Z.J. Chen

HYDROTHERMAL EPITAXY OF HIGHLY ORIENTED TIO2 THIN FILMS ON SILICON

Highly oriented thin films (0.15 μm) of titania on Si (100) substrates have been prepared first by hydrothermal treatment of TiO42− solution (0.6–1.2M) at relatively low temperatures. Films made at 100–200u2009°C contain only the anatase phase with (112) orientation, adhere well to the substrates. The hydrothermal temperature, time, and the pH value of TiO42− solution are the critical parameters determining the formation of films.

Deposition and microstructural characterization of NiO thin films by a spray pyrolysis method

Abstract Thin films of NiO (200 nm) with a preferred [lcub]110[rcub] orientation were deposited by a spray pyrolysis method. Ethanol solutions of nickel acetylacetonate were ultrasonically nebulized and thermally decomposed onto Si(111) and NaCl(100) in the temperature range 400–430°C. The microstructure of as-deposited NiO thin films was studied by XRD, SEM and TEM.

Preparation of nanocrystalline manganic oxide Mn2O3 powders by use of γ-ray radiation

Abstract Nanocrystalline manganic oxide (Mn2O3) powders have been prepared for the first time from potassium permanganate (KMnO4) aqueous solutions by use of γ-ray radiation. Transmission electron micrographs and X-ray powder diffraction patterns show that the average particle sizes are in the range 12–28 nm. The influence of various experimental conditions on the particle size was studied.

Preparation of nanocrystalline antimony oxide powders by use of γ-ray radiation — oxidization route

Abstract γ-ray radiation-oxidization route has been used to prepare nanocrystalline metal oxide Sb 2 O 3 powders from aqueous solutions at room temperature and ambient pressure. Experimental results reveal that Sb 3+ concentration, radiation dose, kind and concentration of surfactant and concentration of OH radicals scavenger affect the particle size and yield. Transmission electron micrograph and X-ray powder diffraction show the average particle sizes of antimony oxide Sb 2 O 3 powders for all the samples are in the range 8–48 nm, in which the particle size distribution of the sample with the smallest average particle size is from 5 to 25 nm. The highest yield is above 70%.

GROWTH OF BI2SR2CA1-XCEXCU2OY SINGLE-CRYSTALS FROM EUTECTIC MELTS

Bi2Sr2Ca1-xCexCu2Oy single crystals with in-plane dimensions up to 8X8 mm(2) were successfully grown by spontaneous nucleation from eutectic melts. For x less than or equal to 0.8, all the grown crystals possess the pure 2212 phase. However, when x = 1.0,

Synthesis and structure of superconductors, (Sr2−xBix) (Ln2−yCey)Cu2O8−δ of T∗ phase

Abstract We have successfully synthesized a new family of superconductors (Sr 2− x Bi x ) (Ln 2− y Ce y )Cu 2 O 8−δ (0.3⩽ x ⩽0.5; 0.6⩽ y ⩽0.9) in which the rock-salt block (Nd,Sr)O in the (Nd 1.18 Sr 0.82 ) (Nd 1.46 Ce 0.56 )Cu 2 O 8 is replaced by (Bi,Sr)O. Its lattice parameters are a=3.82 A and c=12.66 A . This structure may be also believed to be the structure resulting from removing the Bi-O bilayers in Bi 2 Sr 2 (Nd,Ce) 2 Cu 2 O y . The maximum zero resistivity temperature was about 30 K. It is found that superconductivity takes place in a narrow range of oxygen content and the thermodynamic stability of these materials is closely related to the value of δ.

Superconductivity in Cd-doped Pb-based layered copper oxides, (Pb1-xCdx)Sr2(Y0.5Ca0.5)Cu2Oy

Abstract Samples of nominal composition (Pb 1- x Cd x )Sr 2 (Y 0.5 Ca 0.5 )Cu 2 O y (0⩽ x ⩽0.6) synthesized at 1000°C in oxygen were investigated. All the as-prepared samples became superconducting at around 25 K, except x =0 and 0.1. For the superconducting samples, the content of Cd has little effect on T c onset . However, the same annealing at 560°C for 1 h in air which induced superconductivity in the non-superconducting “as-prepared” sample of x =0.1 led to the depression of the superconductivity of the “superconducting as-prepared” samples of 0.2⩽ x ⩽0.6. The post-treatments in air and oxygen (1 and 5 atm) substantially increase the resistivities at 300 K of the samples.

SINGLE-CRYSTAL GROWTH AND CHARACTERIZATION OF THE PB0.5SR2.5Y1-XCAXCU2OY SYSTEM

Two kinds of methods such as spontaneous nucleation from flux-free stoichiometric melt and CuO flux method have been used for the growth of Pb0.5Sr2.5Y1-xCaxCu2Oy single crystals. The morphologies, phases, and compositions occurring in the crystals grown

Systematic evolution of electron localization in Bi2Sr2CuOy

The electronic transport properties in Bi2Sr2CuOy crystals have been investigated with the focus on the localized behaviours at low temperature. It is found that in the passage of transition from metallic to insulating states the samples first show two-dimensional weak localization behaviour, and cross over to the variable-range hopping conduction corresponding to the strong-localization regime. We analyse the experimental results and suggest that the metal-insulator transition is caused by the effects of both disorder in the lattice and electron correlations.

Growth of 1212 phase PbSrYCaCuO single crystals

Relatively large single crystals of 1212 phase PbSrYCaCuO have been grown by spontaneous nucleation from a eutectic melt. Pure phase 1212 single crystals up to 5 × 4 × 3 mm3 were obtained. The length of the c-axis of the as-grown single crystals is 11.784 A. The crystals have been characterized by X-ray fluorescence spectrometry, X-ray diffraction data (rocking curves), multiple order (001) diffraction and back-reflection Laue photography. The results indicate that the crystals are highly oriented.