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When Ta2O5 dielectric film was deposited on an indium-tin-oxide (ITO)-coated glass substrate by rf reactive sputtering, the blackening of ITO was observed. It was confirmed that the residual gas during sputtering is related to the blackening of ITO. The presputtering in argon-oxygen mixture gas and the following evacuation to basal pressure (less than 1×10-6 Torr) yield Ta2O5 films without ITO blackening.

SiC fiber reinforced SiC matrix (SiC/SiC) composites are one of the most promising materials for high temperature structural applications such as power generation and propulsion systems. SiC/SiC composites are, however, susceptible to accelerated attacks in water vapor environments through oxidation and volatilization reaction. For protection from such attacks, Environmental Barrier Coatings (EBCs) are indispensable. We have investigated some oxides and rare-earth silicates as topcoat candidate materials for EBCs. Topcoat materials must be stable in the high-water-vapor pressurized environments at high temperatures. Also, it is important that the thermal expansion coefficient of topcoat materials is similar to that of the SiC/SiC composites. In this study, first, zirconium oxides, lutetium silicates and yttrium silicates were selected as topcoat candidate materials. They were exposed in a water-containing atmosphere at a temperature of 1673 K for 100 h under a total pressure 0.96 MPa. Mass changes, structure of crystals and microstructures were investigated after the exposure experiments in order to evaluate the thermal stability of these materials. After their estimation, lutetium silicates were considered to be promising for topcoat materials. Then, lutetium silicates were coated as the topcoat of an EBC system on SiC/SiC composites, and their fracture toughness and microstructures were investigated after exposure to an oxidizing atmosphere. The evaluation results of the topcoat materials are reported in this paper.

Sr Metal.-An advanced preparation method for SrS:CeCl3 thin film electroluminescent (TFEL) devices using Sr metal, H2S, and CeCl3 is described. The H2S gas is introduced through a variable leak valve, which eliminates many problems concerning the sulfur coevaporation. The H2S pressure during deposition is found to affect the crystallinity of the film and the luminance-voltage (L-V) characteristics of the device. -(CHUBACHI, Y.; AOYAMA, K.; J.

initial source of some ZnO 3 together with oxygen in the adsorbed H20. Furthermore, it is known that ZnS is thermodynamically unstable in the presence of oxygen and should be converted to ZnO. The following reaction may be occurring along the grain boundaries of the filmThe continued formation of ZnO on the grain boundaries would result in successively lower recorded resistivities with time.The above results could explain the humidity effect on the resistivity of the samples. Water could easily enter the films along the grain boundaries and continue growth of ZnO.Water enters the ZnS film during the high humidity portion of the humidity cycle through the grain boundaries. The ZnO is quite conductive and decreases the resistivity of the ZnS film considerably. This effect is more pronounced for the .large grain film. The fact that ~r of both devices returns to nearly the same values at low humidity indicates that the new phase has a dielectric constant similar to that of ZnS. ZnO, with its a~ of 9.0 (in a dry atmosphere) is a possibility. Also, the volume of ZnS converted to ZnO would be small and e~ would still be dominated by the ZnS and H20 phases. ConclusionWe have demonstrated Q-V figure analysis as a useful way to characterize the humidity dependence of an EL