Impact of mechanical activation of reactant powders on the solid-state-densification of Zn1-xLixO and Zn0.7Li0.28Mg0.02O ceramics

This paper presents effects of powder mechanical activation and controlled sintering on the densification properties of ZnO ceramics with Lithium (Li) and Magnesium (Mg) dopants. Dense bodies of Zn1-xLixO and Zn0.7Li0.28Mg0.02O ceramics were prepared via solid-state-reaction of mechanically activated mixtures of ZnO, Li2CO3 and MgO reactant raw powders. The density, surface microstructure, porosity and phase purities of the ceramics were investigated with a Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD) techniques. The study highlights mechanical activation processes such as milling, calcination and compaction steps that are needed to overcome complicated interactive reactions during conventional sintering of Zn1-xLixO and Zn0.7Li0.28Mg0.02O ceramics that have been reported to show ferroelectric behavior. The results show that, densely packed single phase Zn1-xLixO and Zn0.7Li0.28Mg0.02O ceramics with average relative density values above 96% and single phase hexagonal wurtzite crystalline structure were achieved at a sintering temperature of 1000 °C for 2 h in air

Pressure effects on interfacial surface contacts and performance of organic solar cells

This paper explores the effects of pressure on the interfacial surface contacts and the performance of organic solar cells. A combination of experimental techniques and analytical/computational models is used to study the evolving surface contacts profiles that occur when compliant, semi-rigid and rigid particles are interlocked between adjacent layers in model solar cell structures. The effects of layer surface roughness and interlocked (trapped) particles are also considered along with the effects of surface energy, adhesion energy, and pressure. The results show that increased interfacial contact lengths and decreased void lengths are associated with the application of increased pressure. Increased pressure also results in significant improvements in power conversion efficiency. These improvements in power conversion efficiency are associated with the closure up of micro- and nano-voids due to the application of pressure to layers produced via spin coating and thermal evaporation. The results suggest that pressure-induced contacts can be used to enhance the performance of organic solar cells