Hypersensitive Transition Research Articles

Preparation and cathodoluminescence characteristics of rare earth activated BaAl2O4 phosphors

Undoped and Pr, Sm and Tb activated BaAl2O4 phosphors have been synthesized by solid state reaction method and combustion method. The structure and morphological observation of the phosphor samples were monitored by X-ray powder diffraction (XRD) and environmental scanning electron microscope (ESEM) coupled to an energy dispersive X-ray spectrometer (EDS). The all diffraction peaks are well assigned to standard data card (PDF♯17–306). Emission properties of the samples were explored using light emission induced by an electron beam (i.e cathodoluminescence, CL) at room temperature (RT). Undoped BaAl2O4 sample exhibits a broad defect emission from 300 to 500 nm from the aluminate defect centres. CL spectra recorded at room temperature display that the as-prepared BaAl2O4:Ln (Ln=Pr, Sm and Tb) phosphors exhibit different luminescence colors coming from different rare earth activator ions. The transition 4G5/2 → 6H7/2 located at 606 and 610 nm for Sm3+ can occur as hypersensitive transition having the selection rule ΔJ = ± 1. For the Tb3+ doped samples, they exhibit D45 green line emissions. The proposed luminescent mechanisms of all doped rare earth ions are also discussed.

Narrow-band red-emitting phosphor, Gd3Zn2Nb3O14:Eu3+ with high color purity for phosphor-converted white light emitting diodes

In this work, we synthesized and characterized a narrow band red emitting Gd3Zn2Nb3O14:Eu3+ phosphor in order to improve the color qualities of warm white light emitting diodes. The phosphors were synthesized via conventional solid state reaction method and investigated the evolution of emission spectra with partial occupation of Zn2+ ions on both A and B site of the fergusonite type structure. The structural and luminescence property analysis corroborates the occupancy of Eu3+ ions in the Gd3+/Zn2+ ion site (A site). The developed phosphor exhibits a strong red emission peaking at 613 nm with a fwhm of merely ∼3.50 nm under the 392 nm excitation. These compounds produce narrow emissions in the visible red spectral regions that are highly professed by human eye and lead to outstanding chromatic saturation of the red spectra. The enhanced electric dipole transition intensity arises from the symmetry distortion of Eu3+ ions caused by the introduction of Zn2+ ions in the lattice. The distortion of the A site symmetry and the red shift of the charge transfer energy leads to an intense 5D0 – 7F2 hypersensitive electric dipole transition under 392 nm excitation. The relative emission intensity was found to be maximum at x = 0.40 and is 3.9 times higher than that of the commercial red phosphor under the 392 nm excitation. These phosphors with remarkable CIE chromaticity coordinates (0.64, 0.35), good CCT values along with high color purity (94.2%) might have significant applications in display devices and evidence as an efficient red phosphor.

Effect of rare earth doping on optical and spectroscopic characteristics of BaZrO3:Eu3+,Tb3+ perovskites

This paper reports structural investigations of rare earth doped BaZrO3 phosphors synthesized by Solid state reaction technique with varying concentrations of Eu3+ and Tb3+ from 0 mol% to 2 mol%. The synthesized phosphors show enhanced variable emissions in the visible region corresponding to different hypersensitive electronic transitions of Eu3+ and Tb3+ ions. With cubic structure confirmed in XRD analysis, the FESEM images show uniform grain connectivity and homogeneity of prepared samples. The TEM micrographs of the synthesized phosphors show agglomerated irregular structures. The synthesized phosphors were also subjected to FTIR, Raman, EDXS analysis along with studies of thermoluminescent and photoluminescent characteristics. On subjecting to 229 nm (UV) excitation, the phosphors show enhanced PL emissions corresponding to 571 nm (5D0-7F0), 591 nm (5D0-7F1), 615 nm (5D0-7F2) and 678 nm (5D0-7F4) hypersensitive transitions of Eu3+ ions and emission peaks at 489 nm (5D4-7F6), 539 nm (5D4-7F5), 589 nm (5D4-7F4) and 632 nm (5D4-7F3) accounting for electronic transitions of Tb3+ ions respectively. The computed average PL lifetime is 14.014 s. In the TL analysis, the second order of kinetics with the activation energy varying from 5.0 × 10−1 eV to 6.6 × 10−1 eV is reported. The maximum TL lifetime is estimated as 19.4985 min in the TL lifetime analysis.

Synthesis, crystal structure and optical properties of new (Nd, Sm) and other lanthanide (Ln = Pr) complexes with 1,10-phenanthroline and thiocyanate

New types of neodymium, samarium and other light lanthanide (Pr) mixed complexes with thiocyanate (NCS) and 1,10-phenanthroline (Phen) were synthesized in solution and as crystals. It was found that these complexes crystallized with the formulae: (phen)·[Nd(phen)2(NCS)4] (1) and [Ln(phen)3(NCS)3]·EtOH (Ln = Sm(2), Pr(3)). The Pr and Sm complexes are isostructural (space group P1¯), but the Nd compound was different (space group P21/n). Compound (1) crystallizes in a monoclinic system with space group P21/n and the following unit cell parameters: a = 12.097(2), b = 16.444(3), c = 19.202(3)Å, β = 93.46(2)°.The optical spectra of these two types of rare-earth compounds were performed at room and low temperatures in order to understand the electrostatic nature of the Ln3+N coordination bonds. The high values of absorption spectral intensities at 293 K for Nd3+ or Pr3+ show low symmetries for these metal centres. The absorption spectrum analysis at 4.2 K and the correlation of the results with the IR spectra of the monocrystals of (phen)·[Nd(phen)2(NCS)4] and [Pr(phen)3(NCS)3]·Et(OH) make it possible to account for vibronic transitions. The observed Stark splitting of f–f transitions for Ln3+ ions in the emission spectra at 77 K for Sm3+ is in agreement with that predicted by group theory for a single low-symmetry Ln3+ ion site. In the absorption spectra, a ‘red shift’ was observed for hypersensitive transitions of lanthanide ions. The variation of the spectroscopic parameters of the title compounds, calculated based on the absorption spectra, the nephelauxetic ratio β, Sinha’s parameter δ and their correlation with the nature of the Ln3+N bond, are discussed.

Doping Sm3+ into ZnB2O4 phosphors and their structural and cathodoluminescence properties

In this study, ZnB2O4:xSm3+ (0.01 ≤ x ≤ 0.05 mol) powder phosphors have been synthesized by low temperature chemical synthesis method. The structure and morphological observation of the phosphor samples were systematically monitored by X-ray powder diffraction (XRD) and environmental scanning electron microscope (ESEM) coupled to an energy dispersive X-ray spectrometer (EDS). The all diffraction peaks are well assigned to standard data card (PDF#39-1126). Emission properties of the samples were explored using light emission induced by an electron beam (i.e cathodoluminescence, CL) at room temperature (RT). When excited with electron beam, CL spectral measurements of scrutinized phosphors exhibit orange-red luminescence at 572 nm, 606 nm and 658 nm due to various transition from ground state to 6H5/2,6H7/2 and 4G5/2 states, respectively. The transition 4G5/2 → 6H7/2 located at 606 nm can occur as hypersensitive transition having the selection rule ΔJ = ±1. The observed peaks are in the region of yellow reddish light of Sm3+. Experimental results verify that the optimum Sm3+ content in terms of intense luminescence for this series of phosphors was 2%. Beyond 2% of Sm3+ ions concentration, luminescence quenching occurs due to an enhanced probability of the energy transfer from one Sm3+ to another that matches in energy via cross-relaxation and dipole-dipole interactions according to Dexter theory. A suitable energy transfer model between two adjacent Sm3+ ions in the ZnB2O4 phosphors was accomplished by the electric dipole-dipole interaction. The critical transfer distance (Rc) for non-radiative energy transfer was found to be 21.52 Å at 2 mol % Sm3+ doped ZnB2O4. Additionally, thermoluminescence (TL) glow curves of undoped and Sm activated ZnB2O4 under beta irradiation of 10 Gy are also discussed here.

Photoluminescence properties of Eu3+ doped HfO2 coatings formed by plasma electrolytic oxidation of hafnium

Plasma electrolytic oxidation was used for synthesis of Eu3+ doped monoclinic HfO2 coatings on hafnium substrate. Results of photoluminescence (PL) measurements show the existence of two distinct regions: one that is related to the blue emission originating from oxygen vacancy defects in HfO2 and the other one characterized with a series of sharp orange-red emission peaks related to f–f transitions of Eu3+ from excited level 5D0 to lower levels 7FJ (J = 0, 1, 2, 3, and 4). PL peaks appearing in excitation spectra of obtained coatings are attributed either to charge transfer state of Eu3+ or to direct excitation of the Eu3+ ground state 7F0 into higher levels of the 4f-manifold. PL of formed coatings increases with PEO time due to an increase of oxygen vacancy defects and the content of Eu3+. Acquired experimental data suggest that hypersensitive electrical dipole transition is much more intense than the magnetic dipole transition, indicating that Eu3+ ions occupy a non-inversion symmetry sites.

Concentration and thermal quenching of SrGdLiTeO<sub>6</sub>: Eu<sup>3+</sup> red-emitting phosphor for white light-emitting diode

A series of SrGd<sub>1-<i>x</i></sub>LiTeO<sub>6</sub>:<i>x</i>Eu<sup>3+</sup> (<i>x</i>=0.1-1) red-emitting phosphors, prepared by high-temperature solid-state reaction at 1100℃, is thoroughly investigated by means of X-ray diffraction, diffuse reflectance spectra, photoluminescence spectra, and electroluminescence spectra. These double-perovskite-type phosphors crystallize into monoclinic systems with space group <i>P</i>2<sub>1</sub>/<i>n</i>(14), accommodate Eu<sup>3+</sup> in a highly distorted <i>C</i><sub>1</sub> site symmetry without inversion center, and facilitate the enhancing of the <sup>5</sup>D<sub>0</sub> → <sup>7</sup>F<sub>2</sub> hypersensitive transition. The excitation spectra, emission spectra and decay curves indicate that the optimum doping concentration of Eu<sup>3+</sup> is <i>x</i>=0.6. The SrGd<sub>0.4</sub>LiTeO<sub>6</sub>:0.6Eu<sup>3+</sup> presents the strongest excitation peak at 395 nm, which is adequate for near-UV light-emitting diode (LED) pumping; meanwhile, it exhibits an intense red emission with chromaticity coordinates of (0.6671, 0.3284), an asymmetry ratio of 7.56, a color purity of 98.6%, and a luminous efficacy of radiation of 249 lm/W. The fluorescence lifetime is 721 μs, from which the internal quantum efficiency is determined to be 89.7% via the Judd-Ofelt analysis. The formula proposed by van Uiter (van Uitert L G 1967 <i>J. Electrochem. Soc</i>. <b>114</b> 1048), is used to elucidate the energy transfer mechanism. However, the plot of log(I/<i>x</i>)-log(<i>x</i>) produces a confusing index <i>s</i>=4.26, which makes it difficult to distinguish the dipole-dipole interaction from the exchange interaction. After analyzing the reason of error, we present a new plot of log(I<sub>0</sub>'/I-1)-log(<i>x</i>), in which I<sub>0</sub>'=I<sub>0</sub>/<i>x</i><sub>0</sub> and I'=I/<i>x</i>, with <i>x</i><sub>0</sub> corresponding to the low doping content without nonradiative energy transfer. This plot gives rise to <i>s</i>=5.25, a more reasonable value for the dipole-dipole interaction. The integrated emission intensity at 423 K is as high as 85.2% of that at ambient temperature. The thermal activation energy is determined to be 0.2941 eV according to the model based on a temperature-dependent pathway through a charge transfer state. The prototypical LED based on it can emit a bright red light beam. In conclusion, the phosphor exhibits favorable luminous efficiency, color purity and thermal stability of luminescence, which promises solid-state lighting and display applications.

Synthesis and luminescence properties of double perovskite Gd2MgTiO6:Eu3+ red phosphors for white light-emitting diodes

A series of double perovskite Gd2(1−x)MgTiO6:xEu3+ (x = 0.01, 0.05, 0.1, 0.15, 0.2, 0.3 and 0.5) phosphors were successfully synthesized. Two rare earth ions occupy the A-site in this host, which benefits the doping of Eu3+ ions. The crystal structure, microstructure were examined by X-ray diffraction and scanning electron microscopy. Luminescence properties, such as excitation and emission spectra, CIE coordinates and concentration quenching were systematically investigated. A weak magnetic dipole transition (5D0–7F1, 590 nm) and a strong electric dipole transition (5D0–7F2, 616 nm) existed in the emission spectra. The quenching concentration for hypersensitive electric dipole transition of Eu3+ reached up to 15.0 mol%. The delayed concentration quenching was observed in Gd2MgTiO6:Eu3+ phosphors. The theoretical quenching concentration was obtained based on Ozawa’s theory, and the quenching mechanism on Dexter’s theory. All the results indicate that Gd2MgTiO6:Eu3+ has great potential in solid state lighting.

Photoluminescence properties of a double perovskite tungstate based red-emitting phosphor NaLaMgWO6:Sm3+

In this work, the conventional solid-state method was applied to synthesize a series of red-emitting NaLaMgWO6:Sm3+ phosphors. The crystal structure, phase purity, morphology, particle size distribution as well as elemental composition of the as-prepared phosphors were investigated carefully with the aid of XRD, SEM, EDS, FT-IR analyses, indicating the high-purity and micron-sized NaLaMgWO6:Sm3+ phosphors with monoclinic structure were prepared successfully. The spectroscopic properties of Sm3+ in NaLaMgWO6 host including UV–vis diffuse reflection spectrum, photoluminescence excitation and emission spectra, decay curves, chromaticity coordinates and internal quantum efficiency were investigated in detail. Upon excitation with UV (290nm) and n-UV (406nm), NaLaMgWO6:Sm3+ phosphor presented red emission corresponding to the 4G5/2→6HJ (J = 5/2, 7/2, 9/2, and 11/2) transitions of Sm3+, in which the hypersensitive electronic dipole transition 4G5/2→6H9/2 (645nm) was with the strongest emission intensity because Sm3+ ions were located at a lattice site with anti-inversion symmetry. The optimal concentration of Sm3+ was different for the given excitation wavelength such as 290nm and 406nm, which was interpreted by the extra effect of the energy transfer from W6+-O2- group to Sm3+. The decay lifetime for 4G5/2→6H9/2 transition of Sm3+ was very short (< 1ms) and decreased with the increasing Sm3+ concentration. The present investigation indicates that NaLaMgWO6:Sm3+ phosphor could be a potential red component for application in w-LEDs.

Dynamics of concentration quenching in Eu3+ and Tb3+ doped calcium dioxide-oxo-zirconium perovskite

The pure and doped calcium dioxide-oxo-zirconium (CaZrO3) phosphors are synthesized by conventional solid state reaction technique. XRD analysis confirms the phase purity, homogeneity and crystalline nature of prepared phosphors. The FESEM and TEM micrographs show agglomerated clusters of particles with spherical symmetry and uniform grain connectivity. The elemental composition is well evident in EDX spectrum. The particle size analysis shows that as the doping concentration increases, the size of particles of synthesized phosphors also increases. The FTIR spectra discuss the molecular structure and bond activities of prepared samples. The PL spectroscopic studies show distinct emissions at 578, 595, 615 and 624 nm corresponding to hypersensitive transitions of Eu3+ and Tb3+ ions under 275 nm, UV excitation. The quenching of quantum yields with increase in doping confirms the occurrence of concentration quenching in the synthesized phosphors. The dynamics of energy transfer and concentration quenching are discussed in detail. The synthesized phosphors show drastically amended spectroscopic, structural and optical characteristics with varying doping concentration of rare earth impurities. The variable emissions with enhanced intensity confirm the color tunability of synthesized phosphors, proposing their applications in display devices, solid state lightings and other optical applications.

Nd3+‐Doped Silicate Glasses as an Efficient Color Filter to Improve the Color Gamut of a White LED

AbstractNd3+‐doped silicate glass (Nd‐glass) was employed as a color filter for a white LED based on red and green phosphor (RG‐LED), to manipulate the photoluminescence spectral shape and thus to provide a wider color gamut. The hypersensitive transition of Nd3+:4I9/2→4G5/2,2G7/2 was adjusted via glass composition and Nd concentration, and improved absorbance as well as reduced the absorption bandwidth. The effective absorption of the Nd‐glass at ~580 nm reduced the spectral linewidth of the green and red emissions, improving the color reproduction range. The color gamut of the RG‐LED was improved from 75.3% to 81.6% NTSC by the introduction of Nd‐glass as a color filter. Reliability under high operating current and high temperature were also examined and discussed.

Physical and optical properties of sodium borate glasses doped with Dy3+ ions

The photoluminescence, optical and physical properties of sodium borate (NB) doped with different concentrations of Dy[Formula: see text] were determined and well discussed. The samples were prepared by the melt-quenching technique and characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Photoluminescence and absorption spectra of NB glasses doped with different concentrations of Dy[Formula: see text] are reported. Ten absorption bands with hypersensitive transition at 1272 nm ([Formula: see text] [Formula: see text][Formula: see text]) and two emission bands for the transitions at [Formula: see text] [Formula: see text][Formula: see text] (blue color) and [Formula: see text] [Formula: see text][Formula: see text] (yellow color) with an excitation of 330 nm have been recorded. A series of considerable physical properties (oscillator strengths, refractive index, ions concentration, polaron radius) was calculated for each dopant concentration.

Improved photoluminescence, thermal stability and temperature sensing performances of K+ incorporated perovskite BaTiO3:Eu3+ red emitting phosphors

Abstract K + ions incorporated perovskite Ba (1−x) TiO 3 :x Eu 3+ red emitting phosphors synthesized via facile solid -state reaction method has been investigated in the current study. The photoluminescence and decay time behavior of Ba (1−x−y) TiO 3 :x Eu 3+ ,yK + phosphors are investigated as a function of Eu 3+ , K + concentration and temperature. An intense and sharp emission peak at 615 nm was exhibited by the phosphors upon excitation at 397 nm ( 7 F 0 → 5 L 6 ). It can be credited to the hypersensitive electric dipole transition 5 D 0 → 7 F 2 , which confirms that Eu 3+ ions are located at non-centrosymmetric site of the host. The incorporation of K + ions in optimized Ba 0.95 TiO 3 :0.05 Eu 3+ phosphor resulted in a remarkable enhancement of photoluminescence intensity by 2.33 times as compared to bare one. The Ba 0.89 TiO 3 :0.05 Eu 3+ , 0.06 K + phosphors were found to observe good temperature sensing along with adequate thermal stability even at 427 K. Furthermore, the photometric parameters have been also studied which are strongly facilitate the prepared ceramic samples as suitable for potential application in lighting.

Enhanced light harvesting with chromium in NaLu0.70−xGd0.10F4:Yb0.18Er0.02Crx (0 ≤ x ≤ 0.25) upconversion system

Cr3+-doped NaLu0.70−xGd0.10F4:Yb0.18Er0.02Crx nanoparticles were synthesized by one step solvothermal method. The structural, emission properties were studied by XRD, FT-IR, emission spectra. The doping of 15mol% Cr3+ into NaLu0.70−xGd0.10F4:Yb0.18Er0.02Crx induced cubic-hexagonal phase transition, with a consequent 20 times improvement in the upconversion fluorescence quantum yield. The roles of Cr3+ in the phase transition as well as the mechanism of the multi-photon upconversion process in the material were discussed. The Yb3+-Cr3+ dimer could play the role of as a sensitizer by transferring energy to Er3+. The Cr3+ ions result an asymmetry in the environment surrounding the rare-earth ions, which would favor the hypersensitive transitions. This research may open up a new perspective to prepare high upconversion luminescent materials.

Luminescence properties of a novel yellow-emitting phosphor NaLaMgWO6:Dy3+

A series of NaLaMgWO6:Dy3+ phosphors were prepared by a conventional solid-state reaction method at high temperature. The phase structure, morphology, particle size distribution and concentration dependent luminescence properties of the phosphors were investigated for the first time. Upon excitation with UV (290nm) and n-UV (388nm), NaLaMgWO6:Dy3+ phosphor exhibited typical Dy3+ emission corresponding to the 4F9/2→6HJ (J = 15/2, 13/2, 11/2) transitions of Dy3+, in which the hypersensitive electronic dipole transition 4F9/2→6H13/2 (575nm) was with strongest emission intensity leading to the yellow emission with the CIE chromaticity coordinates (0.441, 0.475). The optimal concentration of Dy3+ was found to be 8%. The luminescence decay lifetime for 4G5/2→6H13/2 transition of Dy3+ was of millisecond level and decreased with the increase in Dy3+ ion concentration. The obtained results indicated that NaLaMgWO6:Dy3+ phosphor could be a potential yellow emitting phosphor for possible application in w-LEDs.

Effect of metal and semiconducting nanoparticles on the optical properties of Dy3+ ions in lead borate glasses

The effect of glass composition and the influence of Ag, CdSe and ZnSe nanoparticles on the optical absorption and fluorescence of Dy-doped lead borate glasses are studied. Optical absorption and fluorescence spectra of Dy3+ ions show significant changes with glass composition, and the presence of semiconducting nanoparticles. We analyzed the hypersensitive transition, intensity parameters, radiative transition probability, stimulated emission cross section (σp), and the area ratio of the yellow to blue peak of Dy3+ ions. Fluorescence spectra of the glass containing CdSe nanoparticles show a well pronounced, characteristic broad emission. Deconvolution of these broad peaks yields average particle sizes that agree with the transmission electron microscope images. σp shows significant increase for the glass containing CdSe nanoparticle of size 8–18nm. Incorporating CdSe nanoparticles into lead borate glasses can produce significant electronic alterations to the local environment of Dy3+ ions to produce favorable enhancements to its optical properties.

The influence of CdSe and ZnSe nanoparticles on the optical properties of Sm3+ ions in lead borate glasses

The effect of glass composition and the presence of CdSe/ZnSe nanoparticles (NPs) on the optical absorption and fluorescence of Sm-doped lead borate glasses are studied. Three sets of glass samples xPbO:(99.5-x) B2O3:0.5Sm2O3, x = 29.5–69.5 mol%, xPbO:(96.5-x) B2O3:0.5Sm2O3: 3CdSe/ZnSe, x = 36.5, and 56.5 mol% are prepared. NPs are grown by annealing these glasses just below the glass transition temperature. Average size of both types of NPs increases with annealing time; however, CdSe NPs grew to a larger size range (2 to 20 nm) compared to ZnSe NPs (1 to 16 nm). We analyzed the hypersensitive transition, intensity parameters, radiative transition probability, stimulated emission cross section (σp), and the area ratio of the electric dipole/magnetic dipole transitions of Sm3+. The intensity parameters show a minimum at 11 h annealing for 36.5 mol% and a maximum for the same annealing duration in 56.5 mol% PbO containing CdSe NPs. The σp for 56.5 mol% of PbO with CdSe NPs is found to be a maximum when the average NP size is around 14 nm. ZnSe NPs containing glasses also show significant changes in σp when the average particle size is ~16 nm, for 36.5 mol% PbO. Our results suggest that the optical properties of Sm3+ in lead borate glasses are sensitive to its electronic environment which can be modified by varying the base glass composition and/or incorporating large NPs of CdSe/ZnSe. The large σp values that we observe for some of the glass compositions make them attractive materials for photonic devices and photovoltaic applications.

Observation of red electroluminescence from an Eu2O3/p+-Si device and improved performance by introducing a Tb2O3 layer

We report red electroluminescence (EL) from an Eu2O3/p+-Si device with Eu2O3 film annealed in oxygen ambient at 700 °C. The red EL is ascribed to the characteristic emissions of Eu3+ ions in Eu2O3 film and the luminescence mechanism is discussed in detail. In order to optimize the device performance, Eu2O3/Tb2O3 multiple films were deposited on Si wafer, and the result showed EL intensity of the device was obviously enhanced and the turn-on voltage was reduced to about 10 V. Moreover, intensity ratio I(5D0–7F2)/I(5D0–7F1) was also significantly increased with the hypersensitive transition 5D0–7F2 as the most prominent group at about 611 nm. The improved performance was attributed to the added Tb2O3 film that it can be served as the hole-injection layer to afford extra holes injected into the Eu2O3 layer.

Structural and optical properties of lithium tetraborate glasses containing chromium and neodymium oxide

Lithium tetraborate glass samples containing Chromium and Neodymium were prepared. The density, molar volume, Oxygen packing density and N4 indicate the glass samples containing 0.25 and 0.75mol% Nd2O3 have the opening glass structure. From the absorption spectra of glass samples the Judd-Ofelt theory has been applied to the measured oscillator strengths and determines the three phenomenological intensity parameters Ω2, Ω4 and Ω6 for glass. Chromium and Neodymium addition a gradual conversion of chromium ions from Cr6+ ion to Cr3+ ion acts as modifiers breaking up local symmetry and introduces coordinated bond defects in these glasses, which effect on the environment around the Nd3+ ions. The large Ω2 value suggests a lower symmetric coordination around the Nd3+ and they attract Nd3+ cations to form various BONd bonds. The deviation parameters δrms, was determined. The hypersensitive transition, found to be 4f9/2→4G5/2+2G7/2.

Spectroscopic investigation of samarium‐doped lead oxyflouroborate glasses using photo and cathode luminescence

AbstractSamarium‐doped lead oxyflouroborate glasses of 60 B2O3‐ xPbO‐ (40‐x)LiF where (x=0‐30 mol%) with 3×1020 ions/cm3 of Sm2O3, were prepared by melt quenching. UVVis absorption, photo luminescence (PL) and cathode luminescence (CL) spectroscopies were used to study the effect of varying PbO content on the spectroscopic properties of these samarium‐doped glasses. The absorption of the UV‐edge shifts toward higher wavelengths, not only because of higher polarizability of lead ions, but also because of the strong allowed s‐p transition of Pb2+. Judd‐Ofelts parameters were determined and indicate that the asymmetry around Sm3+ ions increases with increasing PbO content. Ω2 probes the asymmetry by the ratio of intensity of the hypersensitive transition (6H9/2) to that of purely magnetic (6H5/2) transition. Furthermore, an increase in the spectroscopic quality factor (Ω4/Ω6) was observed with increasing PbO content which indicates that these glasses have the potential to be used as efficient active laser glasses. The calculated energy transfer parameter increases with increasing PbO content. Also, stark splitting increases with increasing PbO concentrations. FWHM of the CL emission peaks and stark splitting, are found to be much larger than that in PL. This was explained by the high electric field generated from the exciting electron pulses.