Perovskite-type mixed oxides, such as La_1-xSr_xCo_1-yFe_yO₃ compounds, are at the present time one of the most widely used materials for cathode of intermediate temperature solid-oxide fuel cells (SOFCs). A significant increase of the specific area of the cathode can be achieved by preparing structures on the nanometric scale. In this work, nanocrystalline tubular structures of La_0.6Sr_0.4CoO₃ and La_0.6Sr_0.4Co_0.2Fe_0.8O₃ were synthesized by denitration, using polycarbonate porous templates, microwave irradiation and a further calcination at 800 °C. The shape and size of the tubes are determined by the characteristics of the template pores. The final thermal treatment is needed to obtain the desired perosvkite-type crystal structure. The resulting products were studied by means of X-ray diffraction and electron microscopy techniques.