Ding Zhanhui

Preparation and Raman Spectrum of Rutile Single Crystals Using Floating Zone Method

With anatase-type titanium dioxide as the raw materials, the rutile type titanium dioxide single crystal is prepared using the floating zone method. The results of XRD measurements show that the grown crystal is highly crystalline with a rutile structure, which has orientation to the c-axis. The four Raman vibration characteristic peaks (143, 240, 450 and 610 cm(-1)) at room temperature show that the crystalline structure of the single crystal is a typical rutile phase, meanwhile a new Raman peak at around 690 cm(-1) is found. The results of the Raman measurement at various temperatures for the single crystal show that the Raman frequency shifts are different.

Raman Active Phonons in RCoO3 (R=La, Ce, Pr, Nd, Sm, Eu, Gd, and Dy) Perovskites

We examine RCoO3 (R=La, Ce, Pr, Nd, Sm, Eu, Gd, and Dy) perovskites prepared with the solid-state reaction method by Raman spectroscopy, and report the Raman active phonons in the RCoO3 perovskites crystallized in cubic symmetry for RCoO3 (R=La, Ce, Pr and Nd) and orthorhombic symmetry for RCoO3 (R=Sm, Eu, Gd, and Dy). It is found that the Raman spectra of RCoO3 perovskites are strongly dependent on the ionic radius of the rare earth elements, and the frequency shift of the most intense modes of the orthorhombic samples are correlated with some structural parameters such as Co-O bond distances, ionic radius of the rare earth elements and Jahn-Teller distortion. It is clear that Raman spectroscopy has the advantage of sensitivity to structure distortion and oxygen motion.

Reactive Mechanical Alloying Synthesis of Nanocrystalline Cubic Zirconium Nitride

Zirconium nitride powders with rock salt structure (γ-ZrNx) are prepared by mechanical milling of a mixture of Zirconium and hexagonal boron nitride (h-BN) powders. The products are analysed by x-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy (RS). The formation mechanism of γ-ZrNx by ball milling technique is investigated in detail. N atoms diffuse from amorphous BN (α-BN) into Zr to form Zr(N) solid solution alloy then the Zr(N) solid solution alloy decomposes into γ-ZrNx. No ZrB2 is observed in the as-milled samples or the samples annealed at 1050° C for 2h.

Synthesis of Nanocrystalline Cubic Hafnium Nitride by Reactive Mechanical Alloying

Nanocrystalline cubic hafnium nitride (HfNx) powders are prepared by the mechanical milling of Hafnium and hexagonal boron nitride (h-BN) powder mixtures. The prepared nanocrystalline HfNx is analyzed and characterized using x-ray diffraction and Raman spectroscopy. HfNx formation mechanisms in both mechanical milling and annealing processes are also studied in detail. It is found that HfNx is probably formed via the phase separation of Hf(N) solid solution alloy driven by reactive mechanical milling in which Hf(N) solid solution alloy is formed by Hf and N atoms through a diffusion reaction process. Meanwhile, a phase separation can also be induced in Hf (N) solid solution as the N content exceeding its solubility limit, leading to an additional way to produce HfNx. No HfB2 has been found during both milling and annealing processes.

Zinc oxide hexagram microrods

Zinc oxide (ZnO) microrods were grown by the floating zone method, the as-grown ZnO microrods have uniform size. Scanning electron microscope image reveals that the ZnO microrods are grown with a hexagonal structure, well faceted ends and side surfaces. Most of ZnO microrods have diameters of about 20–30nm and lengths of about 1–2 mm. Polarizing microscopy image of ZnO microrods shows that they have high crystal quality. The X-Ray diffraction pattern shows that microrods have vertical orientation. The Raman spectra demonstrate that the vibrational mode of wurtzite-type ZnO clearly. The room temperature photoluminescence measurements indicate that the microrods have a relative strong ultraviolet (UV) emission and very weak green emission.