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He pointed out that the processing of ceramic powders for a variety of applications is commonly carried out using particles with very small sizes. Solid materials with nanoscale crystallite sizes are particularly attractive for potential applications because of the high number of interfaces in these materials. For example, work over recent years has shown that the sintering behavior of ultrafine grained ceramics such as zirconia (ZrO2) and titanium dioxide (TiO2) with initial crystallite sizes in the 10-nm region exhibit improved sintering behavior compared with conventional microcrystalline powders. One key to understanding the high-temperature properties of ultrafine grained materials is the diffusion of atoms along and across the grain boundaries between the nanocrystallites. But diffusion data, particularly on nanocrystalline ceramics, are scarce, according to Würschum. The transport of atoms in nanocrystalline materials is an important issue since it controls both the physical properties, such as plasticity, and the structural stability of these materials," he said.
Last year, Würschum and coworkers reported data on the diffusion of oxygen in ultrafine-grained ZrO2. The group used a secondary ion mass spectrometer to measure diffusion profiles of an 18 O tracer in the material. "The measurement of oxygen diffusivity in nanocrystalline ZrO2 is relevant for the assessment of whether or not a high number of interfaces can improve the performance of solid-state oxide electrolytes
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