Optical and electrical conductivity properties of rare earth elements (Sm,Y, La,Er) co-doped CeO2

In this research, un-doped CeO₂ and Ce_0.85La_0.10M_0.05O₂ (M: Sm, Er, Y) compounds were synthesized by hydrothermal method and the multi-functional properties are reported. Oxygen defects were created with the additives of rare earth ions. The electrical and luminescence behaviors of the synthesized compounds were investigated in accord with the types of additives. The synthesized products were characterized by X-ray diffraction (XRD) analysis, Brunauer–Emmett–Teller (BET) measurement, UV–vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy and electrochemical impedance spectroscopic (EIS). All synthesized compounds are found to be nano-structured and have cubic phase. The total conductivity of all samples was calculated. Hence, the total conductivity of un-doped CeO₂, Ce_0.85La_0.10Y_0.05O₂, Ce_0.85La_0.10Er_0.05O₂ and Ce_0.85La_0.10Sm_0.05O₂ is found to be 2.07 × 10^?10, 5.70 × 10^?4, 1.0 × 10^?3 and 0.0747 S/cm, respectively. Also, bandgap energy (E_g) of these samples calculated from UV visible absorption spectra is discussed, and the optical results show variation between 3.2 and 2.15 eV. Additionally, the luminescence properties of the compounds were investigated and different emissions occur depending on the additive type. Accordingly, photoluminescent emission spectra of Ce_0.85La_0.10Y_0.05O₂, Ce_0.85La_0.10Er_0.05O₂ and Ce_0.85La_0.10Sm_0.05O₂ phosphors indicate that these phosphors have red, green and orange-red colors, respectively.     

Catalytic combustion of toluene over Pd-based monolithic catalysts with a novel washcoat Ce0.8Zr0.15La0.05Oδ

Two novel washcoats Ce_0.8Zr_0.15La_0.05O_δ and Ce_0.8Zr_0.2O₂ was prepared by an impregnation method, which acted as a host for the active Pd component to prepare Pd/Ce_0.8Zr_0.15La_0.05O_δ/substrate and Pd/Ce_0.8Zr_0.2O₂/substrate monolithic catalysts for toluene combustion. The washcoats was characterized by X-ray diffraction (XRD), Raman spectroscopy, Brunauner-Emmett-Teller (BET), and H₂-temperature-programmed reduction (H₂-TPR). The result indicated that both the washcoats had strong vibration-shock resistance according to ultrasonic test. Doping La³⁺ into CeO₂-ZrO₂ solid solution could generate more oxygen vacancies, and could inhibit the sinter of CeO₂-ZrO₂ solid solution when calcined at high temperatures (800, 900 and 1000 °C). The washcoat Ce_0.8Zr_0.15La_0.05O_δ had much better redox properties. The reductive temperature of Ce⁴⁺ species shifted to low temperature by 60 °C when the washcoats calcined at high temperatures (800, 900 and 1000 °C). The Pd/Ce_0.8Zr_0.15La_0.05O_δ/substrate monolithic catalyst calcination at 500 °C had the best catalytic activity and the 95% toluene conversion at a temperature as low as 190 °C. When calcined at low temperature (500 and 700 °C), the catalytic activity has little improvement, however, when calcined at high temperature, the catalytic activity of Pd/Ce_0.8Zr_0.15La_0.05O_δ/substrate monolithic catalysts had significant improvement. As catalyst washcoat, the Ce_0.8Zr_0.15La_0.05O_δ had better thermal stability than the washcoat Ce_0.8Zr_0.2O₂, the developed Pd/Ce_0.8Zr_0.15La_0.05O_δ/substrate monolithic catalyst in this work was promising for eliminating Volatile organic compounds.     

La_2Ce_2O_7 supported ruthenium as a robust catalyst for ammonia synthesis

La_2Ce_2O_7 nanoparticles were prepared by citric acid complexation method followed by calcination at varied temperatures. Then, supported with 4 wt% Ru, they were evaluated as the catalysts for ammonia synthesis under conditions similar with industry. With La_2Ce_2O_7 being calcinated at 700 or 800℃, the experimental results indicate that the Ru/La_2Ce_2O_7 catalyst exhibits much higher ammonia concentration or ammonia synthesis rate than that of Ru/CeO_2 and Ru/La_2O_3. In addition, Ru/La_2Ce_2O_7 possesses high stability under over-heating test. In the absence of any promotor, ammonia concentration of Ru/La_2Ce_2O_7 catalyst approaches 14% at 450℃, GHSV of 10000 h~(-1) and pressure of 10 MPa. The rate-determining step of ammonia synthesis, dissociation of N_2 is significantly facilitated by the strong metalesupport interaction(SMSI) between Ru and La_2Ce_2O_7. Due to the interaction, La_2Ce_2O_7 tends to donate electrons to Ru,resulting in the high electron density over the surface of Ru active sites which is favorable for the dissociation of N_2. Consequently, high activity is achieved.     

Mechanical properties,thermophysical properties and electronic structure of Yb3+ or Ce4+-doped La2Zr2O7-based TBCs

First-principles calculations based on density functional theory were performed to investigate the cohesive energies, elastic modulus, Debye temperatures, thermal conductivities and density of states of La_2−xYb_xZr₂O₇, La₂Zr_2−xCe_xO₇ and La_2−xYb_xZr_2−xCe_xO₇ (x = 0.00, 0.25, 0.50, 0.75, 1.00) ceramics. The results show that doping Yb³⁺ or Ce⁴⁺ into La₂Zr₂O₇ reduces its elastic modulus, thermal conductivity and Debye temperature. Compared with La_2−xYb_xZr₂O₇ (x ≠ 0.00), La₂Zr_2−xCe_xO₇ compounds have better ductility and lower Debye temperature. The Debye temperature values of La₂Zr_2−xCe_xO₇ (x ≠ 0.00) compounds are in the range of 485.0–511.5 K. Among all components, the fluorite-type La_2−xYb_xZr_2−xCe_xO₇ (x = 0.75, 1.00) compounds exhibit better mechanical and thermophysical properties, and their thermal conductivity values are only 1.213–1.246 W/(m∙K) (1073 K), which are 14.5%–16.7% lower than that of the pure La₂Zr₂O₇. Thus, our findings open an entirely new avenue for TBCs.     

Magnetoelectric,Raman, and XPS Properties of Pb0.7Sr0.3[(Fe2/3Ce1/3)0.012Ti0.988]O3 and Pb0.7Sr0.3[(Fe2/3La1/3)0.012Ti0.988]O3 Nanoparticles

The Pb_0.7Sr_0.3[(Fe_2/3Ce_1/3)_0.012Ti_0.988]O₃ (PSFCT) and Pb_0.7Sr_0.3[(Fe_2/3La_1/3)_0.012Ti_0.988]O₃ nanoparticles were prepared by chemical synthesis route using polyvinyl alcohol as surfactant. X-ray diffraction pattern has been used to analyze the phase structure and average particles size. The phase structure is also confirmed by Raman spectra. The chemical states of Pb²⁺, Sr²⁺, Fe³⁺; Ti⁴⁺, Ce³⁺, La³⁺, and oxygen ions have been analyzed by X-ray photoelectron spectroscopy. The magnetoelectric coupling effect is confirmed by magnetic phase transition near ferroelectric phase-transition temperature. The magnetoelectric effect is also confirmed by measuring the value of magnetoelectric coefficient (α _E) as the function of applied dc magnetizing field under the influence of ac magnetic field of 10 Oe and frequencies of 847 and 997 Hz. The higher value of α _E is observed in PSFCT sample.     

Blue-emitting Sr_(1-x)Ca_xLu_2O_4:Ce~(3+) phosphors for high CRI white LEDs

A broadband blue-emitting Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+)(x=0-0.2) phospho rs were synthesized,which can be used for near-UV pumped white light-emitting diodes(w-LEDs).The crystal structures,photoluminescence pro perties,external quantum efficiency,the rmal stability and application perfo rmance of Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+),by partially substituting Sr~(2+) with Ca~(2+)(x=0-0.2),were studied by various analytical techniques.When the Ca/Sr ratio of Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+) gradually increases,the emission peak of Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+) red-shiftes from 459 to 465 nm,corrected external quantum efficiency increases from 31.8% to 42.9%,and the thermal stability is also improved.The mechanism of the changes of the photoluminescence emission and excitation spectra,external quantum efficiency and thermal stability properties was also investigated in detail.In addition,a w-LED was fabricated by using SrLu_2 O_4:Ce~(3+)(blue),β-sialon:Eu~(2+)(green) and(Sr,Ca)AlSiN_3:Eu~(2+)(red) phosphors combined with a 405 nm near-UV LED chip,and its color rendering index(CRI) reaches 96.0.When Sr_(0.8)Ca_(0.2)Lu_2 O_4:Ce~(3+)is applied as blue phosphor to substitute SrLu_2 O_4:Ce~(3+),the obtained w-LED devices have high luminous efficiency,and CRI greater than 95.0.These re sults show that the Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+) can be potential blue phosphors for n-UV pumped high CRI w-LEDs application.     

Effect of grain size on thermal stability and oxygen storage capacity of Ce0.17Zr0.73La0.02Nd0.04Y0.04O2 solid solutions

Nanostructured CeO_2-ZrO_2 materials are an irreplaceable constituent in catalytic systems for automobile exhaust purification due to their unique oxygen storage capacity(OSC). However, traditional CeO_2-ZrO_2 materials are easy to sinter at high temperature, which causes a sharp decrease of OSC. In this paper,La~(3+) , Nd~(3+) and Y~(3+) are chosen as dopants for CeO_2-ZrO_2 to improve anti-sintering and OSC properties.The Ce_(0.17) Zr_(0.73) La_(0.02) Nd_(0.04) Y_(0.04) O_2 powders(CZLNY) were prepared by co-precipitation method. The effects of grain sizes with different mixed chlorinated solution concentrations on performances were investigated. X-ray diffraction(XRD) and transmission electron micrograph(TEM) were performed to calculate the grain sizes of CZLNY. The specific surfaces, OSC and redox properties were investigated by N_2 adsorption/desorption and temperature programmed reduction(H2-TPR). The results show that introducing La~(3+) , Nd~(3+) and Y~(3+) into CeO_2-ZrO_2 lattice can improve the stability of phase structure and anti-sintering ability. Moreover, low concentration of mixed chlorinated solution remarkably improves structural and textural properties of CZLNY. Relatively large fresh grain exhibits superior thermal stability and OSC under the condition of being calcined at 800℃ for 3 h. The specific surface and OSC are42.37 m~2/g and 333.13 mmol/g after calcining at 1000℃ for 10 h, respectively. This is owing to the low sintered driving force of large grain and long-range migration energy of large pores during the sintering process, which are beneficial to the stability of structure in CZLNY materials.     

2 μm mid-infrared optical spectra of Tm3+-doped germanium gallate glasses

Glasses with the composition of 65GeO212Ga2O3-10BaO-8Li2O-5La2O3(molar ratio) doped with 1.526 wt.%, 3.006 wt.%, 5.836 wt.%, 11.028 wt.%, and 15.678 wt.% Tm2O3, respectively, were fabricated by conventional melting method. According to the absorption spectra and the Judd-Ofelt theory, the J-O strength parameters (Ω2,Ω4, Ω6) were calculated, with which the radiative transition probabilities,branching ratios and radiative lifetimes were obtained. The infrared emission spectra (with 808 nm LD excitation) at～1.47 and～1.8 μm of various concentrations of Tm3+-doped glasses were studied. The emission intensity at～1.8 μm reached to the maximum when the Tm2O3-doping concentration was near to be～3.006 wt.% (1.0 mol.%), and then decreased as doping concentration increased further. The mechanism of the fluorescence intensity change was explained with the cross-relaxation effect and the concentration quenching effect of Tm3+. Meanwhile, according to McCumber theory, the absorption and emission cross-sections corresponding to the 3F4→3H6 transitions of Tm3+ at 1.8 μm was obtained. For Tm3+-doped germanate glasses, the maximum emission cross-section reached a value higher than that re-ported for fluorozircoaluminate glasses. It is expected to be a favorable candidate host for～2.0 μm mid-inflated laser because the glass shows favorable optical spectra.     

Luminescent properties of Ce3+, Er3+ co-doped La3Si6N11

In order to obtain near-infrared phosphor pumped by blue chip with high luminous efficiency, a novel near-infrared phosphor Ce³⁺/Er³⁺ doped La₃Si₆N₁₁ was designed and firstly prepared via conventional solid-state reactions. The structure and morphology of Ce³⁺/Er³⁺ doped La₃Si₆N₁₁ were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Compared with Er³⁺ doped La₃Si₆N₁₁, the emission intensity of the Ce³⁺, Er³⁺ co-doped phosphor can be increased more than 5 times. Meanwhile, the mechanism of energy transfer from Ce³⁺ to Er³⁺ is confirmed according to the excitation, emission spectra and decay lifetimes curve. Above results suggest that La₃Si₆N₁₁:Ce³⁺,Er³⁺ is a promising near-infrared phosphor for blue pumped LEDs (light-emitting diodes).     

An optical thermometer with high sensitivity and superior signal discriminability based on dual-emitting Ce3+/Eu2+ co-doped La5Si2BO13 thermochromic phosphor

A novel non-contact optical thermometer, qualified with high sensitivity and temperature resolution, is urgently needed for temperature measuring of micro devices, moving objects and specific severe environments. Hence, a series of dual-emitting La₅Si₂BO₁₃:Ce³⁺,Eu²⁺ phosphors were synthesized. The two ions show diverse responses with the changing in temperature. The variational emissions of Ce³⁺ and Eu²⁺ can be converted to FIR (fluorescence intensity ratio) signals. The maximal absolute sensitivity S_a and relative sensitivity S_r reach up to 0.07526%/K and 3.2241%/K, respectively. It is worthy noting that the S_a and S_r possess the same variation tendency and both have high values in the low temperature region (293–373 K), showing the great temperature measuring property especially in low temperature region. The temperature sensing characteristics are superior to the results of most previous reports. The energy transfer (ET) process is certified to occur from Ce³⁺ to Eu²⁺ ions. These studies indicate that La₅Si₂BO₁₃: Ce³⁺,Eu²⁺ phosphor could have a good prospect for optical thermometry.     

Characterization and electrochemical performance of CeO2 and Eu-doped CeO2 films as a manganese redox flow battery component

Hexagonal CeO_2 and Eu-doped CeO_2 nanoparticles were obtained using a facile microwave-hydro thermal method under mild conditions and their application towards manganese redox flow battery component were studied. The structural properties were studied by X-ray diffraction and indicate that samples present a fluorite structure. Raman spectroscopy shows Eu3+ ions substitute Ce~(4+) and generate oxygen vacancies. Electrochemical properties of pure and Eu-doped CeO_2 films deposited at graphite substrates investigated by cyclic voltammetry and galvanostatic charge—discharge indicate that dopant concentration affects the electrochemical properties of CeO_2. The increase in the reversibility redox of electrochemical systems observed is attributed to coexistence of Ce~(4+)/Ce~(3+) redox couple confirmed by XPS.Charge—discharge tests display coulombic and voltage efficiency values of above 80% and 90%, respectively. The obtained specific capacity for Ce_(0.99)Eu_(0.01)O_2(372.49 mAh/g) and pure oxide(334.84 mAh/g)indicates that both samples are promising for application in Mn-batteries.     

Luminescence properties of BaAl12O19:Tb,Ce and energy transfer between Ce3+, Tb3+

BaAl₁₂O₁₉:Tb,Ce phosphors were prepared by sol-gel technique, the crystalline structures of samples characterized by XRD, and the luminescence properties and energy transfer between Ce³⁺ and Tb³⁺ were investigated. The results indicated that the emission intensity and the excitation wavelength range of Tb³⁺ increased when Ce³⁺ was doped. It demonstrated that the Ce³⁺ added in the BaAl₁₂O₁₉:Tb could deliver energy to Tb³⁺, and Ce³⁺ was not luminous by itself. The relative emission intensity of Tb³⁺ at wavelength of 548 nm was the strongest by Tb³⁺/Ce³⁺ ratio of 2:1, when excited at 310 nm, which was the characteristic adsorption wavelength of Ce³⁺.     

Tunable luminescence in co-doped Zn3Al2Ge2O10:Cr3+ by controlling crystal field splitting and nephelauxetic effect

Ce³⁺/Dy³⁺/Tb³⁺/Eu³⁺/Mn²⁺ and Cr³⁺ ions co-doped Zn₃Al₂Ge₂O₁₀ phosphor were prepared by a high-temperature solid-state method. X-ray diffraction patterns prove the cubic phase structure of prepared Zn₃Al₂Ge₂O₁₀ phosphor. Emission, excitation spectra and decay curves confirm the tunable luminescence. Different degrees of the decrease of emission FWHM in Zn₃Al₂Ge₂O₁₀:0.02Cr³⁺,RE (RE = Ce³⁺, Dy³⁺, Tb³⁺, Eu³⁺) and Zn₃Al₂Ge₂O₁₀:0.02Cr³⁺,Mn²⁺ are observed. The reason of variable FWHM is the effect of crystal field splitting and nephelauxetic effect, and the nephelauxetic effect is dominant. Therefore, the emission FWHM decreases with the increasing concentration of Mn²⁺/Tb³⁺/Eu³⁺ in Zn₃Al₂Ge₂O₁₀:0.02Cr³⁺, and for Zn₃Al₂Ge₂O₁₀:0.02Cr³⁺,Ce³⁺ and Zn₃Al₂Ge₂O₁₀:0.02Cr³⁺,Dy³⁺, it is a constant. The variation of Zn₃Al₂Ge₂O₁₀:0.02Cr³⁺,Tb³⁺ is more obvious than that of Zn₃Al₂Ge₂O₁₀:0.02Cr³⁺,Eu³⁺, because Tb³⁺ ion has smaller electronegativity. Thus, the tunable luminescence of Cr³⁺ can be realized by co-doping different ions. And these phosphors have potential applications in light-emitting diodes for plant growth.     

Effect of rare earth ions doping on properties of LiFePO4/C cathode material

LiFe0.99RE0.01PO4/C cathode material was synthesized by solid-state reaction method using FeC2O4·2H2O, Li2CO3, NH4H2PO4, RE(NO3)3·nH2O as raw materials and glucose as a carbon source. The doping effects of rare earth ions, such as La3+, Ce3+, Nd3+, on the structure and electrochemical properties of LiFePO4/C cathode material were systematically investigated. The as-prepared samples were characterized by means of X-ray diffraction(XRD), scanning electron microscopy(SEM) and particle size analysis. The electrochemical properties were investigated in terms of constant-current charge/discharge cycling tests. The XRD results showed that the rare earth ions doping did not change the olivine structure of LiFePO4, and all the doped samples were of single-phase with high crystallinity. SEM and particle size analysis results showed that the doping of La3+, Ce3+ and Nd3+led to the decrease of particle size. The electrochemical results exhibited that the doping of La3+ and Ce3+ could improve the high-rate capability of LiFePO4/C cathode material, among which, the material doped with 1% Ce3+ exhibited the optimal electrochemical properties, whose specific discharge capacities could reach 128.9, 119.5 and 104.4 mAh/g at 1C, 2C and 5C rates, respectively.     

The solution rate of alumina in CaF2-Al2 O3 slags

The rate of solution of A1₂O₃ in CaF₂ + 30 wt pct A1₂O₃ (at 1518° and 1509°C) and CaF₂ + 20 wt pct A1₂O₃ (at 1500°C) liquids has been determined. The operative process is diffusion-controlled, with an interdiffusion coefficient,D for the process varying between 8.5 and 8.1 x 10^-5 sq cms ^- 1 in the CaF₂ + 30 wt pct A1₂O₃ slags, and 4.0 × 10^-5 sq cms ^- 1 in the CaF₂ + 20 wt pct A1₂O₃ slag. Estimations of the rate at which alumina inclusions would react with these slag during the electroslag processing of steels, indicate that electrode inclusions approaching 100 μ in diam will be dissolved.     

Effect of Li+ ion concentration on upconversion emission and temperature sensing behavior of La2O3:Er3+ phosphors

The effects of Li~+ co-doping concentration on the structure, upconversion luminescence and temperature sensing behavior of Er~(3+):La_2O_3 phosphors were investigated. X-ray diffraction and scanning electron microscopy observations reveal that Li~+ ion co-doping can change the lattice parameter of La_2O_3 host and increase the particle size of the samples. The optical investigation shows that co-doping of Li~+ ions can enhance the upconversion emission of Er~(3+) ions in La_2O_3 matrix effectively. Most importantly, the temperature sensing sensitivity of the samples is found to be dependent on Li~+ co-doping concentration,when the emission intensity ratio of the(~2H_(11/2)→~4 I_(15/2)) and(~4 S_(3/2)→~4 I_(15/2)) transitions of Er~(3+) is chosen as the thermometric index. Both of the optimum upconversion luminescence and temperature sensing sensitivity are obtained for 7 mol% Li~+ co-doped sample. When the Li~+ concentration is beyond 7 mol%,both the quenching in upconversion intensity and the degradation of temperature sensitivity are observed, which may be due to the serious distortion in local crystal field around Er~(3+) ions caused by the excess Li~+ ions.     

Optical studies of Y_3(Al,Ga)_5O_(12):Ce~(3+),Cr~(3+),Nd~(3+) nano-phosphors obtained by the Pechini method

The Y3(AI,Ga)_5O_(12):Ce~(3+),Cr~(3+),Nd~(3+)(YAGG) nano-phosphors with homogeneous particle-size distribution,low aggregation and average crystalline size of about 65 nm were obtained using a modified Pechini method.Only slight aggregation of the crystallites occurs after post-annealing at 1100℃.The intense Ce~(3+)bands in the excitation spectra of the Ce~(3+),Cr~(3+),Nd~(3+)co-doped materials monitoring the Cr~(3+) emission at 690 nm indicate energy transfer from Ce~(3+) to Cr~(3+).Weak Nd~(3+) lines are observed,as well.In addition,the emission of Nd~(3+)at 1060 nm with excitation of Ce~(3+) and Cr~(3+) confirms the Ce~(3+)/Cr~(3+)to Nd~(3+)energy transfer.The short average luminescence decay times for the Ce~(3+) emission indicate the Ce~(3+)/Cr~(3+)to Nd~(3+)energy transfer.Eventually,the Y_3(AI,Ga)_5O_(12):Ce~(3+),Cr~(3+),Nd~(3+) nano-phosphors exhibit persistent luminescence originating from the 4f~3→4f~3 transitions of Nd~(3+) which matches well to the first biological window to be used in bioimaging applications.     

La2O2CO3 supported Ni-Fe catalysts for hydrogen production from steam reforming of ethanol

La2O2CO3 was prepared by calcination of La2 (CO3)3 in the air. Catalysts Ni-Fe/La2O2CO3 with different mole ratios of Ni to Fe, Ni/La2O2CO3 and Fe/La2O2CO3 were prepared by impregnation method. The catalytic properties were evaluated on steam reforming of ethanol (SRE) from 300 to 700 ℃ under atmospheric pressure and the samples were characterized by Brunauer-Emmett-Teller method (BET), X-ray diffraction (XRD) and temperature programmed reduction (TPR). The results showed that Ni-Fe bimetallic catalysts exh...     

Tunable emission properties of tri-doped Ca_9LiY_(2/3)(PO_4)_7:Ce~(3+),Tb~(3+),Mn~(2+) phosphors with warm white emitting based on energy transfer

Tri-doped Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+),Tb~(3+),Mn~(2+)phosphors were prepared by a high-temperature solid state method.Under UV light excitation,Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+)samples exhibit a broad band ranging from 320 to 500 nm.At 77 K,the emission spectra of Ca_9 LiY_(2/3)(PO_4)7:Ce~(3+)samples present two obvious emission peaks,indicating that Ce~(3+)ions occupy two different kinds of lattice sites(Ca(1/2) and Ca(3)),As a good sensitizer for Tb~(3+),Ce~(3+)ions in Ca_9 LiY_(2/3)(PO_4)_7 lattice can effectively transfer part of energy to Tb~(3+),and the energy trans fer mechanism is determined to be dipole-dipole interaction.Consequently,the emitting color for Ce~(3+) and Tb~(3+) co-doped Ca_9 LiY_(2/3)(PO_4)_7 samples can be tuned from bluish violet to green.In order to further enlarge the emission gamut,Mn~(2+)ions as red emission components were added,forming tri-doped single-phase Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+),Tb~(3+),Mn~(2+)phosphors.The Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+),Tb~(3+),Mn~(2+)phosphors exhibit tunable emission properties through controlling the relative doping concentration of Ce~(3+),Tb~(3+)and Mn~(2+).Especially,Ca_9 LiY_(2/3)(PO_4)_7:0.09 Ce~(3+),0.12 Tb~(3+),0.30 Mn~(2+)can emit warm white light.The sample shows good thermal stability.At 150℃,the emission intensity for Ce~(3+)(360 nm),Tb~(3+)(545 nm) and Mn~(2+)(655 nm) decreases to 63%,69%,and 72% of its initial intensity,respectively.Moreover,the sample obtains good stability after 10 cycles between room temperature and150℃.     

Preparation and characterization of Ce_(0.8)La_(0.2–x)Y_xO_(1.9) as electrolyte for solid oxide fuel cells

In this study, ultrafine Ce0.8La0.2–x Y x O1.9（for x=0, 0.05, 0.10, 0.15, 0.20） powders were successfully prepared by the sol-gel method.The samples were characterized by fourier transform infrared（FTIR）, thermogravimetric and differential scanning calorimetry（TG-DSC）, X-ray diffraction（XRD）, scanning electron microscopy（SEM）, AC impedance and thermal expansion measurements.Experimental results indicated that highly phase-pure cubic fluorite electrolyte Ce0.8La0.2–x Y x O1.9 powders were obtained after calcining at 600 °C.The as-synthesized powders exhibited high sintering activity, the Ce0.8La0.2–x Y x O1.9 series electrolytes which have higher relative densities over 96% could be obtained after sintered at 1400 °C for 4 h.Ce0.8La0.15Y0.05O1.9 electrolyte sintered at 1400 °C for 4 h exhibited higher oxide ionic conductivity（σ800 oC=0.057 S/cm）, lower electrical activation energy（E a=0.87 e V） and moderate thermal expansion coefficient（TEC=15.5×10-6 K-1, temperature range 25–800 °C）.