Ferroelasticity was observed in 18-mol% ceria-stabilized zirconia using polarized confocal Raman spectroscopy. Samples were either indented using a diamond Vickers indenter or loaded uniaxially in a diamond anvil cell to induce the ferroelastic behavior. The presence and formation of the ferroelastic domains were observed by monitoring the relative intensities of the B 1g and A 1g Raman modes for the tetragonal phase. Domain switching was found to be present on the surfaces in the damaged materials both inside and around cracks. Loading of the ceramic materials revealed hysteresis in the relative intensities of the Raman peaks as a function of loading and unloading.
The strength of brittle ceramic materials is typically tested using simple uniaxial compression or by three-or four-point bending techniques. While these methods provide reliable results, they do not depict a realistic characterisation of the load-bearing capacity of structural materials, and a method that involves the application of multiaxial stress is required, such as the ring-on-ring biaxial flexural strength test. In this paper, an in-house ring-on-ring fixture was developed and validated by comparing the experimental and simulated biaxial strength tests of a model ZrB 2 -30wt-%SiB 6 ceramic composite. A description of the simulated finite element analysis is provided, and the stress field acting on the sample with maximum principal stress located at the surface under tension at the centre of the ceramic disk is shown.
The development of thermal stresses in solid oxide fuel cells (SOFCs), and thus their structural stability and reliability, depends directly on the thermal expansion and elastic moduli of the constituent materials. Therefore, it is important to study these properties of SOFC materials. In this study, the thermal expansion and elastic properties of common electrolyte materials, namely yttria stabilized zirconia (YSZ), scandia and ceria stabilized zirconia (SCSZ) and gadolinia doped ceria (GDC), are reported. High temperature X-ray diffraction (HT-XRD) was used to show that the cubic structure of YSZ and GDC samples is stable throughout the temperature range of 30-800 C. However, SCSZ undergoes partial cubic to rhombohedral phase transition at around 300 C but transferred completely back to cubic phase at around 500 C upon heating. The coefficient of thermal expansion (CTE) of electrolyte materials was measured using
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