Selenic acid electrolyte provides porous anodic aluminium oxide (AAO) films with low porosity and high optical transparency. Here, the high-temperature behaviour of AAO obtained in a selenic acid electrolyte is reported for the first time. The crystallization of as-prepared amorphous AAO at about 800 °C is accompanied by the elimination of electrolyte impurities, an increase in pore diameter from 15 to 21 nm, and an increase in specific surface area to 55 m²·g⁻¹ due to the mesopore formation inside the cell walls. The second crystallization stage at about 1150 °C results in the formation of coarse-grained corundum (α-Al₂O₃) films with a mean grain size of about 11 μm. Each of the grains consists of regularly arranged 27-nm-diameter pores, which are stable up to 1300 °C. AAO physicochemical properties depend on the annealing temperature. In particular, chemical stability is up to three orders of magnitude higher after two-step crystallization. Optical properties and thermal expansion of selenic-acid-made porous AAO films with different phase composition are quantified. The crystallization of as-prepared AAO to low-temperature Al₂O₃ polymorphs has a minor influence on optical transmittance and effective refractive index of AAO, whereas the coarse-grained structure of corundum causes an order of magnitude decrease in average transmittance in the visible region. The coefficient of thermal expansion increases by 25% to 8.5 × 10⁻⁶ K⁻¹ for α-Al₂O₃ porous films compared to as-prepared AAO.

硒酸电解质提供具有低孔隙率和高光学透明度的多孔阳极氧化铝 (AAO) 薄膜。在这里，首次报道了在硒酸电解质中获得的 AAO 的高温行为。所制备的无定形 AAO 在约 800 °C 结晶伴随着电解质杂质的消除，孔径从 15 nm 增加到 21 nm，比表面积增加到 55 m ² ·g ^-1，这是由于细胞壁内的中孔形成。大约 1150 °C 的第二个结晶阶段导致形成粗晶刚玉（α-Al ₂ O ₃) 平均晶粒尺寸约为 11 μm 的薄膜。每个晶粒都由规则排列的 27 nm 直径的孔组成，在 1300 °C 下仍保持稳定。AAO的物理化学性质取决于退火温度。特别是，两步结晶后化学稳定性提高了三个数量级。量化了具有不同相组成的硒酸制备的多孔 AAO 薄膜的光学性质和热膨胀。所制备的 AAO 结晶为低温 Al ₂ O ₃多晶型物对光学透射率的影响较小，并且有效AAO 的折射率，而刚玉的粗粒结构导致可见光区域的平均透射率下降一个数量级。与制备的 AAO 相比，α-Al ₂ O _3多孔膜的热膨胀系数增加了 25%，达到 8.5 × 10 ^-6  K ^{-1 。}