Wang Yening

Study on the anomalies of YBa2Cu3O9-x between 90 and 260 K by elasticity measurements and X-ray diffraction

The internal friction (Q-1), ultrasonic attenuation ( alpha ) and variation of Youngs modulus ( Delta E/E) of YBa2Cu3O9-x were measured with frequencies of 5 kHz, 120 kHz and 5 MHz. Several Q-1 (or alpha ) peaks and corresponding minima of Delta E/E were observed. According to X-ray diffraction results, the Q-1 peak as well as other anomalies can be attributed to a discontinuous change of lattice parameters. The tendency to elastic softening above 90 K may play an important role in superconductivity.

Structural, Ferroelectric, Dielectric Properties and Leakage Characteristics of Neodymium-Doped Bi4Ti3O12Thin Films Prepared by Metalorganic Deposition Method

Thin films of Nd3+-substituted Bi3.15Nd0.85Ti3O12 (BNT) were fabricated on the (111)Pt/TiO2/SiO2/Si substrates by a metalorganic deposition (MOD) technique. These thin films are possessed of a single-phase bismuth-layered structure showing the preferred (001) and (117) orientation. The values of the remanent polarization Pr and coercive field Ec of the BNT thin film are 27 μC/cm2 and 157 kV/cm, respectively. The results of fatigue and retention tests revealed that the BNT thin film was not fatigued up to 1.44×1010 switching cycles and the retained charge was unchanged after 1×105 s. The leakage current behaviour of the BNT thin film was investigated at room temperature and their conduction mechanisms were also discussed. The I–V characteristics of the film show the ohmic behaviour for applied field lower than 40 kV/cm. Nonlinearity in the I–V behaviour was observed at an applied field above 40 kV/cm. In the high field region (E>95 kV/cm) the sample shows Schottky emission.

Phase-transition-like behaviour associated with the superconducting transition in Tl2Ca2Ba2Cu3Ox and BiSrCaCu2Ox compounds

A structural instability shown in the form of a phase-transition-like internal friction peak and step-like change of lattice parameters appears at 135 K in a Tl2Ca2Ba2Cu3Ox sample with zero resistance at 115 K. It was confirmed that the structural instability at 135 K coexisted with the superconducting transition at 115 K. In addition, a small internal friction peak and an ultrasonic attenuation peak, which may be related to the lower temperature superconductive phase, were observed at 90 K in the Tl-Ca-Ba-Cu-O material.

A study of pseudo-elasticity in the superconducting oxide YBa2Cu3O7-δ

The pseudo-elasticity in YBa2Cu3O7- delta has been investigated by a mechanical method from room temperature to 79 K. Several ferroelastic-type loops were observed near room temperature, 240, 220 and 170 K. These phenomena are discussed in conjunction with the results of X-ray diffraction.

Domain structure, domain wall mobility and electric properties for PbTio3 and SrBi2Ta2o9thin film

Abstract TEM studies on domain structure in PbTiO3 thin film show that the domain density depends on the grain size and indirectly on the film thickness. The mobility of domain walls (DWs) has been investigated by in situ TEM and mechanical dissipation techniques, and its contribution to the permittivity (ϵ) and coercive field (Ec) was analyzed. The weak pinning of DWs in SrBi2Ta2O9 (SBT) was further confirmed by experimental results of the voltage and frequency dependence of the fatigue as well as retention.

A superstructure in single-crystal YBa2Cu3O7-δ

A new form of superstructure with a square root 2*2 square root 2*1 supercell oriented at 45 degrees to the original unit-cell axes has been found in a YBa2Cu3O7- delta single crystals by means of electron diffraction and electron microscopy. It is suggested that this superstructure results from a substructure modulation.

Ferroelectric Properties of Both Nd Substituted and W Doped Bi4Ti3O12 Thin Films Deposited by Chemical Solution Deposition Technique

Both Nd substituted and W doped bismuth titanate thin films were deposited by chemical solution deposition (CSD) technique on the (111)Pt/Ti/SiO2/(100)Si substrates. B-site doping with W6+, enhanced the remnant polarization and improved the fatigue property. Remnant polarization of Bi3.15Nd0.85Ti2.98W0.02O12 (BNTW) is 27 μ C/cm2, which is higher than that of Bi3.15Nd0.85Ti3O12 (BNT) deposited in the same condition. Good fatigue endurance was confirmed at 1 M Hz frequency up to 1010 switching cycles in both BNTW and BNT thin films. However, at the frequency of 50 kHz, the BNTW thin films show an improved fatigue property. W-doped effect is discussed.

Anelastic relaxation near Tc in Zn-substituted YBCO

Abstract The anelastic properties of Zn-doped ceramic YBa 2 Cu 3 O 6+ δ superconductors were measured and two thermally activated relaxation peaks were observed in acoustic-frequency internal friction spectrum at 100 and 110 K. The intensity of the lower-temperature peak was found to decrease rapidly upon zinc substitution while the other one remains almost unaffected. The relaxation mechanisms for the two relaxation peaks are studied and the deteriorative effect of zinc substitution on superconductivity is also discussed.

63Cu NMR Study of Cu83-Zn17 Mixed Powders During Mechanical Alloying

The variations of the 63Cu NMR spectra of Cu83-Zn17 powder mixtures with time of ball milling are shown and analyzed. With increasing the ball-milling time, the α phase is developed as terminal phase over 5 h, accompanying the emergence and following disappearance of small amount β phase. The microstructural changes after aging at room temperature are also detected. Some valuable conclusions related to the alloying reaction on an atomic scale have been drawn.

The effects of thermal cycling from 5 to 350 degrees C on elasticity and superconductivity of YBa2Cu3O7-δ

The effects of thermal cycling from 5 to 350 degrees C on the elastic and superconducting properties of YBa2Cu3O7- delta have been studied. In internal friction (Q-1) measurements, variation of the peak temperature, peak height and background with thermal cycling was observed. The conductivity transformed from metallic to semiconducting after several thermal cycles. These phenomena are attributed to the decrease of oxygen content. Sample-dependent variations in elastic moduli were observed.