La0.5Sr0.5CoO3−δ (LSCO) can be used as a cathode material for low temperature solid oxide fuel cell applications. LSCO epitaxial thin films have been deposited on LaAlO3 substrates by pulsed laser deposition (PLD). The transient behavior of the thin film conductivity with the pressure changes was recorded as a function of temperature and partial oxygen pressure. The surface exchange coefficient k of the LSCO thin film was obtained from analysis of the electrical conductivity relaxation data. The measured surface exchange coefficient increases with temperature and with final pressure but is not sensitive to the initial pressure. After prolonged annealing at 900°C, the k value was found to have greatly increased. The mechanism of the dependence of the measured k on pressure is discussed.

Polycrystalline, theoretically dense silicon carbide was deposited onto graphite substrates via the reductive pyrolysis of methyltrichlorosilane in a hot-walled chemical vapor deposition (CVD) chamber. The resulting product can be considered a bulk material with deposit thicknesses in the range of 4 to 8 millimeters. The material was characterized using powder x-ray diffraction and Laue back-reflection techniques. Under the deposition conditions investigated in this study, the crystallographic orientation varied as a function of distance from the substrate. The material exhibited a high degree of randomness in proximity to the substrate, and progressively showed a higher degree of preferred crystallographic orientation as the deposit progressed. This phenomenon is correlated with the microstructure of the material as well as such mechanical properties as hardness and fracture toughness.

Some of the most promising materials for electrostrictive response are Pb(Mg1/3, Nb2/3)O3 (PMN) - ceramics; however, the properties of a given composition are only optimum in a limited range of temperatures. In a previous study, it was found that sol coating of PMN particles modified and improved the electromechanical and/or dielectric properties of the resulting product--doubling induced strain in some cases. Understanding the origin of these changes will help to produce an optimized PMN ceramic for a given application from a single source powder. This work concentrates on the Ti and Zn coatings which gave superior properties within the concentration matrix. The relation between the structure and the enhanced electrostrictive behavior is studied. Structural characterization is done by XRD, TEM and SEM.Electrical measurements of dielectric constant, loss, polarization and strain, the property determinations needed to complete the structure-property suite.

ZnO addition for low-T sintering of ZST has serious side effects such as decrease of Q × f value. In this work, the curing of these side effects without any further chemical additivesand causing degradation of other dielectric properties have been presented. After sintered at 1350°C for 2h. samples were annealed in oxygen at 900 ∼ 1100°C for 5hr. It was observed that Q × f value of post-annealed sample at 900°C could recovered up to 46000 from the as-sintered value of 40000. Because there were no formations of second phases or significant changes inlattice constants, which could affect microwave properties of ZST. However, it was found that only for the specimens annealed at 900°C, Zn was almost depleted from grin inside and diffused toward grain boundary. So, it is suggested that the out-diffusion of Zn is responsible for the recovery of Q × f value. Moreover, when the amount of Zn incorporation increased via successive calcination and sintering of pre-mixed powder of ZST and ZnO, Q × f value of 33000 also could enhanced up to 39000 due to the redistribution of Zn near grain boundary by out-diffusion.

Sodium-covered silica films formed on silicon substrates have been examined by X-ray photoemission spectroscopy (XPS) and X-ray absorption spectroscopy (EXAFS) in ultra-high vacuumconditions at 300K. The results show that sodium diffuses into the silica layer on a reversible manner and that it modifies the silica network in order to create its own site. Sodium atoms are surrounded by oxygen atoms at an average distance of 2.3 Å and by a second shell which is assigned to silicon atoms located at 3.8 Å. At high Na concentrations, sodium atoms are also present in the close environment of one sodium atom.