A modified sol–gel method for low-temperature synthesis of homogeneous nanoporous La1−x Sr x MnO3 with large specific surface area

Abstract

A modified sol–gel (MSG) method was developed to synthesize perovskite La1−x Sr x MnO3 (x = 0.2, 0.4, 0.6, 0.8) with large specific surface area that allows for control of their particle size from the micrometer level to the nanometer level with novel nanoporous structure. The MSG method utilized carbon black (Vulcan XC-72R) as a pore-forming material during the preparation process. Two important process parameters, the calcination temperature and the pore former material addition, were investigated to control the size of the La1−x Sr x MnO3 particles. The phase evolution of La1−x Sr x MnO3 powders was investigated by thermogravimetric analysis (TG/DSC) and X-ray diffraction pattern. The results showed that the pure La0.6Sr0.4MnO3 phase has been obtained at about 550 °C in air, which is lowered around 150 °C comparing to conventional sol–gel method. In scanning electron microscope studied, it presented novel homogeneous nanoporous morphology with the average particle size from 30 to 100 nm. Based on the Brunauer–Emmett–Teller method analysis, the specific surface area of La1−x Sr x MnO3 was significantly influenced by the calcination temperature, the pore former material addition and the strontium content. The largest specific surface area of La0.2Sr0.8MnO3 reached 114.3 m2/g.