Effects of heat treatment conditions and Y-doping on structure and phase transition temperature of VO2 powders

The VO2 powders were prepared by hydrothermal synthesis.The effects of heat treatment conditions and Y-doping on the structure and phase transition temperature of VO2 were studied.The XRD,SEM and TEM results show that the heat treatment temperature has a significant effect on the crystal transformation of VO2 precursor.Increasing temperature is conducive to the transformation of precursor VO2(B)to ultrafine VO2(M).The Y-doping affects the structure of VO2.Y^3+can occupy the lattice position of V4+to form YVO4 solid solution,which can increase the cell parameters of VO2.Due to the lattice deformation caused by Y-doping,the aggregation of particles is prevented,and the grain is refined obviously.DSC curves show that Y-doping can reduce the phase transition temperature of VO2(M).After adding 9 at.%Y,the phase transition temperature can be reduced from 68.3 to 61.3℃.

Gas sensing properties of Y-doped ZnO nanosheets synthesized via combustion method

ZnO nanosheets doped with yttrium（Y） were synthesized via a solution combustion method using zinc nitrate and tartaric acid as raw materials.The scanning electron microscopy and X-ray powder diffraction were used to characterize ZnO nanosheets and the gas sensing properties of them were investigated.The results show that the as-synthesized ZnO nanosheets with diameters of20-100 nm have a wurtzite structure with rough surface.The sensor made from the 2%Y-doped ZnO nanosheets exhibits a stronger response toward 100x10-6（volume fraction） ethanol,its sensitivity at 300℃ is 17.50,and its optimal operating temperature（300℃）is lower than that of the pure ZnO（330℃）.The obvious sensitivity（about 2.5） can be observed at the volume fraction of ethanol as low as 5×10-（-6）,while its the response time is only 2s at 300℃.Moreover,the Y-doped ZnO sensor has a better selectivity to ethanol than other gases.

Preparation and electrochemical properties of Y-doped Li_3V_2(PO_4)_3 cathode materials for lithium batteries

Y-doped Li3V2（PO4）3 cathode materials were prepared by a carbothermal reduction（CTR） process.The properties of the Y-doped Li3V2（PO4）3 were investigated by X-ray diffraction（XRD） and electrochemical measurements.XRD studies showed that the Y-doped Li3V2（PO4）3 had the same monoclinic structure as the undoped Li3V2（PO4）3.The Y-doped Li3V2（PO4）3 samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram（CV）, and electrochemical impedance spectra（EIS）.The optimal doping content of Y was x=0.03 in Li3V2-xYx（PO4）3 system.The Y-doped Li3V2（PO4）3 samples showed a better cyclic ability.The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Y-doping.The improved electrochemical perormances of the Y-doped Li3V2（PO4）3 cathode materials were attributed to the addition of Y3＋ ion by stabilizing the monoclinic structure.

Preparation and Electrochemical Studies of Y-doped LiVPO_4F Cathode Materials for Lithium-ion Batteries

Y-doped LiVPO4F cathode materials were prepared by a carbothermal reduction（CTR） process. The properties of the Y-doped LiVPOaF samples were investigated by X-ray diffraction （XRD） and electrochemical measurements. XRD studies show that the Y-doped LiVPOaF samples have the same triclinic structure as the undoped LiVPO4F. The Li extraction/insertion performances of Y-doped LiVPO4F samples were investigated through charge/discharge, cyclic voltammogram （CV） , and electrochemical impedance spectra（EIS）. The optimal doping content of Y is x=0.04 in LiYxV1-xPO4F system. The Y-doped LiVPO4F samples show a better cyclic ability. The electrode reaction reversibility is enhanced, and the charge transfer resistance is decreased through the Y-doping. The improved electrochemical performances of the Y-doped LiVF＇OaF cathode materials are atlributed to the addidon of Y^3＋ ion by stabilizing the Iriclinic structure.

Synthesis and Characterization of Y-Doped Mesoporous CeO_2 Using A Chemical Precipitation Method

Using cetyltrimethylammonium bromide （CTAB） as the template agent, cerium nitrate as the cerium resource, yttrium nitrate as the yttrium resource, and ammonium carbonate as the precipitating agent, mesoporous CeO2 powders doped with different yttrium contents were successfully synthesized using a chemical precipitation method, under an alkalescent condition. Properties of the obtained samples were characterized and analyzed with X-ray diffraction （XRD）, energy dispersive analysis of X-rays （EDAX）, transmission electron microscopy （TEM）, infrared （IR） absorbance, and the BET method. For the prepared samples with 20% （molar ratio） Y-doped content, a BET specific surface area of 106. 6 m^2 · g^- 1, with an average pore size of3~27 nm were obtained. XRD patterns showed that the doped samples were with a cubic fluorite structure. TEM micrographs revealed that the doped samples showed a spherical morphology with a diameter ranging from 20 to 30 nm and a round pore shape. IR results indicated that the Ce-O-Ce vibration intensity decreased as the Y-doped content increased. N2 adsorption-desorption isotherms showed that the samples possessed typical mesopore characteristics. The average pore size of the samples decreased alter mesoporous CeO2 was doped with yttrium, and the average pore size decreased largely as the Y-doped content increased.

Synthesis and Characterization of Y-Doped SnO_2 as Sensor Materials

Yttrium-doped SnO2 powders were successfully synthesized by solution co-precipitation method and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The sensitivity of sensors based on Y-doped SnO2 and SnO2 nanocrystals were investigated comparatively. The results indicated that Y-doped SnO2 was with the result of enhancement of sensitivity and selectivity to ethanol and reduction of sensitivity to other gas components. The enhancements of selectivity and sensitivity could be contributed to for two reasons. The first is that rare metal yttrium has a high alkalescence and good catalysis, and the second is that the nanosized crystallite and large specific surface area of Y-doped SnO2 is advantageous for gas-diffusion control as well as an increase in active sites for gas detection.

Synthesis and study the influence of yttrium doping on band structure,optical,non-linear optical and dielectric results for Ca_(12)Al_(14)O_(33) (C12A7) single crystals grown using traveling-solvent floating zone (TSFZ) method

Ca_(12)Al_(14)O_(33)(C12A7)and Y_(0.02)Ca_(11.98)Al_(14)O_(33)(Y-C12A7)single crystals were grown by using the traveling-solvent floating zone(TSFZ)method.The temperature was increased to avoid the bubbles and cracks which may be formed during the preparation of the ingot material.We have started with the flux higher than the normal to avoid the bubbles and make good treatment for the solid-liquid interface.The structures of both Ca_(12)Al_(14)O_(33)(C12A7)and Y_(0.02)Ca_(11.98)Al_(14)O_(33)(Y-C12A7)were studied by using x-ray diffraction(XRD).Optical properties for C12A7 and Y-C12A7 single crystals have been studied in order to determine the optical parameters such as optical energy gap(Eg),refractive index n,oscillating energy(Eo),dispersion energy(Ed),volume energy loss function(VELF),and surface energy loss function(SELF).Finally,a new result for these samples is that the third-order nonlinear optical susceptibility(χ(3))was determined.The results have been discussed with effect of Y-doping on the C12A7 single crystals for optical and industrial applications.

Physical-Properties of Oxygen-Deficient Co-Based Perovskites: Co(Sr_1-xY_x)O_3–δ(0.05 ≤ x ≤ 0.4)

In this work, the syntheses and characterization of oxygen deficient perovskite cobalt oxides prepared under ambient pressure conditions with different “x” in the Co(Sr1-xYx)O3–δ;0.05 ≤ x ≤ 0.4 series are reported. The system studied in the present investigation undergoes structural phase transition at room temperature from cubic to tetragonal symmetry. The samples with x ≥ 0.2 show a tetragonal structure with I4/mmm space group, while the samples with 0.05 ≤ x ≤ 0.15 reveal cubic with pm3m group symmetry. Quite similar to Ho-substituted system [J. Appl. Phys. 103, 07B903 (2008)], the present Y-doped magnetization data clearly show the appearance of an enhanced ferromagnetic component at ~350 K for 0.15 ≤ x ≤ 0.225. Unlike the Ho-substituted system, the present narrow compositions behave as hard ferromagnet with quite high coercive field, Hc = 11.02, 12.25 and 14.0 kOe for x = 0.15, 0.2 and 0.225 compositions, respectively at T = 10 K. All the compositions show a semiconducting-like behaviour and some interesting features of temperature dependence of magnetoresistance (MR) are observed. The Co(Sr1-xYx)O3–δ samples seemly to obey variable range hopping conduction model showing a linear ln ρ versus T–1/4 dependence at the temperature range 80 K ≤ T ≤ 300 K.

Yttrium-Doped SnO_2 Prepared by Co-Precipitation Method for Lithium-Ion Battery Anodes

SnO2 doped with Y were prepared by co-precipitation method and tested in lithium-ion cells. The structure and morphology of the materials were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD patterns presented that the all the as-prepared materials had tetragonal rutile structure but a second phase (Y2O3) was observed when Y content reached 4%. TEM micrograph indicated that Y doped SnO2 had a small particle size ranging from 20 to 25 nm. The electrochemical properties for an anode active material in lithium-ion batteries were investigated at room temperature, including the observed capacity involved in the first-discharge and the reversible capacity values during subsequent charge-discharge cycles. The as-prepared Y-doped SnO2 exhibited promising electrochemical properties as anodes for lithium-ion batteries.

Structural and electrical properties of reactive magnetron sputtered yttrium-doped HfO_2 films

Hafnium oxide thin films doped with different concentrations of yttrium are prepared on Si（100） substrates at room temperature using a reactive magnetron sputtering system.The effects of Y content on the bonding structure,crystallographic structure,and electrical properties of Y-doped HfO2 films are investigated.The x-ray photoelectron spectrum（XPS） indicates that the core level peak positions of Hf 4 f and O 1 s shift toward lower energy due to the structure change after Y doping.The depth profiling of XPS shows that the surface of the film is completely oxidized while the oxygen deficiency emerges after the stripping depths have increased.The x-ray diffraction and high resolution transmission electron microscopy（HRTEM） analyses reveal the evolution from monoclinic HfO2 phase towards stabilized cubic HfO2 phase and the preferred orientation of（111） appears with increasing Y content,while pure HfO2 shows the monoclinic phase only.The leakage current and permittivity are determined as a function of the Y content.The best combination of low leakage current of 10-7 A/cm^2 at 1 V and a highest permittivity value of 29 is achieved when the doping ratio of Y increases to 9 mol%.A correlation among Y content,phase evolution and electrical properties of Y-doped HfO2 ultra-thin film is investigated.

Phase and particle of Y-doped Ni(OH)_2 prepared from different nickel sources and Na_2CO_3 amount

Multiple nano-sized a-Ni（OH）2was synthesized by ultrasonic-assisted precipitation under different conditions. The crystal structure and particle size distribution of the sample were characterized with X-ray diffraction（XRD）, infrared spectroscopy, and laser particle size analyzer（PSA）. The results show that the samples are anisotropic polycrystalline of a and b Ni（OH）2, and the ratio of a and b changes with the difference of nickel source, resulting in the largest ratio of a-Ni（OH）2using nickel nitrate as reactant. Larger amount of Na2CO3is conducive to the formation of a-Ni（OH）2; while the resultant phases are all b with the same conditions but no doping. The results of PSD indicate that the samples are about 100–120 nm in size, and the sample with nickel sulfate as nickel source has the minimum particle size. The three ions of nickel source appear in the absorption peaks in the Fourier transform infrared spectrum showing that the ions change the crystal structure of Ni（OH）2. EDS testing shows that Y and anion distribute in the lattice of aNi（OH）2uniformly.

Ab initio study of a Y-doped Σ31 grain boundary in alumina

The atomic structures and energetics of clean and Y-doped general grain boundary (GB) Σ31/(0001) models in α-Al2O3 are studied by a series of high precision ab initio calculations. A large supercell with 700 atoms and periodic boundary conditions is adopted for undoped and Y-doped GB with different substitution sites and con-centrations. It is shown that Y atoms preferably segregate to the central column of the 7-member Al ring. This is explained as more favorable bond formation for Y in this position and lower GB energy. The calculated GB formation energy for the clean and Y-doped cases is respectively 3.99 and 3.67 J/m2. On the average, the GB region in Σ31 has a slightly lower charge density than the bulk crystalline region. In addtition, the GB induces a long ranged asymmetric electrostatic potential distri-bution on each side of the grain boundary.

SO_(4)^(2-)-modified La,Y-doped ceria-zirconia with high oxygen storage capacity and its application in Pd-only three-way catalysts

As the oxygen redox ability shows great effects on the catalytic performances of ceria-zirconia based materials,many strategies have been utilized to improve the oxygen storage capacity.Here in this study,we report a simple and facile approach to prepare a SO_(4)^(2-)-modified La,Y-doped ceria-zirconia material(SO/CZLY-f)with high oxygen storage capacity.Due to the additional redox process between SO_(4)^(2-)and S^(2-),oxygen storage capacity of SO/CZLY-f(745.3μmol O_(2)/g)is about 1.6 times higher than that of La,Ydoped ceria-zirconia material without SO_(4)^(2-)modification.Moreover,the catalytic activities and stability of the corresponding Pd-only three-way catalyst were measured.Compared to that of Pd@CZLY-f,the operation window of CO,full conversion temperature of HC and NO over Pd@SO/CZLY-f are obviously widened and lowered,respectively.After aging treatment at 1100℃for 4 h,the superiority of aged Pdloading composite is still maintained.