Dry thermal oxidation of single‐crystal silicon carbide (6H‐SiC) at 1400°C in low‐water oxygen using an alumina tube furnace initially yields a predominantly vitreous oxide scale. After 28 h, approximately one quarter of the oxide scale's surface becomes crystalline, with disk‐like cristobalite aggregates (radialites) statistically distributed within the vitreous matrix. Crystalline areas were found to be thinner than vitreous regions using optical microscopy and atomic force microscopy/hydrofluoric acid (AFM/HF)‐etching analysis, providing evidence for different oxidation rates of SiC covered by vitreous silica and cristobalite. As the bulk oxide scale continues to grow during devitrification, the radialites assume their characteristic morphology with a deepened center. Line profiles of the oxide scale's thickness across radialites obtained from AFM/HF etching were used to determine the oxidation rate of SiC covered by crystalline silica and the crystallisation rate applying a two‐stage parabolic equation. As a result, it was found that the parabolic rate‐constant Bvitreous is ≈4.2 times larger than the corresponding rate‐constant in crystalline areas (Bcristobalite), suggesting similar differences in effective oxygen diffusion coefficients. For the crystallization rate ν, we determined a value of 1.5±0.1 μm/h.

The relationship between Y2O3 content in tetragonal and cubic ZrO2 phases and the shift of the Raman band at ∼645/cm was investigated. With increasing Y2O3 content, the 645/cm Raman band position decreases to lower Raman shift values. A fit of x=13.66·(40.69(y−602,36)−1)0.1976, x = Y2O3 content in wt% and y = Raman band position in per cm, was found to be valid for low Y2O3‐stabilized t‐ZrO2, t′′‐ZrO2 transition, and fully stabilized c‐ZrO2. Modeling the change in lattice parameters due to the incorporation of Y2O3 in ZrO2 as obtained from Rietveld‐refined XRD data confirms that the peculiar sigmoidal form of the band shift with Y2O3 content is mainly due to a variation of the amount of oxygen vacancies. The resultant method is highly attractive in fields of Y2O3 determination in ZrO2 materials where a fast, spatially resolved, and nondestructive analysis is required.

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