Effect of Fe doping on optical absorption properties in KTiOAsO4 crystals

The optical absorption spectra of both undoped KTA crystals and KTA crystals doped with Fe2O3 at room temperature in the UV–visible and infrared regions are reported. The wavelength dependence of absorption coefficient α is calculated in the UV–visible range, and the characteristics of the optical absorption edges are discussed. Our analysis reveals that the absorption edges for these crystals can be attributed to indirect transition. It is shown that doping with Fe2O3 makes the indirect band gap E′g of KTA decrease, causing the indirect transition absorption edge to move towards lower energy. In addition, the infrared transmission spectra of these crystals are inspected in the region between 4000 and 1700 cm−1. The characteristics of OH− absorption bands of Fe:KTA are also discussed, in comparsion with those for undoped KTA.