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The solar spectral converters mainly involve the energy transfer between two codoped ions. Here, we report a series of Ce3+, Cr3+, Ln3+ (Ln = Yb, Nd, Er) tridoped Gd3Sc2Ga3O12 (GSGO) phosphors with improved absorption and increasing near infrared (NIR) emission. We observed the multiple energy transfer behaviors of Cr3+→Ln3+, Ce3+→Ln3+, Ce3+→Cr3+, and Ce3+→Cr3+→Ln3+ in GSGO matrix. When Ce3+ is introduced into the GSGO:Cr3+,Ln3+ phosphors, the energy transfer of Ce3+→Cr3+→Ln3+ has been realized by utilizing the energy transfer bridge of the Cr3+ ion. Consequently, GSGO:Ce3+,Cr3+,Ln3+ can absorb almost all ultraviolet and visible (UV–Vis) light and produce strong NIR light thanks to the synergistic effect of Ce3+→Cr3+→Ln3+, improving the photovoltaic conversion efficiency of c-Si solar cells. Our results show that the prepared GSGO:Ce3+,Cr3+,Ln3+ have the potential application in the solar spectral material for c-Si solar cells. Meanwhile, the strategy of multiple energy transfers gives a new way to design the spectral conversion materials with wider absorption for c-Si solar cells.

Dual-emitting and thermochromic manganese ion single doped ZnGa2-yAlyO4 phosphors were prepared by solid-state reaction. The regulation of the valence state and the luminescent properties, especially the luminescent thermal stability of manganese ions in ZnGa2-yAlyO4, are discussed in detail. When excited by ultraviolet (UV) light, the emission spectra of ZnGa2O4:Mn2+,Mn4+ present an ultranarrow green emission band at 503 nm with a fwhm of 22 nm, which derives from the Mn2+ ions formed by the self-reduction of doped Mn4+, and a red emission band of the Mn4+ ions at 669 nm. In addition, a ZnGa2-yAlyO4:Mn2+,Mn4+ solid solution was designed and synthesized by Al3+ replacing Ga3+. The doping of Al3+ effectively inhibited the degree of Mn4+ self-reduction to Mn2+, thus realizing the regulation of valence state of manganese ions. Interestingly, the thermal stability of luminescence shows that the response of Mn2+ and Mn4+ to temperature is obviously different in ZnGa2-yAlyO4, implying the potential of the prepared phosphors as optical thermometers. Subsequently, three kinds of optical thermometers with superior color discrimination and high relative sensitivity (Sr) based on the fluorescence intensity ratio (FIR) technique were realized in 100-475 K. The Sr value of ZGO:0.005Mn/ZGA0.5O:0.005Mn/ZGAO:0.005Mn phosphors can be as high as 4.345%/4.001%/3.488% K-1 (at 350/325/400 K), reflecting the great potential of ZnGa2O4:Mn2+,Mn4+ for optical thermometry applications.

Traditionally, phosphors are developed by doping activators on standard crystallographic sites of selected inorganic hosts, thus enabling the prediction of their luminescence with some empirical mo...

Novel orange-red-emitting phosphors Ca3M2Ge3O12:Mn2+,Mn4+ (M = Al, Ga) with sufficient red light component were developed, and their lattice occupancy and luminescent properties of different color ...

Gd3Ga5–x–δAlx–y+δO12:yMn solid solutions with improving luminescence properties were prepared via cation substitution and a controllable Mn valence state. The abnormal autoreduction from Mn4+ to Mn...

A series of novel Y3Ga5O12:Bi3+,Mn2+ phosphors with controllable luminescence have been synthesized and their photoluminescence characteristics have been studied in detail with the purpose of developing a single-component white light-emitting phosphor suitable for pc-WLEDs. The Bi3+ singly-doped phosphor shows an intense blue–green emission, while the Mn2+-doped phosphor presents a narrow red emission with a FWHM of 59 nm, which is comparable to the previously reported nitride red phosphor Ca[LiAl3N4]:Eu2+. When Bi3+ and Mn2+ were co-doped into the Y3Ga5O12 matrix, effective energy transfer from the Bi3+ to Mn2+ ions was observed. Subsequently, a single-component warm white light-emitting phosphor was obtained by adjusting the doping ratio of Bi3+ and Mn2+ and by utilizing the energy transfer from the Bi3+ to Mn2+ ions. Moreover, the thermal quenching properties show that the prepared Y3Ga5O12:Bi3+,Mn2+ samples possess good thermal stability of luminescence. Finally, a WLED device with a high Ra of 90, a low CCT of 3908 K, and a CIE color coordinate of (0.3503, 0.3158) has been fabricated using the synthesized phosphor. The results indicate that Y3Ga5O12:Bi3+,Mn2+ phosphors are potential candidates as single-component white light emission phosphors applied in WLEDs. Moreover, this strategy is also conducive for the design of novel white light emission phosphors for pc-WLEDs.

Novel La8Ba2(Si4P2O22N2)O2:Eu2+/Ce3+/Tb3+ apatite phosphors with tuneable light emission have been successfully synthesized by the conventional solid-state method. The structural and luminescence properties of the newly obtained samples have been studied systematically. The photoluminescence properties show that the Eu2+-, Ce3+- and Tb3+-doped La8Ba2(Si4P2O22N2)O2 samples have strong absorption in the near ultraviolet (n-UV) region. Under n-UV light irradiation, Eu2+-doped samples exhibit a narrow bluish green emission band peaking at 496 nm with a full width at half-maximum (FWHM) of 55 nm, which is comparable to the commercial blue emitting BaMgAl10O17:Eu2+ (FWHM = 55 nm) phosphor, while La8Ba2(Si4P2O22N2)O2:Ce3+,Tb3+ presents adjustable emission colour from violet to green by adjusting the concentration of Tb3+. The energy-transfer efficiencies and mechanisms have been discussed in detail. The temperature dependent luminescence measurements show that the obtained samples have low thermal quenching. Moreover, a series of white LED devices have been obtained by using the La8Ba1.99(Si4P2O22N2)O2:0.01Eu2+/(Sr,Ca)AlSiN3:Eu2+/(Ba,Sr)SiO4:Eu2+/(Sr,Ba,Ca)10(PO4)Cl2:Eu2+/Sr2SiO4:Eu2+ phosphor blend. By adding the as-prepared narrow bluish-green-emitting La8Ba1.99(Si4P2O22N2)O2:0.01Eu2+ phosphor, the Ra values can increase from 68 to 98, the R9 values increase from 42 to 95, and the corresponding CCT continuously decreases from 6210 to 3086 K, respectively. Our results reveal that the Eu2+, Ce3+ and Tb3+ activated phosphors are promising candidates for WLEDs.

Dual-emitting and thermochromic manganese ion single doped ZnGa

Gd

Abinit is a material- and nanostructure-oriented package that implements density-functional theory (DFT) and many-body perturbation theory (MBPT) to find, from first principles, numerous properties including total energy, electronic structure, vibrational and thermodynamic properties, different dielectric and non-linear optical properties, and related spectra. In the special issue to celebrate the 40th anniversary of CPC, published in 2009, a detailed account of Abinit was included [Gonze et al. (2009)], and has been amply cited. The present article comes as a follow-up to this 2009 publication. It includes an analysis of the impact that Abinit has had, through for example the bibliometric indicators of the 2009 publication. Links with several other computational materials science projects are described. This article also covers the new capabilities of Abinit that have been implemented during the last three years, complementing a recent update of the 2009 article published in 2016. Physical and technical developments inside the abinit application are covered, as well as developments provided with the Abinit package, such as the multibinit and a-tdep projects, and related Abinit organization developments such as AbiPy . The new developments are described with relevant references, input variables, tests, and tutorials. Program summary Program Title: Abinit Program Files doi: http://dx.doi.org/10.17632/csvdrr4d68.1 Licensing provisions: GPLv3 Programming language: Fortran2003, Python Journal reference of previous version: X .Gonze et al, Comput. Phys. Commun. 205 (2016) 106–131 Does the new version supersede the previous version?: Yes. The present 8.10.3 version is now the up-to-date stable version of abinit , and supercedes the 7.10.5 version. Reasons for the new version: New developments Summary of revisions: • Many new capabilities of the main abinit application, related to density-functional theory, density-functional perturbation theory, GW, the Bethe-Salpeter equation, dynamical mean-field theory, etc. • New applications in the package: multibinit (second-principles calculations)and tdep (temperature-dependent properties) Nature of problem: Computing accurately material and nanostructure properties: electronic structure, bond lengths, bond angles, primitive cell, cohesive energy, dielectric properties, vibrational properties, elastic properties, optical properties, magnetic properties, non-linear couplings, electronic and vibrational lifetimes, etc. For large-scale systems, second-principles calculations, building upon the first-principles results, are also possible. Solution method: Software application based on density-functional theory and many-body perturbation theory, pseudopotentials, with plane waves or wavelets as basis functions. Different real-time algorithms are implemented for second-principles calculations.

We study from first principles the stability of neutral and charged oxygen vacancies in lutetium oxyorthosilicate, Lu2SiO5, as well as its possible modification due to the presence of Ce 3 + , as present in commercial scintillators. We show that the neutral oxygen vacancy with the lowest formation energy forms at the oxygen sites within the [SiO4] tetrahedra instead of the interstitial oxygen site bonded exclusively to lutetium atoms. The discrepancy with a previous study is attributed to the quality of the pseudopotential. Support for these results is found by performing a bonding analysis of the oxygen sites, as well as oxygen vacancy calculations in the iso-structural Y2SiO5 compound. In addition, we find that the incorporation of Ce 3 + ion does not affect the stability of oxygen vacancies in Lu2SiO5.

The recently discovered Sr[Li$_2$Al$_2$O$_2$N$_2$]:Eu$^{2+}$ red phosphor, candidate for the next generation of eco-efficient white light-emitting diodes, exhibits excellent emission spectral position and exceptionally small linewidth. It belongs to the UCr$_4$C$_4$-structure family of phosphors, containing many potential candidates commercial phosphors, whose small linewidth, tentatively ascribed to the high-symmetry cuboid environment of the doping site, has drawn the attention of researchers in the last five years. We use density functional theory, $\Delta$SCF method and configuration coordinate models (CCM) to provide a complete characterization of this material. Using a multi-dimensional CCM, an accurate description of the coupling of the vibronic structure with the electronic 5d$\rightarrow$4f transition is obtained, including the partial Huang-Rhys factors and frequency of the dominant modes. We show that, in addition to the first-coordination shell cuboid deformation mode, low-frequency phonon modes involving chains of strontium atoms along the tetragonal axis shape the emission linewidth in Sr[Li$_2$Al$_2$O$_2$N$_2$]:Eu$^{2+}$. This finding sheds new light on the emission properties of UCr$_4$C$_4$-structure phosphors, possessing similar Ca/Sr/Ba channel. Our approach provides a robust theoretical framework to systematically study the emission spectra of such Eu-doped phosphors, and predict candidates with expected similar or even sharper linewidth.

The one-dimensional configuration coordinate model (1D-CCM) is widely used for the analysis of photoluminescence in molecules and doped solids, and relies on a linear combination of the equilibrium nuclear configurations of ground and excited states. It delivers an estimation of the energy barrier at which ground and excited state curves cross, semi-classically linked to non-radiative transition rate and thermal quenching. To assess its predictive power for the latter properties, we propose a new \textit{optimized configuration path (OCP) method in which} the ground-state and excited-state forces are mixed instead of their configurations. We also define another one-parameter model thanks a double energy parabola hypothesis (DEPH). We compare the OCP method and the DEPH reference with the 1D-CCM for three paradigmatic 4f-5d phosphors Y$_3$Al$_5$O$_{12}$:Ce, Lu$_2$SiO$_5$:Ce, and YAlO$_3$:Ce. We find that the OCP and DEPH methods yield similar results with geometries that have significantly lower ground-state energies than the 1D-CCM for the same 4f-5d energy difference. However, the OCP method suffers from the appearance of multiple local minima, rendering the clear determination of the optimal geometry very difficult in practice. Still the OCP method allows one to quantify the deviations from the 1D-CCM, therefore increasing confidence in the lower bound obtained from the DEPH for the 4f-5d crossing barrier, and its comparison with the energy of the auto-ionization thermal quenching mechanism. We expect the OCP approach to be applicable to other luminescent materials or molecules., Comment: 12 pages, 6 figure (Accepted by Phys. Rev. B)

Understanding the physical mechanisms behind thermal effects in phosphors is crucial for white light-emitting device (WLEDs) applications, as thermal quenching of their photoluminescence might render them useless. We analyze from first-principles, before and after absorption/emission of light, two chemically close Eu-doped Ba3Si6O12N2 and Ba3Si6O9N4 crystals for WLEDs. The first one has an almost constant emission intensity with increasing temperature whereas the other one does not. Our results, in which the Eu-5d levels are obtained inside the band gap thanks to the removal of an electron from the 4f7 shell, and the atomic neighborhood properly relaxed in the excited state, attributes the above-mentioned experimental difference to an autoionization model of the thermal quenching, based on the energy difference between Eu5d and the conduction band minimum. Our depleted-shifted 4f method can identify luminescent centers and therefore allows for effective crystal site engineering of luminescent centers in p...

An emitting tunable Mg 2 Al 4 Si 5 O 18 :Ce 3+ /Mn 2+ /Tb 3+ phosphors have been synthesized by high-temperature solid-state reaction technique. In this system, Mg 2 Al 4 Si 5 O 18 :Ce 3+ , Mn 2+ samples exhibit two dominating bands situated at 430 and 640 nm, originating from the Ce 3+ , Mn 2+ ions, respectively. Photoluminescence and energy transfer in Mg 2 Al 4 Si 5 O 18 :Ce 3+ , Mn 2+ are investigated as a function of Mn 2+ concentrations. The intensity ratios of red to blue band as a function of Mn 2+ concentrations are calculated based on the analysis of the luminescence dynamical process as well as fluorescence lifetime measurements, and the results are in good agreement with that obtained directly from emission spectra. Additionally, by incorporation of Tb 3+ , an efficient energy transfer from Ce 3+ to Tb 3+ was found and the energy transfer efficiency reaches 52% at y = 0.05. Results indicated that the emitting colors can be adjusted from blue to red via the energy transfer of Ce 3+ → Mn 2+ and from blue to green via the energy transfer of Ce 3+ → Tb 3+ .

We performed a Raman scattering study of thin films of ${\mathrm{LiTi}}_{2}{\mathrm{O}}_{4}$ spinel oxide superconductor. We detected four out of five Raman active modes, with frequencies in good accordance with our first-principles calculations. Three ${\mathrm{T}}_{2g}$ modes show a Fano lineshape from 5 K to 295 K, which suggests an electron-phonon coupling in ${\mathrm{LiTi}}_{2}{\mathrm{O}}_{4}$. Interestingly, the electron-phonon coupling shows an anomaly across the negative to positive magnetoresistance transition at 50 K, which may be due to the onset of other competing orders. The strength of the electron-phonon interaction estimated from the Allen's formula and the observed lineshape parameters suggest that the three ${\mathrm{T}}_{2g}$ modes at 0 momentum are not sufficient to drive superconductivity.

The luminescence of fifteen representative Eu$^{2+}$-doped phosphors used for white-LED and scintillation applications is studied through a Constrained Density Functional Theory. Transition energies and Stokes shift are deduced from differences of total energies between the ground and excited states of the systems, in the absorption and emission geometries. The general applicability of such methodology is first assessed: for this representative set, the calculated absolute error with respect to experiment on absorption and emission energies is within 0.3 eV. This set of compounds covers a wide range of transition energies that extents from 1.7 to 3.5 eV. The information gained from the relaxed geometries and total energies is further used to evaluate the thermal barrier for the $4f-5d$ crossover, the full width at half-maximum of the emission spectrum and the temperature shift of the emission peak, using a one-dimensional configuration-coordinate model. The former results indicate that the $4f-5d$ crossover cannot be the dominant mechanism for the thermal quenching behavior of Eu$^{2+}$-doped phosphors and the latter results are compared to available experimental data and yield a 30$\%$ mean absolute relative error. Finally, a semi-empirical model used previously for Ce$^{3+}$-doped hosts is adapted to Eu$^{2+}$-doped hosts and gives the absorption and emission energies within 0.9 eV of experiment, underperforming compared to the first-principles calculation., 17 pages, 13 figures, (Phys. Rev. B 2017 Accept)

In search of a reliable methodology for the prediction of light absorption and emission of Ce$^{3+}$-doped luminescent materials, 13 representative materials are studied with first-principles and semiempirical approaches. In the first-principles approach, that combines constrained density-functional theory and $\Delta$SCF, the atomic positions are obtained for both ground and excited states of the Ce$^{3+}$ ion. The structural information is fed into Dorenbos' semiempirical model. Absorption and emission energies are calculated with both methods and compared with experiment. The first-principles approach matches experiment within 0.3 eV, with two exceptions at 0.5 eV. In contrast, the semiempirical approach does not perform as well (usually more than 0.5 eV error). The general applicability of the present first-principles scheme, with an encouraging predictive power, opens a novel avenue for crystal site engineering and high-throughput search for new phosphors and scintillators., Comment: 12 pages, 3 figures

Monodisperse β-NaYF4:Ln(3+) (Ln = Yb/Er, Yb/Tm) single micro/nanocrystals were first one-pot fabricated at 50 °C through a novel synthetic route containing two pivotal processes: (a) synthesis of a β-NaYF4 {0001} unit layer through a novel style of ion-exchange from Y2(OH)5NO3·nH2O (LYH) and (b) the subsequent oriented-assembly process.

Multifunctional BaGdF5 nanospheres with mesoporous, luminescent, and magnetic properties have been successfully synthesized with the assistance of trisodium citrate by a hydrothermal method. The mesoporous structure is revealed by scanning electron microscope and transmission electron microscope images as well as N2 adsorption-desorption isotherm. The as-synthesized BaGdF5 nanospheres exhibit an intense broad bluish emission (centered at 450 nm) under the excitation of 390 nm, which might originate from the CO2·(-) radical-related defect produced by Cit(3-) groups. It is also shown that these BaGdF5 nanospheres brightened the T1-weighted images, suggesting that they could act as T1 contrast agents for magnetic resonance imaging. Using metformin hydrochloride as the model drug, the luminescent porous spheres show good drug storage/release capability. Furthermore, the emission intensity varies as a function of the cumulative drug release, making the drug-carrying system easily trackable and monitorable by detecting the luminescence intensity. Additionally, the paramagnetic property, originating from the unpaired electrons of Gd(3+) ions, opens the possibility of directing the magnetic targeted carrier to the pathological site by magnetic field gradient.

Pseudo-octahedrons of Ba2GdF7 were successfully synthesized through a solution-based method in a hydrothermal environment for the first time. The preferential adsorption of ethylene glycol (EG) molecules on the {111} planes contributed to the formation of the octahedral shape. Hydrazine was employed as the alkaline source to adjust the adsorption affinity of EG and the hydrolysis rate of NaBF4 (fluorine supply), thereby controlling the morphology and phase structure. A series of contrast experiments were conducted to investigate the growth mechanism of the Ba2GdF7 nanocrystals. As a proof-of-concept experiment, Eu3+, Tb3+, Dy3+, and Yb3+/Er3+ ions were doped to demonstrate the potential of the Ba2GdF7 crystals as host material for phosphors.

We reported a single-phased CaScAlSiO 6 :Ce 3+ , Tb 3+ , Eu 3+ as a potential full-color emitting phosphor for the application in fluorescent lamps. The CaScAlSiO 6 :Ce 3+ , Tb 3+ , Eu 3+ phosphor exhibits three bands under 254 nm excitation: one band situated at 380 nm is attributed to the 5d → 4f transitions of Ce 3+ ions, the second band with sharp lines peaked at 542 nm is assigned to the 5 D 4 → 7 F J transitions of Tb 3+ ions, the third band in the orange–red region (580–700 nm) is originated from 5 D 0 → 7 F J transitions of Eu 3+ ions. The Commission Internationale de I’Eclairage (CIE) chromaticity coordinates (0.30, 0.30) and high color rendering index (CRI=88) can be achieved upon excitation of 254 nm light. It is suggested that CaScAlSiO 6 :Ce 3+ , Tb 3+ , Eu 3+ can serve as a potential single-phased full-color emitting phosphor for phosphor-converted fluorescent lamps.

In this paper, a novel divalent europium-doped green emitting blue convertible K2Ba7Si16O40:Eu2+ phosphor has been synthesized successfully via high-temperature solid-state reaction. The structure of K2Ba7Si16O40:Eu2+ has been refined on the basis of X-ray powder diffraction by Rietveld refinement method, which consists of two infinite dimensional layers of corner-sharing [SiO4] tetrahedral parallel to (201) linked together through eight-coordinate K and seven- and nine-coordinate Ba atoms. Under excitation of blue light, the K2Ba7Si16O40:Eu2+ phosphor emits a strong green emission band peaking at 500 nm. The concentration quenching mechanism of the Eu2+ ion was discussed and the critical distance was calculated. Furthermore, the phosphor exhibits high quantum efficiency and good thermal stability, indicating that the K2Ba7Si16O40:Eu2+ phosphor can serve as an effective green emitting candidate for blue light down-conversion white light emitting diodes.

In this paper, Ce3+ doped and Ce3+,Mn2+ co-doped Na2Ba6(Si2O7)(SiO4)2 phosphors were synthesized via a high temperature solid-state reaction. The Rietveld refinement analysis of the X-ray diffraction patterns confirmed the formation of the single phase of Na2Ba6(Si2O7)(SiO4)2. The PL spectrum of the Ce3+ single-doped phosphor shows a broad asymmetric band extending from 350 to 600 nm peaking at 420 nm under the excitation of UV light. Also, the low temperature (5 K) PL spectrum shows clearly three peaks at 375, 420, and 451 nm, which is in accordance with the Ce3+ ion site in the host. The Ce3+,Mn2+ co-doped phosphors show a blue emission band and an orange emission band, and the corresponding CIE coordinates intuitively indicate the tunable colors from the blue to green area. And the energy transfer mechanism from Ce3+ to Mn2+ in the host has been verified to be a dipole–quadrupole interaction. In addition, the emission intensity of Na2Ba6(Si2O7)(SiO4)2:0.01Ce3+ phosphor slightly changed with the temperature increase from 300 to 450 K, revealing that the obtained phosphor possesses an excellent thermal stability, which makes it an attractive candidate phosphor for white lighting emitting diodes.

A series of Eu2+ and Ce3+/Tb3+ doped Ca2NaSiO4F (CNSOF) phosphors have been synthesized and their structure and photoluminescence properties have been investigated in detail. Rietveld structure refinement indicates that the phosphors crystalized in an orthorhombic system with a space group of Pnma (no. 62) and there are two kinds of cation sites for the doped ions to occupy in forming emission centers. The CNSOF:Eu2+ and CNSOF:Ce3+ phosphors both have broad excitation bands, which match well with the commercial UV LED chips. The CNSOF:Eu2+ phosphor can have intense green emission with a maximum at 530 nm under irradiation at 380 nm, while the CNSOF:Ce3+ sample can emit intense blue light, peaking at 470 nm with excitation at 365 nm. By codoping the Tb3+ and Ce3+ ions into an CNSOF host and varying their relative ratio, tunable blue-green colors are obtained due to efficient energy transfer from the Ce3+ to Tb3+ ions. Moreover, energy transfer mechanisms for the Eu2+ ions in CNSOF:Eu2+ and Ce3+ → Tb3+ in CNSOF:Ce3+,Tb3+ have been studied systematically. Our investigation indicates that CNSOF:Eu2+ and CNSOF:Ce3+,Tb3+ may be potential green and blue-green phosphors for UV WLEDs, respectively.

A series of Eu2+ and Mn2+ activated novel Sr3GdNa(PO4)3F phosphors have been prepared through a high temperature solid state reaction. The investigation revealed that Sr3GdNa(PO4)3F crystallized in a hexagonal crystal system with the space group P (no. 147). The Eu2+ activated phosphors can be efficiently excited in the range of 250 to 420 nm, which matches well with the commercial n-UV LED chips, and give intense blue emission centering at 470 nm. By codoping the Eu2+ and Mn2+ ions into the SGNPF host and singly varying the doping content of the Mn2+ ion, tunable colors from blue to white and then to yellow are obtained in SGNPF:Eu2+,Mn2+ phosphors under the irradiation of 390 nm. The energy transfer from the Eu2+ to Mn2+ ions is demonstrated to be a dipole–quadrupole mechanism in terms of the experimental results and analysis of photoluminescence spectra and decay curves of the phosphors. The critical distance between the Eu2+ and Mn2+ ions in SGNPF:Eu2+,Mn2+ was determined by the spectral overlap method. The investigation indicates that our prepared samples might have potential application in WLEDs.

Well-defined t-LaVO4:Eu3+ microcrystals have been synthesized through a facile hydrothermal route using La0.95Eu0.05(1,3,5-BTC)(H2O)6 as a precursor for the first time. It was found that the pH value and temperature have a remarkable influence on the morphology determination. By tuning the initial pH value, uniform micro cubes and cuboid rods can be obtained. The possible growth mechanism has been discussed, underlying the systematic time-dependent phase transition and morphological evolution. In addition, the luminescence properties showed that the cuboid rod-shaped LaVO4:Eu3+ sample shows a slightly stronger red emission than the cube-shape one. Our novel synthetic route may provide some new guidance in the design and controlled synthesis of inorganic nano/micromaterials.

A series of Ca2SrAl2O6:Ce(3+),Li(+),Mn(2+) phosphors have been synthesized by traditional solid state reactions. The structure and photoluminescence properties of the samples together with the energy transfer from Ce(3+) to Mn(2+) ions have been investigated in detail. The obtained phosphors can be excited efficiently by UV excitation and exhibit a broad blue-green emission band peaking at 470 nm and an orange-red emission band at 610 nm, which result from the f-d transition of the Ce(3+) and the (4)T1-(6)A1 transition of the Mn(2+) ions, respectively. By varying the doping concentration of the Mn(2+) ion, a series of tunable colors including white are obtained at an irradiation of 355 nm. The possible energy transfer mechanism was proposed in terms of the experimental results and analysis of photoluminescence spectra and decay curves of the phosphors. The critical distance between the Ce(3+) and Mn(2+) ions has been calculated by both the concentration quenching method and the spectral overlap method. Preliminary studies on the properties of the phosphor indicated that our prepared Ca2SrAl2O6:Ce(3+),Li(+),Mn(2+) phosphor might have potential application as a single-phase white-emitting phosphor for WLEDs.

In this paper, a novel green phosphor ca8mg3al2si7o28:eu2+ is synthesized via a conventional high-temperature solid-state reaction. the crystal structure of the phosphor is confirmed from the rietveld method. the obtained phosphor has a wide absorption band from the uv to the visible spectral region, ranging from 230 to 450 nm, which fits well with the characteristic emission of uv light-emitting diode (led) chips. upon excitation at 420 nm, the phosphor shows a bright and broad green color emission band with a maximum centered at 535 nm, which is attributed to the parity and spin allowed 5d-4f transition. the longer emission wavelength is caused by both the d orbital preferential orientation and the lowered symmetry of the eu2+ ions caused by the discrepancy of the tetrahedrons composed of mgo4, sio4, and alo4. additionally, the energy transfer mechanism among eu2+ ions is demonstrated via a dipole-dipole interaction by the luminescence spectra and the fluorescence decay analysis calculations on the basis of the inokuti-hirayama model. furthermore, the thermal stability of the phosphor is investigated in detail. these results suggest that the ca8mg3al2si7o28:eu2+ phosphor has great potential to be a green phosphor for white light emitting diodes (wleds).

We have synthesized a series of (Ce3+,Tb3+,Eu3+) singly doped & (Ce3+/Tb3+, Ce3+/Mn2+) codoped NaY9(SiO4)(6)O-2 phosphors via high temperature solid state reaction and investigated their crystal structures and luminescent properties in detail. The singly doped phosphors exhibit the characteristic emission of activators under UV excitation, respectively. And the decay curves can be fitted well by the two exponential functions, which is consistent with the presence of two various Y3+ sites in the host. On the basis of the photoluminescence emission spectra of codoped NaY9(SiO4)(6)O-2 samples, we clearly observed the sensitizing effects from the Ce3+ ions to the Tb3+ or Mn2+ ions and coarsely calculated the energy transfer efficiency. Furthermore, the color tune of these codoped NaY9(SiO4)(6)O-2 phosphors can be easily obtained by adjusting the relative content between the Ce3+ and Tb3+/Mn2+. (C) 2013 The Electrochemical Society. All rights reserved.

Uniform YF3:Eu3+ micro-single crystals with diamond-like, truncated octahedral, and octahedral morphologies have been synthesized by adjusting the molar ratio of KF/Y(NO3)3 and the amount of dilute HNO3 through a facile hydrothermal route without using any morphology controlling agent. It has been found that the excess K+ ions favor for the formation of {111} facets. The morphological evolution has been presented on the basis of a series of time-dependent experiments, from which a truncating growth mechanism has been proposed. Besides, the investigation on morphology-dependent luminescence properties reveals that the as-obtained truncated octahedral samples exhibit the strongest orange–red emission, while the intensity of diamond-like ones is the lowest.

Single-phased Ca3Si2O7:Ce3+,Eu2+ phosphor has been successfully prepared by the high temperature solid-state method. The phosphor shows efficient excitation bands from 200 to 400 nm and adjustable emission bands through the energy transfer from the Ce3+ to Eu2+ ions. The color hues can change from blue towards white ultimately to orange by adjusting the percentage content of doping ions. The investigation reveals that an electric dipole-dipole reaction mechanism should be responsible for the energy transfer from the Ce3+ to Eu2+ ions. The critical distance was obtained from the spectral overlap in terms of Dexter's theory. The developed phosphor Ca3Si2O7:Ce3+,Eu2+ exhibits two bands at 440 and 625 nm, respectively, which reveling that it has a great potentiality to be an UV-convertible phosphor for white-light emitting diodes with low color temperature. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.

Novel three-dimensional (3D) hierarchical architectures of Lu(2)O(3):Eu(3+) have been successfully prepared through a simple hydrothermal process followed by a subsequent calcination process without using any surfactant, catalyst, or template. According to the X-ray diffraction, thermogravimetric analysis and differential scanning calorimetry, and Fourier transform infrared spectroscopy results, the precursors were determined to have the structure formula of Lu(4)O(OH)(9)NO(3). The morphologies of the precursors could be modulated by altering pH value of the reaction system. On the basis of detailed time-dependent experiments, the growth process of architectures was discussed. The as-formed precursors could transform into Lu(2)O(3):Eu(3+) with their original hierarchical structures maintained. The Lu(2)O(3):Eu(3+) submicro-architectures exhibit strong red emission corresponding to the (5)D(0)→(7)F(2) transition of the Eu(3+) ions under ultraviolet (UV) excitation, which have potential applications in novel optoelectronic devices.