A new route to synthesizing La-doped SrTiO3 nanoparticles using the sol-gel auto combustion method and their characterization and photocatalytic application

Abstract The Sr1-xLaxTiO3 (SLTO) nanopowder with varied La contents was successfully synthesized by a new route sol-gel auto combustion technique. The results of the X-ray Diffraction (XRD) patterns of the undoped and La-doped SLTO samples showed a pure phase with cubic perovskite structure, together with the position of the (110) peak slightly shifted toward the lower 2θ angle with increasing amounts of La dopant. The La doping increases the lattice parameter and the unit cell density due to the substitution of the larger ionic radius of La3+ into the smaller ionic radius of the Sr2+. As well, the crystallite size and particle size of the SLTO samples decreased as the La doping content increased. Specific surface area and total pore volume increased with the increase of La doping content. The band gap (Eg) was determined for the samples to be 4.10–4.12 eV. The photoluminescence (PL) at room temperature showed violet, green, and blue emissions at an excitation of 327 nm. The photocatalytic activity of SLTO, resulting from degrading methylene blue (MB) under UV irradiation, increased with increasing La content and reached a maximum at x = 0.07. The effect of La doping on Eg, PL, and mechanism photocatalytic activity of SLTO nanopowders, resulting from the oxygen vacancy in the SLTO structure, was also proposed and discussed. The results emphasize the significance of sol-gel auto combustion technique, which preserves the nanostructure of SLTO and improving photocatalytic activity.