Effects of co-precipitation temperature on structure and properties of La and Y doped cerium zirconium mixed oxides

Due to the oxygen storage and release properties,cerium zirconium mixed oxides are recognized as the key material in automotive three-way catalysts.To reveal the effects of co-precipitation temperature on structure,physical and chemical properties of multi-doped cerium zirconium mixed oxides,a series of La and Y doped cerium zirconium mixed oxides(CZLYs)were synthesized via a co-precipitation method,and the physical and chemical properties of CZLYs were systemically characterized by XRD,N_(2) adsorption−desorption,TEM,XPS,oxygen storage capacity(OSC)and hydrogen temperature programmed reduction(H_(2)-TPR).The results show that co-precipitation temperature is an important parameter to influence the crystal size,oxygen storage capacity and thermal stability of CZLYs.When the co-precipitation temperature was 60℃,the best redox properties and thermal stability of CZLYs were obtained.After thermal treatment at 1100℃for 10 h,the specific surface area and oxygen storage capacity of the corresponding aged sample were 15.42 m^(2)/g and 497.7μmol/g,respectively.In addition,a mechanism was proposed to reveal the effects of co-precipitation temperature on the structure and properties of CZLYs.

Structure and bonding properties of Y doped Σ37 grain boundary in alumina

The microscopic structures and the bonding properties of Y-doped and undoped （011^-8）/[044^-1]/180° （∑37） grain boundaries in alumina are investigated by using ab initio method. The formation energy of grain boundary and the segregation energy of Y to grain boundary are acquired. Electronic structures, potential distributions, bond orders and effective charges of Y-doped and undoped ∑37 GB systems are calculated. Our results reveal that the higher strength Y-O bond than Al-O bond is ascribed to the hybridization of Y（4p, 3d） with O（2s）. Meanwhile, dopant Y also causes a change in potential distribution in the grain boundary region, thereby further affecting the transport property of ceramic alumina.

Effects of thickness on superconducting properties and structures of Y_2O_3/BZO-doped MOD-YBCO films

We report the thickness dependence of critical current density （Jc） in YBa2Cu3O7-x （YBCO） films with BaZrO3 （BZO） and Y2O3 additions grown on single crystal LaAlO3 substrates by metalorganic deposition using trifluoroacetates （TFA-MOD）. Comparing with pttre YBCO films, the Jc of BZO/Y2O3-doped YBCO films was significantly enhanced. It was also found that with the increase of the thickness of YBCO film from 0.25 μm to 1.5 μm, the Ic of BZO/Y2O3-doped YBCO film increased from 130 A/cm to 250 A/cm and yet Jc of YBCO film decreased from 6.5 MA/cm2 to 2.5 M A/cm2. The thick BZO/Y2O3-doped MOD-YBCO film showed lower Jc, which is mainly attributed to the formation of a-axis grains and pores.

Enhanced electrical transport performance through cation site doping in Y-doped Mg_(3.2)Sb_(2)

Mg_(3)Sb_(2)-based alloys are promising thermoelectric materials through n-type doping in Mg-rich growth conditions to overcome their intrinsic p-type behavior.First principle calculations are employed to investigate the dopant formation energy and electronic structures of Y-doped Mg_(3)Sb_(2).Results indicate that the Y atom is more favorable for substitution at the cation site.Simultaneously,the flattened band structure and increased density of state near the Fermi level of Y-doped Mg_(3)Sb_(2) indicate an enhanced electronic transport performance.The carrier concentration rises to 5.31×10^(19) cm^(-3) at room temperature,resulting in a significant increased power factor for Mg_(3.17)Y_(0.03)Sb_(2).The available optimization of electrical transport contributes to excellent thermoelectric performance,and a peak ZT~0.83 at 773 K was achieved for Y concentration x=0.03 in Mg_(3.2-x)Y_(x)Sb_(2).This work provides an alternative measure for optimizing the thermoelectric performance of n-type Mg_(3)Sb_(2) alloys by cation site doping.

Study on the preparation and electrochemical performance of rare earth doped nano-Ni(OH)_2

Multiphase nano-Ni（OH）2 doped with Y or La was prepared by supersonic co-precipitation method. The crystal morphology, structure and particle size were characterized by transmission electron microscopy （TEM）, X-ray diffraction （XRD） and particle size distribution （PSD）. The electrochemical performance of samples was investigated by electrochemical workstation and battery tested system. The results indicated that micro-morphology and grain size were changed with the changing of supersonic power, pH values and doping elements. The morphology of Y doped sample was from the flake-like to the needle-like with the increase of supersonic power; Particles were from quasi-spherical particles into needle-like with the increase of pH values; As the supersonic power increased, the proportion of α-Ni（OH）2 increased initially and then decreased. pH value was very important to the formation of crystalline phase. Lower pH value was beneficial to the formation of α-Ni（OH）2. However, the pH values had a slight effect on the reaction reversibility. Complex electrodes were prepared by mixing 8 wt.% nickel hydroxides with commercial micro-size spherical nickel. The discharge capacity of electrodes increased initially and then decreased with the increase of supersonic power. When the supersonic power was 60 W and the pH value was 9, the sample had the largest dis-charge capacity （358 mAh/g） at 0.5 C rate, which was 122.7 and 76 mAh/g higher than the spherical nickel electrode and La doped sample electrode, respectively.

Absorption behavior of lattice oxygen in Ce_(0.8)Y_(0.2)O_(2-δ) at intermediate temperature

The absorption behavior of lattice oxygen for Ce0.8Y0.2O2-δ(YDC) crystal was investigated. Combined with TG-DSC, XRD, Raman and XPS characterization, lattice oxygen absorption occurs at intermediate temperature(from 500 to 800 ℃),which is related to the oxygen vacancies consumption,and no phase change is observed in this process. In electric conductivity relaxation(ECR) experiment, prolonged oxygen diffusion process is observed above 600 ℃, which may be caused by oxygen absorption process. And through ECR experiments,the bulk diffusion coefficient Dchemand surface exchange coefficient Kexfor YDC dense sample are measured as 6,5×10-5-2×10-4cm2/s and Kex=2×10-4-9×10-4cm/s at intermediate temperature range.

Relaxor behavior and superior ferroelectricity of Y_(2)O_(3)-doped(Ba_(0.98)Ca_(0.02))(Ti_(0.94)Sn_(0.04)Zr_(0.02))O_(3) lead-free ceramics

To upgrade the electric properties of lead-free piezoceramics,(1-x)(Ba_(0.98)Ca_(0.02)Ti_(0.94)Sn_(0.04)Zr_(0.02))O_(3)-xY_(2)O_(3)(abbreviated as(1-x)BCTSZ-xY,x=0 mol%,0.02 mol%,0.04 mol%,0.06 mol%,0.08 mol%and 0.1 mol%)ceramics were successfully synthesized by traditional solid-state sintering method.The phase structure and microstructure of ceramics were investigated by X-ray diffraction(XRD),scanning electron microscopy(SEM)and piezoresponse force microscopyeramics(PFM).The electric properties of ceramics were researched through piezoelectric,dielectric and ferroelectric test instruments.The results show that all samples have pure perovskite structure and favorable electric properties.The optimal electric properties which especially include superior ferroelectric properties are gained when Y_(2)O_(3)content is 0.06 mol%(d_(33)=419 pC/N,k_(p)=52%,T_(c)=89.5℃,ε_(r)=26900,tanδ=2.86%,P_(r)=14.41μC/cm^(2),Ec=1.8 kV/cm).Moreover,the temperature-dependent dielectricity of samples shows apparent relaxor behavior under different frequencies.The Curie-Weiss law further proves that all samples are typical relaxor ferroelectrics,and the relaxor degree of samples decreases with increase of Y_(2)O_(3)content.In conclusion,Y_(2)O_(3)plays a significant role in enhancing electric properties of BCTSZ ceramics.

Characteristics of sputtered Y-doped IZO thin films and devices

Yttrium-doped IZO （YIZO） thin films with different thickness have been prepared on soda-lime glass （SLG） and P-Si substrates by radio frequency magnetron sputtering at room temperature. Structural morphology and optical properties of the films have been investigated. gate-structure are fabricated on P-Si substrates. The output YIZO thin film transistors （TFTs） with the bottomand transfer characteristics of YIZO-TFT have been studied. It has been found that all YIZO thin films prepared at room temperature are amorphous, and the YIZO TFTs exhibit n-channel depletion mode. Y1ZO-TFT with active layer thickness of 20 nm shows an on/offratio over 105, a sub-threshold swing of 2.20 V/decade at a low operating voltage of -1.0 V, and saturation mobility values over 0.57 cm3/（V.s）.