Current Understanding of Structure–Processing–Property Relationships in BaTiO3–Bi(M)O3 Dielectrics

As part of a continued push for high permittivity dielectrics suitable for use at elevated operating temperatures and/or large electric fields, modifications of BaTiO₃ with Bi(M)O₃, where M represents a net‐trivalent B‐site occupied by one or more species, have received a great deal of recent attention. Materials in this composition family exhibit weakly coupled relaxor behavior that is not only remarkably stable at high temperatures and under large electric fields, but is also quite similar across various identities of M. Moderate levels of Bi content (as much as 50 mol%) appear to be crucial to the stability of the dielectric response. In addition, the presence of significant Bi reduces the processing temperatures required for densification and increases the required oxygen content in processing atmospheres relative to traditional X7R‐type BaTiO₃‐based dielectrics. Although detailed understanding of the structure–processing–property relationships in this class of materials is still in its infancy, this article reviews the current state of understanding of the mechanisms underlying the high and stable values of both relative permittivity and resistivity that are characteristic of BaTiO₃‐Bi(M)O₃ dielectrics as well as the processing challenges and opportunities associated with these materials.     

Impedance spectroscopy of bismuth sodium titanate: Barium titanate ceramics with manganese doping

In this work we use Impedance Spectroscopy (IS) to study lead‐free ceramics of perovskite structure (Bi_1/2Na_1/2TiO₃)_0.925(BaTiO₃)_0.075 with Mn doping of 0, 0.2, 1.0, and 2.0 at.%. We compare our IS results with permittivity results, using dielectric to resistivity transformation equations which allow us to display results either as permittivity or as resistivity. We observe ionic conductivity dominating at lower temperatures, giving way to electronic conductivity at higher temperatures. The permittivity shows deviations from Curie‐Weiss behavior characteristic of relaxor ferroelectrics. The 0.2% Mn samples show the highest ionic resistivity, which will reduce heating for high voltage piezoelectric applications. They also have the highest Curie‐Weiss temperature and Burns temperature.     

退火处理对钛酸钡微弧氧化铁电薄膜物相的影响

以工业纯钛板作为阳极,在Ba(OH)2溶液中微弧氧化制得BaTiO3薄膜。研究了BaTiO3薄膜的表面形貌和物相组成,着重研究了退火处理对BaTiO3薄膜物相的影响。微弧氧化所得薄膜表面凹凸不平,且存在大量分布不均的孔洞,主要由六方相BaTiO3组成,经不同温度退火后,其物相组成发生很大变化。在1 100°C下退火1 h后,薄膜中开始出现四方相BaTiO3;随着热处理温度的升高和保温时间的延长,更多的BaTiO3由六方相向四方相转变。但高温退火过程中基体Ti与微弧氧化膜反应形成的氧化物层会影响薄膜的铁电性能。     

BaTiO_3粉体中Ti/Ba比分析方法的比较

提出了用ＫＯＨ熔融分解ＢａＴｉＯ３粉体〔１〕，再用浓ＨＣｌ酸化后，用感应耦合等离子体发射光谱法（ＩＣＰ—ＡＥＳ法）测定试样中的Ｔｉ／Ｂａ比，并与化学分析法的结果作了比较，显示出ＩＣＰ—ＡＥＳ法简便，快速，结果更好。     

基于ERT技术的硫酸钡颗粒形成过程研究

采用电阻层析成像技术（ERT）实时监测反应器内横截面电导率变化,进而考查络合法形成球形硫酸钡颗粒的过程中溶液电导率变化趋势。在拟均相条件下,根据ERT实时监测、采集、分析硫酸钡颗粒生成过程中电导率变化情况,得出电导率变化曲线,并采用扫描电子显微镜方法观察随着反应时间变化硫酸钡颗粒的形态变化情况。实验结果表明,使用ERT监测电导率变化可以得出不同浓度条件下电导率变化趋势及其浓度条件下的最适宜反应时间,并验证了采用电阻层析技术（ERT）对研究硫酸钡颗粒的形成具有较高的灵敏度,可用于研究硫酸钡颗粒的形成最适宜时间;用扫描电子显微镜观察络合法合成硫酸钡最开始形成一种梭型颗粒,随着钡离子的缓慢释放,硫酸钡颗粒不断生长,最终得到粒度均匀、分散性良好的球形硫酸钡颗粒。     

Absence of ferromagnetism in ferroelectric Mn-doped BaTiO3 nanofibers

Pure and Mn-doped barium titanate nanofibers were synthesized by the electrospinning method. The morphology, microstructure and crystal structure of as-spun and annealed composite nanofibers were characterized by scanning electron microscopy and transmission electron microscopy. After annealing at 850°C, we obtain nanofibers a few μm long, formed by nanoparticles of irregular shape with sizes around 100 nm. X-ray diffraction and Raman spectroscopy show that a partial phase transition from tetragonal to hexagonal takes place for BaTi_0.90Mn_0.10O₃. Vibrational phonon modes were calculated for BaTiO₃ within the density functional theory (DFT) framework. Ferroelectricity has been probed on pure and Mn-doped BaTiO₃ nanofibers, by means of piezoresponse force microscopy in an atomic force microscope, confirming the polar domain switching behavior of the fibers. The measured piezoelectric coefficient d₃₃ were 31 and 22 pm/V for BaTiO₃ and BaTi_0.90Mn_0.10O₃. Magnetic properties of the samples were probed in a superconducting quantum interference device. Diamagnetic and paramagnetic behaviors were found in pure and Mn-doped samples, respectively.     

钛酸钡制备新方法研究

用ＢａＣｌ２．２Ｈ２Ｏ和Ｈ２ＴｉＯ３作反应物,（ＮＨ４）２ＣＯ３作沉淀共沉淀法制备钛酸钡。研究了（Ｎ４）２ＣＯ３和ＢａＣｌ２．２Ｈ２ｏ及ＢａＣｌ２．２Ｈ２Ｏ和Ｈ２ＴｉＯ３的配比、反应温度和时间、煅烧温度和时间、液固比对产品质量的影响。     

掩蔽锶-铬酸钡-碘量法测定碳酸锶中钡

采用乙二胺四乙酸二钠掩蔽锶,在ＰＨ值为５．９条件下,钡离子重铬酸钾生成铬酸钡沉淀,分离后,用碘量法测定。相对标准偏差１．０２％－２．１７％,加标回收率９５％－１０３％。     

Electrophoretic Deposition and Characterization of Micrometer-Scale BaTiO3 Based X7R Dielectric Thick Films

Uniform and relatively dense BaTiO₃ thick films of 1–5 μm were prepared by an electrophoretic deposition process using submicrometer BaTiO₃ powders (mean particle size: ∼0.2 μm). Two different BaTiO₃ powders and solvent media were used to investigate the film quality and thickness control. The surface charge mechanism of BaTiO₃ particles was explained according to the observed results. The microstructures were examined by means of SEM. The experimental results show that the thickness could be controlled independently of suspension concentration by keeping a constant applied voltage and a constant current drop in a given suspension. BaTiO₃ thick films have good insulation resistance and dielectric properties such as a dielectric constant and a dissipation factor that are compatible with the data from conventional tape-cast BaTiO₃ thin layers.