A new far-red emission from Zn2SnO4 powder synthesized by modified solid state reaction method

Abstract

In this work, far-red-emitting Zn2SnO4 phosphor has been successfully synthesized by a facile modified solid-state reaction method from ZnO and SnO2 powders. FESEM images reveal that as-milled particles are nearly spherical, with size in the range of 10–30 nm. The particle size increases with increasing annealing temperature and it reaches the value of about 4 μm at 1200 °C. XRD patterns indicate that Zn2SnO4 phase starts occurring at ~700 °C with its single phase at 900 °C and the best crystalline quality of Zn2SnO4 phase is obtained at 1000 °C. UV–Vis spectra analysis reveals that ZnO phase reappears at high annealing temperature (≥1100 °C), reflecting the deterioration of the single phase of Zn2SnO4. A broad visible band centered at 684 nm, which has never been explicitly reported, is clearly observed in the PL spectrum of the single Zn2SnO4 crystals. The intensity of this new band is influenced by annealing temperatures. It reaches the maximum value at 1000 °C, corresponding to the highest quality of the Zn2SnO4 phase. By using data fitting, the PL spectrum is deconvoluted into four Gaussian peaks at ~2.20 eV (563.5 nm), ~1.98 eV (626.1 nm), ~1.80 eV (688.8 nm), and ~1.68 eV (738.0 nm). The peak at ~2.20 eV (563.5 nm) is ascribed to oxygen vacancy (Vo) while the other emission peaks are possibly associated with a significant number of trapped states due to the high concentration of deficiencies such as oxygen vacant defects, zinc interstitials, zinc/tin vacancies (VZn/VSn), Zn/Sn stoichiometry or point defects.