Phase Formation Study of The Substituted Lanthanum Manganites Solid Solutions

It is well known that the manganites-based solid solutions are interesting for their electric and magnetic properties. LaMnO₃ exhibits a distorted perovskite structure due to Mn³⁺ ion, which determines the presence of the Jahn–Teller effect. Replacing La³⁺ host ions by cations of lower valence leads to the disappearance of this effect and changes the characteristics of these materials. Although the formation of manganites-based solid solutions has been intensively studied, there are some unelucidated aspects concerning their formation mechanism, depending both on the precursors used and on the thermal treatment applied in order to obtain suitable properties. In this work the formation mechanism of La_0.7M_0.3MnO₃ (M=Ca, Sr, Ca+Sr in equimolecular mixture) solid solutions, in isothermal and non-isothermal conditions, was studied. For this purpose XRD, DTA/TG and spectral techniques were used. The solid solutions formation was found to be more dependent on the Mn-precursors type than the thermal treatment conditions. This revised version was published online in July 2006 with corrections to the Cover Date.