Solid State Diffusion Method Research Articles

Photo and thermoluminescence in K2Mg(SO4)2: Dy phosphor and evaluation of trapping parameters

The prepared phosphor K2Mg(SO4)2:Dy is synthesized by solid state diffusion (SSD) method. The sample was studied for its photoluminescence (PL) and thermoluminescence (TL) characteristics. In the emission spectra of K2Mg(SO4)2:Dy excited by 350nm UV light, the emission line at 576nm(4F9/2–6H13/2) and 487nm (4F9/2–6H15/2)from the Dy3+ions coexist with the wide emission band from the K2Mg(SO4)2host. The excitation spectra of the emission at 576nm consist mainly of the strong excitation band of the K2Mg(SO4)2host at 350nm.TL characteristics show excellent results by the same SSD method. The samples were irradiated by γ-radiation for 5–30Gy from 60Co source at the dose rate of 0.322kGyh−1. The TL glow curve shows the simple structure having the peak temperature nearly at 185°C. The single peak is due to the possibility of formation of only one kind of trapping site due to γ-irradiation. The effect of concentrations of Dy and γ-radiation doses does not change the general structure of the TL glow curve but the intensity is found to be increased as per the higher concentrations and dose. The trapping parameters are also evaluated by Chen׳s method. The values of trap depth (E) and frequency factor (s) were found to be 0.77±0.002eV and 3.5×108s−1 respectively. The study of PL, TL and evaluation of trapping parameters has been done and discussed for first time.

A Novel Gd3+–Pb2+ Doped LiSrPO4 Phosphor for Phototherapy Lamp Applications

The phosphors LiSrPO4:Gd3+ and LiSrPO4:Gd3+, Pb2+ with different concentration of Gd3+ and Pb2+ were synthesized by combination of re-crystallization and modified solid state diffusion method. The synthesized phosphors were characterized using XRD, SEM and PL spectroscopies. The PL excitation spectra of LiSrPO4:Gd3+ phosphor exhibit peak at 275 nm due to the 8S7/2 →4IJ transition of Gd3+ ions and gave narrow UVB emission at 312 nm. The effect of Pb2+ ions on the PL properties of LiSrPO4:Gd3+have also been investigated. Upon the addition of Pb2+ ions, the excitation of phosphors shows broad peak with maximum at 247 nm, overlapping the Hg 253.7 nm line. This addition of Pb2+ ions improved the emission intensity of narrow band UVB i.e. 312 nm under the excitation of 247 nm. The phosphor could be good candidate as phototherapy lamp phosphor material.

Dy3+‐, Sm3+‐, Ce3+‐ and Tb3+‐activated optical properties of microcrystalline BaMgP2O7 phosphors

Photoluminescence (PL) and thermoluminescence (TL) properties of rare earth (RE) ion (RE=Dy3+ , Sm3+ , Ce3+ , Tb3+ ) activated microcrystalline BaMgP2 O7 phosphors are presented in this work. Non-doped and doped samples of BaMgP2 O7 were prepared using a solid state diffusion method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), PL and TL. The XRD measurement confirmed the phase purity of the BaMgP2 O7 host matrix. The average particle size was found through SEM measurement to be around 2μm. All activators using the PL technique displayed characteristic excitation and emission spectra that corresponded to their typical f→f and f→d transitions respectively. Thermoluminescence measurements showed that BaMgP2 O7 :RE (RE=Dy3+ , Sm3+ , Tb3+ , Ce3+ ) and co-doped BaMgP2 O7 :Ce3+ ,Tb3+ phosphors have also TL behaviour.

Synthesis and TL/OSL properties of CaSiO3:Ce biomaterial

The polycrystalline CaSiO3:xCe (x=0.001, 0.002, 0.005) biomaterials were prepared by using solid state diffusion (SSD) method. The structure of CaSiO3:Ce phosphor was confirmed by X-ray diffraction technique. Moreover, photoluminescence (PL), thermoluminescence (TL) and optically stimulated luminescence (OSL) properties were studied. The TL glow curves consist overlapping peaks in temperature range 40–450°C. The peak shape method was adopted for the calculation of the kinetic parameters such as activation energy, frequency factor and shape factor. The OSL sensitivity of CaSiO3:Ce phosphor was 2.8 time than that of OSL sensitivity of Al2O3:C (BARC) phosphor. The minimum detectable dose (MDD) was found to be 43.6μGy corresponding to 3σ background.

Magnetic and electrical studies of Ho0.9RE0.1CrO3 (RE = Gd and Yb) multiferroics

Summary We report magnetic and electrical studies on multiferroic systems Ho 0.9 (RE) 0.1 CrO 3 where RE symbolizes rare earths like Gd and Yb. Solid state diffusion method has been used to synthesize the samples. Structural phase formation has been confirmed with the help of powder X-ray diffraction. Magnetization measurements show canted antiferromagnetic nature with a weak ferromagnetic phase. Neel temperature for Cr 3+ –Cr 3+ ordering shifts to higher side with increasing radii of rare earth cations. Frequency (100 Hz to 1 MHz) and temperature (300–650 K) dependent resistivity measurements are suggestive of semiconducting nature of the samples.

Nanocrystalline SrS:Ce3+ system for the generation of white light-emitting diodes.

Nanocrystalline SrS phosphors doped with Ce3+ ions at different concentrations (0.5, 1, 1.5 and 2mol%) are synthesized via the solid-state diffusion method (SSDM), which is suitable for the large-scale production of phosphors in industrial applications. The as-prepared samples are characterized using an X-ray diffraction (XRD) technique, field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray (EDX) analysis. The optical properties of these phosphors are analyzed using reflectance spectra, photoluminescence spectra and afterglow decay curves. The cubic structure of the SrS phosphor is confirmed by XRD analysis and the crystallite size calculated by Scherer's formula using XRD data shows the nanocrystalline nature of the phosphors. No phase change is observed with increasing concentrations of Ce3+ ions. The surface morphology of the prepared phosphors is determined by FESEM, which shows a sphere-like structure and good connectivity of the grains. The authenticity of the formation of nanocrystalline phosphors is examined by HRTEM analysis. Elemental compositional information for the prepared phosphors is gathered by EDX analysis. Photoluminescence studies reveal that the emission spectra of the prepared phosphor shows broad band emission centered at 458 and 550nm due to the transition of electrons from the 5d→4f energy levels. The afterglow decay characteristics of different as-synthesized SrS:Ce3+ nanophosphors are conceptually described. Copyright © 2016 John Wiley & Sons, Ltd.

Dielectric studies of multiferroic orthochromites Ho0.9(RE)0.1CrO3 (where RE=Gd and Yb)

Dielectric studies have been made on two orthochromite systems, Ho0.9Gd0.1CrO3 and Ho0.9Yb0.1CrO3. In the known multiferroic system of HoCrO3, Ho is substituted by one lower and one higher atomic number rare earth element (Gd and Yb respectively). Solid state diffusion method has been used to synthesize these polycrystalline samples. X-ray diffraction patterns for both the samples show a distorted orthorhombic perovskite phase. Temperature and frequency dependent dielectric measurements on the Gd and Yb substituted samples show ferroelectric nature with ferroelectric to paraelectric (FE–PE) transitions occurring at Curie temperature (Tc)∼530(5)K and ∼490(5)K (at excitation frequency of 1kHz) respectively. The two studied systems are non-Debye relaxor ferroelectrics and the FE–PE transitions exhibit high diffusiveness.

The helical melamine–Keggin hybrid nanorods: syntheses and characterizations with two strategies, one-step solid-state chemical reaction and experimental solvent diffusion method

Two new Melamine-Keggin hybrid nanorods, MELH-PMo12 and MELH-PW12, for the first time are successfully synthesized by two chemical methods, one-step solid-state chemical reaction method and experimental solvent diffusion method at room temperature. One-step solid-state reactions involve grounded nanorod materials along with grinding of row material and with solvent diffusion method these nanorods synthesized in single crystals form. These compounds crystallized in trigonal space groups P-3. Elemental analysis, infrared spectroscopy, UV spectroscopy and XRD analysis results prove that the samples still possess Keggin type structure. Transmittance electron microscopy and single-crystal X-ray have shown that the samples have nanorod structures.

Dosimetry characteristics of NaLi2PO4:Ce3+ OSLD phosphor

High Sensitivity NaLi2PO4:Ce3+ optically stimulated luminescence dosimetry (OSLD) phosphor material was prepared by a simple solid state diffusion method. The material was characterized by XRD to confirm its formation in a single phase. Comparison of the experimental data with that of the data available in the literature (JCPDF # 80-2110) shows formation of a single orthorhombic phase, with the space group Pmnb (62). Study on the particle size effect shows that particle size in the range 50–150μm is more suitable for the continuous wave-optically stimulated luminescence (CW-OSL) dosimetry. Dosimetric properties of the phosphor material (particle size 50–150μm) using CW-OSL technique for blue light stimulation (λ≈470nm) show that it is highly sensitive (~6 times more sensitive than the commercially available Al2O3:C phosphor) in the linear dose range. The phosphor has found to have all the other good dosimetric characteristics, such as, easy method of synthesis, tissue equivalence, i.e., low-Z material (Zeff. ~10.8), low fading (~ 25% in 20 days), wide range of dose response (3mGy–500Gy), easy optical bleaching for its reuse, excellent reusability, etc., which make it useful for OSL dosimetry of high-energy radiations. Another advantage of this OSLD phosphor is that its dosimetric TL glow peak does not fade much on taking OSL and thus it could also be used as TLD phosphor for re-estimating doses in case of any doubts.

Photoluminescence and PhotoCatalytic Properties of Zinc doped Strontium Sulphide Nanocrystals

Photoluminescence and PhotoCatalytic Properties of Zinc doped Strontium Sulphide Nanocrystals Pure Strontium Sulphide (SrS) and Zn doped SrS nanocrystals have been synthesized by solid state diffusion method. Crystallographic characterization carried out by using powder X-ray diffractometer confirmed the single phase rock salt with average particle size in the range of 24.7 nm. Topographic and Morphological studies were carried out by using Scanning electron microscope (SEM) and Transmission electron microscope (TEM) respectively. EDS studies confirm elemental composition of nanoparticles. TEM studies confirm spherically distributed nanoparticles with average size in nm range. Band gap and. Photoluminescence (PL) studies confirmed dopant dependant behavior. Photo-Catalytic activity confirms that SrS is a good degrading agent.

Synthesis, structural and dielectric properties of Magnesium calcium titanate (1-x)MgTiO3-xCaTiO3 (x=0, 0.1, 0.2 and 0.3)

Magnesium Titanate-based ceramics is one of the popular microwave dielectric materials. These are widely used as dielectrics in resonators and filters for communication, capacitors and radar systems operating at microwave frequencies. The pure and Calcium doped Magnesium Titanate ceramic materials are synthesised by conventional Solid-state route diffusion method. High purity chemicals of MgO, TiO2 and CaO which are taken in according to their compositions for the preparation of Mg1-xCaxTiO3 (x=0,0.1,0.2 and 0.3) ceramics. They are grounded well for 12h in a Ball Mill. Then the powders are calcined at 1175°C to 1200°C for 36h and are pressed into pellets. These pellets are sintered at 1270°C to 1300°C for 6h. The dielectric constant from room temperature to 350°C is calculated using HIOKI 3532-50 LCR HiTESTER in the frequency range of 100Hz-5MHz. The dielectric constant at room temperature at a frequency of 0.1KHz for pure Magnesium Titanate is found to be 14.13 and as the concentration of Calcium increases dielectric constant increases. The AC conductivity and Dielectric loss of the samples are measured. XRD studies revealed that the compound exhibits major phase of MgTiO3 with Hexagonal structure and space group 148: R-3.

Luminescence study of Eu(3+) doped Li6 Y(BO3 )3 phosphor for solid-state lighting.

In this study, Li6 Y1-x Eux (BO3 )3 phosphor was successfully synthesized using a modified solid-state diffusion method. The Eu(3+) ion concentration was varied at 0.05, 0.1, 0.2, 0.5 and 1 mol%. The phosphor was characterized for phase purity, morphology, luminescent properties and molecular transmission at room temperature. The XRD pattern suggests a result closely matching the standard JCPDS file (#80-0843). The emission and excitation spectra were followed to discover the luminescence traits. The excitation spectra indicate that the current phosphor can be efficiently excited at 395 nm and at 466 nm (blue light) to give emission at 595 and 614 nm due to the (5) D0 → (7) Fj transition of Eu(3+) ions. Concentration quenching was observed at 0.5 mol% Eu(3+) in the Li6 Y1-x Eux (BO3 )3 host lattice. Strong red emission with CIE chromaticity coordinates of phosphor is x = 0.63 and y = 0.36 achieved with dominant red emission at 614 nm the (5) D0 → (7) F2 electric dipole transition of Eu(3+) ions. The novel Li6 Y1-x Eux (BO3 )3 phosphor may be a suitable red-emitting component for solid-state lighting using double-excited wavelengths, i.e. near-UV at 395 nm and blue light at 466 nm. Copyright © 2015 John Wiley & Sons, Ltd.

Synthesis and characterization of Ba3Si6O12N2:Eu(2+) phosphor.

Eu(2+)-doped Ba3Si6O12N2 phosphors were prepared successfully via a modified solid-state diffusion method. The phosphors were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence measurements. These phosphors were effectively excited at 355 nm and an intense emission peaking in the range 480 nm to 525 nm in the blue region was observed. The optimized dopant concentration was determined to be 1 mol% of Eu(2+) ion. The colour coordinates for phosphor were found to be (0.196, 0.326) in the blue region. This phosphor may find application for near-ultraviolet (NUV) excited lamp phosphors. The thermoluminescence study shows the complex glow curve. Trapping parameters (activation energy and frequency factor) were calculated for individual deconvoluted peaks by Chen's peak shape method, the initial rise method and the whole glow peak method.

Structural and optical properties of SrS nanophosphors influenced by Ce3+ ions concentrations and particle size reduction

The SrS nanophosphors doped with different concentrations of Ce3+ are synthesized by solid state diffusion method (SSDM). Various characterization and spectral studies are reported in the light of varied dopant concentrations and reduction in particle size by milling. The as-obtained phosphors are characterized by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) including selected area electron diffraction (SAED) and energy dispersive X-ray spectroscopic (EDX) studies. The FESEM and HRTEM results explain the surface morphology, agglomeration of particles, crystallite size, etc. The results of XRD studies confirm the cubic structure of most intense SrS: Ce3+ nanophosphors and exhibit wider diffraction peaks for 4h milled sample. The EDX profiles are used to authenticate the occurrence of different starting materials in final products. Upon excitation with UV light (375nm), two emission peaks are observed at around 459nm and 551nm due to transitions of electrons from the 2T2g(5d)→2F5/2(4f) and 2T2g(5d)→2F7/2(4f) energy levels. The afterglow decay behavior of different SrS: Ce3+ nanophosphors is presented and discussed systematically.

The effects of Ce3+ doping on the structural and optical properties of SrS nanoparticles synthesized by solid state diffusion method

A solid state diffusion method (SSDM) is employed to synthesize the nanocrystalline SrS phosphors doped with varying concentrations of Ce3+ ions. The surface morphology and structural properties of as prepared phosphors are characterized by various techniques including X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction pattern (SAED) and energy dispersive X-ray spectroscopy (EDX). The optical properties are investigated and discussed in terms of absorption spectra, photoluminescence (PL) and thermoluminescence (TL) measurements. The cubical crystal structure and average crystallite size estimated by X-ray diffractograms are found to lie in nano-range is also supported by HRTEM analysis. FESEM is used to describe the surface morphology and confirm the crystallite size of as-prepared nanophosphors. The absorption spectra and corresponding Tauc׳s plots confirm the wide band-gap nature of prepared samples. When excited with 375nm wavelength of ultraviolet (UV) light at room temperature, the SrS:Ce3+ nanophosphors exhibit two emission bands at around 459 (blue region) and 551nm (green region) originating from the 2T2g(5d)→2F5/2(4f) and 2T2g(5d)→2F7/2(4f) transitions respectively. The results of thermoluminescence (TL) studies in terms of TL glow curves, corresponding kinetic parameters and dopant concentration dependence of intensity for nanocrystalline SrS:Ce3+ phosphor are presented and discussed.

Thermoluminescence of γ-irradiated BaCa(SO4)2:Eu,Dy

In this paper, thermoluminescence (TL) studies of BaCa(SO4)2:Eu,Dy phosphor are reported. A microcrystalline sample of BaCa(SO4)2:Eu,Dy was prepared by a solid state diffusion method and the formation of the compound was confirmed by the X-ray diffraction study. Morphology of the phosphor was analyzed by scanning electron microscopy (SEM). The sample is found to have an average particle size of 5 µm. TL glow curves of the γ-irradiated samples with different concentrations of Eu and Dy were studied and compared with BaCa(SO4)2:Eu and BaCa(SO4)2:Dy. It has been found that a single peak was located at around 230°C with the highest TL intensity in BaCa(SO4)2:Eu,Dy which is eight times and two times more than singly Dy- and Eu-doped BaCa(SO4)2 phosphor, respectively. For TL analysis, BaCa(SO4)2:Eu,Dy (0.2 mol%, 1 mol%) is annealed at different temperatures ranging from 900°C to 1100°C. Analysis of the TL glow curve was carried out by a glow curve deconvoluted method. Trapping parameters (activation energy and frequency factor) of all TL glow curves were evaluated by Chen's peak shape method. A comparison of trapping parameters between BaCa(SO4)2:Eu,Dy; BaCa(SO4)2:Eu and BaCa(SO4)2:Dy phosphors at 900°C, 1000°C and 1100°C is also reported in this paper.

Uniform Doping of Titanium in Hematite Nanorods for Efficient Photoelectrochemical Water Splitting.

Doping elements in hematite nanostructures is a promising approach to improve the photoelectrochemical (PEC) water-splitting performance of hematite photoanodes. However, uniform doping with precise control on doping amount and morphology is the major challenge for quantitatively investigating the PEC water-splitting enhancement. Here, we report on the design and synthesis of uniform titanium (Ti)-doped hematite nanorods with precise control of the Ti amount and morphology for highly effective PEC water splitting using an atomic layer deposition assisted solid-state diffusion method. We found that Ti doping promoted band bending and increased the carrier density as well as the surface state. Remarkably, these uniformly doped hematite nanorods exhibited high PEC performance with a pronounced photocurrent density of 2.28 mA/cm(2) at 1.23 V vs reversible hydrogen electrode (RHE) and 4.18 mA/cm(2) at 1.70 V vs RHE, respectively. Furthermore, as-prepared Ti-doping hematite nanorods performed excellent repeatability and durability; over 80% of the as-fabricated photoanodes reproduced the steady photocurrent density of 1.9-2.2 mA/cm(2) at 1.23 V vs RHE at least 3 h in a strong alkaline electrolyte solution.

Synthesis and photoluminescence characteristics of (Y,Gd)BO3:RE (RE = Eu(3+), Ce(3+), Dy(3+) and Tb(3+)) phosphors for blue chip and near-UV white LEDs.

A series of Eu(3+)-, Ce(3+)-, Dy(3+)- and Tb(3+)-doped (Y,Gd)BO3 phosphors was synthesized by a solid-state diffusion method. X-Ray diffraction confirmed their hexagonal structure and the scanning electron microscopy results showed crystalline particles. The excitation spectra revealed that (Y,Gd)BO3 phosphors doped with Eu(3+), Ce(3+), Dy(3+) and Tb(3+) are effectively excited with near UV-light of 395 nm/blue light, 364, 351 and 314 nm, respectively. Photoluminescence spectra of Eu(3+)-, Ce(3+)- and Tb(3+)/Dy(3+)-doped phosphor showed intense emission of reddish orange, blue and white light, respectively. The phosphor Y0.60Gd0.38BO3:Ce0.02 showed CIE 1931 color coordinates of (0.158, 0.031) and better color purity compared with commercially available blue BAM:Eu(2+) phosphor. The phosphor (Y,Gd)BO3 doped with Eu(3+), Dy(3+) and Tb(3+) showed CIE 1931 color coordinates of (0.667, 0.332), (0.251, 0.299) and (0.333, 0.391) respectively. Significant photoluminescence characteristics of the prepared phosphors indicate that they might serve as potential candidates for blue chip and near-UV white light-emitting diode applications.

Lyoluminescence dosimetry of high-energy γ radiation using MgB4O7:Mn2+

Lyoluminescence (LL) is a good technique for radiation dosimetry of high-energy radiations. Dosimetry of γ rays from 60Co radioactive source has been done using MgB4O7:Mn2+ phosphor material. It was synthesized by simple solid state diffusion method. The material shows good linear LL response with the γ rays for the dose rage of 10 Gy–10 kGy. The studies have also been done for different particle sizes (250–45 µm) and particles having average size ~85 µm were found to be the most suitable for this dosimetry. Effect of solvent pH on LL and fading on storage has also been studied.

Luminescence characteristics of C5+ ions and 60Co irradiated Li2BaP2O7:Dy3+ phosphor

In this work a study on some thermoluminescence characteristics of Li2BaP2O7:Dy phosphor is presented. The phosphor was synthesized by solid state diffusion method and characterized for its phase purity by X-ray diffraction (XRD). FT-IR spectrum was also carried out to confirm the presence of phosphate family and vibrations corresponding to P–O–P group. Spectroscopic investigation was approached through photoluminescence (PL) and thermoluminescence (TL). PL emission spectrum of Dy3+ ions corresponding to 4F9/2→6H13/2 (483nm) and 4F9/2→6H15/2 (574nm) transitions is revealed under 351nm excitation wavelength. This characteristic emission confirms the presence of Dy3+ ions in the Li2BaP2O7 host matrix. To induce TL properties in Li2BaP2O7:Dy phosphor was irradiated with C5+ ion beams and gamma rays (60Co). A nearly simple glow curve was observed for Li2BaP2O7:Dy under two different excitation sources. TL response is almost linear over a wide range. Average absorbed dose (D¯) and mean linear energy transfer (LET‾) of C5+ ion beams in Li2BaP2O7:Dy have also been calculated. Values of parameters like E and S known as trap depth and frequency factor respectively were obtained by using TLanal computer program. Also SRIM based calculations were performed to study the effect of C5+ ion beams on the samples of Li2BaP2O7:Dy. SRIM calculations show that Ba2+ vacancies are highest in number. Till date no such luminescence information on Li2BaP2O7:Dy phosphor is available.