The interactions of ferroelectric (FE) perovskite oxides (ABO3) with light are increasingly being studied for different applications such as photovoltaics and optoelectronics. Combination of different cations at the A- and B-site to form solid solutions allows tuning of the material’s properties, most importantly the band gap (Eg) that sets the wavelength range of light absorption. Classic FE perovskite oxides such as BaTiO3, KNbO3 and PbTiO3 exhibit Eg >3 eV, which limits their implementation in visible-light absorbing devices. Furthermore, the tuning of their Eg via solid solution strategy to a lower Eg range is limited by the requirement for the presence of a d0 metal at the B-site that is necessary for the FE distortion but leads to a larger Eg. This gives rise to the challenge of decreasing the Eg while maintaining FE distortion. Here, we use first-principles calculations to explore the FE and optical properties of the novel [KNbO3]x - [KTi1/2Mo1/2O3]1-x (KNTM) perovskite oxide solid solution. The introduction of Ti4+ and Mo6+ into the parent KNbO3 decreases the Eg to 2.2 eV for x = 0.9, while preserving or enhancing the polarization. Experimental fabrication and characterization show that the obtained KNTM at x = 0.9 has an orthorhombic structure close to the tetragonal phase at room temperature, suggesting its proximity to a morphotropic phase boundary, and a direct gap of …

中文翻译：

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可见光吸收铌酸钾钛酸钼铁电体

铁电（FE）钙钛矿氧化物（ABO3）与光的相互作用正在越来越多地研究用于不同的应用，例如光伏和光电。在A和B位置结合不同的阳离子形成固溶体，可以调节材料的性能，最重要的是可以设定光吸收波长范围的带隙（Eg）。经典的FE钙钛矿氧化物，例如BaTiO3，KNbO3和PbTiO3的Eg> 3 eV，这限制了它们在可见光吸收设备中的应用。此外，通过固溶策略将其Eg调节到较低的Eg范围受到在FE畸变所必需的B位置存在d0金属但导致更大Eg的要求的限制。这就带来了在保持FE失真的同时降低Eg的挑战。这里，我们使用第一性原理计算来探索新型[KNbO3] x-[KTi1 / 2Mo1 / 2O3] 1-x（KNTM）钙钛矿氧化物固溶体的FE和光学性质。将Ti4 +和Mo6 +引入母体KNbO3中时，对于x = 0.9，Eg降低至2.2 eV，同时保留或增强了极化。实验制备和表征表明，所获得的KNTM在x = 0.9时具有正交结构，在室温下接近于四方相，表明它接近同晶相边界，并且存在直接间隙。