Microstructure,optical and magnetic properties of Zr-doped SnO synthesized by the hydrothermal method

Sn_1?xZr_xO was successfully synthesized by the one-step hydrothermal method. X-ray diffraction and Raman patterns reveal that the lattice distortion of SnO occurs with an increase in Zr concentration, and Zr ions are located at the substituted (Zr_Sn) and interstitial (Zr_i) sites successively. Scanning electron microscope and transmission electron microscope images showed that Zr concentration does not affect the well-crystalline nature of Sn_1?xZr_xO. However, the system's morphology changes from three-dimensional flowerlike to two-dimensional sheetlike. Furthermore, X-ray photoelectron spectroscopy and Raman spectra indicate that there are inherent oxygen vacancies (V_O) in pure SnO lattice. UV–Visible absorption spectra show that the optical bandgap first decreases and then increases with Zr doping, which is explained by the sp–d exchange interactions in the case of Zr_Sn and the Burstein–Moss effect in the case of Zr_i. Additionally, Sn_1?xZr_xO samples exhibit room temperature ferromagnetism (RTFM), and the magnetic variation couples with the variation of the relative intensity of the Raman vibration modes. From the experimental results and the first-principles calculations, it can be seen that V_O and the exchange interaction between Zr 4d and O 2p states are accountable for the RTFM of Sn_1?xZr_xO. Meanwhile, the lattice distortion and the Zr–O–Zr super-exchange interaction caused by excessive doping could decrease FM.