Bismuth vanadate (BiVO4) has recently been under focus for its potential use in photocatalysis thanks to its well-suited absorption edge in the visible light range. Here, we characterize the optical absorption of a BiVO4 single crystal as a function of temperature and polarization direction by reflectance and transmittance spectroscopy. The optical band gap is found to be very sensitive to temperature, and to the monoclinic-to-tetragonal ferroelastic transition at 523K. The anisotropy, as measured by the difference in absorption edge for light polarized parallel and perpendicular to the principal axis, is reduced from 0.2 eV in the high-temperature tetragonal phase to 0.1 eV at ambient temperature. We show that this evolution is dominantly controlled by the ferroelastic shear strain. These findings provide a route for further optimization of bismuth-vanadate-based light absorbers in photocatalytic devices.

中文翻译：

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铁弹性应变在 BiVO4 光吸收中的作用

钒酸铋 (BiVO4) 由于其在可见光范围内的非常合适的吸收边缘，最近因其在光催化中的潜在用途而受到关注。在这里，我们通过反射和透射光谱将 BiVO4 单晶的光吸收表征为温度和偏振方向的函数。发现光学带隙对温度和 523K 处的单斜至四方铁弹性转变非常敏感。通过平行和垂直于主轴的偏振光的吸收边缘差异测量的各向异性从高温四方相中的 0.2 eV 降低到环境温度下的 0.1 eV。我们表明这种演变主要由铁弹性剪切应变控制。