共查询到20条相似文献,搜索用时 78 毫秒
1.
2.
3.
La0.2Ba0.8(Co0.2Fe0.8)1-xZrxO3-δ透氧膜材料的微结构与氧分离性能研究 总被引:2,自引:0,他引:2
采用固相法制备了La0.2Ba0.8(Co0.2Fe0.8)1-xZrxO3-δ(x=0、0.05、0.1、0.15)片状陶瓷膜,用稳态法测试了不同成分制备样品的透氧性能,并利用XRD和SEM手段分析研究了样品的相结构和晶粒形貌及它们对材料性能的影响.研究表明固相法较难合成x=0的纯钙钛矿相,可用改进的Pechini法合成,另B位Zr的替代有利于去除材料中非钙钛矿杂相;x=0.1的样品中有少量BaZrO3析出,并导致晶粒细化(1~2μm),而这种微结构状态稳定且不受高温长时间退火和氧分压梯度的影响.晶粒细化样品的力学性能和氧渗透性能均有较大提高,x=0.1的样品较x=0样品的氧渗透性能提高了一个数量级,在1010℃,样品厚1.2mm时体系的透氧率达到4.6×10-7mol.cm-2.s-1. 相似文献
4.
添加La2O3对Mg2TiO4陶瓷的显微结构与微波介电性能的影响 总被引:4,自引:0,他引:4
采用传统烧结工艺,制备了具有不同La2O3含量的镁钛镧陶瓷,并研究了La2O3组份对材料晶相构成、晶粒、晶界的演变、介电常数和品质因数的影响。结果表明,不含La2O3的钛酸镁陶瓷主晶相为Mg2TiO4,其平均晶粒尺寸>60μm;引入La2O3后,出现新晶相La0.66TiO2.99,材料的晶粒尺寸明显下降;随La2O3含量的增加,材料的介电常数线性增加,材料的品质因数Q在10GHz出现最大值(16558)。 相似文献
5.
混合导电体Y1-xLaxBa2Cu3O7-δ透氧膜的透氧性能研究 总被引:2,自引:0,他引:2
用稳态法研究了具有类钙钛矿结构的Y1-xLaxBa2Cu3O7-δ(x=0.1、0.3、0.5、0.8和1.0)致密透氧膜在750~1000℃之间的透氧量.实验发现,透氧速率随着La替代Y的比例x的增加而增加;在大约875℃,氧空位的有序-无序转变导致透氧率有一个突然增加.透氧膜的两侧分别为He气氛和空气,当La完全替代Y时,厚1.0mm的LaBa2Cu3O7-δ膜的透氧量达到1.22μmol/s.cm2(1.64 mL/min.cm2). 相似文献
6.
7.
采用溶胶-凝胶法制备了纳米La(1-x-y)CaxSryMnO3系列粉体,经压片后烧结成陶瓷.用振动样品磁强计测量样品的磁化强度随温度的变化,结果表明各样品的居里温度在250~330K温度范围内,|(e)M/(e)T|最大值在1.353~3.392A·m2/kg·K范围内变化.用差示扫描量热仪(DSC)测定了各样品相变温度和相变潜热,得出各样品的相变潜热在0.852~2.381J/g范围内,相变潜热较大的样品其|(e)M/(e)T|最大值也较大;另外,La0.8-xCao.20SrxMnO3(x=0.05、0.08、0.10)样品的|(e)M/(e)T|最大值较大,并且居里温度在室温附近,有可能成为室温附近的磁制冷材料. 相似文献
8.
采用溶胶.凝胶法制备了负载型复合半导体光催化材料ZnFe2O4-TiO2/SiO2,并通过DTA-TG、XRD、XPS、Raman、TPR及UV-Vis DRS等实验技术对复合材料的晶体结构、表面组成及光响应性能进行了表征和评价.结果表明:ZnFe2O4晶相以高分散状态存在于光催化材料的表面;ZnFe2O4与TiO2复合可使部分Fe^3+进入体相TiO2的晶格中,促进其由锐钛矿向金红石的相转变,同时表面剩余的少量Zn计聚集形成ZnO物相;TiO2的相变由体相开始,随着ZnFe2O4含量的增加逐渐向表面扩展;SiO2的加入使活性组分更加分散,TiO2平均粒径〈10nm;ZnFe2O4的加入明显拓宽了TiO2的吸光域,并增强了对可见光的吸收. 相似文献
9.
10.
用SEM和XRD技术测定和分析了不同超声波作用时间下Ti/SnO2 Sb2O3/PbO2电极材料的表面形貌和结构,应用循环伏安法研究了超声波作用时间对Ti/SnO2 Sb2O3/PbO2电极在1.0mol/LH2SO4溶液中的伏安特性的影响.实验结果表明:超声波作用于电极材料会对电极表面的形貌和结构产生影响;电极经超声处理20min后,其循环伏安峰电流与未经超声波作用时相比增加了近1倍;电极的电化学活性表面积随超声波作用时间的延长呈先增大后减小的趋势,在本实验中超声波作用时间为20min时,伏安电荷最大,即活性表面积最大. 相似文献
11.
C.P. Tavares 《Materials Research Bulletin》1985,20(8):979-987
Further evidence of the second-order nature of the semiconductor-metal transition in La2NiO4 in the range 570K < T < 680K is provided from the results of heat capacity measurements. High-temperature X-Ray crystallographic measurements show that the metallic phase undergoes a crystallographic distorition. 相似文献
12.
Measurement of a continuous increase in unit cell c/a ratio of La2NiO4 with temperature — but without change of symmetry from 77 to 773 K, refinement of the local distortion of the Ni2+-ion octahedral site to tetragonal () symmetry ( at room temperature) as against a in K2NiF4, and determination of a constant oxygen content in air for all temperatures below 100 K provide evidence that the nickel dz2 spin is localized whereas the dx2?y2 electrons occupy a narrow band of itinerant-electron states containing strong electron correlations that increase with decreasing temperature. 相似文献
13.
Electrical resistivity of La2NiO4+
δ
single crystals has been investigated. Results showed several anomalies that are related to the onset of spin and charge ordering, either static or dynamic. 相似文献
14.
用固相反应法制备了BiFe1-xTixO3(BFTxO)陶瓷样品,研究了不同Ti掺杂量对BFO陶瓷结构、形貌、铁电性能和铁电-顺电相变温度(Tc)的影响. XRD结果表明,当Ti含量x从0增大到0.2,相的结构由菱方钙钛矿逐渐变为斜方结构. Raman光谱的测试和模拟也证实了掺Ti后晶体结构有向三斜晶系转变的趋势. I-V曲线说明Ti掺杂显著降低了BFO陶瓷的漏电流,当Ti掺杂量为0.05时,漏电流最小,在100V电压下,漏电流密度为7.3×10-6A/cm2. Ti掺杂还增强了BFO陶瓷的铁电性,Ti掺杂量为0.05时的剩余极化强度甚至是纯BFO的两倍. 另外,DTA测试显示,Ti掺杂能影响BFO的铁电顺电相变温度. 随着Ti掺杂量的增加,铁电顺电相变温度逐渐降低. 相似文献
15.
X-ray, magnetic susceptibility, and electron paramagnetic resonance measurements have been made on La2CuO4. Magnetic measurements in the range 4.2 – 300 K are consistent with the metallic nature of La2CuO4, and the itinerant - electron susceptibility is estimated to be 239 × 10?6 emu mol?1. The high susceptibility and density of states indicate that the conduction band is narrow. The results are discussed in terms of previous models of the level structure of La2CuO4, and it is concluded that conduction occurs via a band. Comparison of La2CuO4 with semiconducting lanthanide cuprates suggests that this compound is on the verge of a semiconductor-to-metal transition. 相似文献
16.
The multiple-phase separation with coexistence of two different superconducting phases in the phase diagram of oxygen-doped La2CuO4+
y
cuprates is interpreted with a modified Van der Waals scheme. The model includes the tendency of intercalated oxygen ions to form clusters at preferential densities. We obtain the coexistence and competition of two different superconducting phases with different T
c and interstitial oxygen content y, in agreement with experiments. 相似文献
17.
A large amount of static and dynamic NMR experiments have been carried out to determine the spin properties in high temperature superconductors cuprates (HTSC). In the majority of cuprates the magnetic shift at the planar copper nucleus is independent of the temperature when the field is applied perpendicular to the CuO2 planes and does not exhibit the expected reduction of the spin susceptibility in the superconducting state. This has been explained by a coincidental cancellation of on-site and transferred hyperfine fields at the copper nucleus, which would lead to a vanishing spin shift. To examine this explanation we determine the hyperfine fields by ab initio cluster calculations for La2CuO4 within the framework of spin-polarized density functional theory. In particular we investigate the sensitivity of the hyperfine fields on the lattice constants. 相似文献
18.
R.N. Shelton A.R. Moodenbaugh P.D. Dernier B.T. Matthias 《Materials Research Bulletin》1975,10(10):1111-1119
The superconducting transition temperatures (Tc's) for La3S4 and La3Se4 vary in a non-linear fashion under hydrostatic compression to 22 kbar. Both Tc and the crystallographic transformation temperature rise with pressure for La3S4 and show a maximum near 10 kbar for La3Se4. Non-transforming isostructural La3Te4 exhibits a linear pressure dependence of Tc. However, the telluride undergoes a pressure induced phase transformation at ~70 kbar. In this case the sign of the pressure dependence is different from the sulfide and selenide. Variation of Tc with the crystallographic transformation temperature shows a new and unexpected behavior. 相似文献
19.
采用共沉淀法制备出纳米级La2O3Eu.并采用相关光谱、X-射线衍射(XRD)、荧光光谱(PL)对所制备的纳米发光粉体进行表征.结果表明制备的纳米发光粉体的粒径均匀,集中在20nm左右;XRD结果证明制备的La2O3Eu粉体属于六方相,PL的结果说明La2O3Eu具有良好的发光性质. 相似文献
20.
稀土掺杂锂锰氧化物LiMn2-xNdxO4(X=0.005~0.1)的结构和电性能研究 总被引:14,自引:1,他引:14
采用微波与传统加热相结合的方法首次合成了稀土掺杂基锂锰氧化物LiMn2-xNdxO4(x=0.005-0.1)材料,电化学性能测试结果表明材料在掺杂量为x=0.01时表现出最大放电比容量,同时具有很好的循环稳定性,经过100次循环其容量衰减仅为14.9%;XRD测试结果表明在LiMn2O4尖晶石晶格中掺入合适量的Nd对稳定尖晶石骨架结构起重要作用;FTIR分析技术揭示了容量少量衰减的原因。 相似文献