Formation of the Liquid Phase in the System Bi-Pb-Sr-Ca-Cu-O

Differential thermal analysis (DTA), powder X-ray diffraction (XRD), and scanning electron microscopy (SEM) were carried out to investigate the origin of the partial melting which is closely related to the formation of the 110 K superconducting phase in the Bi-Pb-Sr-Ca-Cu-O system. The occurrence of a liquid phase in the presence of the Bi₂Sr₂Ca-Cu₂O _y , Ca₂PbO₄, and CuO phases was demonstrated. Large grain growth and promotion of the 223 phase formation resulting from the reactive liquid-phase-aided sintering were also observed.     

Nitride-based LEDs with an SPS tunneling contact Layer and an ITO transparent contact

The indium-tin-oxide [ITO(80 nm)] and Ni(5 nm)-Au(10 nm) films were separately deposited on glass substrates, p-GaN layers, n/sup +/-InGaN-GaN short-period-superlattice (SPS) structures, and nitride-based light-emitting diodes (LEDs). It was found that ITO on n/sup +/-SPS structure could provide us an extremely high transparency (i.e., 93.2% at 465 nm) and also a reasonably small specific contact resistance of 1.6/spl times/10/sup -3//spl Omega//spl middot/cm/sup 2/. Although the forward voltage which corresponds to 20-mA operating current for LED with ITO on n/sup +/-SPS upper contact was slightly higher than that of the LED with Ni-Au on n/sup +/-SPS upper contact, a 30% higher output intensity could still be achieved by using ITO on n/sup +/-SPS upper contact. Moreover, the output power of packaged LED with ITO was about twice as large as that of the other conventional Ni-Au LEDs.     

A microstructural examination of the flow behaviour of a superplastic copper alloy

There are important differences in the microstructures of specimens of a superplastic copper alloy deformed in the three regions of flow associated with superplasticity. There is very extensive dislocation activity at high strain rates in Region III, whereas at intermediate and low strain rates in Regions II and I the dislocation density is low and many of the grains appear to be dislocation-free. Measurements show that grain-boundary sliding is important in Region II but decreases in magnitude in the less superplastic Regions I and III.