电子陶瓷用钛酸钡粉体制备方法研究进展

介绍了国内外钛酸钡(BaTiO3)粉体的主要制备方法及其发展现状,指出低温燃烧合成法(LCS)法、机械力化学法、水热法方法由于具有许多优良特性而极具发展潜力,并预言钛酸钡的制备方法将会得到迅猛发展。     

芳纶纳米纤维/钛酸钡纳米纤维复合电介质薄膜制备与介电性能研究

选用芳纶纳米纤维（ANF）作为耐高温基体,并填充钛酸钡纳米纤维（BTNF）制备ANF/BTNF纸基复合薄膜,研究不同BTNF填充量对复合薄膜介电性能的影响。结果表明：ANF/BTNF复合薄膜的厚度约为10μm。当BTNF质量分数为0～20%时,随着BTNF填充量的增加,复合薄膜的介电常数和电气强度均提升。当BTNF的质量分数增大到40%时,复合薄膜的介电常数显著提升,但是在高频区快速降低,介质损耗因数显著增大,同时复合薄膜的电气强度略微下降。因此,BTNF质量分数为20%的ANF/20BTNF复合薄膜综合介电性能最佳,在1 kHz时介电常数达到4.78,电气强度为8.90 kV/mm。     

钛酸钡陶瓷浆料流变性研究

为了获得高固相体积含量、低粘度的钛酸钡(BaTiO3)陶瓷凝胶注模用浆料,研究了粉体粒度、分散剂、球磨时间、pH值对该浆料流变性的影响.结果表明:在相同的固相体积含量下,粉体粒径3μm相比1/μm的BaTiO3浆料具有较小的粘度;用聚丙烯酰胺分散剂,最佳用量相对粉体质量3‰～5‰;球磨8 h浆料的流变性最好;pH值在7～8时浆料的粘度最小.并获得固相体积含量为63%、粘度为690 mPa·s、可易于浇注的BaTiO3陶瓷浆料.     

分散剂对钛酸钡介电性能的影响

通过水煮损耗测试、温度特性、电导率和化学分析、瓷片表面显微结构等测试手段,研究了在固相反应制备钛酸钡的工艺中,向BaCO3粉体和TiO2粉体的混合球磨的浆料中加入聚乙烯醇作为分散剂对合成的钛酸钡粉体均匀性的影响。研究结果表明,碱性聚乙烯醇改善合成BaTiO3粉体均匀性的效果最好,介电常数峰值提高了2313、游离BaO含量降低了93.33％。     

锡钛酸钡薄膜材料的研究现状

铁电薄膜是一类重要的功能材料,其中锡钛酸钡（BTS）薄膜由于具有较优异的介电性能而成为研究热点。本文综述了锡钛酸钡薄膜材料的制备方法和介电性能的研究现状,提出了研究中需要解决的问题。     

纳米LiFePO4材料的制备及性能研究

以FeCl2.4 H2O、(NH4)2HPO4及LiOH·3 H2O和柠檬酸为原料,采用水热模板法制备花形结构的LiFePO4纳米棒。此方法合成的LiFePO4形貌可控,粒径均匀,分散性好,电压平台稳定,具有高于160 mAh/g的比容量。还研究了柠檬酸浓度以及前驱体的煅烧温度对LiFePO4的形貌以及电化学性能的影响。实验表明在柠檬酸浓度为0.1 mol/L、煅烧温度650℃下,样品为分布均匀的纳米"花形棒状"结构,尺寸均匀、晶形稳定,电压平台为3.45 V,且电压平台宽,首次充放电比容量高达162.5 mAh/g,0.5 C充放电50次容量保持率将近100%。     

微波烧结高介电常数钛酸钡复合材料的研究

分别采用微波烧结和传统烧结的方法对钛酸钡复合材料进行烧结。从微观结构、烧结后样品的收缩率、样品的电容以及介质损耗因数等几个方面进行了比较分析。结果表明：微波烧结比传统烧结得到的样品具有更致密、更均匀的微观结构。微波烧结对样品线性收缩率终值影响不大,但会增强烧结密度,使开始收缩温度降低20～25℃,得到的样品具有更小的介质损耗。     

纳米多孔硅可控制备研究

采用了自制双槽和电化学腐蚀法在不同电阻率的硅片上制备出表面平整度很好的纳米多孔硅层,利用场发射扫描电子显微镜对多孔硅的微观形貌进行了分析表征。实验表明多孔硅的孔径、孔隙率和厚度随电化学腐蚀的电流密度和腐蚀时间增加而增加,且电解液中HF(40%)和无水乙醇(99.7%)的配比很趋近时,多孔硅的孔洞分布均匀性越好。在电阻率为0.01~0.02Ω·cm的P型硅片上制备的纳米多孔硅其效果相比其他电阻率的要好。     

纳米结构Sb2Te3的合成与分析

介绍了在开放和封闭两种状态下采用水热合成方法制备纳米结构Sb2Te3材料,并对不同反应温度、反应条件的样品进行测试分析,包括X射线衍射光谱法(XRD)、透射电子显微镜法(TEM)以及粒度分布等.实验结果表明.不同的合成工艺条件所获得产物均为Sb2Te3,但其反应进行的程度、尺寸大小以及形貌都不尽相同.获得的Sb2Te3纳米颗粒的直径最大不超过140 nm.     

层状正极材料LiMnO2制备及电化学性能研究

利用水热混合碱法制备出了一种结构较稳定的层状正交LiMnO2,并对其电化学性能、晶型进行了研究。结果表明该方法制备出的正极材料结构属于O3式碱青铜结构,其晶格参数分别为a=0.2808nm,b=0.5748nm,c=0.456nm,与标准数值相差很少。充放电曲线表明开始时容量下降很快,而后下降就趋于平缓,容量几乎为恒定值,同时XRD显示材料在充放电过程中存在着结构的转变,经过充放电后材料中出现了杂质,材料的比容量在前15次循环中比容量下降了24mAh·g-1(占初始放电比容量的17.1%)。     

Ferroelectric and dielectric properties of sol-gel and excimer-laser-deposited lead zirconate titanate and barium titanate films

Abstract

Switched remanent polarization was measured as a function of accumulated switching cycles for a variety of ferroelectric films using sinusoidally driven hysteresis loops. Switched remanent polarization and dielectric constant and loss were also obtained as a function of the cycling frequency. PZT films with niobium additives appeared to lose switched remanent polarization with accumulated cycles at a lesser rate than films without niobium. The switched remanent polarization was found to decrease with increasing frequency, which we attribute to the effect of grain size. Also, a decrease of dielectric constant with increasing frequency and an increase of dielectric constant with increased applied voltage are attributed to the effects of domain wall motion contributions to dielectric constant.     

改性对钛酸钡基陶瓷储能密度的影响

基于钛酸钡(BaTiO_3)基陶瓷在储能方面的重要应用,介绍了电介质储能的物理基础和影响因素。在此基础上,主要讨论了等价离子掺杂改性、异价离子掺杂改性和包覆改性等对钛酸钡基陶瓷介电性能和储能密度的影响。同时指出优化掺杂改性和包覆改性的组合是提升钛酸钡基陶瓷储能密度的重要途径。     

Dielectric properties of nanocrystalline barium zirconate titanate synthesized by glycine-nitrate autocombustion

Abstract

Dielectric properties of nanocrystalline barium zirconate titanate (Ba(Zr_xTi_1-x)O₃; BZT for x?=?0.1 and 0.3) synthesized by glycine-nitrate autocombustion method were investigated in this study. The phase formation examined by TGA-DTA, XRD, FT-IR and Raman spectroscopy confirmed that high purity single-phase BZT with perovskite structure was obtained by using glycine-to-nitrate molar ratio of 2.2:4 and calcining in air at 1100?°C for 4?h. TEM analysis showed that BZT had agglomerate particles consisted of primary spherical nanocrystals with the size of 8-11?nm. The diffuse phase transition behavior of BZT ceramics increased with increasing Zr concentration and for x?=?0.3, the Curie temperature; T_c, shifted to below room temperature. The BZT ceramics for x?=?0.1 had relatively high dielectric constant (ε), 13007, low T_c, 76?°C and comparable dielectric loss (tan δ) at T_c, 0.012 which caused by the high degree of Zr diffuseness into the perovskite structure. These results suggest that glycine-nitrate autocombustion is the effective method for preparing high quality BZT ceramics.     

改良水热法合成磷酸亚铁锂的研究

采用水热法制备的磷酸亚铁锂(LiFePO4)正极材料具有颗粒细小、粒径分布窄等特点;且水热法本身具有工艺条件易于控制、能耗低等优点,有望解决当前LiFePO4生产批次不稳定的难题,是一种有应用前景的LiFePO4生产方法。传统水热制备工艺需要加入过量锂,增加了生产成本。改良水热法制备LiFePO4,选择非纯水溶剂,极大地减少了锂用量,有利于Li+沉淀,且抑制了晶体的过度发育和颗粒间的团聚,加快LiFePO4成核、降低晶体生长速率,减小粒径。材料的大倍率放电性能比传统水热法优越,10 C放电比容量达94 mAh/g。随后研究水热合成温度、时间对样品性能的影响,结果表明:反应温度170℃,反应时间12 h合成的样品晶型结构完善,循环电性能最佳。     

钛酸锶合成方法研究进展

介绍了钛酸锶的特点,综述了钛酸锶合成方法的研究进展,包括溶胶一凝胶法、化学沉淀法、高温固相法、微波方法、等离子体法和水热法,指出了用新型方法合成纳米级、多功能的钛酸锶的重要性。     

Investigation of ferroelectric domains and structural twins in barium titanate crystal

Abstract

The Ferroelectric domain patterns and the {111} twin boundaries are frequently observed in the BaTiO₃ ceramics. The ferroelectric domain structures in BaTiO₃ single crystal were investigated by a conventional and a synchrotron white beam X-ray topographies. The domain structure of {111} twinned crystal sample was also observed under a polarizing microscope and under a TEM. The relation between the {111} twin and the ferroelectric domain structure was verified by insitu observation of the behaviors of 90° domains during the phase transitions. It is observed that the 90° ferroelectric domain boundaries around the {111} twin boundary which was produced during the crystal growth obey the symmetry relation of the {111} twinning and that they meet each other coherently at the same position of the {111} twin boundary.     

Size-controllable barium titanate nanopowder synthesized via one-pot solvothermal route in a mixed solvent

Barium titanate nanopowder was synthesized via solvothermal route using water-ethanol-ethylene glycol monomethyl ether as mixed solvent and TiCl₄-Ba(OH)₂ · 8H₂O as precursors. The effects of water amount in a mixed solvent, synthetic temperature and reaction time on microstructure and particle size of the as-prepared barium titanate powder were investigated systematically. The results show that the particle size of barium titanate powder could be tuned by varying the synthetic parameters. The procedure presented here provides a simple route to the preparation of barium titanate nanopowder with controllable particle size.     

超声处理对水热合成LiV3O8电化学性能的影响

以NH4VO3和Li2CO3为原料,采用水热合成/低温焙烧方法制备了层状结构的锂离子蓄电池正极材料LiV3O8.研究发现,对合成粉末的超声处理具有细化颗粒和提高有效表面积的作用,特别是对300 ℃和350 ℃烧结试样的作用更明显.电化学性能测试表明,300 ℃烧结试样经超声处理后在0.1 C倍率下首次放电比容量达到350 mAh/g,放电平台、循环性能和阻抗也有了较为明显的改善.