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121.
Tomáš Grygar 《Journal of Solid State Electrochemistry》1999,3(7-8):412-416
Voltammetry of immobilised microcrystalline perovskites La(Ni,Cr)O3 and La(Ni,Fe)O3 revealed that these oxides yield three types of reactions in acidic aqueous solutions (0.1 M HClO4): irreversible oxidative dissolution of Cr-rich oxides, irreversible reductive dissolution of Fe-rich oxides, and a quasi-reversible
reaction most likely related to alteration of the valencies of Cr, Fe and/or Ni in the solid state. The samples of La(Cr1−
x
Ni
x
)O3 with x = 0.3 and 0.5 especially showed limited cycling stability that is particularly surprising in the very strongly acidic solution.
Received: 4 January 1999 / Accepted: 16 February 1999 相似文献
122.
利用sol-gel法在单晶硅Si(100)衬底上,制备了钙钛矿La 相似文献
123.
Tuong Lan Nguyen Masayuki Dokiya Shaorong Wang Hiroaki Tagawa Takuya Hashimoto 《Solid State Ionics》2000,130(3-4):229-241
The electrical property of (La1−xSrx)1−z(Al1−yMgy)O3−δ (LSAM; x≤0.3, y≤0.15 and z≤0.1) was measured using the DC four-probe method as a function of temperature (500–1000°C) and oxygen partial pressure (1–10−22 atm). Among LSAMs, (La0.9Sr0.1)AlO3−δ showed the highest ionic conductivity, σi=1.3×10−2 S cm−1 at 900°C. A simultaneous substitution at A and B sites or A site deficiency is expected to create larger oxygen vacancy and higher ionic conductivity. However, it showed a negative effect. The effect of the vacancy increase did not effect monotonously the ionic conductivity. It was found that the concentration of oxygen vacancy, [VO], influences not only the oxide ion conductivity, σi, but also the mobility, μv, of [VO]. These properties exhibit a maximum at around [VO]=0.05. With the increase in [VO], the activation energy, Ea, of the ionic conduction dropped from 1.8 to ca. 1.0 eV at [VO]=0.05 and became almost constant at [VO]>0.05. The dependency of the pre-exponential term, μ0v, and Ea on [VO] was analyzed and their effect on μv and σi was discussed with respect to crystal structure and defect association. It was estimated that the crystal structure mainly governs these properties. The effect of defect association could not be ignored but is considered to be a complicated correlation. 相似文献
124.
借助电子顺磁共振技术,对Mn3+/Mn4+=2∶1和1∶1的两个典型体系 在居里温度TC以上温区的顺磁行为进行了实验研究.实验表明,存在一特征温度 Tmin,通过该温度将TC以上的磁行为分成两个明显可区分的温区: 在Tmin以上,共振谱由一对称的单线构成,Lande 因子g值与温度无关且接近 自由电子的值(~20023),线宽随温度呈线性变化等;而在Tmin
关键词:
稀土锰氧化物
电子顺磁共振
交换变窄
自旋-自旋相互作用
自旋-晶格相互作用 相似文献
125.
Perovskite‐type phases SrFe1–xTixO3–y with 0.1 ≤ x ≤ 0.7 have been prepared from the oxides, and, in order to reach high oxygen contents and FeIV fractions, annealed at oxygen pressures of 60 MPa. The materials were characterised by powder x‐ray and neutron diffraction, 57Fe Mössbauer spectroscopy, and magnetic susceptibility measurements. All samples of the series crystallise in a cubic perovskite structure and reveal considerable oxygen deficiency. The Mössbauer parameters suggest that for x = 0.1, where the FeIV fraction is about 90%, the itinerant electronic state of SrFeO3 is essentially retained. In materials with larger x increasing amounts of TiIV and FeIII ions lead to a stronger localisation of the σ* (Fe 3 d – O 2 p) electrons. There is no evidence for a charge disproportionation of FeIV in any of the materials. Magnetic susceptibility measurements show a divergence of zero‐field cooled and field‐cooled data below a temperature Tm and deviations from Curie‐Weiss behaviour above Tm. The data are indicative of spin‐glass behaviour due to disorder and competing exchange interactions. 相似文献
126.
The effects of the PbO volatilization, excess Pb content of PbZr0.52Ti0.48 (PZT) precursor, PbTiO3 (PT) seeding layers and annealing condition on the microstructures, surface morphologies, preferred orientation and ferroelectric properties of PbZr0.52Ti0.48 films were systematically investigated. PZT films with a variety of excess Pb (0-20%) were spin-deposited on Si(1 0 0) and Pt(1 1 1)/Ti/SiO2/Si(1 0 0) substrates by sol-gel technique. The films composition, Pb/Zr/Ti/O atom rate and Pb loss were semiquantitative analyzed by X-ray photoelectron spectrometer (XPS). When the excess Pb of PZT precursor was 10%, the Pb/Zr/Ti/O atomic rate of the fabricated films was very close to the designed rate of 1:0.52:0.48:3. The XRD and AFM investigations confirmed that PT seeding layer promoted the PZT films perovskite phase transformation and grains growth with (1 1 0) plane preferred orientation, accordingly lowered perovskite phase crystallization temperature and reduced Pb loss. The PZT films annealed in O2 flow demonstrated better microstructure and ferroelectric properties comparing with films annealed in air by double remnant polarization increase and 8% coercive field increase. The underlying mechanism was also investigated. 相似文献
127.
《Opto-Electronics Review》2019,27(2):137-142
Three low molecular weight compounds bearing carbazole units (1,6-di{3-[2-(4-methylphenyl)vinyl]carbazol-9-yl}hexane and 9,9'-di{6-[3-(2-(4-methylphenyl)vinyl)-9-carbazol-9-yl]hexyl}-[3,3']bicarbazole) and phenoxazine structure (10-butyl-3,7-diphenylphenoxazine) were tested as hole-transporting materials in perovskite solar cells. Two of them were successfully applied as hole transporting layers in electroluminescent light emitted diodes. The examined compounds were high-thermally stable with decomposition temperature found at the range of 280–419 °C. Additionally, DSC measurement revealed that they can be converted into amorphous materials. The compounds possess adequate ionization potentials, to perovskite energy levels, being in the range of 5.15–5.36 eV. The significant increase in power conversion efficiency from 1.60% in the case of a device without hole-transporting layer, to 5.31% for device with 1,6-di{3-[2-(4-methylphenyl)vinyl]carbazol-9- yl}hexane was observed. 相似文献
128.
Influence of CO2 on Oxygen Surface Exchange Kinetics of Mixed-Conducting Ba0.5Sr0.5Co0.8Fe0.2O3?δ Oxide
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The poisoning effect of CO2 on the oxygen surface exchange kinetics of BSCF (Ba0.5Sr0.5Co0.8Fe0.2O3-δ) is investigated with a novel pulse isotopic exchange technique. The surface exchange rate of BSCF severely decreases after in situ exposure to CO2, which is ascribed to carbonate formation on the material surface. The detrimental effect of CO2 starts at a low temperature of 375 oC and concentration as low as 1%, and becomes more pronounced at higher temperatures. Degradation of the surface exchange kinetics is associated with a rapid loss of oxygen permeation performance of BSCF in CO2. 相似文献
129.
The dependence of Li mobility on structure and composition of Li0.5 − xNaxLa0.5TiO3 perovskites (0 ≤ x ≤ 0.5) has been investigated by means of neutron diffraction, nuclear magnetic resonance and impedance spectroscopy. At 300 K, all samples display a rhombohedral superstructure (R-3c S.G.), where octahedra are out of phase tilted along [111] direction of the ideal cubic cell. The elimination of the octahedral tilting is responsible for the rhombohedral–cubic transformation, detected near 1000 K. In these perovskites, La and Na cations are randomly distributed in A sites, but Li ions are fourfold coordinated at unit cell faces of the cubic perovskite. Lithium conductivity, σ300 K, decreases with the sodium content, decreasing from values typical of fast ionic conductors, 10− 3 S/cm, to those of good insulators, 10− 10 S/cm, when the interconnectivity between vacant A sites is lost (x > 0.3). In samples with x < 0.3, dc conductivity displays a non-Arrhenius behaviour, decreasing activation energy from ~ 0.37 to 0.25 eV when the sample is heated between 77 and 500 K. The temperature dependence of BLi factors shows the existence of two regimes for Li motion. Below 373 K, Li ions remain partially located near square oxygen windows that connect contiguous A sites, but above 400 K, extended Li motions become dominant. The additional decrease of activation energy from 0.25 to 0.16 eV (low-temperature 7Li NMR value), should require the full elimination of octahedral tilting which is only produced above 1000 °C. 相似文献
130.