Sc2O3 Content Research Articles

Preparation of Tetragonal Zirconia Ceramics in ZrO<sub>2</sub>-Sc<sub>2</sub>O<sub>3</sub> System by Hydrolysis and Homogeneous Precipitation and Their Phase Stability

Fine zirconia powders doped with 3 to 6mol% Sc2O3 have been prepared by the urea-based homogeneous precipitation method using monoclinic zirconia sols previously formed by the hydrolysis of ZrOCl2 solution. Highly dense Sc2O3-doped tetragonal zirconia ceramics, Sc-TZP (>99%) with a homogeneous microstructure were obtained by sintering these powders at 1300°C or 1400°C for 1h and their phase stability was investigated. The average grain size and the crystal phase of ZrO2(+Sc2O3) materials were observed to depend on the Sc2O3 contents. Addition of 3.5mol% Sc2O3 was necessary to fabricate zirconia bodies consisting of fully tetragonal phase by sintering at 1300°C. This value corresponds to nealy 1.5 times the content of Y2O3 in the ZrO2-Y2O3 system. The average grain size of the 4mol%Sc-TZP sintered at 1400°C was <0.5μm. Although the grain size is depending on the sintering temperature, it increased gradually with increases in Sc2O3 content from 3 to 6mol% and in the content of the cubic phase. The monoclinic zirconia contents transformed from the tetragonal phase in the surface of the 4 to 6mol% Sc-TZP under hydrothermal conditions at 180°C for 50h were about 93 to 70%.

Impregnated cathode coated with tungsten thin film containing Sc2O3

An impregnated cathode of a novel structure is proposed, fabricated, and evaluated. A thin tungsten film 100–400 nm in thickness containing various amounts of Sc2O3 is coated on a standard impregnated cathode composed of a porous tungsten body in which electron emissive materials are impregnated. The electron emission property measured with a diode configuration is found to be dependent on Sc2O3 content and surface atom distribution. Surface atom distribution is depicted by means of Auger electron spectroscopy. For high electron emission enhancement it is necessary for Sc2O3 content to be 2.5–6.5 wt. % and for a layer of the order of a monolayer in thickness composed of Ba, Sc, and O to develop on the cathode surface.