Nb2O5掺杂对TiO2陶瓷性能的影响

在Nb2O5含量x为0.1～1.5%的范围内,研究了Nb2O5掺杂对TiO2压敏陶瓷电性能的影响.发现x＝0.7%的样品显示出最低的压敏电压(Eb=8.57V/mm )以及最高的相对介电常数2.385×104.分析认为Nb2O5掺杂的实质是Nb5 固溶于 TiO2中取代Ti4 使晶粒半导化,但掺杂量受晶格畸变作用有一定限制.     

原位热压合成Nb掺杂Al2O3/TiAl复合材料

利用Al-Ti-TiO2-Nb2O5体系的放热反应,原位热压合成了Nb掺杂Al2O3/TiAl复合材料.借助DTA结合XRD探讨了Al-Ti-TiO2-Nb2O5体系的反应过程,并采用XRD、OM和SEM研究了复合材料的物相组成及显微结构.结果表明:Al熔化的同时,体系发生了Al和Nb2O5的铝热反应,生成了NbO2和Nb等中间产物,并放出了较多热量,这些热量促使Ti和Al较早化合生成TiAl3,随即引发Al和TiO2较早的还原反应,进而促使材料在较低温度下致密烧结;产物由γ-TiAl、α2-Ti3Al、Al2O3和NbAl3相构成,Al2O3颗粒分布于基体交界处,存在一定的团聚;Nb2O5的引入,对基体γ-TiAl相和α2-Ti3Al相的的分布有一定的影响,使得基体晶粒细化,较好地改善了材料的力学性能.     

Nb2O5对ZTM-Al2O3烧结和性能的影响

研究了Ｎｂ２Ｏ５ｘ对ＺＴＭ－Ａｌ２Ｏ３烧结、微观结构和性能的影响,发现当Ｎｂ２Ｏ５含量低于１．０５％（质量分类,下同）时,它对烧结没有影响,甚至阻碍烧结：当Ｎｂ２Ｏ５含量大于１．０５％时,它可以显著促进烧结。Ｎｂ２Ｏ５的引入可以明显提高瓷体中ｍ－ＺｒＯ２含量,并使得瓷体机械性能得到大幅度的改善,微裂纹增韧被认为是瓷体性能改善的根本原因,另外,由于晶界玻璃相软化使得裂纹钝化和裂纹尖端应力集中消弱等原     

铌、钴掺杂BaTiO3及表面改性对BaTiO3/PVDF复合材料介电性能的影响

采用铌、钴氧化物共掺杂钛酸钡(BaTiO_3,BT)制备铌钴钛酸钡(BTNC)粉体,采用硅烷偶联剂KH550对BTNC进行表面改性,制得改性铌钴钛酸钡(R-BTNC)粉体,再采用溶液共混法与聚偏氟乙烯(PVDF)制得BTNC/PVDF复合材料,并对复合材料进行了表征。研究结果表明,KH550能有效地改善填料在基体中的分散性和相容性,BTNC的加入使得PVDF中具有极化效应的β相增加,在10~2 Hz,R-BTNC用量为50%(体积分数)条件下,制得的R-BTNC/PVDF复合材料的介电常数为79.4,介电损耗为0.0520。     

Al2O3基复合陶瓷的研究进展

介绍了Al2O3基复合陶瓷材料的研究进展状况,对目前已经研究的体系、制备工艺、力学性能及其增韧机理等做了一个简要的综述.     

Bi2O3掺杂对Nb2O5-TiO2电容-压敏双功能陶瓷的影响

研究了Bi2O3掺杂对Nb2O5-TiO2电容压敏双功能陶瓷材料的烧结温度,相对介电常数,非线性,压敏电压的影响.实验发现,烧结温度为1200℃,Bi2O3掺杂量为0.2%时,非线性系数α高达6.6148;Bi2O3掺杂量为1.0%时,相对介电常数εr高达1.3733×104.烧结温度在1450℃时,压敏电压最低,Eb=1.979 V·mm-1.     

Mg4Nb2O9/SrTiO3复合陶瓷的烧结特性和微波介电性能

制备Li_2CO_3-V_2O_5(LV)共掺杂0.6Mg_4Nb_2O_9-0.4SrTiO_3复合陶瓷,研究了LV掺杂对其烧结特性、相结构和微波介电性能的影响。结果表明:一定量LV掺杂使0.6Mg_4Nb_2O_9-0.4SrTiO_3复合陶瓷生成了Sr(NbTi)O_(3+δ)和MgO杂相,并使其致密化烧结温度降低(至1175℃);1.5%LV掺杂,在1175℃烧结5 h的样品具有较高的微波介电性能:τ_f=0.15 ppm/℃,ε_τ=20.1,Q·f=10240 GHz(at 8.5 GHz)。     

掺杂Yb2O3的氧化锆基固体电解质材料的研究

探讨了掺杂Yb2O3对氧化锆基固体电解质材料的电导性能的影响.实验结果表明,随着操作温度的提高,8YbSZ材料的电导性能得到大幅度的提高.与8YSZ的相比,8YbSZ烧结体具有更佳的电导率.在500℃的操作温度下所测的电导率就大于10-3 S·cm-1,完全符合中温固体电解质的基本要求.     

Analysis of Planar Defects in Nb2O5- and Bi2O3-doped BaTiO3 Ceramics

The structure and chemistry of planar defects in Nb2 O5- and Bi2O3-doped BaTiO3 ceramics that exhibit core-shell microstructures have been examined using a combination of conventional transmission (CTEM) and high-resolution (HREM) and scanning transmission (STEM) electron microscopy and microanalysis. In addition to ferroelectric domain boundaries within the core, twins and stacking faults were observed, both with interface planes lying along 1 1 1. Unlike the twins, stacking faults were observed only within the paraelectric shell region of the BaTiO3 grain; these planar defects are enriched in Nb and Bi relative to the surrounding matrix. The combined CTEM contrast analysis and HREM observations suggest a fault displacement vector normal to the fault plane of magnitude 1/2 1 1 1+x1 1 1(=0.1); a proposed fault structure is based on a double BiO33- layer with bismuth cations occupying barium sites and charge compensation by Nb5+ substitution in adjacent octahedral sites. In addition, the incorporation mechanism of Nb2O5 and Bi2O3 into BaTiO3is discussed with respect to microanalysis results.     

Defect profile and electrical properties of Nb2O5-doped BaTiO3 materials

This work deals with the changes in properties induced by the incorporation of donor ions into the BaTiO₃ lattice. We focused on the relationship between microstructural development and the defect profile of Nb-based compositions around the semiconducting–insulating transition at 0.3% of donor oxide. The results indicated that the defect structure that developed controlled both microstructural and electrical properties. On sintering slightly doped BaTiO₃, large semiconducting grains and low barium vacancy concentration were detected. This behavior was explained by considering an electronic compensation mechanism based on dopant incorporation. Further dopant addition led to a dramatic grain-growth inhibition and a clear transition to a material with higher resistivity. In addition, an extraordinary generation of barium vacancies was observed. Heavily doped materials consisted of core-shell structures with a Ti-rich phase surrounding BaTiO₃ grains. This phenomenon originated a significant grain-boundary barrier layer response.     

Aurivillius phase formation in Nb2O5 − and Bi2O3 − doped BaTiO3

The reaction sequence in the BaTiO₃–Nb₂O₅–Bi₂O₃ system leading to the core-shell microstructure that causes the temperature-stable dielectric response has been examined using X-ray diffraction. The starting oxides react to form bismuth oxide layer Aurivillius phases at low temperatures which, in turn, react with remnant oxides to form the tetragonal tungsten bronze phase, Ba₄Bi₂Ti₄Nb₆O₃₀, which acts as the source of dopants responsible for core-shell formation.     

La2O3-doped BaTiO3 thin films obtained by pulsed laser deposition

Abstract

La²O³-doped barium titanate (BaTiO³) thin films have been obtained by pulsed laser deposition. The structure and quality of deposited films were characterized by X-ray diffraction and scanning electron microscopy. A smooth surface was obtained when the films were deposited in 30 Pa ambient oxygen. The composition (elements and oxides) of the thin films were close to those of the target. The layer obtained by pulsed laser deposition from a target of BaTiO³ doped with 0.5 at.% La exhibits good dielectric characteristics: capacitance 88 pF, Curie temperature 59°C and dielectrics loss, tanδ, 0.084.     

Fe2O3掺杂MgTiO3-CaTiO3微波陶瓷的介电性能研究

采用固相法制备0.93MgTiO3-0.07CaTiO3-xFe_2O_3(摩尔分数x=0.01~0.025)微波介质陶瓷材料,研究添加Fe_2O_3后,体系的晶体结构、显微结构和微波介电性能之间的变化规律。利用XRD、SEM、网络分析仪对样品的相组成、微观结构、介电性能进行测试分析。研究表明:该复合陶瓷样品的致密度、介电常数和Q·f值随Fe_2O_3含量的增加先增大后减小。当x(Fe_2O_3)为0.015,在1290℃烧结4h时,获得最优的介电性能:εr=21.32,Q·f=37448GHz,τf=0.577×10-6/℃。     

BaTiO3-ZnNb2O6陶瓷介电及储能性能研究

采用固相法制备(1-x)BaTiO₃-xZnNb₂O₆ (x=0.5mol%, 1mol%, 1.5mol%, 2mol%, 3mol%, 4mol%) (简称BTZN)陶瓷, 研究了BTZN陶瓷的烧结温度、结构、介电性能和铁电性能。BTZN陶瓷烧结温度随着ZnNb₂O₆含量增加逐渐降低。XRD结果表明当ZnNb₂O₆含量达到3mol%时出现第二相Ba₂Ti₅O₁₂。介电测试结果表明随ZnNb₂O₆含量的增加, BTZN陶瓷介电常数逐渐减小, 而介电常数的频率稳定性逐渐增强。介电温谱表明所有BTZN陶瓷均符合X8R电容器标准。BTZN陶瓷的极化强度值随着ZnNb₂O₆含量的增加逐渐降低。当x=4mol%时, BTZN陶瓷获得240 kV/cm的击穿电场和1.22 J/cm ³的可释放能量密度。     

Sm2O3掺杂BaTiO3陶瓷的结构与电性能研究

采用溶胶-凝胶法制备了掺杂不同浓度Sm₂O₃(分别为0.001,0.002,0.003,0.005,0.007mol)的BaTiO₃陶瓷,并对其结构与电性能进行了研究.结果表明:Sm₂O₃掺杂BaTiO₃陶瓷的晶型在室温下为四方相,而且随着Sm₂O₃掺杂浓度的增加,BaTiO₃陶瓷的晶粒尺寸变小,说明Sm₂O₃掺杂对BaTiO₃陶瓷晶粒的生长有一定的抑制作用;Sm₂O₃掺杂BaTiO₃陶瓷的电阻率比纯BaTiO₃陶瓷明显下降,当添加量为0.001mol时,电阻率最小,.从4.3×109Ω·m下降为6.536×103Ω·m;Sm₂O₃掺杂BaTiO₃陶瓷的晶粒电阻随着温度的变化,呈现NTC效应,而晶界电阻随着温度的变化,呈现PTC效应,且晶界电阻远远大于晶粒电阻,说明该材料的PTC效应是由晶界效应引起的.     

Effect of the level of addition of Nb2O5/Co2O3 and Ba(Nb2/3Co1/3)O3 on the structure, microstructure, and dielectric properties of BaTiO3

In this work attempt is made to study the effects of the level of the addition of two dopant systems, that is, Nb₂O₅/Co₂O₃ and Ba(Nb_2/3Co_1/3)O₃ on the structure, microstructure, and dielectric properties of BaTiO₃(BT) prepared by ceramic route. For the BT samples doped with 2 and 3 at % Nb₂O₅/Co₂O₃ a broad maxima for _r–T variations was observed. Higher levels of addition, that is, 6, 8, and 10 at % Nb₂O₅/Co₂O₃, however, caused a drastic reduction in the magnitude of _r and vanishing of maxima peaks observed. The reduction in the magnitudes of the _r for these samples is related to the observed reduction of the tetragonality of doped BT samples as well as the existence of some non-ferroelectric extra phase, evidenced by our XRD analysis. The existence of this extra phase is also believed to be mainly responsible for the observed increase of the dielectric loss. For the BT samples doped with Ba(Nb_2/3Co_1/3)O₃ perovskite solid solution, the _r maxima peak could only be detected for the samples doped with 2 at %. In the case of the samples doped with 4, 6, 8, and 10 at % perovskite solid solution, however, a very uniform distribution of _r–T was observed. The increase of the level of dopant for these series of samples was also seen to give rise in the reduction of the magnitude of _r. However, this reduction was not as strong as the cases observed for the samples doped with 8 and 10 at % Nb₂O₅/Co₂O₃. XRD patterns obtained for these series of samples also revealed the reduction of tetragonality of the BT samples when doped with Ba(Nb_2/3Co_1/3)O₃. Further, microstructural studies carried out by scanning electron microscopy (SEM) on both series of samples revealed a contrasting picture. While a uniform grain size distribution was observed for the whole series of the samples doped with Ba(Nb_2/3Co_1/3)O₃, a non-uniform size distribution of grain sizes was observed in the case of samples doped with Nb₂O₅/Co₂O₃. This is thought to be due to the possible formation and non-uniform distribution of a liquid phase due to the formation of Ti-rich region in the shell region of Nb₂O₅/Co₂O₃-doped samples. The existence of such liquid phase, in case of Nb₂O₅/Co₂O₃-doped samples, would have the consequence of an increased rate of diffusion of Nb/Co into the BT cores leaving narrow compositional fluctuations for the shell regions.