RESUMEN
Pure and Na, Ca, and Sr doped lanthanum manganites (LaMnO3, La0.85Na0.15MnO3, La0.7Ca0.3 MnO3, La0.7Sr0.3MnO3) were prepared in form of bulk nano-structured materials through a two-step process. Nanometric powders were synthesized by the Pechini method and subsequently densified by Spark Plasma Sintering at 1273 K for 5 minutes under a pressure of 140 MPa. The method allowed the preparation of single phase manganites with a theoretical density above 98% together with a very limited growth of the grain size. Grain sizes below 70 nm were obtained for all materials except La0.85Na0.15MnO3 which showed a much larger grain size. Curie temperatures (Tc) and magnetoresistivity properties of the samples were measured by a Superconducting Quantum Interference Device (SQUID). The decrease in the resistivity below Tc occurred in a much wider range of temperature compared to ceramics having micron-size grains.