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.     

Studies on the structure and microstructure of lead strontium titanate thin films

Pb1-xSrxTiO3 （0≤x≤0.9） thin films on Si （100） substrate were prepared by the sol-gel process and their characteristics were investigated as a function of strontium content（x）. With increasing of the strontium content, the tetragonality （c/a） was slightly decreased, the splitting peaks become less prominent and the splitting peaks tend to merge into a single peak. Furthermore, the grain size of the films was systematically reduced with the increase in strontium content.     

Strontium Zirconate and Strontium Titanate Ceramics for High-Voltage Applications: Synthesis, Processing, and Dielectric Properties

The synthesis, processing, and electrical properties of SrZrO₃ and SrTiO₃ materials have been examined. Phase-pure powders of SrZrO₃ and SrTiO₃ materials were synthesized using the Pechini method. Powder processing routes that used water and 2-propanol as carrier fluids were developed to achieve high green densities, which resulted in sintered densities of >99% of the theoretical density. The relative permittivity and average breakdown strength for carefully processed SrZrO₃ were 60 and 40 V/μm; the corresponding values for SrTiO₃ were 400 and 35 V/μm. The higher breakdown strengths suggest that these materials can be used in high-voltage capacitor applications.     

Performance improvement by metal deposition at the cathode active site in solid oxide fuel cells

In this study, the performance improvement of the SOFC single cell and its underlying mechanism was investigated. Furthermore, an application of the identified electrochemical mechanism is proposed and tested experimentally. The deposition of Platinum (Pt) at electrochemically active sites for the oxygen reduction reaction is determined to be responsible for the improved performance. Pt migration from a current collector to the cathode active sites originates from the oxygen partial pressure difference between current collector and triple phase boundary, and the electrochemical reduction reaction. It is supported by the confirmation of Pt particles at the cathode active sites by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and calculations of the thermodynamic equilibrium partial pressure values. In addition, correlation of the initial performance change and the quantities of Pt deposition are investigated. This selective Pt deposition mechanism at the active sites is applied to the LSCF cathode, as well.     

聚锑酸离子交换剂的制备及分离锶和钇

以三氧化二锑为原料,双氧水为氧化剂,经氧化回流法制备聚锑酸无机离子交换剂.该聚锑酸离子交换剂对锶-钇混合溶液中的锶具有较好的选择性吸附能力.通过正交实验设计法对反应影响因素进行了优化,结果表明,在60 ℃时加入40 mL水和12 mL H_2O_2氧化10 g Sb_2O_3固体,反应120 min可制得对Sr~(2+)和Y~(3+)具有较高分离系数的聚锑酸离子交换剂.理化性能研究表明,产物是一种阳离子交换剂,对溶液中的Sr~(2+)和Y~(3+)的动态吸附分离具有较高的选择性.     

Thermal Instability and Microstructure of Strontium M-type Hexaferrite Nanoparticles Synthesized by Citrate Approach

The dried gel of SrFe12O19, prepared by citrate approach, was investigated by means of infrared spectroscopy （ IR ）, thermogravimetric analysis （ TG ）, differential scanning calorimetry （ DSC ）, X- ray diffraction（ XRD ） techniques, energy dispersive spectroscopy（ EDS ）, and transmission electron microscopy（ TEM ）. The thermal instability and the thermal decomposition of low-temperature strontium M-type hexaferrite crystallized at about 600℃ were confirmed for the first time by XRD method. The decomposition of the low-temperature strontium M-type hexaferrite took place at about 688.6℃ determined by DSC investigation. The low-temperature strontium M-type hexaferrite nanopartieles were decomposed into SrFeO2.5 with an orthorthombic cell and Fe2O3 with a tetragonal cell as well as possibl α-Fe2O3 . The agglomerated particles with sizes less than 200 nm obtained at 800℃ were plesiomorphous to strontium M-type hexaferrite. The thermally stable strontium M-type hexaferrite nanopartieles with sizes less than 100um cotdd take place at 900 ℃ . Up to 1000 ℃ , the phose transformotion to form strontium M-type hexaferrite was ended, the calcinations with the sizes more than 1μm were composed of α-Fe2O3 and strontium M-type hexaferrite. The method of distinguishing γ-Fe2O3 with a spinel structure from Fe2O3 with tetragonal cells by using powder XRD method was proposed. Fe2O3 with tetragonal cells to be crystallized before the crystallization of thermally stable strontium M-type hexaferrite was confirmed for the first time. The reason why α- Fe2O3 as an additional phase appears in the calcinations is the cationic vacancy of stroutium M-type hexaferrite , SrFe12-x□O19 （0≤x ≤0.5）.     

Relaxor Behavior of (Sr0.8Ba0.2)TiO3 Ceramic Solid Solution Doped with Bismuth

The dielectric properties of (Sr_0.8Ba_0.2)_1-1.5xBi_xTiO₃ ceramics in the range 0 x 0.18 are investigated. A ferroelectric relaxor behavior is observed. The degree of the diffuseness and the relaxation of the phase transition increases as the Bi content increases. A random electric field is suggested to be responsible for the relaxor behavior observations. The dependence of the diffuseness on the grain size is presented.     

氯化锶水溶液的净化和SrCl2的制取

生产锶盐的过程中都存在ＳｒＣｌ２溶液的净化，本文讨论了锶的氯盐溶液净化的方法和影响因素，得到了ＳｒＣｌ溶液沉淀法降钙钡及其它杂质净化方法。     

Synthesis of Sr0.5Ba0.5Nb2O6 by Coprecipitation Method—Dielectric and Microstructural Characteristics

Sr_0.5Ba_0.5Nb₂O₆ (SBN50) has been synthesized by coprecipitation method using Sr(NO₃)₂, Ba(NO₃)₂ and Nb-oxalate as precursors and ammonium hydroxide as precipitant. Calcination at 1150C resulted in pure SBN50 phase (XRD) and nano powder with size varying between 100–250 nm (TEM). The average grain size (SEM) in the sintered pellets ranged from 2.5 to 5 m as the sintering temperature varied from 1250 to 1350C. The maximum sintered density was observed to be 93% of _th. The plot of dielectric constant vs. temperature clearly showed a shift of dielectric maxima (_max) with frequency, indicating the relaxor nature of SBN50. The room temperature dielectric constant (_RT > 2300) observed for all these samples is higher compared to the earlier reported values (_RT 1500). The T_c (for 1 KHz) varied from 47–60C depending on the sintering conditions. The hystersis loops were recorded at various temperatures. The maximum saturation polarization for the unpoled pellets was found to be 2.3 C/cm² when sintered at 1350C. The improvement in dielectric and ferroelectric behavior is attributed to the enhanced homogeneity attained by the coprecipitation synthesis route used in the present study. Correlations between microstructure (sintering conditions) and dielectric behavior is explored.     

A/B-Ratio and Transport Properties of (La0.85Sr0.15)sCoO3−δ Perovskites

The perovskites (La_0.85Sr_0.15)_0.98CoO_{3 –} and (La_0.85Sr_0.15)_1.00CoO_{3 –} have been investigated using x-ray diffraction (XRD), scanning electron microscopy (SEM) and electrical conductivity relaxation (ECR). This system was chosen in order to investigate the influence of cation vacancies on the transport properties in the materials. From ECR-measurements it is concluded that no difference in the chemical diffusion coefficient for oxide ions between the two samples can be found. The activation energy for the chemical diffusion coefficient has been found to be 107 ± 5 kJ mol^{– 1}. However, the surface exchange coefficient differs between the two samples. The Co-rich sample has a significantly higher surface exchange coefficient than the A/B-stoichiometric sample. For both samples the surface exchange coefficient was almost independent of the temperature. At all temperatures the Co-rich sample had a significantly higher electrical conductivity. The difference in electrical conductivity between the two samples diminished when going to higher temperatures. Both materials can be assigned to a single phase hexagonal perovskite. An annealed sample of (La_0.85Sr_0.15)_0.98CoO_{3 –} did however contain an unidentified secondary phase on the surface.