Electrical Conductivity of SrCe_(0.9)Ho_ (0.1)O_ (3-α) Ceramics

Electrical Conductivity of SrCe_(0.9)Ho_ (0.1)O_ (3-α) Ceramics     

Electrical Conductivity of SrCe0.9Ho0. 1O3- α Ceramics

Proton-conducting SrCe0.9Ho0.1O3-α ceramics was prepared by high-temperature solid state reaction. X-ray powder diffraction patterns show that the ceramics is of a single orthorhombic phase of perovskite-type SrCe03. Using the ceramics as solid electrolyte and porous platinum as electrodes, the protonic conduction in the ceramics was investigated by using ac impedance spectroscopy and gas concentration cell methods in the temperature range of 600 ~ 1000 ℃.     

不同结构的超级电容器阻抗谱

研究了不对称超级电容器和碳/碳超级电容器在化成前后的阻抗谱变化规律.由锰酸锂(LiMn₂O₄,LMO)和活性碳(activated carbon,AC)组成的不对称超级电容器经过化成,电容器的高频(10 kHz)交流阻抗没有明显变化,而低频电容明显提高.不对称超级电容器由于采用电池型电极材料作为其中一极,使得其阻抗特性与碳/碳超级电容器的阻抗特性不同.通过对化成前后的超级电容器交流阻抗谱进行分析,利用复数电容和复数功率两种形式讨论了不对称超级电容器的阻抗变化规律,确定了不对称超级电容器的时间常数;通过碳/碳超级电容器与不对称超级电容器的阻抗行为的比较,说明电池型电极的引入对电容器的频率响应特性造成的影响.     

Defect structure and electrical properties of LaSr_3Fe_3O_(10-δ)

As a mixed conductor,LaSr3Fe3O10-δ with triple layer perovskite intergrowth structure can be used as an oxygen separation membrane material and cathode material in solid oxide fuell cells.LaSr3Fe3O10-δ was synthesized via citrate acid route.Iodine titration method was used to determine the average valence of transition metal Fe and oxygen nonstoichiometry δ.Conductivities of LaSr3Fe3O10-δ were measured in the oxygen partial pressure range from 10-2×105 to 1×105 Pa,by Ac four probe method.Seebeck coefficient...     

Structural and electrical transport properties of a rare earth double perovskite oxide：Ba2ErNbO6

The double perovskite oxide barium erbium niobate,Ba2ErNbO6(BEN) was synthesized by solid state reaction technique.Rietveld refinement of the X-ray diffraction pattern of the sample showed cubic(Fm3m) phase at room temperature.Fourier transform infrared spectrum showed two primary phonon modes of the sample at around 387 and 600 cm–1.Raman spectrum of the sample taken at 488 nm excitation wavelength showed four primary strong peaks at 106,382,747 and 814 cm–1.Lorentzian lines with 10 bands were used to fit the Raman spectrum.A group theoretical study was performed to assign all the Raman modes.Impedance spectroscopy was applied to investigate the ac electrical conductivity of BEN in a temperature range from 303 to 673 K and in a frequency range from 100 Hz – 1 MHz.The dielectric relaxation mechanism was discussed in the frame work of permittivity,conductivity,modulus and impedance formalisms.The complex plane plot of the impedance data was modeled by an equivalent circuit consisting of two serially connected R-CPE units,(one for the grain and the other for the grain boundary),each containing a resistor(R) and a constant phase element(CPE).The R-CPE units were used to incorporate the non-ideal character of the polarization phenomenon instead of an ideal capacitive behaviour.The relaxation time corresponding to dielectric loss was found to obey the Arrhenius law with activation energy of 0.85 eV.The frequency dependent conductivity spectra followed the Jonscher power law.The Cole-Cole model was used to investigate the dielectric relaxation mechanism in the sample.     

Conductivity and electric properties of La1-xSrxMnO3-δ nanopowders

La_0.8Sr_0.2MnO_3−δ was synthesized by the Pechini's method. The XRD pattern and TEM indicate the formation of the perovskite without the presence of secondary phases. It was found that La_0.8Sr_0.2MnO_3−δ sample prepared at 1000 °C in air atmospheres, contains about 13.11% of the manganese as Mn⁴⁺ and 86.89% of the manganese as Mn³⁺. The electric measurements were carried out for La_0.8Sr_0.2MnO_3–δ nanoceramics by using impedance spectroscopy methods and found to be 0.1 S/cm at 250 °C similar to the typical value of La_0.8Sr_0.2MnO_3-δ materials. Its dependence on reciprocal temperature shows quite complicated mechanism of conduction.     

High-resolution Fourier spectroscopy as a tool for studying quality of rare-earth-doped crystals

Three examples were considered of the use of high resolution Fourier-transform optical spectroscopy for studying quality of rare-earth-doped crystals. The first example was connected with defects present in crystals grown by flux techniques. The second example dealt with detection of stresses and deformations in rare-earth-containing crystals, by registering splitting of spectral lines. The third example showed that a very small amount （at the level ofppm） of different RE ions present in a crystal could be determined using high-resolution spectroscopy. This work was carried out by the author＇s group in collaboration with several institutions in Rus- sia and abroad.     

Formation and Characterization of Li0.24 ＋ 2x La0.59-x Mx TiO3-LaPO4 （M = K, Na） System

Ionic conductingsolid materials has received con-siderable attention in the last few years due to theirpotential utilityin high energy batteries and other elec-trochemical devices . Several systems of lithium fastion conductors ,such as γ-Li3PO4-type sol…     

Activity improvement of Pt/C catalysts by adding CeO2 nanoparticles

Carbon-supported platinum catalysts were prepared by NaBH4 reduction of metal precursors and the CeO2 nanoparticles were pre-pared by citric acid sol-gel method.The structure and morphology of two kinds of nanoparticles were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM),respectively.The Pt particles were uniformly dispersed on the carbon surface and showed the rod-like morphology.The CeO2 was spherical in shape.The appropriate amount of CeO2 nanoparticles was added into Pt/C sys-tems to improve activity of the catalysts.Several electrochemical techniques such as cyclic voltammogram (CV),chronoamperometry (I-t) and electrochemical impedance spectroscopy (EIS) were used to investigate the properties of CeO2-Pt/C catalysts for methanol electrooxidation in 1 mol/L CH3OH+0.5H2SO4 aqueous solutions.The results revealed that compared with Pt/C catalysts CeO2-Pt/C exhibited a higher activity and stability for methanol electro-oxidation.Moreover,the effect of CeO2 content on the activity of Pt/C catalysts was discussed in detail.     

Effects of CeO_2 on microstructure and corrosion resistance of TiC-VC reinforced Fe-based laser cladding layers

The effects of CeO2 on microstructure and corrosion resistance of TiC-VC reinforced Fe-based laser cladding layers were investigated. The results showed that carbides presented in cladding layers were TiVC2 and VC. A small quantity of CeC appeared with 2.0 wt.% CeO2 addition. The amount of lamellar pearlite increased while the amount of residual austenite decreased with increasing CeO2 addition. The corrosion resistance of cladding layers increased firstly and then decreased with the addition of CeO2 increasing. The EIS spectrum of the cladding layer without CeO2 was composed of an inductive arc at low frequency and a capacitive arc at high frequency. The cladding layer with 0.5 wt.% CeO2 addition showed the best corrosion resistance, and then the inductive arc at low frequency transformed into a capacitive arc.     

Electric properties of La0.8Sr0.2CoO3 nanoceramics

The electric measurements were carried out for La_0.8Sr_0.2CoO₃ nanoceramics by using impedance spectroscopy methods. The resistance of sample was practically independent of frequency in measurement range. Its dependence on reciprocal temperature showed quite complicated mechanism of conduction. The most striking property of investigated sample was its resistance decreasing with increasing applied polarization.     

Structural and electrical properties of La2-xSrxMo2O9-δ

Sr-doped La2Mo2O9 were prepared by solid state reaction and characterized by XRD,impedance spectroscopy and HebbWagner polarization method.XRD patterns of the samples indicated that the solubility limit of Sr2+ in La2-xSrxMo2O9-δ was in the range of 7 mol.% to 7.5 mol.%,i.e.,the maximum stoichiometric coefficient x in La2-xSrxMo2O9-δ was larger than 0.14 and less than 0.15.The cubic lattice parameter of La2-xSrxMo2O9-δ(0相似文献   

Structure and Dielectric Study of Ce3 NbO7＋δ

The structure, phase composition, and migration of oxygen ion in Ce3 NbO7＋δ were reported on the basis of lone-pair substitution concept. X-ray diffraction study revealed that Ce3 NbO7＋δ sample was comprised of Ce3 NbO7＋δ phase and CeNbO4.25 phase. In the dielectric study of Ce3 NbO7＋δ sample, two dielectric loss peaks were observed both in temperature spectra and frequency spectra. Both peaks were shifted towards higher temperature with increase in frequency in temperature spectra and towards higher frequency with increase in temperature in frequency spectra, indicating the relaxation essence of these two peaks. It was suggested that the short distance diffusions of oxygen ions in both Ce3 NbO7＋δ phase and CeNbO4.25 phase gave rise to the two dielectric relaxation peaks.     

Relaxation process and phase transition of lanthanide liquid crystalline complexes by photoacoustic spectroscopy

Lanthanide-containing liquid crystals exhibiting smectic A phase close to room temperature were obtained. Photoacoustic （PA） spectroscopy was used to study the spectral properties and phase transitions of liquid crystalline metal complexes. It was found that PA intensity of the ligand had a relationship with the probability of nonradiative transitions, which increased in the order of Eu（tta）3L2〈La（tta）3L2〈 Tb（tta）3L2〈Er（tta）3L2. The relaxation processes of the complexes were studied in depth from two aspects： radiative and non-radiative processes, combining with their fluorescence spectra. Phase transitions of europium（m） and erbium（m） complexes, in the temperature range of 383-358 K, could be clearly monitored by both PA amplitude and PA phase signals. As the temperature crossed the transition point, PA amplitude showed a minimum and PA phase a maximum. The results indicated that PA technique could serve as a new tool for investigating the physicochemical properties of liquid crystals containing metal ions.     

Tm^3＋ interactions in LiYF4 studied by high-resolution spectroscopy

We used the high-resolution spectroscopy to study the interactions that Tm³⁺ ion in a LiYF₄ crystal is subjected to. Several crystal field transitions with low integral intensity were found not registered before by means of ordinary spectroscopy. Spectral evidences for interionic, hyperfine, isotopic interactions, and for a resonant broadening of the ground state are presented.