Sr2+ ions in the structure. The required amount of urea was added to the mixture and to dissolve the mixture, 20 ml of deionized water was added, the mixture was well dispersed using the magnetic stirrer at 80°C. °C for 10-15 minutes. The stoichiometry of the redox mixture used for combustion was calculated using the total oxidizing and reducing valencies of the compounds. By balancing the total oxidizing and reducing valencies of the compound, the stoichiometry of the redox mixture was calculated for combustion. Into the preheated muffle furnace maintained at 550 + 10°C, the homogeneous mixture was introduced, the solution first boiled and underwent dehydration, followed by the release of a large amount of CO2, H2O, N2 gas . Then, a spontaneous spark occurred and underwent a combustion reaction. The whole process was completed in 10 minutes. The foamy product was slowly cooled to room temperature, the product was ground in a mortar and pestle and then calcined at 1000 °C for 4 h. The complete combustion equation for the redox mixture used for the synthesis can be written as: 12 Sr(NO3)2).9H2O + 6 Ce(NO3)3.6H2O + 34CH4N2O → 6 Sr2CeO4 + 34 CO2 + 68H2O + 55N2 12Sr1- x (NO3)2 + 6Ce(NO3)3.6H2O + 34CH4N2O + xEu(NO3)3.XH2O → 6Sr2CeO4:xEu + 55 N2 + 104 H2O + 34CO2 2.2 Characterization and instrumentation The phase purity and crystal structure of the products obtained were characterized by powder X-ray diffraction, using an nickel, is used to obtain the diffraction data. The XRD patterns were collected in the range of 10°<2θ<70°. The UV-visible absorption spectrum was recorded on the Shimadzu 2600 UV-visible dual-beam spectrophotometer. Photoluminescence (PL) measurements were carried out on a Cary Eclipse fluorescence spectrophotometer (Agilent Technologies) equipped with a halogen lamp. 450 W xenon as excitation source. The morphology of the product was examined by FE-SEM (Hitachi SU 70). All measurements were carried out at room temperature. Color coordinates were calculated by the CIE Chromaticity color calculator. Results and discussion Pure Sr2CeO4 and doped Sr2-xEuxCeO4 phases (x = 0.1-2 mol%) were synthesized by a low-temperature, stepwise combustion method to modify the structural properties and as Consequently, the luminescence characteristics thanks to the replacement of Sr2+ ions by Eu3+ ions in the structure. The compounds are highly crystalline, very pale yellow in color, stable in air, insoluble in water.DRX analysisThe diffraction patterns of the synthesized Sr2CeO4 doped with 0.5 mol% of Eu3+ ions calcined at 1000°C are shown in Figure 1. Based on the measured X-ray diffraction analysis and in comparison with the reported data, it indicates the formation of a single orthorhombic phase with the Pbam space group. The introduction of Eu3+ doping ions into the crystal structure of the oxide is confirmed without notable distortion of the diagram.diffraction. This confirms that Eu3+ ions successfully exist in the lattice site rather than the interstitial site. Dopant site substitution can be inferred from the percentage difference in ionic radii of the host and dopant ions. In our system, the ionic radius of Eu3+ is 0.947Å, while that of Se2+, Ce4+ is 1.18Å, 0.87Å respectively under the coordination number (CN=6). The percentage difference in ionic radii (Dr) between the host and doped ions is calculated using Eq. Dr = Rh(CN) -- Rd(CN) Rh(CN) Where CN is the coordination number, Rh(CN) is the radius of the host cations, Rd(CN) is the radius of the doped ion. The calculated Dr values ​​between Eu3+ and Sr2+ at six coordinated sites are 19.74%, while that between Eu3+ and Ce4+ is -8.85%. This proves that the Eu3+ dopant would clearly replace the strontium sites. Therefore, Eu3+ preferentially replaces Sr2+ rather than Ce4+. Similar results have been reported for various Sr2CeO4phosphorus-doped rare earth ions. Atomic mobility causes grain growth which results in better crystallanity because all samples were calcined at a higher temperature (1000°C). The average crystallite size was estimated by the Debye-Scherrer method. D = [ 0.9λ ] Βcosθ Where D is an average crystallite (grain) size, the factor 0.9 is the Scherrer constant, λ designates the wavelength of the X-ray radiation, β is the half-maximum width ( FWHM) and θ the Bragg angle of an observed diffraction peak. The particles were found to be smaller, in the nanometer range, and some large grains were also present. This led to a slight deviation in Scherer's calculations. The nanophosphorus obtained was composed of nanocrystallites with an average size of 64.16 nm. Increasing the dopant concentration introduces deformation and alteration of the lattice periodicity, resulting in a decrease in crystal symmetry. The crystallite size was also calculated from the broadening of the X-ray powder diffraction line (β) using the analysis described by the Williamson and Hall (WH) plot. βcosθ= ɛ(4 sinθ) + 1 /D λ λ Where β is the FWHM in radian, ɛ is the developed strain and D is the size of the crsyatallite. The equation represents a straight line between 4Sinθ/ λ (X axis) and β cosθ/ λ (Y axis). The slope of the line gives the inhomogeneous strain (ɛ) and the intercept (1/D) of this line on the Y axis gives the size of the crystallites (D). The particle size calculated by WH was 54.64 nm. The dislocation density was estimated using the relationship δ=1/D2. There is a slight difference in the crystallite sizes determined from the WH plots and those calculated using the Scherrer formula. The small variation is due to the fact that in Scherrer's formula the strain component is assumed to be zero and the observed broadening of the diffraction peak was considered to be the result of grain size reduction only. FE-SEM analysis It shows a soft and porous agglomerated morphology due to combustion synthesis. However, the FE-SEM images obtained in this study show rod-shaped structures with nanometer diameters. During combustion synthesis, the temperature immediately rises to a higher level and stays there for a few seconds and quickly drops back down to a lower temperature. In a very short time, the crystals undergo a rapid shape evolution process for the formation of various morphologies. UV-Vis Absorption Spectroscopy The optical absorption spectra were recorded in the wavelength region of 200–450 nm. A blatant absorption peak around 330 nm and 260 nm is observed in all samples while peaks at 220 nm arepresent in concentrations greater than 0.1 mol% of dopant. With the change in dopant concentration, the absorption wavelength varies slightly, as shown by the increase in doping concentration, the absorption edge shifts to a higher wavelength. The optical energy interval, Eg of the doped samples was calculated using the Tauc relation. αhν ~ (hν - Eg)n Where hν is the photon energy and α is the optical absorption coefficient near the fundamental absorption edge. The absorption coefficient α is calculated from the optical absorption spectra. The optical bandgap energy values ​​are obtained by plotting (αhν)n Vs hν in the high absorption range and then extrapolating the linear region of the plots to (αhν)n=0. For example is the optical band gap and n is the constant associated with the different types of electronic transition n = ½, 2.3/2, 3 for the direct allowed, indirect allowed, forbidden and indirect forbidden transitions respectively. The optical energy bandgap of nanophosphors varies between 3.08 and 3.21 eV. The variation in Eg values ​​with different concentrations of Eu3+ in Sr2CeO4 is mainly attributed to structural defects such as vacancies, a degree of structural disorder in the lattice, which is capable of changing the optical energy of nanophosphors. distribution of the intermediate energy level in the band gap. Photoluminescence studies the luminescence properties of single-phase Sr2CeO4 blue light generation. The figure shows the excitation spectra of strontium-cerium oxide. It consists of two peaks, a broad band at 260 nm and a shoulder at 340 nm. Due to the different types of Ce4+ and O2- network bonds, the spectra show two excitation peaks due to different charge transfer transitions. The characteristic emission of the blue phosphorus Sr2CeO4 is linked to the CT phenomenon from the orbitals of the O2- ions to the empty 4f shell of the Ce4+ ions. The upper energy band (245 nm) arises from the O1toCe4+ transition, where O1 is the terminal oxygen ion in the structure of Sr2CeO4, and the peak at 330 nm results from the CT transition between the equatorial oxygen ion and the Ce4+ ion (O2-toCe4+). The figure shows the emission spectra of strontium-cerium oxide. It is a simple broad band whose center is located at 475 nm attributed by the Ce4+ charge transfer emission, in Ce4+ the 4f layer is vacant, so the only possible transition is the one in which an electron is excited from the oxygen ligand to the Ce4+ ion. : a charge transfer transition. Under UV radiation, the excitation of the ground state towards one of the excited states, t1u-f or t1g-f, associated with two groups of O2- ions (equatorial and terminal) occurs. Due to the t1u-f spin forbidden transitions, the associated absorption or excitation band is less intense than the band connected to the t1g-f transition. The emission between 400 and 600 is linked to the radiative relaxation process of the excited CT state of the CeO6 complex. It is associated with a reduction in the size of crystallites. It directly influenced the energy band gap of Sr2CeO4, widening the distance between the ground and excited CT states. Luminescence properties of Sr2CeO4 doped: Eu3+ (0-2 mol%) Emission of white light at low concentration and red light at higher concentration is observed. The excitation spectra were recorded by setting the highest emission intensity of Eu3+ (615 nm) as the observation wavelength for the entire dopant concentration. The recorded spectra show the same characteristics for all measured samples with a broad band in the range of 200–320 nm and a shoulder at 340 nm, which are attributed to the Ce4+-O2-CT transition of undoped Sr2CeO4. The Eu3+ ions in the oxide present.