Cunyi Xu

Study of the Raman spectrum of nanometer SnO2

The Raman spectra of nanometer‐sized particles of SnO2 (3–90 nm) at room temperature are reported. In the Raman spectra of the particles of SnO2, which are quite different from that of single‐crystal SnO2, there appear two new characteristic peaks, and their intensities decrease gradually with the increase of crystal size. It is concluded that the new peaks can be explained by the surface phonon modes of nanometer SnO2, consequently there is a relation between the structures of surface layers and bulk. It is believed that it is possible to determine the exact positions of atoms in surface layers of some nanometer crystals from their laser Raman spectra.

Crystallite size effects on the Raman spectra of Mn3O4

Abstract The Raman spectra of nanometer Mn3O4 with different sizes at room temperature are reported. The Mn3O4 powder was prepared by γ-irradiation then annealed at different temperatures to obtain different crystal sizes. The result of experiment shows that the shifting and broadening of Raman spectrum was mainly due to grain size effect. In principle, Raman spectroscopy is relatively simple and easier to use for determination of crystallite size of some materials.

Identification of the pigment in painted pottery from the Xishan site by Raman microscopy

Shards from the archaeological site of Xishan (Henan, China) were analyzed by Raman microscopy to determine the pigments used in the decoration of this ancient (ca 4300–2800 BC) pottery. It was found for the first time that anatase was used for white coating 5000 years ago and this represents a contribution to the current knowledge of the history of pigments. The brown coating was identified as graphite. The red and black coatings were mainly haematite and magnetite; the colour of the coatings depends on the ratio of haematite to magnetite. Copyright

Raman Spectra of NanophaseCr2O3

The Raman spectra of nanometer-sized Cr2O3 particles (annealed in air and in vacuum at different temperatures) at room temperature are reported. The results show that the correlation between the change of the Raman spectrum of nanometer Cr2O3 and its crystal size is different from that of other nanometer-sized materials. It was shown that the shifting and broadening of the Raman spectra were related to the defect structures produced by an oxygen deficiency in the material and was not due to a grain size effect.

Raman spectroscopy and x-ray diffraction study of PbTiO3 thin films prepared by sol–gel technique

PbTiO3 (PT) thin films were prepared by the sol–gel technique on Si(111) single crystal, fused quartz, and NaCl substrates using two precursor solutions: methanol and 2-methoxyethanol. Raman spectroscopy and x-ray diffraction were used to determine the effects of the precursor solution, substrate, annealing temperature, and film thickness on the film structure and crystallization behavior. The results indicate that the precursor solution plays an important role in the fabrication of pure perovskite PbTiO3 films. The films deposited from methanol solution are able to form the perovskite structure at lower crystallization temperature (∼430 °C). In contrast, the films deposited from 2-methoxyethanol solution easily form the pyrochlore phase. This is ascribed to the different mechanism of hydrolysis and condensation polymerization of the two precursor solutions. The Raman scattering results on various substrates have significant and interesting differences, especially for the films deposited from 2-methoxyeth...

Photoemission and Raman studies of Y1-xPrxBa2-ySryCu3O7-δ system

Abstract Photoemission spectra (PES) and Raman measurements have been performed for Y1 − xPrxBa2 − ySryCu3O7 − δ polycrystalline samples, especially for the x = 0.6 series. It is shown that Y3d, Ba3d, Sr3d and Ols electron binding energies shift towards lower values with increasing Sr concentration y; Cu2p core level has no apparent changes; Pr3d (obtained by subtraction of Pr3d + Cu2p from the Cu2p of YBa2Cu3O7 − δ) level tends to go up with increasing Sr content. The core level results imply that Sr-doping enhances the Ba SrO covalency but weakens the PrO covalent mixing. The valence band spectra display regular changes upon Sr-doping. We have discussed them in terms of the PrO covalent bonding effect, which may account for the puzzled ‘ion-size effect’ and probably plays an important role in suppression of superconductivity by Pr. Raman measurement shows an extra peak at 575 cm−1 while the orthorhombic-totetragonal (OT) transition takes place aty = 0.75 in Y 0.4Pr0.6Ba2 − ySryCu3O7 − δ system, suggesting that the OT transition be originated from the oxygen disorder in Cu(1)O layer. In addition, the out-of-phase O(2,3) bending mode is softened with increasing Sr-doping. This fact suggests that the chemical bonding strength of Y PrO decreases, which is consistent with the result of PES.

Phonon spectroscopy and transport properties of Y1-x Nd x Sr2Cu2.7Mo0.3O7-δ

The Raman and infrared spectra, resistivity as well as thermoelectric power of Y1-xNdxSr2Cu2.7Mo0.3 O7 δ(.x =0, 0.1. 0.2. 0.5, 0.8 and 1.0) are studied carefully. It was found that the structure characteristics of RSr2Cu2.7Mo0.3O7 δ cuprates are different from those of RBa2Cu307 δ. The variations of the microstructure in Y1-x NdxSr2Cu2.7Mo0.3O7 δ with Nd-doping affect the carrier distribution. so as a result the superconductivity changes. Furthermore, it is pointed out that the microstructure variations with the large rare earth ionic substitution cause the widely existing rare earth ionic size effect in HTSC.

Effect of extra oxygen intercalation on the modulation structure and electronic structure of the Bi2201 system

The incommensurate modulation structure and electronic structure of the system were investigated by means of Raman scattering, transmission electron microscopy and x-ray photoemission. Analyses of Raman spectra and electron diffraction reveal that, even though the extra oxygen behaviours in layers for the three samples are very different, they possess a similar monoclinic modulation characteristic with modulation wavelength , which supports the crystal misfit model. Analysis of XPS results indicates that extra oxygen intercalation has a strong influence on the electronic structure; a possible Bi 6s contribution to the valence band is suggested.

Study on the transport properties in Bi2−xPbxSr1.65La0.35CuOy system

Abstract Two series of samples of Bi2−xPbxSr1.65La 0.35 CuOy (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.6) system with different oxygen concentration were obtained. By means of XRD, resistivity and Raman spectrum, we studied the relation between structure and superconductivity. Pb doping can increases T c onset and T c o to 45K and 37K. Our experimental results indicate that besides carrier concentration, the crystal microstructural characteristic has strong influence on the normal-state transport properties and superconducting transitions.