The electric resistance of single-walled nanotube mats has been studied systematically under both ambient and high hydrostatic pressures up to 1.5 GPa. Both the temperature dependence of the resistance and the magnetoresistance indicate that electrical transport occurs by variable range hopping, apparently in 2D. We suggest that this unexpected dimensionality arises from a fractal network of tubes and bundles. Under hydrostatic pressure (HP) the resistance still shows 2D variable range hopping and decreases with increasing HP. An irreversible increase in localization length and DOS is induced below 0.5 GPa. The behavior is reversible and due to strong interaction of tubes from 0.5 GPa up to 1.05 GPa. These results indicate that 2D variable range hopping occurs within bundles.

Bingbing Liu;B. Sundqvist;O. Andersson;T. Wågberg;E. B. Nyeanchi;X. M. Zhu;广田 邹

Solid State Communications

2001-3-20

The Tm,Ho:BaY₂F₈ single crystal was successfully grown by the Cz method. The optimal technical parameters obtained are as follows: the pulling rate is 0.5-0.6mm/h; the rotation speed is 5 -7rpm; the cooling rate is 10°/h. The result of XRD curve shows that as-grown Tm,Ho:BaY_2F8 laser crystal belongs to the monoclynicsystem and space group I41/a, the cell parameters calculated are: a = 0.69829 nm, b = 1.0519 nm, c = 0.42644 nm, β=99.676°, Z=2. Absorption spectra of Tm,Ho:BaY₂F₈ laser crystal at room temperature were measured and analysed, the absorption cross-section at 781nm calculated are 7.66×10^-21cm^-2.

Fanming Zeng;广田 邹;Jinghe Liu

2011

The electrical properties of stoichiometric iron sulfide (FeS) were investigated under high pressure with a designed diamond anvil cell (DAC). The process of phase transition was reflected on the discontinuity of electrical conductivity changing with high pressure. The conductivity of FeS with NiAs structure was found to be much smaller than other phases. Two new phase transitions without structural change were observed at 34.7 GPa and 61.3 GPa.

Ming Li;Chun Xiao Gao;Dong Mei Zhang;Ai Min Hao;Chun Yuan He;Xiao Wei Huang;Cui Ling Yu;广田 邹

Gaoya Wuli Xuebao/Chinese Journal of High Pressure Physics

2008-3

The structural transition of AIN nanocrystals and nanowires were investigated simultaneously under pressures up to 37.2 GPa by in situ angle dispersive high-pressure x-ray diffraction using synchrotron radiation source and a single diamond anvil cell. The size of hexagonal AIN nanocrystals and the diameter of nanowires are 45 nm on average. A pressure-induced wurtzite to rocksalt phase transition starts at 21.5 GPa and completes at 27.8 GPa for the nanocrystals and nanowires, respectively. The high-pressure behaviors of AlN nanocrystals the same as the AIN nanowires might arise from the similar size and diameter in nanocrystals and nanowires. Hexagonal AIN nanocrystals (45 nm) display an apparent volumetric contraction as compared to the AlN nanocrystals (10 nm) which might induce the difference of transition pressure.

W. W. Lei;D. Liu;J. Zhang;Q. L. Cui;广田 邹

Journal of Physics: Conference Series

2008

The high-pressure/high-temperature behavior of boron has been investigated up to 30 GPa using x-ray diffraction techniques. We have investigated the isothermal compressibility of rhombohedral-105 (formula presented) boron to 30.7 GPa, and determined the bulk modulus (formula presented) to be (formula presented) with (formula presented) We found that the a direction of (formula presented) boron (hexagonal setting) is less compressible than c, which indicates that the B10-B-B10 chain is less rigid than the (formula presented) cluster. High P-T studies were conducted using double-sided laser heating to temperatures of 3500 K. (formula presented) boron transforms above 10 GPa at high temperature to a tetragonal phase that remains on P-T quenching. The transformation results in both a higher density and higher entropy phase and is consistent with the formation of the (formula presented) phase of boron.

Yanzhang Ma;Charles T. Prewitt;Ho Kwang Mao;Russell J. Hemley;广田 邹

Physical Review B - Condensed Matter and Materials Physics

2003-5-30

The Raman spectra of Na_0.5Bi_4.5Ti₄O₁₅ and its solid solutions Na_0.5Bi_4.5-xLa_xTi₄O₁₅, Na_0.5Bi_4.5-xGd_xTi₄O₁₅ and (NaBi)_0.5(1-x)Ba_xBi₄Ti₄O ₁₅ were investigated. It was found that a first order phase transition takes place in the systems Na_0.5Bi_4.5-xLa_xTi₄O₁₅ and Na_0.5Bi_4.5-xGd_xTi₄O₁₅ at room temperature. The microscopic origins of the phase transitions are analysed. On the basis of an internal and external mode analysis, the nature of the various vibrations is discussed.

Jianjun Liu;广田 邹;Yanrong Jin

Journal of Physics and Chemistry of Solids

1996-11

PbMoO₄, with high acousto-optic figure of merit, low acoustic loss and nicer acoustic impedance matching, has received much attention because of applications as acousto-optic deflector, modulator, adjustable filter, surface acoustic wave devices and great potential to act as an effective low-temperature scintillator for nuclear instrumental applications. In this study, in-situ Raman spectrum of PbMoO₄ was measured in a diamond anvil cell (DAC). The electrical conductivity measurement of PbMoO₄ was performed at different pressure and temperature. All Raman peaks disappeared at 12.5 GPa, which indicated that the PbMoO₄ experienced gradually the crystal to amorphous transition between 10.8 GPa and 12.5 GPa. Upon decompresstion from 26.5 GPa to 9.4 GPa a broad Raman peak occurred at a low frequency, while the peak of 858 cm^-1 occured at 2.4 GPa again, thus suggesting that the PbMoO₄ crystal was gradually recovered from the amorphous state. Above 10.8 GPa, the electrical conductivity of PbMoO₄ increased obviously with increasing temperature and pressure.

Cui Ling Yu;Qing Jiang Yu;Chun Xiao Gao;Bao Liu;Chun Yuan He;Xiao Wei Huang;Ai Min Hao;Dong Mei Zhang;Xiao Yan Cui;Cai Long Liu;Yue Wang;广田 邹

Gaoya Wuli Xuebao/Chinese Journal of High Pressure Physics

2007-9

The physical and chemical stability of different reaction-cell container material under HPHT is systematically studied. The synthesis experiments of growing gem diamond are carried out with three kinds of reaction-cell container, namely pure pyrophyllite tube sintered under 1000°C, powder-mixture tube of pyrophyllite and MgO, and quartz tube. With pure pyrophyllite tube sintered under 1000°C, powder-mixture tube of pyrophyllite and MgO as container, the heating voltage is always increasing, although constant power heating ways is used. So, it is concluded that, as the cell container, they are not fit for growing high-purity gem diamond. When transformed into coesite completely, the quartz tubes are more stable than pure pyrophyllite or pyrophyllite-containing mixture sintered under high temperature. And the surfaces of crystals grown with the quartz tube are perfect, and there is almost no any inclusion or defect in the crystals. Therefore, it is concluded that quartz tubes are fit for high-purity gem diamond.

Lixue Chen;Hongan Ma;Weili Guo;Pinwen Zhu;Chuanyi Zang;Xiancheng Wang;晓鹏 贾;广田 邹

Jingangshi yu Moliao Moju Gongcheng/Diamond and Abrasives Engineering

2005-8

Raman spectra of the system Na_0.5Bi_4.5-xLa_xTi₄O₁₅ have been obtained. It was found that it undergoes a first order phase transition at room temperature for x = 1.6. The phase transition seems to be a ferro-to para-electric phase transition related to a ferroelectric soft mode.

Jianjun Liu;广田 邹;Yanrong Jin

Physics Letters, Section A: General, Atomic and Solid State Physics

1996-2-5

A RF sputtering was used for preparing cubic boron nitride (c-BN) films. The results from infrared spectra and transmission electron diffraction show that a pure c-BN film with a high crystallinity was obtained. The analyzing of IR spectra indicate that the negative substrate bias is an important condition, and also the reason to form the stress, the higher the bias, the higher the stress. Comparing the reflecting IR absorption spectra with the transmission IR absorption spectra, it is first found that the stress on the surface layer of c-BN film is smaller than that in c-BN film. In terms of its compressive stress mode of the growth of c-BN should be limited by a very small stress on the surface layer of c-BN film. A BN film with the layer-built was specially prepared for investigating the distribution of the stress on the surface layer of c-BN film. The cracks resulted from the stress of c-BN film were first kept miraculousness. The arrangement of the cracks shows the distribution of the stress on the surface layer of c-BN film at the horizontal direction.

Yong Nian Zhao;广田 邹;Bo Wang;Zhi He;Pin Wen Zhu;Yan Chun Tao

Kao Teng Hsueh Hsiao Hua Heush Hsueh Pao/ Chemical Journal of Chinese Universities

1998