X-ray diffraction studies of perovskite or derived perovskite phase formation

The formation of the perovskite and derived perovskite oxides via polymeric route has been studied by both in situ X-ray diffraction and thermogravimetric analyses. The dried gel of La1 − xSrxMnO3 and LaMn1 − yCuyO3 oxides have been synthesized following the methods used in previous studies. The temperature of crystallization was found to depend on the strontium content: the higher the strontium content, the lower the crystallization temperature. Similarly, the La2NiO4 + δ series showed that the formation temperature is also function of both the nature of the chelating agent and the chelating agent/transition metal ratio (r). Whatever is the structure of the oxides, the first germs have an average size of about 10 nm. When the temperature is increasing, the growth of the particles depends on the nature of the oxides and specifically on the nature of the doping. In La-Sr-Mn-O series, the presence of strontium results in formation of small particles, 17 nm. Thus, the particle size can be controlled by the synthesis conditions such as the CA/TM ratio and the nature of chelating agent and by the nature of the doping.