Papers by Author: Wen Liang Zhu

Abstract: With the proliferation of several types and classes of high performance ceramic materials, the screening, evaluation and integration of new materials into structures and devices require a new and more effective approach. Evaluation on the nano-scale of the mechanical characteristics of new ceramic materials requires multiple complementary metrology tools. We report here about an advanced metrology tool, cathodoluminescence (CL) spectroscopy, which has a potential to rapidly screen and evaluate residual stress characteristics in advanced ceramic materials and structures. Nano-scale stress measurements are made in situ into an integrated metrology vacuum chamber in a field-emission gun scanning electron microscope (FEG-SEM). Complementing this tool, we also describe a new image analysis based on CL emission for fast screening and ranking of domain structures in ferroelastic ceramics. The end result of this paper is to show how crystallographic and mechanical characteristics of ceramics can be quantitatively characterized in a hybrid device combining electro-stimulated imaging and spectroscopic outputs.

Abstract: A non-destructive assessment of phase transformation and residual stress is presented for a 3 mol.% Y2O3 added ZrO2 ceramic using Raman microprobe spectroscopy. Low CIP pressure has been selected in the sample procedure to increase a potential to transform ZrO2. Aging tests were made and the transformation depth and residual stresses caused by transformation were evaluated by Raman spectroscopy A Raman microprobe technique using a visible wavelength laser coupled with a confocal optical device may enable one to retrieve spatially resolved information along the material subsurface. To demonstrate the potentiality of the confocal technique, aging of a ZrO2 sample has been made in autoclave and phase transformation gradually promoted from the surface towards the sub-surface of the sample (up to ～60 µm, in a sample autoclaved 168 h). Then, a quantitative spatially resolved assessment was attempted on these samples from their surface. The confocal information from the subsurface was compared with results of Raman spectroscopy collected from a cross-section. Accordingly, a quantitative equation was proposed, which allows the quantitative assessment of the thickness of the surface layer, which underwent phase transformation in ZrO2 ceramics, according to in-depth non-destructive assessments.