Increase Of Bi3 Research Articles

Red emission enhancement in BaYF5:Eu3+ phosphor nanoparticles by Bi3+ co-doping

Herein, we report the photoluminescence properties of Bi3+-sensitized BaYF5:10 mol%Eu3+ nanoparticles. The emission spectra feature Eu3+ peaks corresponding to transitions from the 5D0 excited to 7FJ (J = 1, 2, 3, 4) lower levels with two dominant emissions positioned in the orange-red (∼ 592 nm, 5D0 → 7F1) and deep-red (∼ 697 nm, 5D0 → 7F4) regions. Upon 265 nm excitation, the emission intensity increases with an increase of Bi3+ concentration up to 20 mol%. Due to the energy transfer from Bi3+ to Eu3+ ions, the integrated intensity of Eu3+ emission in the Bi3+ co-doped BaYF5:10 mol%Eu3+ is 216% stronger than in the Bi3+-free sample. Our findings demonstrated that BaYF5:Eu,Bi has potential in plant lighting technology due to strong emission in red and deep-red spectral areas.

Tuneable Red and Blue Emission of Bi3+-Co-Doped SrF2:Eu3+ Nanophosphors for LEDs in Agricultural Applications.

Tunable blue/red dual-emitting Eu3+-doped, Bi3+-sensitized SrF2 phosphors were synthesized utilizing a solvothermal-microwave method. All phosphors have cubic structure (Fm-3m (225) space group) and well-distinct sphere-like particles with a size of ~20 nm, as examined by X-ray diffraction and transmission electron microscopy. The diffuse reflectance spectra reveal a redshift of the absorption band in the UV region as the Bi3+ concentration in SrF2: Eu3+ phosphor increases. Under the 265 nm excitation, photoluminescence spectra show emission at around 400 nm from the host matrix and characteristic orange 5D0 → 7F1,2 and deep red 5D0 → 7F4 Eu3+ emissions. The red emission intensity increases with an increase in Bi3+ concentration up to 20 mol%, after which it decreases. The integrated intensity of Eu3+ red emission in the representative 20 mol% Bi3+ co-doped SrF2:10 mol% Eu3+ shows twice as bright emission compared to the Bi3+-free sample. To demonstrate the potential application in LEDs for artificial light-based plant factories, the powder with the highest emission intensity, SrF2: 10Eu, 20 Bi, was mixed with a ceramic binder and placed on top of a 275 nm UVC LED chip, showing pinkish violet light corresponding to blue (409 nm) and red (592, 614, and 700 nm) phosphors' emission.

Microstructure, optical, dielectric, and nonlinear properties of Cd1-xBi2x/3Cu3Ti4O12 ceramics

Microstructure features along with optical, dielectric and nonlinear properties of Cd1-xBi2x/3Cu3Ti4O12 (x = 0, 0.3, 0.6, 0.9, and 1.0) ceramics were investigated systematically. With increase in Bi3+ doping content, Cd1-xBi2x/3Cu3Ti4O12 structure sightly distorted and eventually formed more stable configuration. Bi3+ doping also caused grain refinement and increased compactness of ceramics, whereas Bi-rich phase appeared at grain boundaries. Optical band gap (Eg) decreased due to increase in defect concentration. Dielectric loss (tanδ) dropped with increase in Bi3+ doping content while dielectric constant (ɛ′) remained high. The most optimal dielectric characteristics (the lowest tanδ of ∼0.033, giant ɛ′ of ∼10028 at 10 kHz and room temperature, the highest nonlinear coefficient (α of 4.62) and breakdown field strength (Eb of up to ∼9.23 kV/cm) were achieved at x = 0.9. Impedance spectra revealed semiconducting grains and insulating grain boundaries. Dielectric response evolution in Cd1-xBi2x/3Cu3Ti4O12 ceramics was described using internal barrier layer capacitor model. Electric modulus values indicated that low-frequency relaxation originated from grain boundaries. High energy barrier of grain boundaries was beneficial for enhancement of nonlinear properties of ceramics. Thus, Bi3+ doping improved both dielectric and nonlinear characteristics of Cd1-xBi2x/3Cu3Ti4O12 ceramics.

Morphological and structural properties of bismuth-nickel ferrite synthesized by a combined sol-gel method

In this paper, Bi x Ni1-x Fe2O4, (x = 0, 0.3, and 0.5), nanoparticles were synthesized by a sol–gel method, and the synthesized samples were calcination at 350 and 650o C for 3 h. The influence of Bi doping on morphological and structural properties was studied. The field emission scanning electron microscopy (FESEM) analysis showed all of the specimens contain a compact order of homogenous nanoparticles with a spherical form and polyhedral particles with an average size ranging from 36.305 nm to 27.554 nm at 350 and 650o C respectively. By studying the energy dispersive spectrometer analysis patterns, the existence of constituent elements, Ni, Bi, Fe, and O, was verified with a proportion very close to the stoichiometry of the chemical formula. The formation of a ferrite phase was confirmed by X-ray diffraction. An increase in the average crystallite and grain size has been observed with an increase in Bi doping. The Fourier Transform Infrared(FT-IR) studies were made in the frequency range 400-4000 cm-1 and observed two strong absorption peaks. The frequency band is found at 555 cm-1 whereas the lower frequency band is at 1338.5 cm-1. It is noticed that the two prominent absorption bands were slightly shifted towards the higher frequency side with the increase of Bi3+ ion concentration.

Fabrication, structural characteristics, and influence of Bi3+ doping concentration on UV-vis spectra of Bi3+:SnO2 nanocomposite materials

The authors report the characteristics and optical properties of Bi3+-doped SnO2 quantum dots prepared bysol-gel and hydrothermal methods. The structure and morphology of the materials as a function of dopingconcentration were studied and analysed by X-ray diffraction (XRD) and scanning electron microscope(SEM). The structure of the material was assigned to the tetragonal crystal structures of the SnO2 rutile phase,reported in JCPDS Card No. 41-1445. With the increase of Bi3+ doping, the crystallinity of Bi-doped SnO2worsened. The average sizes of the SnO2 nanocrystals were within 3-8 nm. The effect of Bi3+ ion concentrationon the absorbance properties of the materials was investigated by UV-Vis absorption spectra. The absorbancedecreased with increasing the concentration of Bi3+ dopant in the SnO2 lattice. The bandgap width decreasedwith Bi3+ dopant concentration. All Bi3+-doped SnO2 samples presented an enlargement of the light absorptionrange due to a bandgap width decrease.

Synthesis, crystal structure, and superconductivity of Ba(Bi0.25Pb0.75)1−xMgxO3−δ

Magnesium has been doped into the B-site of BaBi0.25Pb0.75O3−δ to form a solid solution Ba(Bi0.25Pb0.75)1−xMgxO3−δ (0 ≤ x ≤ 0.10) by solid-state reaction. The X-ray, neutron, and selected area electron diffraction are used to confirm that this solid solution crystallizes in triclinic space group P1. The unit cell volume of Ba(Bi0.25Pb0.75)1−xMgxO3−δ increases with Mg, which is surprising because the radius of Mg2+ is smaller than any radius of Bi3+, Bi5+, Pb2+, and Pb4+. XPS and iodometric titration data of samples show that the oxygen vacancies increase with Mg in Ba(Bi0.25Pb0.75)1−xMgxO3−δ. The increased oxygen vacancies result in increase of Bi3+:Bi5+ and Pb2+:Pb4+ ratios, which is the utmost possible reason for unit cell volume increase. They are all superconductors with TCzero (the highest temperature at which the electrical resistivity becomes “zero”) between 11.2 and 9.2 K.

Effect of Bi3+ ions substitution on the structure, morphology, and magnetic properties of Co–Ni spinel ferrite nanofibers

In this study, various Co0.5Ni0.5BixFe2-xO4 (x ≤ 0.10) spinel ferrite nanofibers (CoNiBi SFNFs) have been synthesized by electrospinning technique. The structure, morphological, and magnetic features of CoNiBi SFNFs was investigated. XRD analysis demonstrated the formation of single-phase cubic spinel structure for all samples. The cell parameter is increasing with the increase of Bi3+ content. The cubic morphology of all products was also verified by SEM and TEM microscopies. Mössbauer analysis was used to determine the hyperfine parameters by fitting room temperature mosspectra. The Bi3+ ions occupy mainly the B site. Vibrating sample magnetometry (VSM) was applied to get magnetic data for CoNiBi SFNFs at 300 and 10 K. The characteristics of the recorded magnetic hysteresis curves revealed the existence of just ferrimagnetic phases for all fabricated spinel nanofiber samples at both temperatures. The remanent magnetization Mr, saturation magnetization MS, magnetic moment per formula nB, coercivity Hc have been determined. Bi3+ ion substitution commonly diminishes the magnetic data except the content of x = 0.04. The maximum and minimum magnitude of magnetic parameters belong to Co0.5Ni0.5Bi0.04Fe1.96O4 and Co0.5Ni0.5Bi0.10Fe1.90O4SFNFs, respectively. Pristine Co0.5Ni0.5Fe2O4 and Bi3+ ion doped samples exhibit soft magnetic at 300 K and hard magnetic nature at 10K conditions. Squareness ratio (SQR = Mr/Ms) provided extra information about the domain structure of fabricated nanofiber samples. At 10K conditions, SQR of the sample Co0.5Ni0.5Bi0.04Fe1.96O4 is almost equal to 0.5 and this critical value is assigned to the formation of single domains with uniaxial symmetry for this nanofiber. This one only and all others have SQRs that are much lower (0.073–0.366) at 300K or higher (0.620–0.781) at 10K. Those ranges specify the multi-domain wall structure for samples.

Effect of Bi doping on the crystal structure, magnetic and magnetocaloric properties of La0.7-xBixSr0.15Ca0.15MnO3 (x = 0, 0.05, 0.10, 0.15) manganites

The influence of Bi3+ doping on the structure, magnetic and magnetocaloric properties of La0.7-xBixSr0.15Ca0.15MnO3 (x = 0, 0.05, 0.10, 0.15) was studied. The samples were prepared by the Pechini sol–gel method. The powder X-ray diffraction data demonstrates that the major phase of samples possesses a single perovskite structure with the Pbnm orthorhombic space group. Rietveld refined data shows that the lattice parameters and unit cell volume become large with an increase of Bi3+. The magnetization measurement demonstrates that the Curie temperature and relative cooling power decrease with the increase of Bi3+ content, while the maximum magnetic entropy change first increases with the increase of Bi3+ content, and then decreases. La0.6Bi0.1Sr0.15Ca0.15MnO3 exhibits a giant value of magnetic entropy (2.16 J/kg·K at around 291 K) under an applied magnetic field of 2 T, and the RCP for this compound is found accordingly as 99 J/kg, which can be used as one of the potential magnetic refrigerant materials close to room temperature.

Role of Bi3+ ions on structural, optical, photoluminescence and electrical performance of Cd0.9-xZn0.1BixS QDs

In this work, the Cd0.9-xZn0.1BixS QDs with different compositions of Bi3+ ions (0 ≤ x ≤ 0.05) were synthesized using a facile chemical route. The prepared QDs were characterized for analyzing the structural, morphological, elemental, optical, band gap, photoluminescence and electrochemical properties. XRD results confirmed that the Cd0.9-xZn0.1BixS QDs have a cubic structure. The mean crystallite size was increased from ~ 2 to ~ 5 nm for the increase of Bi3+ ions concentration. The optical transmittance behavior was decreased with increasing Bi3+ ions. The scanning electron microscope images showed that the prepared QDs possessed agglomerated morphology and the EDAX confirmed the presence of doped elements as per stoichiometry ratio. The optical band gap was slightly blue-shifted for initial substitution (Bi3+ = 1%) of Bi3+ ions and red-shifted for further increase of Bi3+ compositions. The optical band gap was ranged between 3.76 and 4.0 eV. High intense red emission was received for Bi3+ (1%) doped Zn:CdS QDs. The red emission peaks were shifted to a higher wavelength side due to the addition of Bi3+ ions. The PL emission on UV-region was raised for Bi3+ (1%) and it was diminished. Further, a violet (422 nm) and blue (460 nm) emission were received for Bi3+ ions doping. The cyclic voltammetry analysis showed that Bi3+ (0%) possessed better electrical properties than other compositions of Bi3+ ions.

Effect of Bi3+ on magnetic properties of nanosized La0.7-xBixSr0.3MnO3

Nanoparticles of La0.7-xBixSr0.3MnO3 (0 ≤ x ≤ 0.40) manganites, prepared by high energy planetary ball mill using the top-down approach, have been subjected to structural and magnetization studies to understand the influence of Bi3+ substitution. In the present work, we compare the properties of nanoparticles of all compositions prepared by milling up to 48 h. The structural analysis carried out on the X-ray diffractograms using Rietveld refinement method suggest that as Bi3+ content increases, the structure changes from rhombohedral (space group R-3c, in hexagonal setting) for × ≤ 0.20 to orthorhombic (space group Pnma) for × ≥ 0.30. We also find that the particle size of ∼ 17 nm observed in × = 0.0 sample, increases to ∼ 40 nm for × = 0.35 sample. It is interesting to note that along with changes in the structure and particle size, we observe a cross-over from ferromagnetism (FM) in × = 0.0 (TC = 370 K) to antiferromagnetism (AFM, for × ≥ 0.40). With increase in Bi3+, FM decreases and AFM evolves in the system. For × = 0.40, no long-range ferromagnetism has been noticed. The observed changes in the structural and physical properties could be attributed to the 6 s lone pair character of Bi3+ ions. In the present work, details of structural analysis and magnetization measurements will be presented and discussed.

Preparation and study of lattice structure and magnetic properties of Bi3+ ion-doped Ni–Mg–Co ferrites by sol–gel auto-combustion method

In this paper, Bi3+ ion-doped Ni–Mg–Co ferrite nanomagnetic materials were prepared by sol–gel auto-combustion method using high-purity nitrates and citric acid experimental materials. The effect of Bi3+ ion content on the lattice structure and magnetic properties of nanoferrite was also studied. XRD diffractogram analysis shows that the Ni–Mg–Co ferrite samples with x = 0 and 0.025 have single-phase cubic spinel structure. It is found that when the doping amount is 0.05 or >0.05, the secondary-phase Bi2O3 peak appears. The average crystallite size of the sample was calculated by Debye–Scheller formula. It was found that the average grain size of the sample was affected by the doping concentration. With the increase in Bi3+ ion content, the average crystallite size increases from 8.3797 nm to 8.3940 nm. The structure of Bi3+ ion-doped Ni–Mg–Co ferrite was further characterized by FT-IR. There are two absorption bands ν1 and ν2 at 584 and 397 cm−1, which further prove the spinel structure. The morphology of the sample particles was observed by SEM, and the distribution of the particle size was calculated. The chemical components of powder samples were analyzed by EDS. Through VSM analysis, the Bi3+ ion-doped Ni–Mg–Co ferrite has the characteristics of ferromagnetism. With the increase in Bi3+ ion content, the residual and saturation magnetization decreased; the magnetic stability is also reduced. The results show that the magnetic properties of Bi3+ion-doped Ni–Mg–Co ferrite are decreased.

Fabrication of Bi3+ substituted yttrium aluminum iron garnet (YAIG) nanoparticles and their structural, magnetic, optical and electrical investigations

In this work, Y3−xBixAl0.5Fe4.5O12 nanoparticles in powder form with composition x = 0.0, 0.5, 1.0,1.5 and 2.0 were fabricated by a sol–gel auto-combustion technique and calcined at 1150 °C for 10 h. The analysis of X-ray diffraction patterns using Rietveld refinement suggests that Bi-substituted yttrium aluminum iron garnet (YAIG) samples crystallize in cubic structure with Ia- $$\bar{3}$$ d space group. The average size of crystallite of the samples calculated by the Scherer formula is found in the range of 19–24 nm which are in consistent with that of measured from Williamson–Hall curve. The absorption bands in Infrared spectra corresponding to garnet are shift to lower frequency with the increase of the Bi3+ concentration. Raman spectroscopy shows the non-vibrational behavior of Bi-substituted YAIG due to the excitation of Y3+ ions from the ground energy level. The morphology of the samples is observed by transmission electron microscopy and field emission scanning electron microscopy which showed most of the particles and grains are in spherical shape. The energy dispersive X-ray (EDS) spectra confirmed the elemental compositions of the selected sample. In UV–Visible spectroscopy, transparency of the samples decreases with increasing in Bi3+ ions substitution in YAIG. The saturation magnetization (Ms) decrease from the 14.59 to 2.25 emu/g with the increase in Bi3+ ions concentration, whereas, the values of coercivity (Hc) and retentivity (Mr) are very low. DC resistivity as a function of temperature shows the semiconducting nature of the synthesized samples and its decreased from 6.17 × 106 to 0.06 × 106 Ω-cm with the addition of Bi3+ ions.

Structural and magnetic properties of Bi3+ ion doped Ni–Cu–Co nano ferrites prepared by sol–gel auto combustion method

Bismuth doped Ni–Cu–Co nano ferrites with the chemical composition Ni0.2Cu0.2Co0.6Fe2−xBixO4 (x = 0.0, 0.025, 0.05, 0.075, 0.1) were prepared by sol–gel auto-combustion technology. The analysis of the X-ray diffraction (XRD) patterns confirms that all the samples have a cubic spinel structure. The particle sizes of the prepared samples (between 51 and 55 nm) are determined by the Scherrer equation. The obtained Fourier transform infrared measurement also confirms the formation of the spinel structure. It was observed that with the increase of Bi3+ ion concentration, the protruding absorption band was slightly shifted to the high frequency side. Transmission electron microscopy images show the presence of particles which are spherically cubic shaped crystallites. It has been proved that the synthesized ferrite has pure phase and structure by Energy dispersive X-ray, and Bi3+-doping was successfully achieved. Cation redistribution in spinel ferrite nanoparticles are confirmed by X-ray photoelectron spectroscopy (XPS). The magnetic parameters of the samples are measured by Vibration sample magnetometer (VSM) at room temperature with a maximum magnetic field of 1 T. It can be clearly observed that the magnetic properties such as saturation magnetization (Ms), remanent magnetization (Mr) and coercivity (Hc) decrease significantly with the bismuth ion concentration increases. This is because Bi3+ ions replace Fe3+ ions, and Bi3+–Fe3+ ion interactions are more predominates than Fe2+–Fe3+ ion interactions. This also indicates that the bismuth doped nickel copper cobalt ferrite has low magnetic properties.

Physical and Optical Studies of Bi3+-Modified Erbium Doped Tellurite Glasses

Er3+-doped tellurite glasses with various compositions (in mole%): 54TeO2-(41-x)ZnO-xBi2O3-2Na2O-3Er2O3 (x = 1, 2, 3, 4, and 5) were prepared with melt quenching method. Studies was aimed at investigating the effect of Bi3+ ion content on the physical and optical properties of the glasses. The density, refractive index, optical absorption, and optical energy band gap measurements were carried out at room temperature using pycnometer, Brewster angle method, and UV-VIS-NIR spectrophotometer, respectively. From the experiment, it was shown that the density and refractive index of the glasses increased with the increase of Bi3+ ions concentration. The absorption band intensity of electronic transition from 4I15/2 to 4H11/2 exhibited an increase as the Bi3+ ions concentration increase suggesting that incorporating Bi3+ ions into this glasses might improve the pumping efficiency.

Effect of lattice mismatch stress on magnetic domain of epitaxial single crystal (BiTm)3(GaFe)5O12 film

Yttrium iron garnet (YIG) film is a kind of magnetic film and has been investigated extensively because of its excellent magnetic properties and various applications in different fields. Generally, the easy-axis of the film is in-plane and can be changed from in-plane to out-of-plane by introducing some Bi3+ ions into the dodecahedral sites as it has big uniaxial anisotropy, which will be very important in magnetic bubble memories, magneto-optical devices and the new development of spin-wave logic devices. In comparison with many other preparation techniques, the liquid phase epitaxy (LPE) has been consider as a potential method of realizing perpendicular magnetization film due to its big growth-induced anisotropy. However, the LPE technique has more stringent requirements for lattice match between garnet film and gadolinium gallium garnet (GGG) substrate, especially in the growth of thick film. The lattice match is the key factor in LPE growth if the aim of experiment is to achieve a perfect quality and thick film. In most of experiments, there always exists the lattice mismatch between the film and substrate. Owing to the film and substrate have different chemical compositions, their lattice mismatch stress is unavoidable. The purpose of this paper is to investigate the effect of the stress on the anisotropy and then the magnetic domain of (BiTm)3(GaFe)5O12 single crystal film. In our experiment, the monocrystalline (BiTm)3(GaFe)5O12 films are prepared on (111)-oriented GGG substrates by LPE technique and the effect of lattice mismatch stress on the uniaxial anisotropy and magnetic domain are investigated. It is found that the lattice constant of the film is mainly determined by the content of Bi3+ in the film composition. and the increase of Bi3+ content leads to the increase of the film lattice constant, which affects the lattice mismatch stress between film and substrate. The lattice mismatch stress can adjust the perpendicular anisotropy of film which is the main reason for the domain changes. As the mismatch stress changes from tensile stress to compressive stress gradually, the magnetic bubble domain is transformed first into maze domain, and then into the partially striped domain, finally into the completely striped domain. The mismatch tensile stress is an effective method to enhance perpendicular anisotropy, when the growth-induced perpendicular anisotropy is not large enough. The bubble domain can only appear on the film with large tensile stress. The domain size is closely related to the stress. The domain width becomes wider as the mismatch stress becomes larger and it has the smallest domain size as the stress is minimum. These experimental results are very useful in controlling the uniaxial anisotropy and magnetic domain based on the change of the lattice mismatch stress in the growth process.

Dielectric, magnetic, ferroelectric, and Mossbauer properties of bismuth substituted nanosized cobalt ferrites through glycine nitrate synthesis method

CoFe2-xBixO4 nanoferrites with x = 0, 0.05, 0.1, 0.5, and 1.0 have been synthesized by the glycine nitrate process. The present study investigates the effect of Bi3+ substitution on the microstructural, dielectric, ferroelectric, magnetic, and Mossbauer properties of CoFe2O4 nanoparticles. The X-ray diffraction technique was used to confirm the phase purity and estimate the crystallite size which revealed the formation of a secondary phase when Bi3+ concentration exceeds x = 0.5. Transmission electron microscopy indicated the formation of grains by aggregation of small crystallites with a reduction in grain size to 20 nm with an increase in Bi3+ content and also divulged the lattice parameter value to be 8.378 Å, confirming the crystalline nature of the synthesised sample. Dielectric properties performed in the frequency range of 100 Hz to 1 MHz determined that the dielectric behavior is attributed to the Maxwell-Wagner polarization and the activation energy of the specimens is calculated from the dielectric measurements. The hysteresis curve indicated the ferrimagnetic nature of the samples. The samples also exhibited a well saturated P-E loop with gradual lowering in remenant polarization, coercive field, and saturation polarization with an increase in bismuth concentration. Mössbauer spectroscopy analysis confirmed the changes in magnetic moment of ions, their coupling with neighbouring ions, and cation exchange interactions. Owing to the high physical, thermal, and chemical stabilities, these magnetic ceramics, CoFe2-xBixO4, possesses tremendous potential in major understanding of magnetism and in magnetic recording applications for high density information storage.

Synthesis and Photoluminescence Properties of Sc<sub>0.88-x</sub>Lu<sub>0.05</sub>VO<sub>4</sub>:Eu<sup>3+</sup><sub>0.07</sub>,Bi<sup>3+</sup><sub>x</sub> Red Phosphor

Sc0.88-xLu0.05VO4:Eu3+0.07,Bi3+x(0≤x≤0.05) red phosphors were synthesized by solid state reaction at 1200°C for 3h. The structure, morphology and luminescence spectra of samples are investigated by X-ray diffraction (XRD), Scanning electron microscope (SEM) and fluorescence spectrophotometer, respectively. The samples doped with Eu3+, Lu3+ and Bi3+ maintain the body-centered tetragonal structure of ScVO4 and the morphology remains essentially unchanged with slight agglomeration. The excitation spectrum of Sc0.88-xLu0.05VO4:Eu3+0.07,Bi3+x emerged redshift and the excitation intensity increase within the near UV excitation (360-400nm). The optimum doping concentration of Bi3+ is 0.02(x value), and the maximum emission intensity of Sc0.86Lu0.05VO4:Eu3+0.07,Bi3+0.02 is higher than 88 % in comparison with Sc0.88Lu0.05VO4:Eu3+0.07 under 365 nm excitation. Decay curve of 5D0 state for as-prepared samples fits the single order exponential behavior, the lifetime of 5D0 increase first and then decrease with the increase of Bi3+ doping concentration. The internal quantum efficiency is up to 74.08% under 365nm excitation; When the temperature raises to 200°C, the emission intensity maintains 79% of that in the room temperature. Sc0.86Lu0.05VO4:Eu3+0.07,Bi3+0.02 phosphor show high internal quantum efficiency and thermal stability, which is suitable for the UV-pumped white LED as red phosphor.

Electrical properties of bismuth doped CoBixFe2-xO4 nano ferrites

The CoBixFe2-xO4 (x = 0.00, 0.05, 0.10, 0.15, 0.20 & 0.25) nano ferrites have been synthesized by sol-gel combustion method. The prepared samples were calcinated at 600°C for 5 hrs. The structural and morphological properties of all prepared samples were characterized by X-ray diffraction (XRD). The effect of bismuth ion substitution on cobalt ferrite samples clearly show fcc spinal structure and confirms the particle size ranges within 17-26 nm. It is also observed that the lattice parameters were decrease in trend with increase of bismuth ion concentration. These samples further characterized the electrical properties by using two-probe type method within the temperature range 300 to 973 K. It is also verified that the electrical conductivity is decreasing with increase of Bi3+ ion concentration. This is the fact that the hopping of electrons decreases in between Fe2+ - Fe3+ ions and samples exhibit semi conducting nature. Further the values of activation energy (ΔE) and Curie temperature (Tc) were determined from the graph of variation of DC electrical resistivity with temperature. As a function of frequency the dielectric properties were measured at room temperature in the range 20Hz to 2MHz. The dielectric properties such as dielectric constant (ε’), dielectric loss tangent (tan δ) and AC conductivity (σAC) were exhibiting normal ferrite behavior as a function of applied frequency. It has been observed that both the dielectric constant and dielectric loss tangent were decreases with the increase of frequency whereas the AC conductivity was increasing in trend with the increase of doping concentration as well.

Crystal structure and luminescence properties of Bi3+ activated Ca2Y3Sb3O14 phosphors in near UV region

A novel Ca2Y3Sb3O14: Bi3+ phosphor was synthesized and its crystal structure, photoluminescence (PL) properties was investigated. Ca2Y3Sb3O14 crystallized as a monoclinic structure with a space group of I2m/11 and lattice constants of a=7.4129(7)Å, b=10.4428(1)Å, c=7.3898(8)Å and α=90.049°. Ca2Y3Sb3O14: Bi3+ could be efficiently excited in the wavelength range of 270–400nm. With the increase of Bi3+ concentration, the most efficient excitation wavelength of the phosphors moved from 320 to 350nm. When excited under 310–350nm, the phosphors emit a broad band with a maximum intensity appearing at about 420–460nm due to the 3P1–1S0 transition of Bi3+. The relationship between the PL properties and the crystal structure was discussed. Due to the efficient excitation in the near UV region and the strong blue to cyan emission, Ca2Y3Sb3O14: Bi3+ would be a potential blue phosphor for near UV white light-emitting diodes, or a potential donor system for designing single-composition white-light phosphors based on energy transfer.

Synthesis and Structural Properties of Bismuth Doped Cobalt Nanoferrites Prepared by Sol-Gel Combustion Method

A series of Bismuth doped Cobalt nanoferrites of chemical composition CoBixFe2-xO4 (where x = 0.00, 0.05, 0.10, 0.15, 0.20 & 0.25) were prepared by sol-gel combustion method and calcinated at 600℃. The structural and morphological studies were carried out by using X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive Spectroscopy (EDS) and Fourier Transform Infrared (FT-IR) spectra showing the single phase spinal structure. The X-ray diffraction (XRD) analysis confirmed a single phase fcc crystal. The crystallite size of all the compositions was calculated using Debye-Scherrer equation and found in the range of 17 to 26 nm. The lattice parameters were found to be decreased as Bi3+ ion doping increases. The surface morphology was studied by Scanning Electron Microscope (SEM) and particle size was confirmed by Transmission Electron Microscopy (TEM). The EDS plots revealed existence of no extra peaks other than constituents of the taken up composition. The Fourier Transform Infrared (FT-IR) studies were made in the frequency range 350 - 900 cm-1 and observed two strong absorption peaks. The frequency band is found at 596 cm-1 where as the lower frequency band at 393 cm-1. It is clearly noticed that the two prominent absorption bands were slightly shifted towards higher frequency side with the increase of Bi3+ ion concentration.