Structural morphological and band gap studies of Al doping in BaSnO3

In this work the role of Al as dopant in BaSnO3 is explored through structural, morphological, compositional and optical studies. The Perovskite structured pure BaSnO3 (BSO) and Al doped BSO 3D nano particles were synthesised through coprecipitation method at pH-13 using BaCO3, SnCl4 and Al2O3 as precursors. Al doped BSO was prepared by mixing BSO (taken from oven before calcinations) with Al2O3 through mortar pestle for one hour and then calcined it at 1100℃ and name it as Al doped BSO. The structural, morphological, compositional and optical studies were carried out through XRD, FESEM, XPS and Uv–Vis spectroscopy respectively. The pure and doped BSO XRD studies reveal that Al doped BSO is a multiphase material with SnO2 as a dominant phase while in pure BSO SnO2 phase was present as impurity phase. The XRD results are in correlation with the XPS results. Through XPS it is observed that Al is active dopant which suppresses the Ba incorporation in BSO and hence results in suppressed BSO phase in Al doped BSO. XPS confirms the Al doping and the spin orbit splitting energy at 8.5 eV of Sn signifies the Sn4+ incorporation, Ba as Ba2+, O as O2– and Al as Al3+. Also, there is noticeable shift of O1s XPS peak towards lower B.E in Al doped sample which is indicative of dopants presence. FESEM studies shows that agglomerated nanoparticles were formed in pure BSO and Al doped samples it seems that Al doping further enhances the agglomeration and increases the average particle size from 300 nm to 600 nm. Uv–Vis studies shows that multiphase Al doped BSO is indirect band gap material for 2.4 eV and direct band gap at 3.3 eV while pure BSO has 2.6 eV as indirect and 2.9 as direct bandgap. Optical studies lead to the conclusion that with Al doped BSO is more transparent in the visible region than pure BSO whereas in pure BSO direct transitions are happening at 427 nm.