Ni-LaFeO3的微波化学制备及气敏性能研究

利用微波化学法制备了Ni掺杂的LaFeO3粉体,并对其晶体结构和性能进行表征与分析,结果表明,Ni掺杂LaFeO3粉体为单一正交钙钛矿结构,没有杂相峰出现,且LaFe0.9Ni0.1O3颗粒呈椭球状,颗粒粒径约为178nm,颗粒分散性较好;LaFe0.9Ni0.1O3元件在工作温度为200℃时对5.0×10-4甲醛气体的灵敏度为9,且具有良好的选择性,响应和恢复时间分别是20和30s。     

双相质子导体BaCe0.9Y0.1O3-δ/La1.95Ca0.05Ce2O7-δ的制备及性能研究

采用固相反应法成功制备了双相质子导体BaCe0.9Y0.1O3-δ/La1.95Ca0.05Ce2O7-δ(7∶3、6∶4、5∶5、4∶6、3∶7)。用X射线衍射仪、扫描电子显微镜分别对样品的物相结构、微观形貌进行了表征,对样品在CO2和沸水中的稳定性进行了研究,并应用IM6e型电化学工作站测定了其在空气、氩气、湿润的4%H2/Ar 3种气氛从450～850℃的电导率。实验结果表明,不同比例复合的样品经1500℃烧结后均形成了明显的双相结构且获得了致密的烧结体。随着样品中La1.95Ca0.05Ce2O7-δ比例的增加,其对CO2和沸水的化学稳定性增加。在所研究的各种比例的复合材料中,BaCe0.9Y0.1O3-δ-La1.95Ca0.05Ce2O7-δ(3∶7)具有最高的电导率,850℃时在湿润的4%H2/Ar气氛下的电导率为2.49×10-2S/cm,电导活化能为1.13eV。     

SnO2(0.9)-Fe2O3(0.1)气敏材料的制备及气敏特性的研究

采用柠檬酸盐法制备SnO2(0.9)-Fe2O3(0.1)粉体材料.XRD结构分析表明,在750℃焙烧温度下制得的粉体材料中铁原子大部分进入SnO2晶格中,以SnO2(0.9)-Fe2O3(0.1)固溶体状态存在.采用750℃焙烧温度下制得的SnO2(0.9)-Fe2O3(0.1)固溶体为基体材料,制作旁热式气敏元件并考察其气敏特性.结果表明此类元件对乙醇、一氧化碳等还原性气体具有较高的灵敏度.同时元件长期稳定性良好,100天内元件阻值及灵敏度变化很小.     

Sr掺杂LaFeO3的微波化学制备及气敏性能的研究

利用微波化学法合成Sr掺杂LaFeO3粉体,并对其晶体结构和形貌进行了表征,结果表明Sr掺杂LaFeO3粉体为单一正交钙钛矿结构,没有杂相峰出现,且La0.91Sr0.09FeO3颗粒呈椭球状,颗粒粒径为65nm左右,颗粒分散性较好。对材料的气敏性能研究结果表明,La0.91Sr0.09FeO3元件在工作温度为180℃时对1.0×10-5甲苯气体的灵敏度为9.5,且具有良好的选择性,响应和恢复时间分别是40和50s。     

微波和真空烧结制备La2O3掺杂Al2O3透明陶瓷

通过共沉淀法制备La2O3掺杂Al_2O_3纳米粉,粉体经压制后分别采用微波和真空烧结制备Al_2O_3透明陶瓷。结果表明:Al_2O_3粉末颗粒大小均匀,近似球形,为40~60nm;两种烧结方式制备的试样XRD图中均为α-Al_2O_3,未检测到其它相。La2O3掺杂量为1%时,随烧结温度升高,两种烧结方法得到的Al_2O_3陶瓷的相对密度和抗弯强度均呈上升趋势,且微波烧结陶瓷的相对密度和抗弯强度明显高于真空烧结。1500℃烧结时,随La2O3掺杂量的增加,Al_2O_3陶瓷的相对密度均先增大后减小,当La2O3掺杂量为1%时,Al_2O_3陶瓷的相对密度和抗弯强度均最大。微波烧结陶瓷的透光率明显高于真空烧结,且其断口晶粒比真空烧结明显细少。     

0.5wt%ZnO添加BaCe0.8Zr0.1Y0.1O3-a涂层提高避雷设施性能的研究

采用溶胶-凝胶法,在铁基底上制备了0.5%(质量分数)ZnO添加的BaCe0.8Zr0.1Y0.1O3-a涂层薄膜。根据原粉的热失重(TGA)和差热(DTA)曲线控制烧结温度和保温时间。采用X射线衍射(XRD)、扫描电镜(SEM)和TEM对其晶体结构、表面和断面形貌进行了表征。XRD分析得到制备的膜层BaCe0.8Zr0.1Y0.1O3-a相为主,SEM表征结果显示,膜层表面涂层均匀、结构致密,没有大的裂纹孔洞等缺陷;膜层与基底断面的SEM显示界面处两者匹配较好。ZnO增强涂层连接性的微观原因由TEM结果表征。分别在干燥和湿润空气条件下测量膜层材料电导率,结果得到湿润空气中膜层材料电导率高,而且温度越高时电导率越大。这种膜层适合作为避雷线的保护层,并能起到提高避雷线性能的作用。     

中温固体氧化物燃料电池阴极材料Ba1-xSrxCo0.7Fe0.2Nb0.1O3-δ的制备与性能研究

采用固相法合成Ba1-x Srx Co0.7Fe0.2Nb0.1O3-δ(x=0、0.1、0.2、0.3、0.4)阴极材料。利用X射线衍射(XRD)和扫描电子显微镜(SEM)对其结构和微观形貌进行了表征。XRD测试结果表明Ba1-x Srx Co0.7Fe0.2Nb0.1O3-δ样品经1000℃,烧结10 h后形成了立方钙钛矿结构。从样品的电镜照片看出样品具有均匀的孔隙率,电解质(Ce0.85Sm0.15O1.925)-阴极(Ba1-x Srx Co0.7Fe0.2Nb0.1O3-δ)之间的界面结合良好。电化学交流阻抗测试结果表明Ba1-x Srx Co0.7Fe0.2Nb0.1O3-δ中掺入Sr可以明显地降低阴极的极化电阻,随着Sr含量的增多,阴极的界面极化电阻(RP)先减少后增大,当Sr的含量x为0.2时Rp值最小。以Ce0.85Sm0.15O1.925(SDC)电解质为支撑体,Ni0.9Cu0.1-SDC为阳极,Ba0.8Sr0.2Co0.7Fe0.2Nb0.1O3-δ为阴极的单电池的最大功率密度在600℃时达到155 mW/cm2。实验结果表明Ba0.8Sr0.2Co0.7Fe0.2Nb0.1O3-δ材料是一种电化学性能较为优良的中温固体氧化物燃料电池阴极材料。     

La0.3Sr0.7Fe0.7Cu0.2Mo0.1O3-δ钙钛矿超细陶瓷粉体制备与催化性能研究

采用溶胶低温燃烧法制备了单一组成的La0.3Sr0.7Fe0.7Cu0.2Mo0.1O3-δ(LSFCM)超细钙钛矿陶瓷粉体。用XRD,SEM以及TA等方法对粉体的物相、形貌、粒度以及导电性能等进行了表征。考察了LSFCM陶瓷粉体对甲烷部分氧化(POM)制备合成气的催化活性与稳定性。结果表明:溶胶燃烧粉末经800℃下煅烧4h可得到平均粒径小于35nm的立方钙钛矿结构LSFCM陶瓷粉体,相对密度为96.7%的LSFCM烧结体在空气气氛600℃温度下电导率达到26.27S·cm-1,在950℃、CH4/O2比为1.5~2.0时,甲烷转化率及一氧化碳与氢气选择性均达到90.0%以上;反应43h后虽产生少量积炭,但仍能保持钙钛矿结构,表明LSFCM粉体对甲烷部分氧化制合成气反应具有良好的催化活性和稳定性。     

铈掺杂Ba0.1Sr0.9TiO3的改性研究

铈掺杂Ba0.1Sr0.9TiO3陶瓷有着较高的介电常数和较低的压敏电压,但其烧结温度高,烧结成功率低,非线性系数小。用ZnO和过量TiO2加以改性,研究表明:适量TiO2起到了烧结助剂的作用,可将样品的烧结温度降低到1325℃,提高了样品烧结率,钛与锶的最佳物质的量比为5∶3;ZnO作为受主掺杂剂将样品的非线性系数提高到10以上,降低了介电损耗,其最佳的掺杂量为0.7%(摩尔分数)。最后用扫描电镜分析了掺杂ZnO样品的微观形貌。     

溶胶-凝胶法纳米WO3材料的合成、表征及气敏性能

采用溶胶-凝胶法制备了一系列掺杂有SiO2的WO3纳米粉体,通过TEM、XRD等分析手段对产物粉体的粒度、晶相结构进行了表征,测试了材料的气敏性能,探讨了煅烧温度、掺杂量、工作温度对材料气敏性能的影响。结果表明：适量SiO2的掺杂有利于提高WO3对NO2气体的灵敏度,其中掺杂量为3％（质量分数）的气敏元件在较低的工作温度下气敏性能突出。     

Study of magnetic and magnetocaloric properties of La0.6Pr0.1Ba0.3MnO3 and La0.6Pr0.1Ba0.3Mn0.9Fe0.1O3 perovskite-type manganese oxides

The compositional dependence of the magnetic and magnetocaloric properties of La_0.6Pr_0.1Ba_0.3MnO₃ (LPBMO) and La_0.6Pr_0.1Ba_0.3Mn_0.9Fe_0.1O₃ (LPBMFO) were investigated. Polycrystalline samples were prepared by the standard solid-state reaction method. Temperature-dependent magnetization measurements and Arrott analysis reveal second-order ferromagnetic transitions in both samples with Curie temperature increasing with doping iron from 94 K for LPBMO to 277 K for LPBMFO. Magnetic entropy change \( | {\Delta S_{\text{M}} } | \) was calculated by applying the thermodynamic Maxwell equation to a series of isothermal field-dependent magnetization curves. However, the analysis of the magnetocaloric effect (MCE) using Landau theory of phase transition shows that the contributions to the free energy from the presence of ferromagnetic clusters are strongly influencing the MCE by coupling with the order parameter around the Curie temperature.     

Composites of 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 prepared by a sol-gel method: effect of atmosphere powders

Dielectric and electrical properties of relaxor ferroelectric 0.9PMN-0.1PT ceramics prepared by a sol-gel method were investigated as a function of PbZrO₃ atmosphere powders. The proper amount of atmosphere powders led to better properties of dielectric constant, polarization, and strain by preventing PbO volatilization from ceramics. Excessive amount of atmosphere powder, however, resulted in aging characteristics such as decreases in dielectric constant and loss exhibiting saddle-shaped dielectric constant and loss vs. temperature curves. A propeller-shaped P-E hysteresis curve indicating aging characteristics was also observed when an excessive amount of atmosphere powder was used during sintering. The aging of ceramics caused by absorption of PbO into the ceramics resulted in decreased polarization and strain. These aging characteristics associated with defects by excessive PbO absorption could not be reversed even though the aged ceramics underwent a heat-treatment above the dielectric maximum temperature.     

Effects of La3+ addition on the phase transition,microstructure, dielectric and piezoelectric properties of Ba0.9Ca0.1Ti0.9Zr0.1O3 ceramics prepared by hydrothermal method

Lead-free Ba_0.9Ca_0.1Ti_0.9Zr_0.1O₃–xLa (x = 0.000, 0.005, 0.010, 0.015, 0.020, 0.025) ceramics were prepared by hydrothermal method and were assisted by fast microwave sintering. The effects of La³⁺ addition on the phase transition, microstructure, dielectric and piezoelectric properties were investigated. Single orthorhombic phase was observed in the composition of x ≤ 0.010 and the coexistence of orthorhombic and tetragonal phase were detected at x = 0.015 and 0.020, which is characterized by the broadening of (002)/(200) peaks at around 2θ ~ 45°. The ceramics show cubic phase when the x was increased to 0.025. The grain size was affected significantly by the La³⁺ content, reaching a maximum value of ~8.2 μm at x = 0.010. The dielectric constant decreases with the addition of small amount of La³⁺ and then increases sharply at x ≥ 0.015, exhibiting a PTC behavior at x = 0.020, while no T _C was observed at x = 0.025. The Curie temperature (T _C ) always decrease with the introduction of La³⁺ and the dielectric loss shows a minimum value at x = 0.015. The piezoelectric constant (d ₃₃ ) measured at 50 °C of the ceramics were increased after the partial substitution of La³⁺ because of the enhancement of coexistence of orthorhombic and tetragonal phases at this temperature. Ferroelectric and piezoelectric properties can not be detected when x was increased to 0.02 while they were observed again with further addition.     

溶胶-凝胶法合成La0.9Sr0.1Ga0.8-xAlxMg0.2O3及其性质研究

利用溶胶-凝胶法首次合成了La0.9Sr0.1Ga0.8-xAlxMg0.2O3 (x=0～0.4)系列固体电解质,系统地研究了其晶体结构随Al含量的变化关系.XRD表明1000℃时可形成立方钙钛矿结构,此合成温度明显低于传统固相法所需合成温度(1300～1400℃),且当掺杂量x＞0.1时,即可分辨出杂相.电导率测试表明该体系的电导率与温度的关系是分区间符合Arrhenius定律的,且Al对LSGM中Ga的适量掺杂能有效地促进该体系的离子电导率.     

由溶胶-凝胶法制备的掺氧化钼的氧化钨薄膜的电致变色性能

钨粉和钼粉在过氧化氢的作用下生成氧化钨和氧化钼的溶液，加入冰乙酸进行酸化，然后在60℃下烘干，用适量的乙醇配得氧化钨和氧化钼母液。用ITO玻璃在该溶液浸泡后拉出并在150℃下烘干1h，便得到掺有氧化钼的氧化钨薄膜。X射线衍射（XRD）显示所得的薄膜为非晶态结构，扫描电镜（SEM）发现整个薄膜的表面较为平滑，但在极其微小的局部仍有裂纹颗粒生成。薄膜的伏安特性显示薄膜对锂离子具有一定的存储能力，其光的透过率测量表明溶胶-凝胶制备的掺有氧化钼的氧化钨薄膜对光具有很好的调节作用。