Synthesis and Properties of Tb^(3+)-Doped Ca_x Sr_(1- x)WO_4

Tb^(3+)-doped Ca_ x Sr_(1- x )WO_4 was prepared by solid state reaction and characterized by powder X-ray diffractometry. According to X-ray diffraction, this material belongs to tetragonal system, which is consistent with space group I4_1/a. Lattice parameters in the systems Ca_ x Sr_(1- x )WO_4 were found to vary linearly with compositions. The emission and excitation spectra were measured. The miscibility, luminescence properties of Tb^(3+)-doped Ca_ x Sr_(1- x )WO_4 and energy transfer mechanism were discussed.

Effect of Substitution Sr Cations on the Structure in the Gd_(1)(Ba_(2−x)Sr_(x))Cu_(3)O_(7−δ) Phases

In an effort to improve the performance of superconductors in the field and high temperatures it is important to study the superconducting mechanism. For this reason, the cation substitution can be conducted. One of the high Tc superconductors Gd1Ba2Cu3O7−δ phase with Sr substitution has been synthesized, i.e. Gd1(Ba2−xSrx)Cu3O7−δ compound. The sample was synthesized by using a solid-state reaction method with a wet mixing, sintered for 12 hours at temperature 900°C. The synthesis results are characterized by using XRD. The results of Match-3 software analysis showed high (higher 85%) Gd1Ba2Cu3O7−δ phase was formed. The Sr substitution causes changes to the structure, i.e. the lattice parameters a, b and c, where the orthorhombicity tends to decrease with increasing Sr content. Refinement results show that based on the oxygen occupancy, the total oxygen content tends to increase.

Sr阳离子和O阴离子空位缺陷调控工程提升钙钛矿Sr_(x)VO_(3-δ)储锂性能

钙钛矿结构氧化物的空位缺陷调控工程在催化和太阳能电池等领域被广泛研究应用,本文进一步拓展了钙钛矿材料空位缺陷工程在储能领域的应用.使用钙钛矿Sr_(x)VO_(3-δ)材料为研究材料,通过调控溶胶燃烧过程中Sr/V化学计量比和还原温度,精确控制样品中的Sr阳离子和O阴离子的空位浓度,并且保持了Sr_(x)VO_(3-δ)材料的钙钛矿结构.电化学研究结果表明,通过提高Sr阳离子和O阴离子空位缺陷浓度,Sr_(x)VO_(3-δ)电极比容量和倍率性能显著提升.其中,Sr空位缺陷的引入为锂离子提供了额外储锂位点和扩散通道,而O空位缺陷的引入则显著提升了Sr_(x)VO_(3-δ)电极的电导率和锂离子扩散系数.因此,空位缺陷工程为钙钛矿结构储能材料电化学性能的提升和设计提供了新思路.

溶胶-凝胶法制备La_(1-x)Sr_(x)MnO_(3)及其电磁性能研究

采用溶胶-凝胶法制备了La_(1-x)Sr_(x)MnO_(3)(LSMO)(x=0,0.1,0.2,0.3)纳米微粉。探究了 Sr^(2+)的掺杂量对LSMO晶体结构、磁学性质、电磁特性和微波吸收性能的影响。结果表明,随 Sr^(2+)含量的升高,样品的晶格常数和Mn-O-Mn键角增大,平均晶粒尺寸逐渐下降,样品出现从反铁磁性向铁磁性的转变,复介电常数呈先增大后减小的趋势。在有效的波频段为2~18 GHz内,x=0的样品在厚度为2 mm时有最佳吸波效果,反射率损耗小于–10 dB对应的有效吸波频段为12.5~18 GHz,有效带宽达到5.5 GHz;Sr^(2+)的掺杂可使吸波频段有效向低频移动,在X波段内,x=0.2的样品在厚度为2.3 mm时的有效带宽达2.6 GHz,证明LSMO是一种性能优异的介电损耗型吸波材料。