Hydrothermal synthesis of perovskite strontium doped lanthanum chromite fine powders and its sintering

Sr doped lanthanum chromite powders with two different compositions, La(0.9)Sr(0.1)CrO(3) and La(0.8)Sr(0.2)CrO(3), were prepared from precursor lanthanum chromite gels obtained by the coprecipitation method, followed by hydrothermal treatments at temperatures from 400 to 450 degrees C, for various reaction times varying from 0.5 to 2 h. The reaction products were characterized by XRD, SEM and TEM techniques. The powder was cold isostatically pressed at 200 MPa, and then sintered in air at 1500 degrees C for several intervals (1-20 h). Relative density measurements were conducted by helium pycnometry and the microstructure was revealed by SEM after thermal etching. The X-ray diffraction patterns of the powders corresponding to La(0.9)Sr(0.1)CrO(3) and La(0.8)Sr(0.2)CrO(3) nominal compositions obtained at 400 and 425 degrees C for 1 h, respectively, were indexed with that of the orthorhombic single LaCrO(3) phase. SEM and TEM micrographs showed that the particles had irregular peanut-like morphology, and the average particle size was 300 nm. Furthermore, the maximum relative density of the La(0.8)Sr(0.2)CrO(3) sample obtained by the heat treatment in air at 1500 degrees C for 20 h was 97% of the theoretical density and the average grain size of the sintered pellet was of 5 mu m. The electric conductivity and activation energy determined for this pellet were 14477.3 S m(-1) and 0.13 eV, respectively. (C) 2010 Elsevier B.V. All rights reserved.