Pr和Co共掺杂BiFeO3结构和多铁性的研究

溶胶-凝胶法制备了BiFe0.95Co0.05O3、Bi0.95 Pr0.05FeO3和Bi0.95Pr0.05Fe0.95Co0.05O3样品。X射线衍射仪、铁电分析仪和振动样品磁强计测量与分析了样品结构、铁电和铁磁性能。结果表明:共掺杂的样品磁性有所增强,这与样品的结构变化有关。Pr掺杂提高了材料的铁电性能,这是因为Pr掺杂减少了氧空位。     

熔盐法快速合成BiFeO3粉体

以Bi2O3和Fe2O3为铋源和铁源,采用NaNO3和KNO3复合熔盐法快速合成BiFeO3粉体.研究了熔盐温度、熔盐比例、保温时间和冷却速率对合成粉体物相演变的影响,探讨了复合熔盐法合成BiFeO3的形成过程.熔盐温度为500℃时,Bi2O3和Fe2O3间开始反应生成Bi25 FeO40相;熔盐温度升高到600℃时,开始生成少量BiFeO3;熔盐温度继续提高到650℃与700℃时,几乎都形成纯相BiFeO3,但仍有微量Bi25 FeO40和Bi2 Fe4O9相.淬火抑制BiFeO3的分解,系统研究后发现:当熔盐比为5∶1时,700℃保温10 min后淬火合成粉体几乎为纯相BiFeO3.     

Pr、Ho共掺杂多铁性材料BiFeO_3的研究

采用溶胶-凝胶法制备了Pr、Ho离子共掺杂下的Pr_xHo_(0.05)Bi_(0.95-x)Fe O_3(x=0.05,0.10,0.15)样品,并表征了其结构特征,磁性能和铁电性能。实验结果表明,随着Pr元素含量的增加,样品从菱方R3c空间群转变为四方P4mm空间群,后又转变为正交Pnma空间群。相比于Pr、Ho离子单掺杂的样品,两种离子的共掺杂进一步提高了样品的磁性。样品的铁电性没有随Pr~(3+)掺杂含量单调变化,Pr~(3+)也不利于抑制漏电流。     

Ho掺杂BiFeO_3陶瓷的制备及介电性能

采用快速液相烧结法制备Ho掺杂BiFeO3系列陶瓷样品Bi1–xHoxFeO3(x=0,0.05,0.1,摩尔分数),X射线衍射物相分析表明:样品均为三方钙钛矿结构,掺杂微量的Ho3+可以有效消除样品中的Bi2Fe4O9杂相,获得单相Bi0.95Ho0.05FeO3。用HP4294A精密阻抗分析仪测量样品介电特性随频率、温度及偏置电压的变化关系,结果表明:Ho掺杂样品的室温相对介电常数(εr)比未掺杂的显著提高,测量频率为40Hz时,Bi0.9Ho0.1FeO3陶瓷样品的εr提高了1个数量级;观测到样品的介电峰,掺杂后介电峰向低温移动且强度显著增加,表明Ho掺杂在降低样品反铁磁Néel温度的同时增强了磁电耦合效应。讨论样品εr随偏置直流电压的变化关系,掺杂后出现明显的介电回滞现象,Ho掺杂可提高样品的剩余极化强度,改善样品的铁电性质。     

Pr3+掺杂对CaBi8Ti7O27陶瓷电学和光学性能的影响

采用传统固相法合成了Pr3+掺杂的CaBi8Ti7O27(CBT-BIT-xPr3+,0≤x≤0.020)共生铋层状结构多功能陶瓷材料,并研究了Pr3+掺杂对CaBi8 Ti7 O27陶瓷样品的结构、电学和光学性能的影响.结果表明,所有样品均为单一的正交相共生铋层状结构,适量的Pr3+掺杂未明显改变陶瓷样品的居里温度;随着Pr3+掺杂量的增大,陶瓷样品的介电损耗tanδ逐渐降低,压电常数d33由7 pC/N逐渐提升至11 pC/N;在450 nm波长光源的激发下,Pr3+掺杂后的样品可在611 nm处观测到一个较强的红光发射峰,并且其荧光强度随Pr3+掺杂量的增加而逐渐增强.     

Sn4+离子改性对BSBNT陶瓷的电储能特性影响研究

本文采用固相法制备了 Ba0.105Sr0.215Bi0.345Na0.325SnxTi1-xO3(简称BSBNSnxTi1-x,其中x=0,0.02,0.04,0.06,0.08)陶瓷,研究了 SnO2掺杂量对BSBNT陶瓷相结构、显微结构、介电及电储能特性的影响.结果表明:BSBNSnxTi1-x 陶瓷主晶相为赝立...     

Fe、Ni掺杂ZnO纳米材料的光学、磁性及光催化性能的研究

采用草酸-氨水两步共沉淀法制备了ZnO以及Fe、Ni掺杂的Zn_(1-x)M_xO(0.00≤x≤0.06)纳米材料,利用XRD、UV-Vis、PL和VSM对其结构、光学和磁学性质进行表征与分析,并以亚甲基蓝溶液为模拟污染物,评价了Zn_(1-x)M_xO材料的光催化降解性能,考察Fe、Ni掺杂对ZnO结构、光学、磁学性质和光催化降解性能的影响。结果表明,所有的Zn_(1-x)M_xO样品都具有六方纤锌矿结构;Fe、Ni掺杂提高了ZnO的可见光吸收,且随着掺杂浓度的增加,Zn_(1-x)M_xO样品的带隙宽度减小;ZnO和Zn_(1-x)M_xO材料的光致发光主要有蓝光发射和绿光发射;Fe、Ni掺杂后的Zn_(1-x)M_xO样品表现出明显的室温铁磁性,随着掺杂浓度的增加,Zn_(1-x)Fe_xO的磁性增加,而Zn_(1-x)Ni_xO的磁性减小;Fe、Ni的掺杂浓度对ZnO的光催化降解性能产生较大的影响,高浓度掺杂反而降低了ZnO的光催化降解性能。     

Pr~(3+)掺杂SrBi_2Ta_2O_9陶瓷的铁电及介电性能研究

以氧化钽为钽源,采用溶胶-凝胶法合成SrBi2Ta2O9(SBT)、Pr0.2Sr0.8Bi2Ta2O9(SPBT)粉体。用X射线衍射技术(XRD)对所制备的SBT、SPBT粉体进行结构表征,并对其介电、铁电性能进行了测试分析。实验结果表明:Pr3+离子掺杂未改变SBT粉体的晶相,但是会使得SBT的介电常数增大,不过随着测试频率的增加介电常数仍然逐渐下降。另外SBT的铁电性能也随着Pr3+的掺杂有了显著的提升。     

Mn掺杂对BiFeO_3陶瓷的电性能影响

采用Bi(NO)3.5H2O.和Fe(NO3)3.9H2O为原料,乙二醇甲醚为溶剂,冰醋酸为脱水剂,Mn(CH3COO)2.4H2O为掺杂剂,通过两步法合成了Mn掺杂BiFeO3(BFO)陶瓷。研究了Mn掺杂对BiFeO3陶瓷的结构和性能的影响。XRD测试表明,Mn掺杂可以明显抑制BFO陶瓷中的杂相(Bi25FeO40、Bi2Fe4O9)和缺陷的生成。SEM测试表明Mn掺杂对BFO陶瓷在两次低温烧成中能够很好地结晶并且晶粒均匀。利用PremierⅡ型综合铁电测试仪对BFO的漏电和铁电极化进行了测试,测试表明Mn掺杂可以显著的改善BFO的漏电特性,漏电流从由最初的10-4Amps降低到10-6Amps,降低了两个数量级。铁电极化测试表明Mn掺杂样品的剩余极化从20Kv/cm下1.1uc/cm2提高到2.5～4.3uc/cm2。此外利用Hp4294A阻抗分析仪在常温常压下对BFO的介电性能进行了研究。     

基于固态法制备Sr_(1-1.5x)Bi_xTiO_3陶瓷的特性研究

Sr Ti O3属于ABO3型钙钛矿结构,具有良好的固溶能力,通过掺加杂质元素改善其性能。本研究利用固态法制备Sr_(1-1.5x)Bi_xTiO_3陶瓷(x=0.00、0.01、0.04、0.07、0.10),并探讨了Bi掺杂对其结构与介电常数的影响。研究结果表明:Bi掺杂量x≥0.04时陶瓷的晶体结构是以立方晶与四方晶两相共存的形式存在,而Bi2+在Sr Ti O3结构中的固溶极限为x≤0.01,当x=0.04时陶瓷的最大介电常数约为1 200,相变温度则随x增加而逐渐向高温度方向偏移。     

P_(204)-HCl-H_3AOH体系萃取Pr(Ⅲ)的机理分析与萃取平衡常数

在pH1、0pH≤1两种不同pH条件下,采用原子吸收光谱测定P204-HCl-H3AOH体系萃取P(rⅢ)过程两相中的Pr浓度,分别考察酸度和萃取剂浓度对Pr的分配比的影响,通过对P204+煤油体系以及P204-HCl-H3AOH体系负载Pr有机相进行红外光谱测试分析探究P204-HCl-H3AOH体系萃取Pr的机理,并确定萃取平衡常数。研究结果表明,当pH1时,萃取过程的实质是Pr离子与P-OH置换,遵循阳离子交换机制。其萃取平衡常数KPr为10-1.26;当0pH≤1时,萃取过程较为复杂,柠檬酸的存在阻碍了P204二聚体的形成,萃取过程是由P=O基团与P-OH基团同时参与与Pr的配合作用,其配合机制为阳离子交换机制和溶剂化配合双重机制,该机制增强了对Pr的萃取能力使萃取容量提高。其萃取平衡常数KPr为100.40。     

Suppression of inherent ferromagnetism in Pr-doped CeO(2) nanocrystals

Ce(1-x)Pr(x)O(2-δ) (0 ≤x≤ 0.4) nanocrystals were synthesized by self-propagating method and thoroughly characterized using X-ray diffraction, Raman and X-ray photoelectron spectroscopy and magnetic measurements. Undoped CeO(2) nanocrystals exhibited intrinsic ferromagnetism at room temperature. Despite the increased concentration of oxygen vacancies in doped samples, our results showed that ferromagnetic ordering rapidly degrades with Pr doping. The suppression of ferromagnetism can be explained in terms of the different dopant valence state, the different nature of the vacancies formed in Pr-doped samples and their ability/disability to establish the ferromagnetic ordering.     

Li2B4O7-Bi2O3-WO3玻璃的光学性能研究

采用熔融淬冷方法制备了(100-x)Li2B4O7-x(Bi2O3·WO3)(5≤x≤20)玻璃.采用比重计测定了玻璃密度,分光光度计测量了玻璃的吸收光谱,V棱镜折射仪测量了玻璃折射率.结果表明,随着Bi2 O3·WO3含量的增加,玻璃样品的密度和摩尔体积增大,而氧堆积密度减小;玻璃的吸收光谱中截止波长逐渐向长波方向移动,玻璃的间接跃迁光学带隙、Urbach能和费米能逐渐减小,折射率增大.光学性能的变化和玻璃网络中部分桥氧转变为非桥氧有关.     

Structural,microstructural, ferroelectric and photoluminescent properties of praseodymium modified Ba0.98Ca0.02Zr0.02Ti0.98O3 ceramics

The ‘x’ wt% (x = 0, 0.02, 0.04 and 0.06) Pr₆O₁₁ modified Ba_0.98Ca_0.02Zr_0.02Ti_0.98O₃ (BCZT – x Pr) piezoelectric ceramics have been fabricated by the solid state reaction method with sintering at 1450 °C (x = 0) and 1350 °C (0.02 ≤ x ≤ 0.06) for 2 h. The impact of Pr concentration on the structural, microstructural, photoluminescence and ferroelectric properties has been systematically investigated. The x-ray diffraction (XRD) patterns revealed the co-existence of tetragonal and orthorhombic phases at room temperature upto x = 0.04 Pr concentration. The grain size was found to decrease upto x = 0.04 Pr content. Room temperature Raman spectroscopy results were consistent with the XRD results. The photoluminescence (PL) spectra showed significant emissions consisting of strong blue (489 nm), green (528 nm) and red (649 nm) wavelengths. The emission intensities of PL spectrum were strongly Pr concentration dependent and a maximum value was obtained for 0.04 Pr modified BCZT ceramic. Further, a large remnant polarization (2P_r ~ 13 µC/cm²) and low coercive field (E_C ~ 22 V/cm) were obtained for BCZT – 0.04 Pr ceramic. The crystal structure and microstructure affect the photoluminescence and ferroelectric properties. Such properties of 0.04 Pr modified BCZT ceramic make it the potential candidate for novel integrated and multifunctional devices.     

Structural evolution of thermal sprayed bismuth sodium titanate piezoelectric ceramic coatings

The structural evolution of lead-free piezoelectric bismuth sodium titanate (BNT) coatings with excess Bi derived from thermal spray process was investigated with transmission electron microscopy (TEM). Bi-rich composition was identified as the nucleation agent of the BNT perovskite phase, and fine-grained microstructure was obtained with more excess Bi. The Bi-rich composition of the perovskite phase crystallized from melt was Bi_xNa_yTiO₃ (0.5 ≤ X ≤ 0.55, 0.46 ≤ y ≤ 0.5). The crystallization of the Bi-rich BNT perovskite phase first from liquid precursor phase would result in continuous depletion of Bi composition in the residual amorphous phase, and thus Ti-rich amorphous phase in the as-deposited coating and sodium titanate secondary phase in the heat-treated coating formed in the composition without enough access Bi. The results and analyses suggest only appropriate compensation with adequate amount of excess Bi can realize single perovskite phase in thermal sprayed BNT-based coatings and hence the superior piezoelectric performance property.     

The enhancement of the Ce-solubility limit and saturation magnetization in the Ce0.25BixPryY2.75-x-yFe5O12 garnet synthesized by the conventional ceramic method

This paper has focused on the structural and magnetic properties of Ce_0.25Bi_xPr_yY_2.75-x-yFe₅O₁₂(x = 0.15, 0.20, 0.25) and (y = 0.25, 0.5) prepared by the solid-state method. The structural and microstructural evaluations were carried out by the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), Raman Spectroscopy (RS) and Fourier-transform infrared spectroscopy (FTIR). Furthermore, the magnetic properties were studied through a vibrating sample magnetometer (VSM). As it can be obtained from the XRD patterns, a single garnet phase with high purity has been formed in all samples in the sintering condition. Also, the FTIR analysis confirmed the formation of the garnet phase and related inorganic bonding. Raman spectroscopy reveals the dominant garnet phase with good incorporation of the Bi, Pr and Ce dopants into the garnet structure. XPS confirmed the presence of Ce⁴⁺ and also its value was measured from the peak areas. The results showed that the amount of Ce⁴⁺ in all the samples is lower than 10%. According to the results, by increasing the Bi content from x = 0.15 up to x = 0.25, saturation magnetization (M_s) increased from 29.31 to 37.79 emu/g, and by enhancing the Pr concentration from x = 0.25 to x = 0.5, this magnetic characteristic enhanced from 29.31 to 33.16 emu/g. Furthermore, the Ce-solubility limit was enhanced from x = 0.2 to x = 0.25 by the charge compensation mechanism. An increase in the Ce-solubility limit and also the saturation magnetization led to an enhancement in the magneto-optical and magnetic properties of YIG for telecommunication applications and memory storages, respectively.     

Photoluminescent Properties of (Ca,Zn)TiO3:Pr,B Particles Synthesized by the Peroxide-Based Route Method

(Ca_{1− x} ,Zn _x )TiO₃:Pr, B red phosphor particles were prepared using the peroxide-based route and their photoluminescent (PL) properties were investigated by changing the sintering temperature, the concentration of the activator, the ratio of Ca to Zn, and the amount of H₃BO₃ flux. For the CaTiO₃:Pr phosphor, a pure perovksite-type CaTiO₃ phase was formed when the sintering temperature was 700°–800°C. It was found that the substitution of Zn atoms instead of Ca considerably enhanced the 614-nm red emissions. The PL intensity of (Ca_{1− x} ,Zn _x )TiO₃:Pr phosphor was also additionally improved by adding an H₃BO₃ flux. Finally, the optimized phosphor Ca_0.85Zn_0.15TiO₃:0.001Pr,0.1B showed the highest PL intensity.     

Phase equilibria in the Bi2O3-CuO-Nb2O5 ternary system

A complete subsolidus ternary phase diagram of the Bi₂O₃-CuO-Nb₂O₅ (BCN) system was constructed. Careful firing control and phase analysis were applied to determine the phase assemblages and compatibilities over a wide range of temperatures, i.e. 700–925 °C. Phase-pure BCN pyrochlores were found to crystallise in cubic symmetry, space group Fd3m, No. 227 with lattice constants in the range of 10.4855 (5)<x<10.5321 (3). The mechanism of this limited subsolidus series could be represented by a general formula, Bi_3.08−xCu_1.84+2x/9Nb_3.08+7x/9O_14.16+6x/9 (0≤x≤0.36) wherein the reduction in Bi content was compensated by a proportion amount of copper and niobium together with non-stoichiometry in oxygen.     

CoFeZrRE非晶薄膜的各向异性研究

研究了磁性稀土元素 (RE)的种类和含量 (0≤x≤ 3) ,对非晶态 (Co73 Fe2 0 Zr7) 10 0 -x (RE) x 薄膜各向异性的影响 ,并着重探讨该类薄膜中出现的平面单轴各向异性 (Ku)和垂直各向异性 (Kp)的起源问题。薄膜是在外加磁场中溅射而成。当掺入的稀土元素为Nd ,Pr,Dy和Tb时 ,获得了显著的平面单轴各向异性Ku ,且Ku与稀土元素的单离子各向异性密切相关。当稀土元素为Gd和Sm时 ,则会出现双轴各向异性 (Ku和Kp) ,这主要是成膜温度高于临界温度时 ,同时形成了 2种局域性的异质的磁结构。     

Partial Bi-Sr-Cu-O Subsolidus Diagram at 800°C with and without Lithium Carbonate

Solid-phase relationships have been determined for the Bi₂O₃–SrO–CuO system at 800°C in air with and without Li₂CO₃ mineralizer. Two ternary compounds were detected with Bi:Sr:Cu ratios of approximately 2:2:1 and a solid-solution phase 11−;x:9+x:5 with 0x0.4. The solid-solution phase is a 9 K super-conductor at x=0.4. Two additional compounds with Bi:Sr:Cu ratios of approximately 4:9:1 and 2:7:2 are apparently stabilized by the presence of Li₂CO₃, but do not form without it. X-ray crystallographic data are provided for each compound. Ramifications for quaternary Bi:Sr:Ca:Cu-O superconductors are discussed.