W.J. Wang

Enhanced dielectric responses in Mg-doped CaCu3Ti4O12

We report the effects of the Mg doping on the dielectric properties of CaCu3Ti4O12 in the frequency range of 200 Hz–200 kHz and in the temperature range of 58–473 K. It is found that the incorporations of Mg2+ result in increases in the dielectric constant by 12%–20% and decreases in the dielectric loss by 41%–64% (with the minimum of 0.042 for CaCu2.7Mg0.3Ti4O12) at room temperature and at 1 kHz. The x-ray photoemission spectroscopy measurements reveal that the content of Cu3+ increases with the increasing concentration of Mg2+. The enhanced dielectric response may be related to the influence of Cu3+ and/or Mg2+. In other words, Mg2+ is an effective ion to optimize the dielectric properties of CaCu3Ti4O12.

Effects of vitamin A supplementation on growth performance, carcass characteristics and meat quality in Limosin × Luxi crossbreed steers fed a wheat straw-based diet

Three experiments were conducted to examine the effects of dietary vitamin A supplementation on performance and carcass parameters in Limosin×Luxi crossbreed finishing steers fed a wheat straw-based diet. Sixteen 12-month old (301±22kg) steers, 16 12-month old (309±15kg) steers and 16 24-month old (411±20kg) steers were used in experiment 1 for 6 months feeding period, in experiment 2 for three months feeding period and in experiment 3 for three months feeding period, respectively. Sixteen steers of each experiment were randomly divided into the four groups of four animals. Treatments consisted of four vitamin A supplementation levels (0, 1100, 2200 and 4400IU/kg DM). The growth rate was affected by dietary vitamin A level in experiment 1 and 2, revealing that the suitable amount of vitamin A supplementation increased the growth rate; excessive vitamin A in the ration decreased the growth rate of 12-month-old finishing steers. The marbling deposition decreased with the increment of vitamin A supplementation level, but possibly associated with vitamin A supplementing duration. Furthermore, the suitable dietary vitamin A level probably decreased lipid and pigment oxidation, and increased the tenderness of beef meat. Vitamin A supplementation had no significant effect on chemical composition of gluteus medius muscle and longissimus dorsi muscle.

Observation of symmetrically decay of A1(longitudinal optical) mode in free-standing GaN bulk single crystal from Li3N flux method

We report Raman analysis of A1(LO) (longitudinal optical) and E2(high) phonon lifetimes in a bulk GaN single crystal and their temperature dependence from 77 K to 770 K. Both the A1(LO) and E2(high) phonons in GaN were observed decaying primarily into two phonons of equal energy [Klemens model, P. G. Klemens, Phys. Rev. 148, 845 (1966)]. This is a rare example of a high-quality free-standing GaN bulk single crystal displaying abnormal A1(LO) phonon decay. These results will have significant impact on designing and understanding of GaN-based high-speed, high-power electric devices.

Amorphous FeTi alloy formed by solid state reaction

Abstract The present paper reports the formation of amorphous Fe 50 Ti 50 alloy by the solid state reaction of pure polycrystalline Fe and Ti thin films at low temperature. X-ray diffraction and reflecting electron diffraction were used to monitor the reaction. The amorphization process of this alloy without large negative mixing heat isexplained in view of the rection kinetics.

Vanadium bound exciton luminescence in 6H-SiC

The source responsible for V2 (1.398 eV) luminescence in 6H-SiC is recognized as a favorable defect for quantum information processing. However, the origin of V2 luminescence is still controversial. With careful photoluminescence measurements, it is found that V2 line shows clear bound exciton luminescence features. Furthermore, a mechanism based on neutral vanadium donor bound exciton is put forward to explain the origin of V2 luminescence. The results may provide some insights to understanding the nature of the promising qubit candidates in SiC.

Formation of amorphous Fe50Si50 alloy by diffusion reaction

Abstract The solid state reaction in the multilayer film with alternative polycrystalline Fe and amorphous Si layers has been studied with X-ray diffraction. Amorphous Fe50Si50 phase was formed after annealing isothermally at 300°C, which is explained in view of the consideration that an amorphous phase can be more favorable to form than a supersaturated solution in thermodynamics as well as than an equilibrium compound FeSi in kenetics.

Room temperature luminescence and ferromagnetism of AlN:Fe

AlN:Fe polycrystalline powders were synthesized by a modified solid state reaction (MSSR) method. Powder X-ray diffraction and transmission electron microscopy results reveal the single phase nature of the doped samples. In the doped AlN samples, Fe is in Fe2+ state. Room temperature ferromagnetic behavior is observed in AlN:Fe samples. Two photoluminescence peaks located at about 592 nm (2.09 eV) and 598 nm (2.07 eV) are observed in AlN:Fe samples. Our results suggest that AlN:Fe is a potential material for applications in spintronics and high power laser devices.

Formation mechanism of Type 2 micropipe defects in 4H–SiC crystals

We report experimental studies on the formation of Type 2 micropipe defects in 4H–SiC crystals grown by a physical vapor transport method. Compared with Type 1 micropipes, Type 2 micropipes exhibit new features allowing them to lie at an oblique angle about 12° to the [0001] crystal axis and are smaller in size than Type 1 micropipes. By changing the growth conditions, we find that a smaller axial temperature gradient and a larger grain size in the SiC source are beneficial to eliminate the Type 2 micropipes. We think that the liquid silicon is responsible for the formation of Type 2 micropipes. A possible formation mechanism for Type 2 micropipes is put forward.