Transparent Tetragonal Yttria-Stabilized Zirconia Ceramics: Influence of Scattering Caused by Birefringence
The correlation between grain size, optical birefringence, and transparency is discussed for tetragonal zirconia (ZrO2) ceramics using the Mie, Rayleigh, and Rayleigh–Gans–Debye scattering models. Our results demonstrate that at the degree of mean birefringence in the range (0.03–0.04) expected for tetragonal ZrO2, only the Mie theory provides reasonable results. At small particle size (<50 nm) the more straightforward Rayleigh approximation correlates with the Mie model. A real in-line transmission of ∼50% at visible light and 1 mm thickness is expected at a mean grain size <40 nm and ∼70% at a mean grain size <20 nm. At an infrared (IR) wavelength of 5 μm there should not be any scattering caused by birefringence for grain sizes <200 nm. Our simulations were validated with experimental data for tetragonal ZrO2 (3 mol% Y2O3) ceramics made from a powder with an initial particle size of ∼10 nm by sintering in air and using hot-isostatic pressing. The maximum in-line transmission of about 77% was observed at IR wavelengths of 3–5 μm.
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