Bi掺杂对Ba_(6-3x)La_(8+2x)(Ti_(0.95)Zr_(0.05))_(18)O_(54)(x=2/3)陶瓷的烧结性能和介电性能的影响

采用传统固相反应法制备Ba6-3x(La1-mBim)8+2x(Ti0.95Zr0.05)18O54(x=2/3)微波介质陶瓷,研究Bi掺杂对Ba6-3xLa8+2x(Ti0.95Zr0.05)18O54(x=2/3)陶瓷的烧结性能、微观结构以及介电性能的影响。结果表明:当0m0.4时,Bi3+取代A1位的La3+生成单相类钨青铜型固溶体;当Bi3+的掺杂量超过这个范围时,La0.176Bi0.824O1.5作为第二相出现在固溶体中;Bi3+的掺入使Ba6-3xLa8+2x(Ti0.95Zr0.05)18O54(x=2/3)陶瓷的烧结温度从1400℃降低到1300℃,同时,其介电常数大幅度提高,谐振频率温度系数减小,但品质因数急剧减小;当m=0.05时,1350℃下保温2h烧结获得的陶瓷具有微波介电性能,εr=88.63,Q·f=4395GHz,τf=6.25×10-6/℃。     

氧化铝掺杂对Ba0.6Sr0.4(Zr0.2Ti0.8)O3陶瓷介电性能的影响

Zr4+取代Ti4+的Ba0.6Sr0.4(Zr0.2Ti0.8)O3固溶体在降低介电常数的同时,保持了BST固溶体优异的可调性。为降低BST材料的介电损耗和介电常数,以氧化铝为改性剂对Ba0.6Sr0.4(Zr0.2Ti0.8)O3材料(BSZT材料)进行了掺杂。随着氧化铝掺杂质量分数从1%到10%增加,BSZT材料的介电常数从5000降低到了1550(100kHz),介电损耗降低到0.001(100kHz)以下,而材料的介电可调性保持在35%左右(1.5kV/mm)。X射线衍射图谱表明,烧结后得到的BSZT材料具有典型的钙钛矿结构。扫描电子显微镜观察表明,氧化铝的掺杂使得陶瓷致密度较高,晶粒均匀。     

B2O3掺杂钇铁氧体的低温烧结及磁性能研究

用传统陶瓷工艺制备了B2O3掺杂的Y1.05Bi0.75Ca1.2Fe4.4V0.6O12铁氧体,并对其低温烧结特性进行了研究.结果表明:掺杂适量的B2O3能够明显降低铁氧体的烧结温度且对磁性能影响显著.当B2O3掺杂量为0.025wt%、烧结温度为1040℃时,可获得晶粒大小均匀、结构致密的铁氧体,其饱和磁感应强度为4.82×10-2T.     

La_(2/3)Ba_(1/3)MnO_3∶Ag_x多晶靶材制备及其性能

采用化学共沉淀法制备了不同Ag掺杂量的La2/3Ba1/3MnO3∶Agx(x为摩尔分数,x=0.00、0.02、0.08、0.10、0.20)多晶靶材,通过XRD、SEM和R-T对La2/3Ba1/3MnO3∶Agx靶材的结构和性能进行测试分析,实验结果表明:所得样品为正交晶系钙钛矿结构;掺Ag(x=0.02、0.08、0.10、0.20)样品比未掺Ag样品的金属-绝缘转变温度Tp值低;随着烧结温度和Ag掺杂量的升高,金属-绝缘转变温度Tp随之增加;随着Ag掺杂量增加,电阻率归一化值先增大后减小。La、Ba、Mn元素的摩尔分数与理论设计的数值基本相同,O元素在烧结过程中缺失较严重,Ag元素的摩尔分数也较低,这与Ag在高温烧结时的挥发有关。     

高压下Fe84Nb4W3B9纳米晶软磁块体合金的制备

采用机械合金化(MA)法和低温高压快速烧结工艺制备了Fe84Nb4W3B9软磁合金粉末及其块体合金,并研究了粉末的晶粒尺寸、热稳定性和块体合金的相组成,晶粒大小以及相对密度与烧结条件的关系.结果表明(1)MA60h后,可获得单相α-Fe纳米晶(8.6nm)过饱和固溶体粉末(2)在MA粉末DSC升温曲线中,分别出现3个强弱不一的放热峰,依次发生了畸变的纳米晶过饱和固溶体的结构弛豫、纳米晶粒长大以及固溶体的相分解过程;(3)在P=5.5GPa,t=3min的烧结条件下,当Pw≥980W后,可获得相对密度98.2%以上、单相α-Fe纳米晶(20.3nm)块体合金,其磁性能为比饱和磁化强度Ms=154.0emu·g-1,矫顽力Hc=7.474×103A·m-1.     

Fe73.5 Cu1 Nb3 Si13.5 B9机械合金化纳米晶粉末的特种烧结及磁性能

研究了放电等离子烧结和高压烧结工艺条件对MA Fe73.5Cu1Nb3Si13.5B9纳米晶粉末的烧结块体合金的组织结构与磁性能的影响.结果表明:球磨70 h后,获得了单相a-Fe纳米晶(约9.5 rm)过饱和固溶体粉末;DSC升温曲线中,出现4个不同强度的放热峰,依次发生了纳米晶过饱和固溶体的结构弛豫、非晶晶化以及过饱和固溶体相析出等过程,且相析出过程分两个阶段完成;在p=30 MPa,t=5 min放电等离子烧结(SPS)条件下,当温度达到1 050℃后,可获得相对密度为98.9%、主相为α-Fe的纳米晶(100nm)块体合金,其中,B3=1.34 T,Hc=7.34 kA/m,在p=5.5 GPa,t=5 min条件下,当Pw=1 150 W后,可获得相对密度约99.1%、单相α-Fe纳米晶(21.4 nm)块体合金,其中,Bs=1.14 T,Hc=8.22 kA/m.     

Zn掺杂对LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2结构与电化学性能的影响

用溶胶凝胶法制备了Li Ni1/3Co1/3-x Mn1/3Znx O2(x=0,1/24,2/24,4/24)锂离子电池正极材料。由X射线衍射和扫描电镜对其分析结果表明,Zn掺杂不改变Li Ni1/3Co1/3Mn1/3O2的α-Na Fe O2层状结构,当掺杂量达到4/24时,杂相产生。电化学研究表明,当Zn掺杂量为2/24时,Li Ni1/3Co1/3Mn1/3O2首次放电容量由未掺杂的169.2 m Ah·g-1降低为160.1m Ah·g-1,但循环性能明显提高,30次循环后的容量保持率由未掺杂的89.2%升至97%。并且在20、40、60和80 m A·g-1不同的电流密度下继续循环20次后,当再次恢复到20 m A·g-1的电流密度时,放电容量可恢复到150.3 m Ah·g-1。     

烧结温度对PMSZT压电陶瓷性能的影响

探讨了烧结温度对SiO2掺杂锑锰锆钛酸铅Pb(Mn1、3Sb2、3)0.05Zr0.47Ti0.48O3(简称PMSZT)压电陶瓷性能的影响.通过X射线衍射及扫描电镜分析Pb(Mn1、3Sb2、3)0.05Zr0.47Ti0.48O3 0.1%(SiO2)(质量分数)陶瓷的相组成和显微结构.结果表明合成温度900℃时,可以得到钙钛矿结构.对于适量SiO2掺杂PMSZT压电陶瓷,可以在1100～1150℃时烧结实现致密化,并且介电压电性能较好,当烧结温度为1100℃时综合性能最佳,E33T/ε0=1290,tanδ=0.45%,d33=264 pC/N,Kp=0.59,Qm=2400.     

溶胶-凝胶法制备La0.67Sr0.33MnO3:Agx多晶材料及其性能

采用溶胶-凝胶法制备La0.67Sr0.33Mn O3∶Agx(LSMO∶Agx,x为摩尔百分比,x=0,0.04,0.08,0.10,0.20)多晶材料。通过XRD和R-T对LSMO∶Agx多晶材料的结构和性能进行分析。结果表明:在950、1050℃烧结的样品具有良好的单相结构。1050℃烧结时,Ag进入晶格替换A位La3+或Sr2+,使晶胞发生畸变、晶胞体积增大。Ag掺杂明显降低了样品电阻率,950℃烧结的Ag掺杂样品的电阻率降低了近两个数量级。提高烧结温度有助于改善LSMO材料的Tp和TCR。烧结温度由950℃变化到1050℃时,x=0样品的Tp增加了将近10 K,x=0.04样品的TCR从0.09%K-1上升到0.50%K-1。Ag掺杂能有效改善LSMO材料的电学性能。     

YF_3掺杂对Ba_(0.6)Sr_(0.4)TiO_3介电可调性的影响

采用传统工艺制备了YF_3掺杂的Ba_0.6Sr_0.4TiO_3陶瓷材料,研究了YF_3掺杂比例对钛酸锶钡材料结构及介电性能的影响.结果表明:烧结后得到的BSTO材料具有典型的钙钛矿结构;YF_3掺杂具有降低Ba_0.6Sr_0.4TiO_3材料的介电常数、细化陶瓷晶粒和提高介电常数温度稳定性的作用.在氟化钇掺杂比例1%时介电常数降至1887(100 kHz),介电可调性达到30%(1.5 kV/mm)以上, 各掺杂比例的钛酸锶钡材料的介电损耗均在1%以下.     

PMN-PNN-PT陶瓷晶粒异常长大研究

采用两步法和等离子放电烧结技术制备出了致密的单一钙钛矿相的PMN-PNN-PT陶瓷,对其高温热处理后晶粒异常长大进行了研究.发现添加5%(质量分数)过量PbO有助于晶粒的异常长大,观察到了3种典型的异常长大晶粒,为下一步固态法制备该组成单晶打下了基础.     

PMN-PNN-PT单晶的固相法生长研究

采用两步法和埋入PMN-PT单晶为模板的等离子放电烧结（SPS）技术制备出了致密的单一钙钛矿相的PMN-PNN-PT陶瓷，随后在1200℃下退火100h来诱导晶体的生长。实验结果表明，PMN-PNN-PT单晶〈111〉方向的生长速度明显快于〈001〉方向，而〈111〉方向生长的晶体形状为V字形，这是由钙钛矿结构的生长机理决定的，钙钛矿结构晶体的生长是通过〈001〉方向的层状生长来实现的。     

A new sol-gel process for preparing Ba(Mg_(1/3)Nb_(2/3))O_3 nanopowders

Commercially available niobium (V) oxide [Nb2O5], with barium acetate [Ba(CH3COO)2] and magnesium acetate [Mg(CH3COO)2-4H2O] was used as the starting material in the sol-gel process for preparing Ba(Mg1/3Nb2/3)O3 (BMN) nanopowders. At first, Nb2O5 reacted with melting sodium hydroxide and transformed into dispersible oxide. The resulting glassy substance after cooling was dispersed and washed several times in distilled water to remove the Na ions. The as-prepared colloidal Nb2O5-nH2O was subsequently mixed with acetic solution of barium acetate and magnesium acetate according to the required molar proportions and followed by gelation. The ultrafine BMN powders were finally obtained after heat-treating the gel at 820℃for 1 h, and the as-sintered nanoceramics revealed a high relative density of 98.2%, and a high microwave Q-factor, of 10397 at 1.45GHz.     

Au/Fe(OH)3/LaFeO3催化剂的稳定性研究

以LaFeO3为载体,通过Fe(OH)3对载体进行改性,采用沉积沉淀法制备纳米金催化剂,并对催化剂进行XRD、XPS、AAS和BET测试,考察催化剂的活性和稳定性。结果显示,Fe(OH)3助剂的加入,对催化剂的活性提高不明显,但大大提高了催化剂在反应过程和放置过程中的稳定性。加入助剂的Au/Fe(OH)3/LaFeO3催化剂,由于Fe(OH)3和活性组分的相互作用,减缓了金颗粒的聚集,使得放置近半年的催化剂和新鲜催化剂具有相近的活性和稳定性。     

Structural evolution of mesoporous graphene/LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2 composite cathode for Li-ion battery

Layered LiMO_2(M=Ni,Co,and Mn) is a type of promising cathode materials for high energy density and high work voltage lithium-ion batteries.However,the poor rate performance and low power density hinder its further applications.The capacity fade is related to the structural transformation in the layered LiMO_2.In this work,the structural changes of bi-material cathode composed of mesoporous graphene and layered LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2(NCM) were studied via in situ X-ray diffraction(XRD).During different C-rate charge-discharge test at the voltage range of 2.5-4.1 V,the composite cathode of NCM-graphene(NCM-G) reveals better rate performances than pure NCM cathode.The NCM-G composite electrode displays a higher rate capability of 76.7 mAh·g~(-1) at 5 C rate,compared to the pure NCM cathode of 69.8 mAh·g~(-1)discharge capacity.The in situ XRD results indicate that a reversible phase transition from hexagonal H1 to hexagonal H2 occurs in layered NCM material during 1 C chargedischarge process.With the current increasing to 2 C/5 C,the structure of layered NCM material for both electrodes reveals few changes during charge and discharge processes,which indicates the less utilization of NCM component at high C-rates.Hence,the improved rate performance for bi-material electrode is attributed to the highly conductive mesoporous graphene and the synergistic effect of mesoporous graphene and NCM material.     

LiOH-Li_2CO_3低共熔混合锂盐体系合成LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2

利用低共熔组成的0.24LiCO3-0.76LiOH混合锂盐体系,与钴、镍、锰的球形氢氧化物按1.1:1混合,无需前期球磨,直接经二段控温程序制备出锂离子正极材料LiNi1/3Co1/3Mn1/3O2。X射线衍射分析表明合成的Li(Ni1/3Co1/3Mn1/3)O2结晶度高,具有规整的层状α-NaFeO2结构,扫描电镜显示产物颗粒均匀,振实密度高达2.89g·cm-3,显著高于用单一锂盐制备的同样产品(2.4g·cm-3)。充放电测试表明,材料具有良好的电性能,首次充放电容量为176和166mhA·g-1,循环50次后,材料的电性能没有明显的衰减。     

Effect of addition of Ba(W0.5Cu0.5)O3 in Pb(Mg1/3Nb2/3)O3-Pb(Zn1/3Nb2/3)O3-Pb(Zr0.52Ti0.48)O3 ceramics on the sintering temperature, electrical properties and phase transition

In this work, we report on the Pb(Mg_1/3Nb_2/3)O₃-Pb(Zn_1/3Nb_2/3)O₃-Pb(Zr_0.52Ti_0.48)O₃ (PMN-PZN-PZT) ceramics with Ba(W_0.5Cu_0.5)O₃ as the sintering aid that was manufactured in order to develop the low-temperature sintering materials for piezoelectric device applications. The phase transition, microstructure, dielectric, piezoelectric properties, and the temperature stability of the ceramics were investigated. The results showed that the addition of Ba(W_0.5Cu_0.5)O₃ significantly improved the sintering temperature of PMN-PZN-PZT ceramics and could lower the sintering temperature from 1005 to 920 °C. Besides, the obtained Ba(W_0.5Cu_0.5)O₃-doped ceramics sintered at 920 °C have optimized electrical properties, which are listed as follows: (K_p = 0.63, Q_m = 1415 and d₃₃ = 351 pC/N), and high depolarization temperature above 320 °C. These results indicated that this material was a promising candidate for high-power multilayer piezoelectric device applications.     

Structure and electrical properties of (1-x)BaTiO_3+(x)La_(2/3)-Sr_(1/3)MnO_3 composites

Liquid-phase sintering method was used to prepare BaTiO 3 powders and the structure and electrical properties of (1-x)BaTiO 3 +(x)La 2/3 Sr 1/3 MnO 3 (LSMO) composites were investigated. The results of X-ray diffraction showed that the prepared BaTiO 3 powders were pure and fine, indicating that sintering temperature was effectively lowered when the NaCl sintering aid was added. X-ray diffraction patterns of (1-x)BaTiO 3 +(x)La 2/3 Sr 1/3 MnO 3 (LSMO) composites showed that LSMO and BaTiO 3 phases were coex...     

Microwave properties of Ba(Zn1/3Ta2/3)O3 dielectric resonators

Ba(Zn_1/3Ta_2/3)O₃ (BZT) dielectric resonators were prepared by solid-state reaction. The starting materials were BaCO₃, ZnO, and Ta₂O₅ powders with high purity. The double calcined BZT pellets were sintered in air at temperatures of 1575, 1600, 1625, and 1650 °C for 4 h. The X-ray diffraction data allowed the study of the unit cell distortion degree and the presence of the secondary phases. A long-range order with a 2:1 ratio of Ta and Zn cations on the octahedral positions of the perovskite structure was observed with the increase of the sintering temperature. The dielectric constant of BZT resonators measured around 6 GHz was between 26 and 28. High values of Q × f product (120 THz) were obtained for BZT resonators sintered at 1650 °C/4 h. The temperature coefficient of the resonance frequency exhibits positive values less than 6 ppm/°C. The achieved dielectric parameters recommend BZT dielectric resonators for microwave and millimeter wave applications.     

(Ba1-xSrx)(Zn1/3Nb2/3)O3固溶体系统的晶体结构

XRD分析表明,(Ba1-xSrx)(Zn1/3Nb2/3)O3系统中生成了一定的第二相,第二相的形成与ZnO的挥发有关.随着Sr含量的增加,晶体结构由无序的立方相向有序的赝立方相转变.在低角度处出现了1:2超晶格衍射峰,在高角度处衍射峰展宽并右向偏移.(Ba1-xSrx)(Zn1/3Nb2/3)O3系统中氧八面体的畸变是相转变形成、有序相产生、晶体结构对称性下降及晶格常数a和c减小的根本原因.