Synthesis and Conductivity of Oxyapatite Ionic Conductor La10-xVx（SiO4）6O3＋x

Apatite-lanthanum silicate has attracted considerable interest in recent years due to its high oxide ion conductivity.In this paper,V-doped samples La10-xVx(SiO4) 6O3+x(0≤x≤1.5) were prepared by sol-gel method and the influences of V-dopant content on calcining temperature and conductivity were reported.The samples were characterized by thermal analysis(TG-DSC) ,X-ray diffraction(XRD) and scanning electron micrograph(SEM) . The apatite was obtained at 800°C,a relatively low temperature in comparison to 1500°C with the conventional solid-state method.The ceramic pellets sintered at 1200°C for 5 h showed a higher relative density than La9.33Si6O26 pellets sintered at 1400°C for 20 h.The conductivities of samples were measured by electrochemical impedance spectroscopy.The conductivity was improved with the increase of V-dopant content on La site.

A new oxyapatite red phosphor Eu^(3+)-doped Ca_(3)Y_(7)(BO_(4))(SiO_(4))_(5)O:Synthesis,structure and luminescence properties

A series of new oxyapatite red phosphors Ca_(3) Y_(7)(BO_(4)) (SiO_(4))_(5) O doped with different concentrations of Eu^(3+)were successfully synthesized by high temperature solid state method.The X-ray diffraction(XRD)Rietveld refinement results show that the structure of the phosphor belongs to space group P6_(3)/m and Eu^(3+)ion replaces Y^(3+)ion.The emission spectrum consists of the characteristic emission peaks corresponding to Eu^(3+)under the excitation of 274 nm and the dominant emission peak is at 614 nm(^(5)D_(0)→^(7)F_(2) of Eu^(3+)).The concentration quenching effect occurs and the optimized Eu^(3+)concentration is 4.0 mol%.The energy level diagram for luminous mechanism is also given and the non-radiative energy transfer mechanism between Eu^(3+)is mainly exchange interaction.The CIE coordinate is close to the ideal red light and the color purity is higher than 99.79%.Moreover,the phosphor exhibits moderate thermal stability because the photoluminescence intensity at 423 K is still maintained at higher than 78.97%of that at room temperature.The internal quantum efficiency of Ca_(3) Y_(7)(BO_(4)) (SiO_(4))_(5) O:4.0 mol%Eu^(3+)phosphor is 58.2%.A red light emitting diode(LED)device based on it can emit bright red light.The CCT values of the device are basically unchanged when driven by various bias current.The results show that Ca_(3) Y_(7)(BO_(4)) (SiO_(4))_(5) O:Eu^(3+)is a new type of oxyapatite red fluorescent material with good comprehensive performances.

Fabrication and Luminescence Properties of Ca_2Gd_8 (SiO_4 )_6O_2:Er^(3+) Phosphors via Sol-Gel Process

Ca2RE8(SiO4)6O2(RE = Y, Gd, La) is a kind of ternary rare-earth-metal silicate with the oxyapatite structure, which was used as host materials for the luminescence of various rare earth and mercury-like ions. Ca2Gd8(SiO4)6O2: Er3 + phosphors were prepared through the sol-gel process. X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectra were used to characterize the resulting phosphors. The results of XRD indicate that the phosphors crystallized completely at 1000℃. SEM study reveals that the average grain size is 400 ~ 1000 nm. In Ca2Gd8 (SiO4)6O2 : Er3+ phosphors, the Er3+ shows its characteristic green emission at 528 nm (2H11/2-4I15/2) and 548 nm (4 S3/2-4 I15/2) upon excitation into 382 nm, with an optimum doping concentration of 5% (mole fraction) of Gd3+ in the host lattices.

Photoluminescent properties of Ca_2RE_8(SiO_4)_6O_2:A (RE=Y, Gd; A=Pb^(2+), Mn^(2+)) phosphor films prepared by sol-gel process

Ca2RE8（SiO4）6O2：A （RE=Y, Gd; A=Pb^2＋, Mn^2＋） phosphor fdms were dip-coated on quartz glass substmtes through the sol-gel process. X-ray diffraction （XRD）, photoluminescence （PL） spectra as well as lifetimes were used to characterize the resulting films. Under short wavelength UV excitation, the film showed a red emission with medium intensity. The decay curve of Mn^2＋ luminescence in Ca2Gd8（SiO4）6O2：Pb Mn film could be fitted into a single exponential function. The lifetime of Mn^2＋ was 10.21 ms in Ca2Gd8（SiO4）6O2.

Luminescence and Energy Transfer Properties of Ca_2Gd_8(SiO_4)_6O_2∶A(A=Pb^(2+), Tm^(3+))Phosphors

Ca_2Gd_8(SiO_4)_6O_2∶ A(A=Pb^(2+), Tm^(3+))phosphors were prepared through the sol-gel process. X-ray diffraction(XRD), scanning electron microscopy(SEM)and photoluminescence spectra were used to characterize the resulting phosphors. The results of XRD indicate that the phosphors crystallized completely at 1000 ℃. SEM study reveals that the average grain size is 300～1000 nm. In Ca_2Gd_8(SiO_4)_6O_2∶Tm^(3+) phosphors, the Tm^(3+) shows its characteristic blue emission at 456 nm(~1D_2—~3F_4)upon excitation into its ~3H_6—^(1)D_2(361 nm), with an optimum doping concentration of 1mol% of Gd^(3+) in the host lattices. In Ca_2Gd_8(SiO_4)_6O_2∶Pb^(2+), Tm^(3+) phosphors, excitation into the Pb^(2+) at 266 nm(~1S_0—~3P_1)yields the emissions of Gd^(3+) at 311 nm(~6P—~8S)and Tm^(3+) at 367 nm(~1D_2 —~3H_6)and 456 nm(~1D_2—~3F_4), indicating that energy transfer processes of Pb^(2+)—Gd^(3+) and Pb^(2+)—Tm^(3+) have occurred in the host lattices.

Luminescence Properties and Site Substitution of Eu^（3＋）and Bi^（3＋） in Me_2Y_8（SiO_4）_6O_2

Under UV excitation, Eu￣(3+) and Bi￣(3+) ions show red (￣5D_0-￣7F_2) and blue emissions (￣3P_1-￣1S_0) in Me_2Y_8(SiO_4)_6O_2, respectively. The luminescence properties of Eu￣(3+) depend strongly on Me￣(2+) and excitation wavelengths. For all Me￣(2+), Eu￣(3+) ions enter 4f and 6h sites simultaneously according to the fluorescence Raman spectra excited by Ar￣+ 476.5 nm laser. Different Me￣(2+) yields different Bi￣(3+) emission intensity and Stokes shift. Bi￣(3+) ions enter 4f and 6h sites mainly for Me=Ca, Zn and for Me=Mg, Sr,respectively.

Luminescent Properties of Ca2 Y8 ( SiO4 ) 6O2: Eu3 + Phosphors Prepared by Spray Pyrolysis Process

Using CaCO3, metal oxides (all dissolved by nitric acid) and tetraethoxysilane Si (OC2H5 )4 (TEOS) as the main starting materials, Ca2Y8 (SiO4 )6O2: Eu3+ phosphors were synthesized by spray pyrolysis.X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting phosphors.The results of XRD indicated that the 1000 ℃ annealed powders crystallize with the silicate oxyapatite structure.SEM study revealed that the phosphors consist of spherical particles with an average size of about 1 ～ 3 μm.In the crystalline Ca2 Y8 (SiO4)6O2: Eu3+ phosphor, the Eu3+ shows its characteristic emission corresponding to 5 D0 - 7 FJ ( J = 0, 1,2, 3, 4) transitions, with 5D0 - 7 F2 red emission (613 nm) as the most prominent group, agreeing well with the structure of the host material.

Synthesis and Conducting Properties of La10-x（SiO4）6O3-1.5x

The synthesis of silicate oxyapatitesLa10-x（SiO4）6O3-1.5x（x=0. 0.17, 0.33, 0.50 and 0.67） via a sol-gel method at 800 ℃ was reported. The apatite phases were characterized by X-ray diffraction （XRD） and conducting properties were studied by electrochemical impedance spectroscopy （EIS）. It is found that the conductivities are influenced by the amount of cation vacancies and interstitial oxygen. The conductivity of La9.33 （SiO4）6O2 with more cation vacancies is higher than that of La9.5 （SiO4）6O2.25. The conductivity of La10 （SiO4）6O3 with more interstitial oxygen is 7.98 ×10^-3 S·cm^-1, which is about 5 times higher than that of La9.33（SiO4）6O2 at 700℃. The electrical conductivity is almost independent of the oxygen partial pressure from 105 to 1 Pa, which suggests that the oxyapatites exhibit almost pure O^2- ion conduction over a wide range of oxygen partial pressure.

Influence of RE^(3+) on the Luminescence Properties of Eu^(3+) and Bi^(3+) in Mg_2RE_8(SiO_4)_6O_2 (RE=Y, La, Gd)

Compounds with apatite structure are very suitable host lattices for luminescentions. The most well-known example is Sb3+- and Mn2+-coactivated calciumhalophosphate which has been applied to fluorescent lamps sinee 1942. Mg2RE8（SiO4）6O2（RE=Y, La, Gd） is a kind of ternary rare earth silicate with oxyapatite

Re-determination of the crystal structure of Ca_2Y_8Si_6O_(26) and study on the luminescent properties of Ca_2Y_8Si_6O_(26):Tb^(3+)

The crystal structure of silicate oxyapatite Ca2Y8Si6O26 was indexed as hexagonal,space group P63/m,a=0.93515 nm,c=0.67872 nm,α=β=90°,γ=120°,V=0.5138692 nm3.Three strong peaks located at 32.079o,32.595o,and 50.104o with d=2.7903,2.74649,1.8194 was in accordance with,(112),and(213) planes.The optimum concentration of Tb3+ in Ca2Y8Si6O26 to yield highest photoluminescence intensity was 10 mol.% of Y3+.The corresponding excitation spectrum consisted of an intense broad band from 220 to 260 nm.The photoluminescence measurements showed that the green emission originated from 5D4-7F5 was predominant in the measured range with strong doublet lines at 543 and 549 nm.