Room temperature photoluminescence spectra on Ba1-xPbxTiO3 and Sr1-xPbxTiO3, with grain sizes of ∼ 60 and ∼ 30 nm, respectively, have been measured. The Pb content dependence of the visible emission can be used to provide evidence for the origin of photoluminescence occurring in these nanocrystalline ABO3 oxides. The phase transitions for Ba1-xPbxTiO3 and Sr1-xPbxTiO3 are found to have an obvious effect on the visible emission band. © 1997 Elsevier Science B.V.

Meng J. F.;Rai Brajesh K.;Katiyar Ram S.;Zou G. T.

Physics Letters Section A General Atomic and Solid State Physics

1997

We employ quantum path-integral Monte Carlo method to investigate the pressure and temperature effects on the system of Li in solid D2. Our results show that under high pressure (0.9-2.4 GPa), when the lithium atom doped into solid D2, it will occupy five-vacancy trapping site. Application of temperature can not change this fact. Pressure and temperature effects on the Li atomic absorption spectrum of Li in solid D2are similar to the results of Li in solid H2. However, at a given pressure and temperature point, the difference between the two kinds of absorption spectrum is significant. With the increase of pressure or temperature, the difference between the two kinds of absorption spectrum is getting less visible.

Ma Yan-Ming;Cui Tian;He Wen-Jiong;Zhou Qiang;Liu Zhi-Ming;Zou Guang-Tian

Gaoya Wuli Xuebao Chinese Journal of High Pressure Physics

2003

Yang Shao-Feng;Luo Wei;Zhu Yan-Chao;Liu Yan-Hua;Zhao Jing-Zhe;Wang Zi-Chen;Zou Guang-Tian

Gaodeng Xuexiao Huaxue Xuebao Chemical Journal of Chinese Universities

2003

Raman spectra for the Bi4Ge3-xTixO12 ceramic system in the wavenumber range 10-1000 cm^-1 are reported, indicating an order-disorder phase transition at x = 0.4. Pressure- and temperature-dependent Raman spectra for Bi4Ge2.8TiO.2O12 provide evidence for order-disorder behavior of this phase transition. A pressure-induced amorphization of crystalline of Bi4Ge2.8Ti0.2O12 occurs at 10.4 GPa. The two lowest phonon modes at 27 and 44 cm^-1 of Bi4Ti3O12 are assigned to vibrations of a Bi - Bi weak metal bond and effects of Ge ion content, pressure and temperature on the phonon modes are discussed. © 1998 John Wiley & Sons, Ltd.

Meng J. F.;Dobal P. S.;Katiyar R. S.;Zou G. T.

Journal of Raman Spectroscopy

1998

The low frequency Raman spectra of Bi2Ti4O11 have been investigated under hydrostatic pressure up to 9 GPa. A pressure induced soft mode phase transition occurs at 3.7 GPa. The half-width of the soft mode satisfies the relation Γ = Γ(0) t^{- 1 3} (t is the reduced pressure (Pc - P)/Pc or temperature (Tc - T)/Tc) in the low pressure phase. © 1992.

Meng Jinfang;Zou Guangtian;Zhao Yongnian;Cui Qiliang;Li Dongmei

Physics Letters A

1992

We have studied polycrystalline brookite TiO 2 using energy-dispersive X-ray diffraction at pressures up to 27.8 GPa and derived an ambient-pressure bulk modulus of 255 GPa using Birch-Murnaghan's equations of state with a fixed value of 4 as its first derivative. The transition from brookite-type to baddeleyite-type was observed to start at 15.8 GPa and finished at 22.8 GPa. Upon decompression, the α-PbO 2 structure appeared at 3.5 GPa and the baddeleyite-type structure remained down to 1.6 GPa, the lowest pressure in the present work. © 2004 Elsevier Ltd. All rights reserved.

Luo W.;Zou G. T.;Wang Y.;Ahuja R.;Johansson B.;Yang S. F.;Wang Z. C.;Liu J.

Solid State Communications

2005

The transition from sp ² to sp ³ hybridization in boron nitride has been induced in plasma. Nano-crystals of cubic boron nitride (cBN) have been synthesized by direct current arc discharge method using hexagonal boron nitride (hBN) as the starting material. The characterization of the as-grown powders is carried out by X-ray diffraction, Fourier transform infrared spectroscopy and transmission electron microscopy. It has been shown that cBN and hBN grains with 20-60 nm in size co-exist in the powders. A reaction route of sublimation - re-hybridization - crystallization had been put forward to explain the mechanism of the hybridization transition and the growth of cBN by this method. © 2004 Elsevier B.V. All rights reserved.

Zhang J.;Cui Q.;Li X.;He Z.;Li W.;Ma Y.;Gao W.;Zou G.;Guan Q.

Chemical Physics Letters

2004

The electron transport properties of g-C3N4 under high pressure were analyzed by in situ resistance measurement both at ambient temperature and 77 K. It was observed that as the pressure increased from ambient to 30 Gpa, three abnormal resistance changes were found at room temperature and two were found at 77 K. The larger resistance value at 77 K indicated that the g-C3N4 and its potential high-pressure phases exhibited semiconductor transport characteristics. The results show that the electron transport behavior of g-C3N4 changes with the pressure.

Han Yonghao;Gao Chunxiao;Ma Hongan;Luo Jifeng;Hao Aimin;Li Ming;Liu Hongwu;Zou Guangtian;Xie Hongsen;Li Yanchun;Li Xiaodong;Liu Jing

Carbon

2005

In situ resistance measurement of Graphitic-C 3N 4 has been performed under high pressure in a diamond anvil cell. The result reveals that there are changes of electron transport behaviour. As the pressure increases from ambient to 30GPa, three abnormal resistance changes can be found at room temperature and two are found at 77 K. The abnormal resistance dropped at 5 GPa is close to the phase transition pressure from the P6̄m2 structure to the p structure predicted by Lowther et al. [Phys. Rev. B 59 (1999) 11683] Another abnormal change of resistance at 12 GPa is related to the phase transition from g-C 3N 4 to cubic-C 3N 4 [Teter and Hemley, Science 271 (1996) 53]. © 2005 Chinese Physical Society and IOP Publishing Ltd.

Han Yong-Hao;Luo Ji-Feng;Gao Chun-Xiao;Ma Hong-An;Hao Ai-Min;Li Ming;Liu Hong-Wu;Zou Guang-Tian;Li Yan-Chun;Li Xiao-Dong;Liu Jing

Chinese Physics Letters

2005

We report room-temperature thermoelectric properties of polycrystalline (PbTe) 100-x (Bi 2 Te 3 -Sb 2 Te 3 ) x (0.1 ≤ x ≤ 5). At x ≤ 0.25, with a decrease of x, the electrical resistivity increases dramatically whereas the Seebeck coefficient and the thermal conductivity nearly keep constant. At x ≥ 0.5, the electrical conductivity, the thermal conductivity and the Seebeck coefficient in absolute value slightly decrease with increasing x. It is found that, the thermal conductivity of the PbTe sample with Bi 2 Te 3 and Sb 2 Te 3 as the sources of dopants is much smaller than that of doping with other dopants at the same carrier concentration. With an increase of x, the figure of merit, Z, which is calculated from the measured quantities, increases at first and then decreases and shows a maximum value of 8.97 × 10 ^-4 K ^-1 at x = 0.2. This value is several times higher than that of small grain-size PbTe containing other dopants. © 2005 The Japan Institute of Metals.

Zhu Pinwen;Imai Yoshio;Isoda Yukihiro;Jia Xiaopeng;Zou Guangtian;Shinohara Yoshikazi

Materials Transactions

2005