B2O3掺杂对Ba0.6Sr0.4TiO3/MgO陶瓷介电性能的影响

采用XRD和SEM对B2O3掺杂Ba0.6Sr0.4TiO3/MgO(简称为BSTM)陶瓷致密化行为和介电性能进行了研究。结果表明:掺杂适量B2O3可明显降低BSTM陶瓷的烧结温度,在1480℃时即可烧结致密化,比未掺杂的BSTM陶瓷烧结温度降低70℃;掺杂量不同,则B2O3在陶瓷体中的存在形式不同,引起其介电性能相应变化;1480℃下烧结,B2O3掺杂量为0.8%(质量分数)时,10kHz下测得试样的εr为138,tanδ为0.0034,εr可调率达12.6%(3MV/m),性能有所提高。     

Effect of lanthanum content on the conduction behaviors and relaxation processes of lead lanthanum zirconate titanate antiferroelectric ceramics

(Pb_1-xLa_x) (Zr_0.92Ti_0.08)_1-x/4O₃ (PLZT x/92/8, x = 3, 5 and 7 at%) ceramics with compositions near the antiferroelectric (AFE)-ferroelectric (FE) phase boundary were fabricated by a solid-state reaction method. The effect of lanthanum content on the conduction behaviors and relaxation processes has been investigated. It was verified that the main phase with orthorhombic structure was formed in all compositions. The increase of lanthanum substitution resulted in an enhancement of diffuse phase transition. Impedance analysis suggested that the ac conductivity decreased with increasing lanthanum content. Moreover, thermally stimulated depolarization current study was utilized to establish the correlation between defect structures and relaxation processes. It showed three peaks with distinct characteristics, which originated from dipole orientation, oxygen vacancy migration and phase transition respectively. The oxygen vacancy-related defects induced by lanthanum doping were mainly responsible for the variation of conduction behaviors and relaxation processes.     

Preparation and corrosion resistance of nonstoichiometric lanthanum zirconate coatings

Lanthanum zirconate is a promising thermal barrier coating material owing to its excellent thermophysical properties and La plays the key role in its corrosion resistance. Here, an amorphous precursor is used as raw feedstock material so as to synthesize lanthanum zirconate coatings with tailorable composition by atmospheric plasma spray (APS). Three lanthanum zirconate coatings of La_1.7Zr_2.3O_7.15, La_2.0Zr_2.0O_7.0 and La_2.3Zr_1.7O_6.85 are fabricated. Furthermore, the corrosion resistance of the as-sprayed coatings against CaO-MgO-Al₂O₃-SiO₂ at 1250℃ is investigated. The increased La content promotes the formation of a sealing layer of the crystalline Ca₂La₈(SiO₄)₆O₂ apatite, which slows down the penetration of molten CaO-MgO-Al₂O₃-SiO₂. Therefore, the infiltration rate of the La_2.3Zr_1.7O_6.85 coating decreased up to 42.6 % compared with the other two coatings. This work develops a feasible preparation strategy to control the La composition for the improved corrosion resistance, which is expected to guide the future coating design and synthesis for the materials with big composition changes during the APS process.     

Structural and thermal behavior of 45S5 Bioglass®-based compositions containing alumina and strontium

The present research exposes the influence of 2 mol% of Al₂O₃ and 2 mol% SrO in 45S5 Bioglass^®-based compositions. Four compositions were produced to elucidate the difference in how both oxides influence structure and thermal behavior separately and their synergy when together. Thermal properties, crystallization tendency, and sintering behavior was evaluated by differential scanning calorimetry, hot stage microscopy, and dilatometry. Changes of medium-range structures were characterized by Qⁿ distribution of Raman spectroscopy and evaluation of ³¹P, ²⁷Al, ²³Na, and ²⁹Si environment obtained by magic angle spinning nuclear magnetic resonance. Despite Qⁿ distribution was predominantly Q² in all samples, the composition criteria used enabled improved processing and stabilibity characteristics. The addition of Al₂O₃ and SrO promoted larger sinterability parameter (S_c) which indicates better sintering behavior, the glass stability against crystallization doubled (K_H) compared to 45S5 and the processing window enlarged from 106 to 171.     

溶胶-凝胶法制备钛酸锶铅薄膜和多层膜及其介电性质

采用溶胶-凝胶法在Pt/Ti/SiO2/Si衬底上制备了多种不同组分的(Pb1-xSrx)TiO3(PST)(x=0.45、0.50、0.55、0.60、0.65)均匀薄膜和多层膜,并研究了它们的介电性质.发现均匀薄膜在x=0.55(PST55)时有最大的介电常数,10kHz下为879,损耗为0.029.在与均匀薄膜相同的条件下分别制备了PST45/PST55,PST50/PST60,PST55/PST65 3种多层膜.发现PST50/PST60多层膜的介电常数得到了明显的增强,在频率为10kHz时相对于同厚度的PST55均匀薄膜从879增加到1008,而损耗依然保持较低(0.027).研究同时表明,PST多层膜在电容-电压可调谐性和介电击穿等性质方面也较均匀薄膜有不同程度提高.与其它两种多层膜比较后发现,在PST50/PST60多层膜中处于PST55左右组分的界面层对介电性质有比较大的影响.     

水泥锶渣混凝土路用性能评价

为了分析水泥锶渣混凝土用于低交通量道路路面的可行性,采用正交方法分析了水泥用量、用水量(坍落度)、砂率、碎石级配等因素对水泥锶渣混凝土抗压强度和抗折强度的影响规律,优选出合理的材料配合比;试验对不同水泥用量的水泥锶渣混凝土的力学性能、干缩性能、温缩性能和抗冻性能进行了系统评价.结果表明:水泥锶渣混凝土强度低于普通C30混凝土,但“折压比”高,弹性模量小,具有较好的抗裂性能;于缩系数比普通混凝土低20％,温缩系数为普通混凝土的53％,具有优良的抗收缩性能;抗冻性能低于普通混凝土;水泥锶渣混凝土可用于非冰冻地区低交通量道路路面.     

无机盐生产中的锶钡分离

锶钡分离对于生产高纯锶、钡盐及利用高锶 钡矿或高钡锶矿具有重要意义。介绍、评论了沉淀、离子交换、溶剂萃取等方法的研究和在无机盐工业中应用的情况。     

锶特效固相萃取片分析技术研究进展

用于放射性锶测量的锶固相萃取片技术是最近几年开发的新技术,它比常规的放射化学分析方法简便快速,溶液能够以较高流速（50 mL/min）通过膜片,这使得该技术更适用于大体积水样品的分析,并可以节省大量的样品分析费用.总结了近年来锶特效固相萃取片分析水样中锶-90的研究进展,重点阐述了样品体积、流速、酸度和干扰离子对锶化学回收率的影响以及在环境水样监测中的应用,旨在为此项研究进展提供一个阶段性的总结,希望能够为我国锶特效固相萃取片分析技术的发展起到一定的作用.     

Two-Phase Calorimetry. II. Studies on the Thermodynamics of Cesium and Strontium Extraction by Mixtures of H+CCD− and PEG-400 in FS-13

Abstract

Thermochemical characterization of the partitioning of cesium and strontium from nitric acid solutions into mixtures of the acid form of chlorinated cobalt dicarbollide (H⁺CCD^?) and polyethylene glycol (PEG-400) in FS-13 diluent has been completed using isothermal titration microcalorimetry and radiotracer distribution methods. The phase transfer reaction for Cs⁺ is a straightforward (H⁺ for Cs⁺) cation exchange reaction. In contrast, the extraction of Sr²⁺ does not proceed in the absence of the co-solvent molecule PEG-400. This molecule is believed to facilitate the dehydration of the Sr²⁺ aquo cation to overcome its resistance to partitioning. The phase transfer reactions for both Cs⁺ and Sr²⁺ are enthalpy driven (exothermic), but partially compensated by an unfavorable entropy. The results of the calorimetry studies suggest that the PEG-400 functions as a stoichiometric phase transfer reagent rather than acting simply as a phase transfer catalyst or phase modifier. The calorimetry results also demonstrate that the extraction of Sr²⁺ is complex, including evidence for both the partitioning of Sr(NO₃)⁺ and endothermic ion pairing interactions in the organic phase that contribute to the net enthalpic effect. The thermodynamics of the liquid-liquid distribution equilibria are discussed mainly considering the basic features of the ion solvation thermochemistry.     

Effect of strontium doping on structural and dielectric behaviour of barium titanate nanoceramics

ABSTRACT

Barium strontium titanate (Ba_(1?x)Sr_xTiO₃ where, x?=?0.0, 0.2, 0.3, 0.4 and 0.5) nanoparticles have been successfully synthesised by sol–gel method and characterised thoroughly. With the increase in Sr concentration (x?>?0.3), the symmetry of the crystal structure changed from tetragonal to cubic phase. The dielectric behaviour of the ceramic nanoparticles was evaluated using impedance analyser with an operating frequency of 1?Hz to 1?MHz. A very high dielectric constant 4915 was obtained for Ba_0.7Sr_0.3TiO₃ at 1?Hz frequency with low dielectric loss of 1.91, which showed very good value than the one previously reported. The density of the material was found to be >98% of theoretical density. Dielectric constants were measured by varying the temperature from 35 to 150°C and the Curie temperatures were also evaluated. The small amount of Sr doping was beneficial for obtaining high dielectric constant material which can be used in various electronic applications.