(Ba_(1-α)Sr_α)_(4.8)(Sm_(0.7)La_(0.3))_(8.8)Ti_(18)O_(54)陶瓷的微波介电性能

采用固相合成法制备了(Ba(1-α)Srα)4.8(Sm0.7La0.3)8.8Ti18O54(α=0.1～0.5)系陶瓷,表征了该陶瓷的相组成和显微结构,测试了微波介电性能.结果表明:α=0.3时,(Ba(1-α)Srα)4.8(Sm0.7La0.3)8.8Ti18O54系陶瓷为单相的新钨青铜结构固溶体.α>0.3时,相继出现了第二相BaLa2Ti4O12和La0.66TiO2.993.随α的增加,(Ba(1-α)Srα)4.8(Sm0.7La0.3)8.8Ti18O54系陶瓷的相对介电常数(εr)先增大后有所波动,品质因数(Qf)先增大后减小,谐振频率温度系数(τf)单调减小.α=0.3时,在1 350℃烧结的陶瓷的微波介电性能最佳:εr=98.77,Qf=5184GHz,τf=10.9×10-6/℃,优于不掺杂的BaO-Sm2O3-TiO2陶瓷的.     

0.7CaTiO3-0.3Sm1-xAlO3陶瓷微波介电性能研究

采用固相反应法制备了0.7CaTiO3-0.3Sm1-xAlO3(CTSA,0≤x≤0.1)微波介质陶瓷,研究了Sm缺位对CTSA陶瓷的晶体结构、微观形貌以及微波介电性能的影响。结果表明,制备的CTSA陶瓷均为正交钙钛矿结构。少量的Sm缺位能够降低CTSA陶瓷的烧结温度,晶粒尺寸增加,同时气孔率增大,陶瓷的Q×f值也有显著提升。当x=0.025、烧结温度为1450℃时,CTSA陶瓷具有最佳微波介电性能:εr=45.2,Q×f=47280GHz和τf=+4.8 ppm/℃。     

CeO2/Ca0.7Bi0.15Na0.15TiO3复合陶瓷微波介电性研究

通过传统固相烧结法制备了(1-x)(Ca0.7Bi0.15Na0.15TiO3)-xCeO2(x=0.6、0.7、0.8、0.9)陶瓷,并对其晶体结构、表面形貌、元素化合价及微波介电性能进行了系统研究.结果 表明:所有组分陶瓷均含有与CaTiO3和CeO2结构相似的两相.在x=0.4中Ce存在两种价态Ce3+和Ce4.两相的存在导致了介电常数和谐振频率温度系数呈现线性变化,品质因数则表现为非线性变化.当x=0.9时,Ca0.7Bi0.5Na0.15TiO3-CeO2复合陶瓷微波介电性能较优,其εr=35.1,Q×f=10889.2 GHz和τf=27 ppm/℃.     

MnCO_3掺杂对BMN陶瓷结构及介电性能的影响EI北大核心CSCD

采用固相烧结法,探讨了MnCO_3掺杂降低Ba(Mg_(1/3)Nb_(2/3))O_3(BMN)烧结温度的机理,研究了MnCO_3掺杂量对BMN陶瓷微波介电性能的影响。结果表明,适量的MnCO_3掺杂可以促进烧结,有效降低BMN陶瓷的烧结温度,改善陶瓷的微波介电性能。当MnCO_3掺杂量为4%(质量分数)时,BMN陶瓷的烧结温度从纯相烧结时的1 550℃降低到1 250℃,表观密度ρ=6.36 g/cm^3,相对理论密度达到98.6%,并具有良好的微波介电特性:高相对介电常数ε_r=31.4,高品质因数与谐振频率的乘积Q·f=99 200 GHz(8 GHz),接近于零的谐振频率温度系数τ_f=3×10^(–7)/℃。     

MnCO_3掺杂对BMN陶瓷结构及介电性能的影响

采用固相烧结法,探讨了MnCO_3掺杂降低Ba(Mg_(1/3)Nb_(2/3))O_3(BMN)烧结温度的机理,研究了MnCO_3掺杂量对BMN陶瓷微波介电性能的影响。结果表明,适量的MnCO_3掺杂可以促进烧结,有效降低BMN陶瓷的烧结温度,改善陶瓷的微波介电性能。当MnCO_3掺杂量为4%(质量分数)时,BMN陶瓷的烧结温度从纯相烧结时的1 550℃降低到1 250℃,表观密度ρ=6.36 g/cm~3,相对理论密度达到98.6%,并具有良好的微波介电特性:高相对介电常数ε_r=31.4,高品质因数与谐振频率的乘积Q·f=99 200 GHz(8 GHz),接近于零的谐振频率温度系数τ_f=3×10~(–7)/℃。     

纳米Al_2O_3对CaTiO_3-(La,Nd)AlO_3陶瓷的烧结温度和介电特性的影响

为了降低Ca Ti O_3-(La,Nd)Al O_3(简称CT-LNA)陶瓷的烧结温度和提高其介电性能,研究纳米Al_2O_3对Ca Ti O_3-(La,Nd)Al O_3陶瓷的烧结温度和介电性能的影响。固相法制备粉料,采用XRD和SEM分析其晶相和显微结构,用网络分析测试样品的介电参数,结果表明,纳米Al_2O_3可促进陶瓷烧结,在1320~1400℃范围内可烧结成瓷,并具有较好的微波介电性能。当纳米Al_2O_3含量为50 wt%时,陶瓷在1340℃烧结可获得优良的微波介电性能:介电常数为42.6,Q×f值高达34,000GHz,频率温度系数为+4.8 ppm/℃。     

Zn2+掺杂对0.965MgTiO3-0.035SrTiO3微波介质陶瓷结构与性能影响研究

采用固相反应法制备了0.965 MgTiO3-0.035SrTiO3 (MST)微波介质陶瓷,选用Zn2+对MST陶瓷进行了A位离子掺杂,研究了不同Zn2+掺杂量对陶瓷烧结性能、晶相组成、显微结构及微波介电性能的影响.结果表明,Zn2的掺入促进了陶瓷的烧结,显著提高了陶瓷的致密度,且没有改变陶瓷的主晶相.在掺杂量小于0.04mol％范围内,随着Zn2+掺杂量的增加,陶瓷的介电常数增加,品质因素和频率温度系数略有降低.中间相MgTi2 O5的衍射峰强度随着Zn2+掺杂量的增加逐渐减弱直至完全消失.当Zn2掺杂量为x=0.03时,陶瓷的烧结温度由1380℃降低至1290℃,并呈现优异的微波介电性能:εr=22.51,Q×f=16689 GHz,τf=-4.52×10-6/℃.     

Ca_(0.6)La_(0.8/3)TiO_3-Li_(0.5)Sm_(0.5)TiO_3复合微波陶瓷的介电性能

采用传统固相合成法制备了xCa0.6La0.8/3TiO3-(1-x)(Li0.5Sm0.5)TiO3(CLT-LST)系列微波介质陶瓷材料,研究了该系列微波介质陶瓷的物相结构、表面形貌、介电性能。实验发现:随着Ca0.6La0.8/3TiO3含量的增多,CLT-LST样品XRD峰轻微左移。陶瓷组成对微波介电性能影响显著,复合体系CLT-LST的微波介电性能随着x值不同而连续变化:当x从0.2上升到0.6时,介电常数(εr)逐步增大,在x=(0.4~0.6),εr变化趋于稳定,达到较佳值;品质因数(Q·f)则先减小后增大再迅速减小;谐振频率温度系数(τf)逐渐从负值向正值方向移动。当复合体系组成为0.4Ca0.6La0.8/3TiO3-0.6(Li0.5Sm0.5)TiO3时,在1 250℃烧结4h所得到的微波介电性能较佳,εr=125;Q·f=2 680GHz;τf=7.0×106/℃。     

低温烧结Mg_4Nb_2O_9-0.75wt%V_2O_5-1.5wt%Li_2CO_3微波介质陶瓷及其性能研究

采用高能球磨法制备陶瓷,研究了0.75wt%V2O5和1.5wt%Li2CO3共掺杂对Mg4Nb2O9陶瓷的烧结性能和微波介电性能的影响。实验结果表明0.75wt%V2O5和1.5wt%Li2CO3共掺杂有助于Mg4Nb2O9陶瓷在烧结过程中形成液相,促进低温致密化烧结,进而降低陶瓷的烧结温度。900℃烧结Mg4Nb2O9陶瓷,结构致密、组织均匀,平均粒径0.75μm,εr=12.58,Q×f=5539 GHz。随烧结温度升高,晶粒长大,密度升高,εr和Q×f值增大。微波介电性能表征表明Mg4Nb2O9-0.75wt%V2O5-1.5wt%Li2CO3陶瓷在950℃下低温烧结,获得εr=13.07,Q×f=10858GHz的亚微米级陶瓷,其优良的微波介电性能使其有望成为新一代低温烧结低介高频微波介质基板材料。     

CaLa4Ti4O15微波介电陶瓷的制备和性能

采用固相法制备了Cata4Ti4O15系微波介质陶瓷.研究了不同预烧温度对CaLa4Ti4O15陶瓷烧结特性和微波介电性能的影响.在1 200℃预烧caLa4Ti4O15粉末.除CaLa4Ti4O15主相外,还存在部分CaTiO3,La2Ti2O7和La2TiO5混合相.在1 300℃和1 400℃预烧后.获得了六方类钙钛矿CaLa4Ti4O15单相.CaLa4Ti4O15粉末预烧后可饶结成高致密陶瓷(相对密度约97%),同时具有高机械品质因数与谐振频率的乘积(Q×f)值和近零谐振频率温度系数(Tf).1 550℃烧结的CaLa4Ti4O15陶瓷具有优异的微波介电性能:相对介电常数εr=45.1,Q×f=46087GHz,tf=-14.1 × 10-6/℃(预烧温度1 200℃);εr=-45.9,Q×f=48871GHz,tf=-14.4 ×10-6/℃(预烧温度1 300℃).     

WO3/BiOCl0.7I0.3光催化剂的制备及其光催化降解机理

通过简单的煅烧法和原位沉淀法制备了WO₃/BiOCl_0.7I_0.3复合光催化材料,利用X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线能谱(XPS)、紫外可见漫反射光谱(UV-Vis DRS)等表征手段对合成材料的微观形貌、化学组成等进行表征。并通过可见光催化降解20mg/L盐酸四环素来评价材料的光催化性能,结果显示,WO₃/BiOCl_0.7I_0.3复合材料较单一的BiOCl_0.7I_0.3和WO₃具有更优的光催化性能,其中W与Bi摩尔比为1∶15时,复合材料具有最高的光降解率,可见光下60min达到最高值93.84%,且四次循环试验后仍具有较好的光催化活性。对自由基捕获试验结果及电子自旋共振光谱进行分析,明确了h⁺和·O₂^-为光催化主要活性物质,提出WO₃/BiOCl_0.7I<...     

Ferroelectric and ferromagnetic properties of Mn-doped 0.7BiFeO3–0.3BaTiO3 solid solution

Binary solid solutions 0.7BiFeO₃–0.3BaTiO₃–x wt.% MnO₂ (x = 0, 0.2, 0.3, and 0.5) were prepared by a traditional ceramic process. All ceramic samples show single perovskite phase. The effect of manganese doping on structure, dielectric, ferroelectric and ferromagnetic properties, and resistivity was investigated. Results show that Mn-dopant can improve the sintering ability of the materials when MnO₂ content is below 0.3 wt.%. When MnO₂ content exceeds 0.3 wt.%, the sintering ability is weakened and the phase structure of 0.7BiFeO₃–0.3BaTiO₃ solid solution changes from rhombohedral into tetragonal phase. With increasing concentration of MnO₂, the resistivity increases at first and then decreases. Whereas the coercive electric field decreases at first and then increases, the remanent magnetization M_r increases and the coercive magnetic field decreases.     

Magnetic properties of La0.7Sr0.3MnO3 under the pressure and the transport property under the magnetic field

Polycrystalline La_0.7Sr_0.3MnO₃ sample (LSMO) was synthesized by the solid phase reaction; it exhibits the paramagnetic-ferromagnetic transition at T_c = 362 K at the ambient pressure; it is paramagnetic metallic state above T_c and the ferromagnetic metallic state below T_c. It was observed that the pressure effect depends on the temperature range: (a) In the paramagnetic region, the magnetization M hardly changes with the pressure P, that is, ΔM≈0. There exist the antiferromagnetic (AFM) coupled ferromagnetic clusters in the paramagnetic region, and the pressure enhances the AFM coupling. (b) In the temperature range around T_c, the pressure increases M, that is, ΔM > 0, with the concomitant increase in T_c; the average pressure coefficient dT_c/dP is 5.40 K/GPa at P = .74 GPa, much smaller than 15.47 and 15.90 K/GPa for La_0.7Ca_0.3MnO₃ and La_0.9Ca_0.1MnO₃, respectively, due to the different distortion degree of MnO₆ octahedra in Ca and Sr doped manganites. (c) In the temperature region below T_c, the pressure reduces M, that is, ΔM < 0. M is determined by the competition between the Mn³⁺-O-Mn⁴⁺ double exchange and the interparticle dipolar interaction. The pressure enhances the interparticle dipolar interaction, leading to a significant decrease in magnetization. The resistivity of LSMO exhibits the metallic behavior in the temperature range of 5 K~370 K; it decreases as the applied magnetic field H increases from 0 to 7 T, that is, the magnetoresistance effect which is more significant around T_c. The fitting to the low-temperature resistivity shows that the applied magnetic field reduces the scattering from the grain boundary, electron, phonon, and magnon, especially reduces the electron-electron scattering.     

Study on photoelectrochemical solar cells of nanocrystalline Cd0.7Zn0.3Se -water soluble conjugated polymer

Cadmium zinc selenide (Cd_0.7Zn_0.3Se) nanocrystalline thin films were chemically synthesized onto indium tin oxide (ITO)-coated glass substrate at relatively low temperature (<90 °C). The as-deposited films were annealed in air at 200, 300, and 400 °C for 60 min. The structure and surface morphology of the films were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The water-soluble conjugated polymer, poly(2-ethynyl-N-carboxy-propyl-pyridinium bromide) (LM3), with quaternary pyridinium salts was layered by dipping the as-deposited and annealed Cd_0.7Zn_0.3Se films in the aqueous polymer solution. This hybrid photoanode system was subjected to photoelectrochemical (PEC) study under a light illumination intensity of 80 mW/cm².     

Fe2O3原料的预处理对0.7BiFeO3-0.3BaTiO3陶瓷绝缘性与电性能的影响

BiFeO₃基无铅压电陶瓷常因漏电流较大而压电性能欠佳,然而,改善其绝缘性和电性能的方法都较为复杂,限制了其产业化生产与应用。本工作在不针对0.7BiFeO₃-0.3BaTiO₃陶瓷进行组分掺杂以及气氛烧结的条件下,仅通过简单的原料预处理(改变Fe₂O₃原料的干燥时间)即实现了其高绝缘性与高压电性能。研究结果表明,0.7BiFeO₃-0.3BaTiO₃陶瓷的晶粒尺寸和绝缘性随Fe₂O₃原料干燥时间的增加而增大,同时其电性能及温度稳定性也随之增强。当原料干燥时间为192 h时,样品晶粒尺寸最大,绝缘性最好,同时其压电性能(d₃₃=203 pC/N,k_p=0.33)和居里温度(T_c=460 ℃)也达到最佳。这为今后BiFeO₃基陶瓷压电性能的研究提供了一个新思路。     

BBS掺杂的Ca0．3（Li1/2Sm1/2）0.7TiO3微波介质陶瓷的中温烧结研究

采用传统电子陶瓷制备工艺,以42BaO-45B2O-13SiO2(BBS)玻璃为烧结助剂,制备了可以中温烧结的Ca0.3(Li1/2Sm1/2)0.7TiO3 微波介质陶瓷,对陶瓷的晶相组成、烧结性能及微波介电性能进行了系统研究.结果表明:通过液相烧结,BBS玻璃能有效降低Ca0.3(Li1/2m1.2)TiO3陶瓷的烧结温度,由1300℃降低至1000℃.XRD结果显示陶瓷主晶相为斜方钙钛矿,没有发现杂相.随着BBS添加量的增大,陶瓷的介电常数,品质因素以及频率温度系数均呈下降趋势,当BBS的添加量为10wt%时,1000℃下保温5h烧结的陶瓷的致密度、体积密度以及介电常数达到最大值,并具有良好的微波介电性能:ετ=62.5,Qf=1019GHz,τf=21.6ppm/℃.     

Enhanced resistance in Bi(Fe1-xScx)O3-0.3BaTiO3 lead-free piezoelectric ceramics: Facile analysis and reduction of oxygen vacancy

We reported a facile analysis and reduction of oxygen vacancy (${\mathrm{V}}_{\mathrm{O}}^{??}$) in 0.7Bi(Fe_1-xSc_x)O₃-0.3BaTiO₃ (0≤x≤0.08) ceramics. The leakage current mechanism was investigated intensively. Our results indicated that oxygen vacancies are the main cause for the high conductivity in BF-BT ceramics, and their concentration was quantitatively estimated from the Bi³⁺ content and the average oxidation state of iron. The ${\mathrm{V}}_{\mathrm{O}}^{??}$ concentration was effectively suppressed and the insulation resistance was enhanced by almost two orders of magnitude after doping 2%mol Sc³⁺. The enhanced insulation resistance contributed to excellent piezoelectric properties with d₃₃ = 165 pC/N, T_C = 505 °C, and k_p = 26%. The proposed analysis method used to quantify the ${\mathrm{V}}_{\mathrm{O}}^{??}$ concentration provides valuable indications to reduce the leakage current density and improve the piezoelectric properties of BF-BT based ceramic.     

LixNi0.7Co0.3O2 electrode material: Structural, physical and electrochemical investigations

The layered LiNi_0.7Co_0.3O₂ cathode material was synthesized by the combustion method using sucrose as fuel at 800 °C for 1 h, which leads to homogeneous size distribution with sub-micron particle size. The characterization of this material was realized using X-ray diffraction, scanning electron microscopy and completed by magnetic measurements. The Rietveld refinement shows the presence of 2.6% extra nickel in the interslab space. The presence of nickel ions in the lithium layers was confirmed by magnetization measurements. The 90° Ni-O-Ni ferromagnetic coupling is the main magnetic interactions. Lithium extraction from this phase occurs without major structural modifications. Cycling tests have shown a very good cycling stability at various current rates. Furthermore, this material delivers high reversible capacity of about 150 mAh/g in the 2.8-4.4 V range at the C/20.     

复合烧结助剂对Ca_(0.3)(Li_(0.5)Sm_(0.5))_(0.7)TiO_3微波介质陶瓷低温烧结与性能研究

研究了以Ca_(0.3)(Li_(0.5)Sm_(0.5))_(0.7)TiO_3(CLST-0.7)为基料,复合添加10 wt%CaO-B_2O_3-SiO_2(CBS)、4 wt%Li_2O-B_2O_3-SiO_2-CaO-Al_2O_3(LBSCA)和0～2 wt%CuO氧化物为烧结助剂的微波介质陶瓷的低温烧结行为及微波介电特性.结果表明:随着CuO添加量的增加,陶瓷体积密度、介电常数ε_r、无载品质因数与谐振频率乘积Qf值,都呈先增加后降低,频率温度系数τ_f呈降低的趋势.添加10 wt%CBS、4.0 wt% LBSCA和1.0 wt%CuO的CLST-0.7微波介质陶瓷,在900 ℃烧结5 h具有较佳的微波介电性能:ε_r ＝ 67.31,Qf ＝ 2197 GHz,τ_f＝40.28 ppm/℃.