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101.
p-Type nano-ZnFe2O4 semiconductors were gained by high-prssure treatment. Surface photovoltaic spectrum(SPS) and transient photovoltaic technology(TPV) were used for studying the photogenerated charge of nano-ZnFe2O4. Results show that the photovoltaic behavior of nano-ZnFe2O4 changed as the processing pressure increased. When the processing pressure was higher than 2 GPa, both SPS response interval and peak changed significantly. XPS results show that the non-lattice oxygen entered into the lattice and the content of lattice oxygen increased with the increase of processing pressure. The material changed from oxygen vacancy type to oxygen excess type and the photoelectric properties changed from n-type to p-type when the processing pressure is higher than 2 GPa. 相似文献
102.
The dependence of two-level systems in disordered atomic chain on pressure, both positive and negative was studied numerically. The disorder was produced through the use of interatomic pair potentials having more than one energy minimum. It was found that there exists a correlation between the energy separation of the minima of two-level systems Δ and the variation of this separation with pressure. The correlation may have either positive or negative sign, implying that the asymmetry of two-level systems may in average increase or decrease with pressure depending on the interplay of different interactions between atoms in disordered state. The values of Δ depend on the sign of pressure. 相似文献
103.
Ravhi S. Kumar Sandeep Rekhi D. Prabhakaran M. Somayazulu Eunja Kim Jeremy D. Cook Timothy Stemmler A.T. Boothroyd Mark R. Chance Andrew L. Cornelius 《Solid State Communications》2009,149(39-40):1712-1716
The crystal structure of Na0.75CoO2 was studied at ambient and low temperatures down to 10 K at pressures up to 40 GPa using synchrotron x-rays and a diamond cell in angle dispersion geometry. A reduction in the c/a ratio was observed at both conditions with the application of pressure. An increase in Co–O bond lengths and a decrease in Na–O bond lengths were observed above 10 GPa. The results of the density functional calculations performed agree well with the pressure induced bond length changes. The anomalous change in the c/a ratio and bond lengths indicate a pressure induced isostructural phase transition above 10 GPa. Bulk modulus calculations show this compound is less compressible than its hydrated analogues. 相似文献
104.
Jinggeng Zhao Liuxiang Yang Fengying Li Changqing Jin 《Journal of solid state chemistry》2009,182(6):1524-1528
The 6H and 6M Ba1−xSrxRuO3 at x?0.6 with the normal and distorted hexagonal BaTiO3 structures were synthesized by using high-pressure and high-temperature method. It is found that the unit cell volume deviates from Vegard's law between 0.3 and 0.4 for the solid solutions due to the increasing distortion degree of crystal structure. With the increasing x, the electrical resistivity at the same temperature is increasing. With the substitution of Sr for Ba ion, the 6H BaRuO3 transforms to a Fermi-liquid metal at x=0.25 from the primal non-Fermi-liquid metal, and then becomes a semiconductor at low temperature when x is larger than 0.4. 相似文献
105.
《Physics letters. A》2019,383(26):125837
Single-phase LaCrO3 ceramics was synthesized successfully by the solid state sintering method under high pressure (5 GPa). X-ray diffraction measurements suggest that the high-pressure synthesized sample is well-crystallized, but the cell volume is larger than that of the sample synthesized under ambient pressure, which can be ascribed to the occurrence of Cr2+ converted form part of Cr3+. Such mixed valent state with coexistence of Cr2+ and Cr3+ could be confirmed by X-ray photoelectron spectroscopy measurements. Magnetic measurement results indicate that in addition to antiferromagnetic superexchange interaction of Cr3+-O-Cr3+ network accompanied by weak ferromagnetism at high temperature, another kind of ferromagnetic behavior can be observed at low temperature (below 30 K), which could be attributed to double exchange interaction of Cr2+-O-Cr3+ networks. 相似文献
106.
Ling-Fang Xu Cong Mao Vyacheslav V. Marchenkov Kang Sun Tatyana V. Dyachkova Alexander P. Tyutyunnik Yurii G. Zainulin Chang-Ping Yang Shi-Heng Liang 《Physics letters. A》2018,382(39):2861-2867
Copper titanate (CaCu3Ti4O12, or CCTO) ceramics sintered in oxygen and vacuum at 1100°C for 12 h have been treated by thermobaric treatment (TBT) at 9 GPa and 1000°C for 10 min and then quenched in liquid nitrogen (LN2). Pure cubic body-centered perovskite-related structure was confirmed from XRD results. Besides, after TBT and quenching, additional minor peaks of TiO2 and Cu were indexed, as well as a little cell volume expansion. A little reduction of the grain size as well as fuzzy grain boundaries can be observed in FE-SEM after TBT. The dielectric constant ε' of CCTO ceramics sintered in oxygen (~4600 @ 100 Hz) were a half of those treated by TBT and quenching (~9600 @ 100 Hz), whereas the value decreased almost by an order of magnitude (from 105 to 104) after TBT and quenching for the samples sintered in vacuum. The complex impedance spectra at high temperature showed three semicircles so a three RC model was used to explain the different relaxation regions consisting of grain, grain boundary and domain boundary. Besides, two relaxation peaks appeared in the frequency dependence of the imaginary part of the electric modulus formalism and the complex impedance . Moreover, the contributions of grain boundaries can be figured out by the relaxation activation energy (338–629 meV) and the conduction one (396–823 meV) fitted by and plots separately. As a result, the disorder and heterogeneity typical of grain boundaries should be responsible for the giant dielectric relaxation characteristics of CCTO ceramics, which can be affected by the sintering atmosphere as well as the extreme treating conditions. 相似文献
107.
FU Xianwei LIU Yang LIU Zhi DONG Ning ZHAO Tianyu ZHAO Dan LIAN Gang WANG Qilong CUI Deliang 《高等学校化学研究》2018,34(1):95-100
Although organic semiconductors have attracted extensive interest and been utilized to fabricate a variety of optoelectronic devices, their electrical transportation characteristics under high pressure have rarely been investigated. However, the weak intermolecular interaction of organic semiconductors endows them with a pre- ssure-sensitive crystal structure and electrical transportation performance, especially the latter. Herein, a new pre- ssure-sensitive transistor was fabricated from an organic semiconductor 1,1'-dibutyl-4,4'-bipyridinium diiodide. It was found that this transistor exhibited increasing resistance as the pressure gradually increased and that it eventually shut off under a pressure of 288 MPa. Such a characteristic makes this organic semiconductor a potential candidate for the use in the fabrication of pressure-sensitive switches and regulators. In addition, these results shed light on the electrical performance of flexible organic optoelectronic devices working under high pressure levels resulted from the bending force. 相似文献
108.
Hyun I. Joo 《Proceedings of the Combustion Institute》2009,32(1):769-775
The effects of pressure on soot formation and the structure of the temperature field were studied in co-flow methane-air laminar diffusion flames over a wide pressure range, from 10 to 60 atm in a high-pressure combustion chamber. The selected fuel mass flow rate provided diffusion flames in which the soot was completely oxidized within the visible flame envelope and the flame was stable at all pressures considered. The spatially resolved soot volume fraction and soot temperature were measured by spectral soot emission as a function of pressure. The visible (luminous) flame height remained almost unchanged from 10 to 100 atm. Peak soot concentrations showed a strong dependence on pressure at relatively lower pressures; but this dependence got weaker as the pressure is increased. The maximum conversion of the fuel’s carbon to soot, 12.6%, was observed at 60 atm at approximately the mid-height of the flame. Radial temperature gradients within the flame increased with pressure and decreased with flame height above the burner rim. Higher radial temperature gradients near the burner exit at higher pressures mean that the thermal diffusion from the hot regions of the flame towards the flame centerline is enhanced. This leads to higher fuel pyrolysis rates causing accelerated soot nucleation and growth as the pressure increases. 相似文献
109.
F. Morales M. Monteverde M. Núñez-Regueiro 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(4):511-514
We measure electrical transport on networks of single wall nanotube of different origin as a function of temperature T, voltage V
and pressure P. We observe Luttinger liquid (LL) behavior, a conductance ∝Tα and a dynamic conductance ∝Vα. We observe a sample dependent P variation of the α parameters, interpreted as Fermi level changes due to pressure induced
charge transfer. We show how, through standard four-leads and crossed configuration methods, it is possible to determine αbulk and αend, respectively. We study and discuss the pressure and doping level dependences of the number of channels N, the LL parameter g
and the intra-rope tube-tube coupling constant U within a phenomenological model. 相似文献
110.
Daisuke Mori Atsuo Yamada Masaki Azuma Katsumi Suda 《Journal of solid state chemistry》2006,179(3):935-940
Single crystals of the thallium ruthenium pyrochlore have been grown by flux method under high oxygen pressure. The growth conditions were determined by direct observations using in situ powder X-ray diffraction (XRD) method under high pressure and high temperature. The crystals were grown using NaCl-KCl flux at 1350 °C and B2O3 flux at 1150 °C. High growth temperature of 1350 °C for the NaCl-KCl flux caused Pt contamination from the crucible and oxygen deficiency for the crystals obtained. The crystal growth using B2O3 flux proceeded at lower temperature by grain growth with material transfer through B2O3. The crystal obtained was characterized by single-crystal XRD method, and was found to have a stoichiometric composition, Tl2Ru2O7−δ (δ=0), with a structural phase transition around 120 K. The grain growth technique with B2O3 is efficient for high-temperature single-crystal growth under high pressure. 相似文献