Effect of monovalent charge compensators on the photoluminescence properties of Ca_(3)(PO_(4))_(2):Tb^(3+),A^(+)(A=Li,Na,K)phosphors

Ca_(3-x)(PO_(4))_(2):xTb^(3+)(0.2≤x≤0.4),Ca_(2.3)(PO_(4))_(2):0.35 Tb^(3+),0.35 A^(+)(A=Li,Na,K),and Ca_(2.3)(PO_(4))_(2):0.35 Tb^(3+),yLi^(+)(0.35≤y≤0.455)phosphors were prepared by solid-state reaction.All the prepared phosphors formed a rhombohedral unit cell with the R3c space group.To improve the photoluminescence(PL)properties of the Ca_(2.65)(PO_(4))_(2):0.35 Tb^(3+)phosphor,monovalent charge compensators such as Li^(+),NA^(+),and K^(+)were added to the Ca_(2.65)(PO_(4))_(2):0.35 Tb^(3+)phosphor.The charge compensators acted as fluxes,so they improved the crystallinity.The excitation and emission properties were significantly improved through the incorporation of charge compensators.In particular,among the charge compensators,Li^(+)ion substantially enhanced the emission intensity and color purity.Furthermore,considering the evaporation of Li_(2)CO_(3)during the annealing process,we optimized the concentration of Li^(+)charge compensator to enhance its PL performance.Impressively,the green emission intensity of the Ca_(2.3)(PO_(4))_(2):0.35 Tb^(3+),0.385 Li^(+)phosphor was 260%higher than that of the Ca_(2.65)(PO_(4))_(2):0.35 Tb^(3+)phosphor.We believe that the effect of charge compensators on the PL properties and the optimum concentration of Li^(+)cha rge compensator are useful for the design of phosphors in light-emitting diodes.

Carbon decorated Li_(3)V_(2)(PO_(4))_(3) for high-rate lithium-ion batteries:Electrochemical performance and charge compensation mechanism

Fast charging and high-power delivering batteries are highly demanded in mobile electronics,electric vehicles and grid energy storage,but there are full of challenges.The star-material Li_(3)V_(2)(PO_(4))_(3) is demonstrated as a promising high-rate cathode material meeting the above requirements.Herein,we report the carbon decorated Li_(3)V_(2)(PO_(4))_(3) (LVP/C) cathode prepared via a facile method,which displays a remarkable high-rate capability and long-term cycling performance.Briefly,the prepared LVP/C delivers a high discharge capacity of 122 mAh g^(-1)(-93% of the theoretical capacity) at a high rate up to 20 C and a superior capacity retention of 87.1% after 1000 cycles.Importantly,by applying a combination of X-ray absorption spectroscopy and full-range mapping of resonant inelastic X-ray scattering,we clearly elucidate the structural and chemical evolutions of LVP upon various potentials and cycle numbers.We show unambiguous spectroscopic evidences that the evolution of the hybridization strength between V and O in LVP/C as a consequence of lithiation/delithiation is highly reversible both in the bulk and on the surface during the discharge-charge processes even over extended cycles,which should be responsible for the remarkable electrochemical performance of LVP/C.Our present study provides not only an effective synthesis strategy but also deeper insights into the surface and bulk electrochemical reaction mechanism of LVP,which should be beneficial for the further design of high-performance LVP electrode materials.

A deep trench super-junction LDMOS with double charge compensation layer

A deep trench super-junction LDMOS with double charge compensation layer(DC DT SJ LDMOS)is proposed in this paper.Due to the capacitance effect of the deep trench which is known as silicon-insulator-silicon(SIS)capacitance,the charge balance in the super-junction region of the conventional deep trench SJ LDMOS(Con.DT SJ LDMOS)device will be broken,resulting in breakdown voltage(BV)of the device drops.DC DT SJ LDMOS solves the SIS capacitance effect by adding a vertical variable doped charge compensation layer and a triangular charge compensation layer inside the Con.DT SJ LDMOS device.Therefore,the drift region reaches an ideal charge balance state again.The electric field is optimized by double charge compensation and gate field plate so that the breakdown voltage of the proposed device is improved sharply,meanwhile the enlarged on-current region reduces its specific on-resistance.The simulation results show that compared with the Con.DT SJ LD-MOS,the BV of the DC DT SJ LDMOS has been increased from 549.5 to 705.5 V,and the R_(on,sp) decreased to 23.7 mΩ·cm^(2).

Charge compensation and capacity fading in LiCoO2 at high voltage investigated by soft x-ray absorption spectroscopy

In order to obtain an in-depth insight into the mechanism of charge compensation and capacity fading in LiCoO2, the evolution of electronic structure of LiCoO2 at different cutoff voltages and after different cycles are studied by soft x-ray absorption spectroscopy in total electron（TEY） and fluorescence（TFY） detection modes, which provide surface and bulk information, respectively. The spectra of Co L2,3-edge indicate that Co contributes to charge compensation below 4.4 V.Combining with the spectra of O K-edge, it manifests that only O contributes to electron compensation above 4.4 V with the formation of local O 2 p holes both on the surface and in the bulk, where the surficial O evolves more remarkably. The evolution of the O 2 p holes gives an explanation to the origin of O2^-or even O2. A comparison between the TEY and TFY of O K-edge spectra of LiCoO2 cycled in a range from 3 V to 4.6 V indicates both the structural change in the bulk and aggregation of lithium salts on the electrode surface are responsible for the capacity fading. However, the latter is found to play a more important role after many cycles.

Modeling of high permittivity insulator structure with interface charge by charge compensation

An analytical model of the power metal–oxide–semiconductor field-effect transistor(MOSFET)with high permittivity insulator structure(HKMOS)with interface charge is established based on superposition and developed for optimization by charge compensation.In light of charge compensation,the disturbance aroused by interface charge is efficiently compromised by introducing extra charge for maximizing breakdown voltage(BV)and minimizing specific ON-resistance(R_(on,sp)).From this optimization method,it is very efficient to obtain the design parameters to overcome the difficulty in implementing the R_(on,sp)–BV trade-off for quick design.The analytical results prove that in the HKMOS with positive or negative interface charge at a given length of drift region,the extraction of the parameters is qualitatively and quantitatively optimized for trading off BV and Ron,sp with JFET effect taken into account.

Unveiling the mechanism of charge compensation in Li_(2)Ru_(x)Mn_(1-x)O_(3)by tracking atomic structural evolution

The relationship between the structural evolution and redox of Li-rich transition-metal layered oxides(LLOs)cathodes remains ambiguous,obstructing the development of high-performance lithium-ion(Li^(+))battery.Herein,the coherent effects of local atomic and electronic structure in Li_(2)Ru_(x)Mn_(1-x)O_(3)(LRMO)with a wide voltage window(1.3–4.8 V)is identified by in situ X-ray absorption fine spectroscopy(XAFS)and chemometrics.We not only skillfully separated the redox active structures to track the electrochemical path,but also visualized the coupling mechanism between the evolution of Ru-Ru dimer and the(de)excitation of cations and anions.Furthermore,introducing manganese triggers the“heterogeneity”of coordination environment and electronic structure between Ru and Mn after discharge to 3 V.The change of thermodynamic and kinetic paths affects the relithiation,and further leads to the hysteresis of the anion activation structure relaxation of Li_(2)Ru_(0.4)Mn_(0.6)O_(3)relative to Li_(2)RuO_(3)(LRO).Additionally,it is demonstrated that the high charge cut-off voltage restrains the relaxation of anionic active structure in LRO from a new perspective through comparative experiments.Our work associates the evolution of atomic structure with charge compensation and negative electrochemical reactions such as voltage hysteresis(VH)and capacity attenuation,deepening the understanding electrochemical reaction mechanism of LLOs during the first cycle and providing a theoretical support for the further design and synthesis of high-efficiency cathodes.

Spatial charge and compensation method in a whirler

Based on particle-in-cell simulation, we studied the motions of ions and electrons. The results have shown that electrons are bounded by a magnetic field and only a small number of electrons can pass through the whirler channel. The plasma becomes non-neutral when it is emitted from the whirler, and the spatial charge leads to a beam divergence, which is unfavorable for mass separation. In order to compensate the spatial charge, a cathode is designed to transmit electrons and the quasi-neutral plasma beam. Experiment results have demonstrated that the auxiliary cathode can obviously improve the compensation degree of the spatial charge.

Effect of Na^(+)and Sr^(2+)Substitution on the Formation of the Oxygen Vacancies in Y_(3)Al_(2)Ga_(3)O_(12):Ce^(3+)Phosphor

The low-valence cations Na^(+)and Sr^(2+)were selected as the co-dopants to increase the vacancies concentration in the Y_(2.982)Ce_(0.018)Al_(2)Ga_(3)O_(12)phosphor.The successful incorporation of Na^(+)and Sr^(2+)was confirmed by the X-Ray Difiraction(XRD)results.All the samples show 5d-4f green persistent luminescence of Ce^(3+)after 450 nm excitation.The decay curves demonstrate that the persistent luminescence is efiectively enhanced with Na+and Sr2+doping.The thermoluminescence glow curves also show not only does the trap concentration increase,but also the distribution of trap depths is broadened.In addition,the air-and H_(2)/Ar-annealing treatments were conducted on every as-made sample.The experimental results prove that the increased traps after the Na^(+)/Sr^(2+)doping are mainly attributed to the oxygen vacancies,and the traps have a continuous and broad distribution of trap depths.We hope this work could give new inspiration for designing a high-performance persistent phosphor.

First-Principles Study of Ca3Sc2Si3O12： Ce3＋ Phosphors

Charge compensation plays a very important role in modifying the local atomic structure and moreover the spectroscopic property of an isolated luminescent center, and so has been widely adopted in phosphor designs. In this work, we carry out first-principles calculations on various cases of Ce3＋ centers in Ca3Sc2Si3O12 by considering the effects of the charge com- pensations related to N3-, Sc3＋, Mn2＋, Mg2＋, and Na＋. Firstly, the local structures around Ce3＋ are optimized by using density functional theory calculations with supercell model. The 4f→5d transition energies of Ce3＋ are then obtained from the CASSCF/CASPT2/RASSI-SO calculations performed on Ce3＋-centered embedded clusters. The calculated energies support the previous assignments of the experimental spectra. Especially, a previously unclear peak is identified to be caused by Sc3＋ substituting Si4＋. The results show that the first-principles calculations can be used as an effective tool for predicting and interpreting spectroscopic properties of the phosphors.

Luminescence of Co-doped SrTiO_3:Pr^(3+)

The SrTiO3 ： Pr^3＋ material, co-doped with monovalent Li^＋ , divalent Mg^2＋ , and trivalent Al^3＋ was prepared by a new sol-gel method. The phase and crystallinity of the synthesized materials were investigated by powder X-ray diffraction（XRD） and scanning electron microcopy（SEM）. Among the co-doped ion, Al^3＋ incorporation caused the least lattice change and had the best crystallinity. Photoluminescence spectra were taken to investigate the luminescence characteristics. We observed a red luminescence change of SrTiO3 ： Pr^3＋ after being co-doped, and a best enhancement on the red luminescence with the trivalent Al^3＋ was observed. The present results indicated that the charge defect associated with Al^3＋ has led to charge compensation of Pr^＋ and also implied that the charge defects（usually the second dopant ions replacing the A or B sites in the lattice） which are closer to PrSr^＋ contribute more to the red luminescence enhancement.

A model for estimating the viscosity of blast furnace slags with optical basicity

Viscosity is an important physical property of blast furnace slags and has a great influence on blast furnace operations. Because of time consumption and difficulties encountered during high temperature experimental measurement, viscosity data are also limited, so a rea-sonable and accurate estimation model is required to provide the data for controlling and optimizing the blast furnace process. In the present study a viscosity model was proposed for blast furnace slags. In the model the activation energy was calculated by the optical basicity cor-rected for cations required for the charge compensation of , and the temperature dependence was described by the Weymann-Frenkel equation. The estimated viscosity values of the CaO-Al2O3-SiO2, CaO-Al2O3-SiO2-MgO, and CaO-Al2O3-SiO2-MgO-TiO2 systems fit well with experiment data, with the mean deviation less than 25%.

Effects of Li^+ on photoluminescence of Sr_3SiO_5:Sm^(3+) red phosphor

The structure and photoluminescence （PL） properties of Sr3 SiO5： Sm3＋ and Li＋-doped Sr3SiOs： Sm3＋ red-emitting phosphors were investigated. Samples were prepared by the high-temperature solid-state method. PL spectra show that the concentration quenching occurs when the Sm3＋ concentration is beyond 1.3 mol% in Sr3SiOs： Sm3＋ phosphor without doping Li＋ ions. The concentration-quenching mechanism can be explained by the electric dipole-dipole interaction of Sm3＋ ions. The incorporation of Li＋ ions into Sr3SiOs： Sm3＋ phosphors, as a charge compensator, improves the PL properties. The lithium ions also suppress the concentration quenching in Sm3＋ with concentration increased from 1.3 tool% to 1.7 tool%.

Simultaneous enhancement of red luminescence and thermal stability of a novel red phosphor:A Li^(+)-Eu^(3+)co-occupied site strategy in BaAl_(2)Ge_(2)O_(8)lattices

The rapid development of phosphor-converted white light emitting diodes(pc-WLEDs)requires new red phosphors with efficient and thermally stable luminescence for high-quality warm-white lighting.However,it is still a challenge to discover red phosphors with facile synthesis,high internal quantum efficiency(IQE),excellent thermal stability and high color purity.Herein,a novel red-emitting Eu^(3+)activated barium dialuminum digermanate(BaAl_(2)Ge_(3)O_(8),EAGO)phosphor showing strong red emission at 610 nm was prepared.The IQE is improved from 32.91%to 78.84%by employing a charge compensation strategy.The lithium-ion co-dop ed BAGO:Eu^(3+)phosphor exhibits a nearly twofold increase in integral photoluminescence(PL)intensity and the high color purity reaches 94.17%.Impressively,the PL intensity of the BAGO:Eu^(3+),Li^(+)phosphor drops by only 2.6%at 150℃of that at room temperature.Finally,the pc-WLED using the red BAGO:Eu^(3+),Li^(+)phosphor exhibits white light with the chromaticity coordinate of(0.3515,0.3495),a high color-rendering index of 92 and a low correlated color temperature of 4746 K.All these results manifest that BAGO:Eu^(3+),Li^(+)phosphor is a suitable red phosphor for nearultraviolet(NUV)chip-based pc-WLEDs.

Luminescence enhancement of CaMoO_(4):Eu^(3+) phosphor by charge compensation using microwave sintering method

CaMoO_(4):Eu^(3+)and CaMoO_(4):Eu^(3+),A+(A=Li,Na,K)phosphors for light-emitting diode(LED)applications have been prepared by microwave sintering method(MSM),and their structure and luminescence properties are investigated.The influences of microwave reaction time and concentration of different kinds of charge compensation A+and Eu^(3+)on luminescence have also been discussed.The samples emit a red luminescence at 615 nm attributed to the^(5)D0→^(7)F2 transition of Eu^(3+)under 464 nm excitation.It is observed that adding charge compensation A+in the sample synthesis increases luminescence intensity.The optimized sample made with 32 mol%Li+and 32 mol%Eu^(3+)has an enhancement factor of 4 in photoluminescence compared to the sample made without charge compensation.The CIE(Commission Internationale de l'Eclairage)coordinates of Ca0.36MoO_(4):0.32Eu^(3+),0.32Li+are x=0.661 and y=0.339,which indicate that the obtained phosphor can be a promising red color candidate for white LED fabrications.

Determination of total ginsenosides in ginseng extracts using charged aerosol detection with post-column compensation of the gradient

AIM: Variation in structure-related components in plant products prompted the trend to establish methods, using multiple or total analog analysis, for their effective quality control. However, the general use of routine quality control is restricted by the limited availability of reference substances. Using an easily available single marker as a reference standard to determine multiple or total analogs should be a practical option. METHOD: In this study, the Ultra-HPLC method was used for the baseline separation of the main components in ginseng extracts. Using a plant chemical component database, ginsenosides in ginseng extracts were identified by Ultra-HPLC-MS analysis. The charged aerosol detection(CAD) system with post-column compensation of the gradient generates a similar response for identical amounts of different analytes, and thus, the content of each ginsenoside in ginseng extracts was determined by comparing the analyte peak area with the reference standard(determination of total analogs by single marker, DTSM). The total ginsenoside content was determined by the summation of reference standard and other ginsenoside components. RESULTS: The results showed that DTSM approaches were available for the determination of total ginsenosides in a high purity ginseng extract because of the removal of impurities. In contrast, DTSM approaches might be suitable for determination of multiple ginsenosides without interference from impurities in the crude ginseng extract. CONCLUSION: Future practical studies similar to the present study should be conducted to verify that DTSM approaches based on CAD with post-column inverse gradient for uniform response are ideal for the quality control of plant products.

Effects of charge compensation on red emission in CaYAl_3O_7:Eu^(3+) phosphor

Monovalent ions Li＋, Na＋, and K＋, as charge compensators, are introduced into CaYA1307： M （M = Eu3＋, Ce~＋） in this letter. Their crystal phases and photoluminescence properties of different alkali metal ions doped in CaYA1307 are investigated. In addition, the influence of charge compensation ion Li＋ which has a more obvious role in improving luminescence intensity on CaYA1307： Eu3＋ phosphor is intentionally discussed in detail and a possible mechanism of charge compensation is given. The enhancement of red emission centered at 618 nm belonging to Eu3＋ is achieved by adding alkali metal ion Li＋ under 393-nm excitation.

Highly efficient K-doped Mn-Ce catalysts with strong K-Mn-Ce interaction for toluene oxidation

In this study,K_(x)-Mn-Ce catalysts prepared by sol-gel method were investigated for toluene oxidation.Compared with Mn-Ce,the catalytic performance of K_(x)-Mn-Ce was further improved.X-ray diffraction(XRD),high resolution transmission electron microscopy(HRTEM)and Raman analyses demonstrate that K ions enter the lattice of CeO_(2) and disperse uniformly.The results of X-ray photoelectron spectroscopy(XPS),H_(2)-temperature programmed reduction(H_(2)-TPR).and O_(2)-temperature programmed desorption(O_(2)-TPD)analyses indicate that there is a strong interaction between K,Mn and Ce;the charge co mpensation effect would be induced when K ions enter the lattice of CeO_(2),which leads to more oxygen vacancies due to the generation of more Ce^(3+).Toluene-TPD shows that K-doping enhances the activation ability of toluene.Among all catalysts,K0.1-Mn-Ce shows the highest concentration of Mn^(4+),Ce^(3+),Osur,and redox ability,resulting in higher low-temperature catalytic activity.Additionally,the results of stability and water resistance also prove that K0.1-Mn-Ce catalyst possesses excellent stability and water resistance.

Li^(+)doping induced zero-thermal quenching in Cs_(3)Zn_(6-x-y)B_(9)O_(21):xEu^(3+),yLi^(+)(0≤x≤0.10,0.06≤y≤0.16)

Thermal stability is a crucial index to assess application value of high-power LEDs,which is related to lattice defects.Herein,an effective structure-engineering strategy is proposed to achieve excellent properties.Under the 394 nm excitation,Cs_3Zn_(5.94)B_9O_(21):0.06Eu^(3+)possesses two characteristic emissions peaked at 591 and 612 nm with limited thermal stability.By introducing Li^(+)ions into the lattice,the sample exhibits high color purity and excellent zero-thermal quenching because the defect contents of the phosphor can be effectively modulated via charge-compensation effect.Then,under the stimulus of high temperature,the corresponding trap levels with a suitable depth(E=1.27 eV)will release electrons to recombine with the luminescent centers,compensating for the energy loss.The study provides a meaningful guide for optimizing and designing novel functional photoluminescent materials.

Synthesis and optical properties of Dy^(3+), Li^+ doped CaMoO_4 phosphor

A series of CaMoO4 phosphors doped with trivalent dysprosium ions （Dy3＋） and lithium （Li＋） were prepared by solid state method at 750 °C for 3 h. X-ray diffraction （XRD） confirmed the crystal structure and quality of phosphors. Scanning electron microscopy （SEM） in- dicated that the phosphors presented good crystalline state, and the crystalline grain sizes were about 0.5–3.0 μm. The emission spectra showed that the phosphors had intense emission at 480 （4F9/2→6H15/2）, 576 （4F9/2→6H13/2） and 660 nm （4F9/2→6H11/2）. Meanwhile, the excited spectra indicated it had intense excitation at 352 （6H15/2→6P7/2）, 390 （6H15/2→4M21/2） and 450 nm （6H15/2→4I15/2）. As a charge compensator, Li＋ ions were incorporated into CaMoO4：Dy3＋ phosphors, which enhanced the PL intensities depending on the doping concentration of Li＋. The optimal molar fraction of Dy3＋ ions in Ca1-xMoO4：xDy3＋, 0.05Li＋ was 0.05.

Luminescence properties of alkali metal ions sensitized Ca FCl:Tb^(3+) nanophosphors

A series of CaFCl：Tb3＋ and CaFCI：Tb3＋,A＋ （A=Li, Na and K） nanophosphors were synthesized by the one-step sol-gel method, which were reported for the first time. The sample consisted of monodisperse particles, the average size of which was 37 nm. The emissions of Tb3＋ ions and oxygen defects OF＇ were demonstrated in the CaFCl：Tb3＋ samples. The former was made up of several peaks at 488, 545, 587 and 623 nm, ascribed to 5D4→7FJ （j=6-3） transitions of Tb3＋ ions. The latter was shown as a broad band peaked at about 450 nm. Alkali metal ions A＋ （A=Li, Na and K） were introduced as the charge compensators to improve the luminescence of samples. The influence of charge compensators on the emissions of Tb3＋ ions and oxygen defects OF＇ was investigated by the measurement of fluorescence spectra and luminescence decay curves. The results indicated that all the charge compensators weakened the defects emission. Furthermore, Li＋ ion was the best charge compensator, because it not only reduced the defects emission but also increased the emission intensity of Tb3＋ significantly. Our results suggested that this nanophosphor sensitized by the charge compensator might broaden potential applications of rare-earth doped CaFCl.