Preparation and Long Persistence Red Luminescence of M0.2Ca0.8TiO3∶Pr3+(M=Mg2+,Sr2+,Ba2+,Zn2+)

M0.2Ca0.8TiO3∶Pr3 (M=Mg2 , Sr2 , Ba2 , Zn2 ) long persistence red phosphors were prepared by solid state reaction. The influence of the partially replacing Ca2 in CaTiO3 with Mg2 , Sr2 , Ba2 , Zn2 on the excitation spectra, the emission spectra and the long persistence properties were studied. The results suggest that certain quantity of Mg2 , Sr2 , Ba2 , Zn2 which partially replace Ca2 can enhance the luminescent intensity and prolong the afterglow persistence of the samples. The intensity of Mg0.2Ca0.8TiO3∶Pr3 is above all of the samples. Take Mg0.2Ca0.8TiO3∶Pr3 as the basic sample, the influence of Pr3 concentrations(C(Pr3 )) on the long afterglow properties were also studied. The results suggest that when the C(Pr3 ) is 0.10%(mol fraction) the intensity of the sample is the highest. The excitation spectra of all these samples show broad band spectra ranging from 300～500 nm peaking at about 342 nm. The emission spectra also exhibit a broad band peaking at 613 nm(CaTiO3∶Pr3 is 612 nm). XRD research indicates that the crystalline phases change due to the replacement of divalent metal ions.The research on the thermoluminescence spectra of Mg0.2Ca0.8TiO3∶Pr3 indicates that the peak is at 107.35 ℃ and the depth of the trap energy is about 0.852 eV.     

Effect of doping of different rare earth (europium,gadolinium, dysprosium and neodymium) metal ions on structural,optical and photocatalytic properties of LaFeO3 perovskites

Different rare earth substituted perovskites LaRE_xFe_(1-x)O_3(where RE=Eu~(3+),Gd~(3+),Dy~(3+),Nd~(3+)and x=0.02,0.04,0.06,0.08,0.1) with orthorhombic structure and narrow band gaps were successfully fabricated via sol-gel autocombustion method.All the substituted perovskites are found to exhibit excellent photocatalytic activity towards the oxidative degradation of dye molecules.An excellent increase in the rate constant values of pure perovskite(LaFeO_3) photocatalytic reactions is observed with the substitution of rare earth metal ions.Best results are obtained for LaNd_(0.1)Fe_(0.9)O_3 which exhibits around 7 times increase in the rate constant values for degradation reaction of SO(1.76×10~(-1) min~(-1))and RBY(1.69×10~(-1) min~(-1)) dyes.     

A comparison of Ce~（3＋） luminescence in X_2Z（BO_3）_2（X=Ba,Sr;Z=Ca,Mg） with relevant composition and structure

The VUV-UV spectroscopic properties of Ce3+ in Ba2Mg(BO3)2,Ba2Ca(BO3)2 and Sr2Mg(BO3)2 were compared,and the relation between the energy of the 4f→5d transition of Ce3+ and the coordination environments of substituted alkaline earth ions was discussed.The chromaticity coordinates of Ce3+ activated X2Z(BO3)2(X=Ba,Sr;Z=Ca,Mg) phosphors were changeable from blue to whitish and further to green range by varying the doping concentration of Ce3+ or the types of substituted alkaline earth ions upon 172 nm excitation.     

Magnetic Transition of La0.8Sr0.2Mn1-xCoxO3（x =0, 0.3, 0.5, 1.0）

A series of rare earth compound oxides with the formula of La0.8Sr0.2Mn1-xCoxO3（ were prepared by the method of citric acid. Structures, figures and magnetic properties of the x=0.0, 0.3, 0.5, 1.0） samples were analyzed by means of XRD, SEM and SQUID. Experiment results prove that all the samples are hexagonal, but their figures and magnetic properties are different. La0.8Sr0.2MnO3 is ferromagnetic. La0.8Sr0.2Mn0.7CO0.3O3 and La0.8Sr0.2Mn0.5Co0.5O3 are ferrimagnetic. La0.8Sr0.2CoO3 is antiferromagnetic. SEM results indicate that the structure of the first three are three-dimensional reticulations which are made up of some small ellipsoids which link up at the head and the end. The fourth sample looks like some dispersed small balls.     

Influence of inorganic anions and organic additives on photocatalytic degradation of methyl orange with supported polyoxometalates as photocatalyst

A novel supported polyoxometalate(POM),phosphotungstic acid immobilized into yttrium-doped TiO2(HPW-Y-TiO2) nano photocatalyst was prepared via sol-gel and impregnation method.The samples were characterized using Fourier transform infrared spectroscopy(FT-IR),X-ray diffraction(XRD) and N2 absorption-desorption analysis.The results showed that the supported POM exhibited Keggin structure and anatase phase with large BET surface area.The influences of inorganic anions and organic additives on the photocatalytic degradation of azo dye methyl orange with HPW-Y-TiO2 as photocatalyst under UV light(λ≥365 nm) were investigated.Results showed that inorganic anions Cl-,SO42-,CO32-and NO3-had inhibition effect on the degradation of methyl orange.A great enhancement of degradation rate was obtained while H2O2 and ethyl alcohol were applied.The degradation rates improved with the increase of H2O2 concentration.The optimum additive amount of ethyl alcohol was 0.5 mol/L.The possible mechanisms of the effects of additives on methyl orange degradation were discussed.     

Characterization of A-site excessive perovskite La0.7-xSmx＋0.02Ca0.3CrO3-δ

La0.7-xSmx+0.02Ca0.3CrO3-δ(0≤x≤0.4) powders with A-site excessive perovskite structure were synthesized by auto-ignition process and characterized. X-ray diffraction (XRD) patterns of samples after sintering at 1400℃ for 4 h were indexed as tetragonal structure. The relative densities were all above 96% although decreased slightly with the increasing content of samarium, indicating that the excessive A-site element was helpful to enhance their sinterability. Conductivities of the specimens in air increased with increasing content of samar-ium. The conductivity of La0.6Sm0.12Ca0.3CrO3-δ was 33.6 S/cm in air at 700 ℃ which was about 1.7 times as high as that of La0.7Ca0.3CrO3-δ (20.1 S/cm). Average thermal expansion coefficients (TECS) of the specimens increased from 11.06×10-6 to 12.72×10-6 K-1 when x in-creased from 0 to 0.4, and they were close to that of Y doped ZrO2 (YSZ). La0.7-xSmx+0.02Ca0.3CrO<3-δ>(0.1≤x≤0.3) were good choices for in-termediate temperature solid oxide fuel cells (IT-SOFCs) interconnect materials.     

Competition between Band Filling and Steric Effect in Ordered Double Perovskites Sr2- x Lax MnMoO6

The ordered double perovskites, Sr2-xLaxMnMoO6, were prepared by sol-gel reaction. Structural, magnetic, and electrical properties were investigated for a series of ordered double perovskites Sr2- x Lax MnMoO6 （0 ≤ x ≤ 1 ）. The compounds have a monoclinic structure （space group P21/n） and the cell volume expands monotonically with La doping. The Tc and the magnetic moment rise and the cusp-like transition temperature below which the magnetic frustration occurs shifts to high temperature as x increases. With La doping, electrical resistivity of Sr2-x LaxMnMoO6 decreases only at low doping levels （x ≤0.2）; while at high doping levels （0.8≤x ≤1）, electrical resistivity tends to increase greatly. The resuits suggest that the competition between band filling effect and steric effect coexists in the whole doping range, and the formation of ferrimagnetic interactions is not simply at the expense of antiferromagnetic interactions.     

Y/Eu co-doped TiO2:synthesis and photocatalytic activities under UV-light

Y and Eu co-doped nano-TiO2 photocatalysts were successfully prepared via a sol-gel method and characterized by X-ray diffraction(XRD), transmission electron microscopy(TEM), ultraviolet-visible spectrophotometry(UV-vis), photoluminescence(PL) and Fourier transform infrared(FT-IR) spectra. Experimental results indicated that Y and Eu doping inhibited the growth of crystalline size and the transformation from anatase to rutile phase and had the function of reducing particle reunion. At the same time, co-doping could also enhance the absorption in visible region and then narrowed the band gap. The photocatalytic activities of the samples were evaluated by the degradation of methylene blue(MB) under ultraviolet(UV) light irradiation, which showed much enhanced photocatalytic activities over un-doped TiO2. The degradation rate of 1.5% Y/Eu-TiO2 of methylene blue was 86%, which was about 5 times of that of un-doped TiO2, and the possible reasons for the improvement of photocatalytic activities were analyzed. In this experiment, the dopant amount of rare earth was 1.5% and the ratio of Y:Eu was 2:3 for the maximum photocatalytic degradation, and the sample calcined at 500 oC showed the best reactivity. For the best samples above, the removal rate of phenol under visble light was 53% whthin 2 h.     

Synthesis and Electrical Properties of La0.6M0.4FeO3-δ(M=Ca, Sr, Ba) as Cathodes for SOFCs

A series samples of La0.6M0.4FeO3-δ (M=Ca, Sr, Ba) perovskite-type oxides were prepared by glycine nitrate process (GNP). FTIR, TG-DSC, XRD and TEM techniques were used to characterize the chemical constitution, thermal stability and phase structure. The electrical conductivity of the samples was investigated by four-probe technique. With the increase of substituted-ionic radius, the temperature of phase formation increases, and the solid solubility decreases gradually, respectively. The La0.6Ca0.4FeO3-δ(LCF)powder is pure cubic perovskite-type crystalline after fired at 850 ℃ for 2 h. The XRD patterns of La0.6Sr0.4FeO3-δ(LSF) powder shows a small quantity of SrO peaks sintered at 1050 ℃ for 2 h. The electrical conductivity of LCF and LSF at 500～800 ℃ is over 100 S·cm-1, and the value of LCF is 1170 S·cm-1 at 800 ℃, which indicate that LCF and LSF may be used as a profitable cathode for IT-SOFCs. The characteristic of La0.6Ba0.4FeO3-δ(LBF) is poor, and the electrical conductivity at intermediate temperatures is 1/20 less than that of LSF.     

XPS study of surface absorbed oxygen of ABO3 mixed oxides

Perovskite-type complex oxides ABO3 （A=Sr, La; B=Mn, Fe, Co） were prepared by citric acid method. The degradation of water-solubilized dyes was carried out using the mixed oxides as photocatalyst. The surface absorbed oxygen was analyzed using X-ray photoelectron spectroscopy （XPS）. The results indicated that there was a relationship between the photocatalytic activity and the content of the surface absorbed oxygen. The higher the content of the surface absorbed oxygen was, the better the performance of the photocatalyst.     

Photocatalytic degradation of pesticide residues with RE³⁺-doped nano-TiO₂

The photocatalytic degradation effects of carbofuran solution under concentration of 0.2,0.4,0.8 g/L Re3+-doped nano-TiO2 were studied.The highest degradation rate of 54.89% was obtained after 4 h degradation when the concentration of nano-TiO2 was 0.4 g/L.Then field trials of photocatalytic degradation with suspension nano-TiO2 were conducted.The photocatalytic degradation effect of organic phosphorus and carbamate pesticides in tomato leaves and soil with different concentratio catalyst(0,0.2,0.4,0.6,0.8 g/L) were studied.The results showed that nano-TiO2 could significantly increase photocatalytic degradation rate of pesticide residues in tomato leaves and soil.Pesticide residues degradation rate could be increased by 20%-30% on the tomato leaves and 15%-20% in soil,and the best concentration of photocatalytic degradation was 0.2-0.4 g/L.     

Enhancement of luminescence and afterglow in Ca0.8Zn0.2TiO3:Pr3+ by Nb5+ substitution for Ti4+

Nb5+ doped Ca0.8Zn0.2TiO3:Pr3+ red long afterglow phosphors were synthesized by solid-state reaction methods. X-ray diffraction, photoluminescence spectroscopy and thermally stimulated spectrometry were used to investigate the effects of Nb5+ content on the crystal characteristics and luminescent properties of Ca0.8Zn0.2Ti1-xNbxO3:Pr3+ phosphors. The results showed that the addition of a small quantity of Nb5+ had negligible effect on the crystal characteristics of Ca0.8Zn0.2Ti1-xNbxO3:Pr3+, but it could change the trapping parameters (the depth of trap, frequency factors and the concentration of trapped charges at t=0) of Ca0.8Zn0.2Ti1-xNbxO3:Pr3+ phosphors, and then led to the enhance-ment of red fluorescence and phosphorescence at 612 nm originating from 1D2→3H4 transition of Pr3+. Both of the red fluorescence intensity and afterglow time reached the largest values in the sample of Ca0.8Zn0.2Ti1-xNbxO3:Pr3+ with x=0.05. The afterglow time of Ca0.8Zn0.2Ti0.95Nb0.05O3:Pr3+ phosphors lasted for over 24 min (≥1 mcd/m2) when the excited source was cut off.     

Preparation and Long Persistence Red Luminescence of M0.2Ca0.8TiO3 ： Pr^3＋ （M = Mg^2＋ , Sr^2＋ , Ba^2＋ , Zn^2＋）

M0.2Ca0.8TiO3 : Pr^3 (M = Mg^2 , Sr^2 , Ba^2 , Zn^2 ) long persistence red phosphors were prepared by solid state reaction. The influence of the partially replacing Ca^2 in CaTiO3 with Mg^2 , Sr^2 , Ba^2 , Zn^2 on the excitation spectra, the emission spectra and the long persistence properties were studied. The results suggest that certain quantity of Mg^2 , Sr^2 , Ba^2 , Zn^2 which partially replace Ca^2 can enhance the luminescent intensity and prolong the afterglow persistence of the samples. The intensity of Mg0.2Ca0.8TiO3: Pr^3 is above all of the samples. Take Mg0.2Ca0.8TiO3:Pr^3 as the basic sample, the influence of Pr^3 concentrations (C (Pr^3 )) on the long afterglow properties were also studied.The results suggest that when the C (Pr^3 ) is 0.10% (tool fraction) the intensity of the sample is the highest. The excitation spectra of all these samples show broad band spectra ranging from 300 - 500 nm peaking at about 342 nm. The emission spectra also exhibit a broad band peaking at 613 nm (CaTiO3: Pr^3 is 612 nm). XRD research indicates that the crystalline phases change due to the replacement of divalent metal ions. The research on the thermoluminescence spectra of Mg0.2Ca0.8TiO3:Pr^3 indicates that the peak is at 107.35℃ and the depth of the trap energy is about 0.852 eV.     

Preparation and performance of Pr-doped Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ) cathode for IT-SOFCs

(Ba0.5Sr0.5)1-xPrxCo0.8Fe0.2O3-δ(BSPCFx;x=0.00-0.30) oxides were synthesized by a sol-gel thermolysis process using combination of PVA and urea,and were also investigated as cathode material for intermediate temperature solid oxide fuel cells(IT-SOFCs).X-ray diffraction(XRD) results showed that all the samples formed a single phase cubic pervoskite-type structure after being calcined at 950 oC for 5 h and the lattice constant decreased with the Pr content increasing.The electrical conductivity of Ba0.5Sr0.5Co0.8Fe0.2O3-δ(BSCF) was greatly enhanced by Pr-doping.The thermal expansion coefficient(TEC) of BSPCFx was increased with the content of Pr increasing,and all the thermal expansion curves had an inflection at about 250-400 oC due to the thermal-induced lattice oxygen loss and the reaction of Co and Fe ion.Ac impedance analysis indicated that BSPCFx possessed better electrochemical performance.The polarization resistance of the sample with x=0.2 was only ～0.948 Ω cm2 at 500 oC,significantly lower than that of BSCF(～2.488 Ω cm2).     

Luminescent properties of MMgP_2O_7：Eu~（3＋）（M=Ca,Sr,Ba） phosphor

A series of red phosphors Eu3+-doped MMgP2O7(M=Ca,Sr,Ba) were synthesized by solid-state reaction method.X-ray powder diffraction(XRD) analysis confirmed the formation of pure CaMgP2O7,SrMgP2O7 and BaMgP2O7 phase.Photoluminescence spectra of MMgP2O7(M=Ca,Sr,Ba):Eu3+ phosphors showed a strong excitation peak at around 400 nm,which was coupled with the characteristic emission(350-400 nm) from UV light-emitting diode.The CaMgP2O7:Eu3+,SrMgP2O7:Eu3+ and BaMgP2O7:Eu3+ phosphors showed strong emission bands peaking at 612,593 and 587 nm,respectively.Due to the difference of the ion sizes between Ba2+(0.142 nm),Sr2+(0.126 nm),Ca2+(0.112 nm),Mg2+(0.072 nm) and Eu3+(0.107 nm),Eu3+ ions were expected to substitute for different sites in CaMgP2O7,SrMgP2O7 and BaMgP2O7 lattice.     

Synthesis and characterization of Ce0.8Sm0.2–xPrxO2–δ（x=0.02–0.08）solid electrolyte materials

Solid electrolytes Ce0.8Sm0.2–xPrxO2–δ(x=0.02, 0.04, 0.06, 0.08) were prepared by citric-nitrate method. The microstructure and electrical properties of such materials were examined by X-ray diffraction(XRD), atomic force microscopy(AFM), Raman spectroscopy(Raman), X-ray photoelectron spectroscopy(XPS) and impedance spectroscopy analyses. Specifically, results from XRD analysis showed that samples calcined at 800 oC for 4 h possessed single-phase cubic fluorite structure, and the average grain size was found to be 36–45 nm. Further Raman spectral analysis indicated that oxygen vacancies should be present in the cubic fluorite structure of Ce0.8Sm0.12Pr0.08O2–δ, and Pr-doping seemed to increase their concentration significantly. AFM images showed that the grain size grew with the increase of Pr substitution. XPS analysis confirmed the existence of oxygen vacancies in the lattice of Ce0.8Sm0.12Pr0.08O2–δ in which Pr3+ and Pr4+ co-existed. AC impedance spectra indicated that the conductivity of Ce0.8Sm0.2–xPrxO2–δincreased with the increase of Pr-doping but the conduction activation energy decreased. Notably, it appeared that sample Ce0.8Sm0.12Pr0.08O2–δ(σ600 oC=1.21×10–2 S/cm, Ea=0.77 e V) exhibited conductivity superior to Ce0.8Sm0.2O1.9(σ600 oC=2.22×10–3 S/cm, Ea=1.02 e V) because it possessed higher conductivity and lower activation energy. At 600 oC, the conductivity of Ce0.8Sm0.12Pr0.08O2–δwas 4.45 times higher than that of the un-doped material.     

Structure and Electrical Conductivity of Compositely Doped Oxide Solid Electrolyte La0.8Sr0.2Ga0.8Mg0.12Co0.08O2.8

(La, Sr) (Ga, Mg) O3-δ, (LSGM) perovskite compositions doped with transition metal Co on the B-site were prepared by solid state reaction. The effect of partial substitution of Ga for Co, La0.8Sr0.2Ga0.8Mg0.12Co0.08O2.8 (LSGMC2008) on the electrical conductivity was discussed. The results showed the compacted samples sintered at 1350℃ possesses increased electrical conductivity at low temperatures. The XRD patterns of the title materials indicated that LSGMC2008 possessed orthorhombic perovskite-type structure. The grains distributed relatively uniform from SEM photo. The Arrhenius plots of ionic conductivity in air of the LSGMC2008 exhibited differing slopes in the low-and high-temperature regions, and the corresponding Ea values were much lower than that of LSGM2020. All of these suggested that even at low sintering temperature, proper amount Co doped was beneficial to improve ionic conductivity of LSGM.     

Preparation and Characterization of Red Luminescent Ca0.8 Zn0.2 TiO3 ： Pr3 ＋ , Na^＋ Nanophosphor

Nanophosphor with the nominal composition of Ca0.8 Zn0.2 TiO3 ： Pr3 ＋ , Na^＋ （CZTOPN） was synthesized at relatively low temperature by the sol-gel method. Metal ions were dispersed by citric acid in ethylene glycol solvent and then react with Ti（OC4H9）4 to form sol and gel. The decomposition process of the precursor, and crystallization and particle size of CZTOPN were examined by thermal analysis （TG-DSC）, powder X-ray diffraction （XRD）, and scan election microscopy （SEM）. Results of TG-DSC and XRD reveal that the composition of Ca0.8 Zn0.2 TiO3 ： Pr3 ＋ , Na^＋ changes with the sintering temperature. SEM data indicate that the diameter of particles is under 50 nm even if the sintering temperature increases to 1000 ℃. In contrast to a solid state reaction, the excitation spectra of samples synthesized by the sol-gel method shift blue about 10 nm and the emission intensity at 617 nm increases significantly.     

Preparation and characterization of La0.9Sr0.1Ga0.8Mg0.2O3–δ thin film deposited by radio frequency magnetic sputtering

La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) electrolyte materials were synthesized by the solid state reaction method.The conductivity of LSGM materials was detected by four probe method,and it was 0.08 S/cm at 850 ℃.Dense and uniform films of LSGM materials were deposited by the magnetic sputtering on substrates of Si and La0.7Sr0.3Cr0.5Mn0.5O3-δ (LSCM).The experimental results showed that the deposition rates dropped and the average grain sizes of the films enlarged with increase in the substrate temperatures.In the sputtering process,the LSGM film was deposited with preferred growth direction.After annealing,the preferred growth direction disappeared and the film surface became smoother and denser.Through observing the deposition process,deposition mechanism was proposed,which was consistent with a model of island growth.